tag:blogger.com,1999:blog-199277872024-03-13T06:34:47.155-04:00Solid-State NMR Literature BlogWelcome to the Literature blog for Rob Schurko's Solid-State NMR group at the University of Windsor.Rob Schurkohttp://www.blogger.com/profile/01891945016835005814noreply@blogger.comBlogger768125tag:blogger.com,1999:blog-19927787.post-45935926659441597112011-02-09T14:40:00.003-05:002011-02-09T14:53:58.819-05:00Phys. Chem. Chem. Phys., 2011<span style="font-weight:bold;">Determination of coordination modes and estimation of the 31P–31P distances in heterogeneous catalyst by solid state double quantum filtered 31P NMR spectroscopy </span><br />Si-Yong Zhang, Mei-Tao Wang, Qing-Hua Liu, Bing-Wen Hu, Qun Chen, He-Xing Li and Jean-Paul Amoureux<br /><br />Phys. Chem. Chem. Phys., 2011, Advance Article<br /><a href="http://dx.doi.org/10.1039/C0CP01191F">http://dx.doi.org/10.1039/C0CP01191F</a><br /><br />To overcome the separation difficulty of the palladium-based homogeneous catalyst, the palladium complex can be anchored on various supports such as silica. However, it is difficult to determine the amounts of the two coordination modes of the Pd nucleus, that is, Pd coordinates with one phosphorus atom and Pd coordinates with two phosphorus atoms. Here a 31P double-quantum filtered (DQ-filtered) method in solid-state NMR is introduced for the palladium-based heterogenous catalyst system. With the DQ-filtered method, we can not only determine the amounts of the two different kinds of palladium coordination modes, we can also estimate the interatomic distance of two 31P nuclei bonded to a palladium nucleus. With the help of this method, we can quickly estimate interatomic distances in our designed system and accurately re-design the palladium system to accommodate either one 31P or two 31P.<br /><br /><br /><span style="font-weight:bold;">A highly ordered mesostructured material containing regularly distributed phenols: preparation and characterization at a molecular level through ultra-fast magic angle spinning proton NMR spectroscopy </span><br />Arthur Roussey, David Gajan, Tarun K. Maishal, Anhurada Mukerjee, Laurent Veyre, Anne Lesage, Lyndon Emsley, Christophe Copéret and Chloé Thieuleux<br /><br />Phys. Chem. Chem. Phys., 2011, Advance Article<br /><a href="http://dx.doi.org/10.1039/C0CP02137G">http://dx.doi.org/10.1039/C0CP02137G</a><br /><br />Highly ordered organic–inorganic mesostructured material containing regularly distributed phenols is synthesized by combining a direct synthesis of the functional material and a protection–deprotection strategy and characterized at a molecular level through ultra-fast magic angle spinning proton NMR spectroscopy.<br /><br /><br /><span style="font-weight:bold;">Influence of particle size on solid solution formation and phase interfaces in Li0.5FePO4 revealed by 31P and 7Li solid state NMR spectroscopy</span><br />L. J. M. Davis, I. Heinmaa, B. L. Ellis, L. F. Nazar and G. R. Goward<br /><br />Phys. Chem. Chem. Phys., 2011, Advance Article<br /><a href="http://dx.doi.org/10.1039/C0CP01922D">http://dx.doi.org/10.1039/C0CP01922D</a><br /><br />Here we report the observation of electron delocalization in nano-dimension xLiFePO4:(1 − x)FePO4 (x = 0.5) using high temperature, static, 31P solid state NMR. The 31P paramagnetic shift in this material shows extreme sensitivity to the oxidation state of the Fe center. At room temperature two distinct 31P resonances arising from FePO4 and LiFePO4 are observed at 5800 ppm and 3800 ppm, respectively. At temperatures near 400 °C these resonances coalesce into a single narrowed peak centered around 3200 ppm caused by the averaging of the electronic environments at the phosphate centers, resulting from the delocalization of the electrons among the iron centers. 7Li MAS NMR spectra of nanometre sized xLiFePO4:(1 − x)FePO4 (x = 0.5) particles at ambient temperature reveal evidence of Li residing at the phase interface between the LiFePO4 and FePO4 domains. Moreover, a new broad resonance is resolved at 65 ppm, and is attributed to Li adjacent to the anti-site Fe defect. This information is considered in light of the 7Li MAS spectrum of LiMnPO4, which despite being iso-structural with LiFePO4 yields a remarkably different 7Li MAS spectrum due to the different electronic states of the paramagnetic centers. For LiMnPO4 the higher 7Li MAS paramagnetic shift (65 ppm) and narrowed isotropic resonance (FWHM ≈ 500 Hz) is attributed to an additional unpaired electron in the t2g orbital as compared to LiFePO4 which has δiso = −11 ppm and a FWHM = 9500 Hz. Only the delithiated phase FePO4 is iso-electronic and iso-structural with LiMnPO4. This similarity is readily observed in the 7Li MAS spectrum of xLiFePO4:(1 − x)FePO4 (x = 0.5) where Li sitting near Fe in the 3+ oxidation state takes on spectral features reminiscent of LiMnPO4. Overall, these spectral features allow for better understanding of the chemical and electrochemical (de)lithiation mechanisms of LiFePO4 and the Li-environments generated upon cycling.<br /><br /><br /><span style="font-weight:bold;">Phase evolution in lithium disilicate glass–ceramics based on non-stoichiometric compositions of a multi-component system: structural studies by 29Si single and double resonance solid state NMR</span><br />Christine Bischoff, Hellmut Eckert, Elke Apel, Volker M. Rheinberger and Wolfram Höland<br /><br />Phys. Chem. Chem. Phys., 2011, Advance Article<br /><a href="http://dx.doi.org/10.1039/C0CP01440K">http://dx.doi.org/10.1039/C0CP01440K</a><br /><br />The crystallization mechanism of a high-strength lithium disilicate glass–ceramic in the SiO2–Li2O–P2O5–Al2O3–K2O–(ZrO2) system, used as restorative dentistry material, has been examined on the basis of quantitative 29Si magic angle spinning (MAS) and 29Si{7Li} rotational echo double resonance (REDOR) NMR spectroscopy. Crystallization occurs in two stages: near 650 °C a significant fraction of the Q(3) units disproportionates into crystalline Li2SiO3 and Q(4) units. Upon further annealing of this glass–ceramic to 850 °C the crystalline Li2SiO3 phase reacts with the Q(4) units of the softened residual glass matrix, resulting in the crystallization of Li2Si2O5. The NMR experiments provide detailed insight into the spatial distribution of the lithium ions suggesting the absence of lithium ion clustering in the residual glassy component of the final glass–ceramic. 31P MAS-NMR spectra indicate that phosphate acts as a lithium ion scavenger, resulting in the predominant formation of orthophosphate (P(0)) and some pyrophosphate (P(1)) groups. Crystallization of Li2SiO3 occurs concomitantly with the formation of a highly disordered Li3PO4 phase as evidenced from strong linebroadening effects in the 31P MAS-NMR spectra. Well-crystallized Li3PO4 is only formed at annealing conditions resulting in the formation of crystalline lithium disilicate. These results argue against an epitaxial nucleation process previously proposed in the literature and rather suggest that the nucleation of both lithium metasilicate and lithium disilicate starts at the phase boundary between the disordered lithium phosphate phase and the glass matrix.<br /><br /><br /><br /><span style="font-weight:bold;">Longer-range distances by spinning-angle-encoding solid-state NMR spectroscopy</span><br />Johanna Becker-Baldus, Thomas F. Kemp, Jaan Past, Andres Reinhold, Ago Samoson and Steven P. Brown<br /><br />Phys. Chem. Chem. Phys., 2011, Advance Article<br /><a href="http://dx.doi.org/10.1039/C0CP02364G">http://dx.doi.org/10.1039/C0CP02364G</a><br /><br />A new spinning-angle-encoding spin-echo solid-state NMR approach is used to accurately determine the dipolar coupling corresponding to a C–C distance over 4 Å in a fully labelled dipeptide. The dipolar coupling dependent spin-echo modulation was recorded off magic angle, switching back to the magic angle for the acquisition of the free-induction decay, so as to obtain optimum sensitivity. The retention of both ideal resolution and long-range distance sensitivity was achieved by redesigning a 600 MHz HX MAS NMR probe to provide fast angle switching during the NMR experiment: for 1.8 mm rotors, angle changes of up to [similar]5° in [similar]10 ms were achieved at 12 kHz MAS. A new experimental design that combines a reference and a dipolar-modulated experiment and a master-curve approach to data interpretation is presented.<div class="blogger-post-footer">Recent articles and reviews featuring solid-state NMR.</div>M.R.http://www.blogger.com/profile/04734312285885188267noreply@blogger.com0tag:blogger.com,1999:blog-19927787.post-15670301480732792122011-01-31T16:50:00.001-05:002011-01-31T16:56:05.583-05:00<span style="font-size:180%;">Solid-State NMR and Density Functional Theory Studies of Ionization States of Thiamin</span><br /><br /><em>J. Phys. Chem. B</em>, 2011, 115 (4), pp 730–736<br /><br />Thiamin diphosphate (ThDP) is a key coenzyme in sugar metabolism. The 4′-aminopyrimidine ring of ThDP cycles through several ionization and tautomeric states during enzyme catalysis, but it is not fully understood which states are adopted during the individual steps of the catalytic cycle. Thiamin has been synthesized with labels selectively inserted into the C2 and C6′ positions, as well as into the amino group, creating [C2, C6′-13C2] thiamin and [N4′-15N] thiamin. Magic-angle spinning (MAS) NMR spectroscopy has been employed to record the 13C and 15N chemical shift anisotropy (CSA) tensors for C2, C6′, and N4′ atoms. Our results indicate that the isotropic chemical shifts as well as the principal components of the 13C and 15N CSA tensors are very sensitive to the protonation states in these compounds and, therefore, permit differentiating between the two ionization states, 4-aminopyrimidine and 4-aminopyrimidinium. Using density functional theory (DFT), we have calculated the magnetic shielding anisotropy tensors of C2, C6′, and N4′ and found excellent agreement between the computed and the experimental tensors. Our findings indicate that MAS NMR spectroscopy in conjunction with DFT calculations is a sensitive probe of ionization states in the thiamin cofactor. The results of this study will serve as a guide for characterization of ionization and tautomeric states of thiamin in complexes with thiamin-dependent enzymes.<br /><br /><span style="font-size:180%;">Siting and Mobility of Deuterium Absorbed in Cosputtered Mg0.65Ti0.35. A MAS 2H NMR Study<br /><br /></span><em>J. Phys. Chem. C</em>, 2011, 115 (1), pp 288–297<br /><br />Nanostructured magnesium titanium alloys are interesting lightweight materials for chemical hydrogen storage. We have therefore investigated the siting and dynamics of deuterium absorbed in a Mg0.65Ti0.35 alloy generated by magnetron cosputtering, and made a comparison to the corresponding features in bulk samples of deuterium-loaded Mg0.65Ti0.35 and Mg0.65Sc0.35 prepared by ball-milling and melt-casting, respectively. Magic-angle spinning 2H NMR of cosputtered Mg0.65Ti0.35D1.1 shows partly resolved signals of deuterium located in nonconductive domains at tetrahedral Mg4 and mixed MgnTi4−n sites (4 ppm) and deuterium at Ti4 sites in conducting TiD2 nanodomains (−29 and −68 ppm). No bulk TiD2 signal at −150 ppm is observed, in contrast to what we find in ball-milled Mg0.65Ti0.35D0.65, which is largely phase separated. The deuterium species with shift values of 4 and −29 ppm undergo complete exchange at a subsecond time scale in one- and two-dimensional exchange NMR and must therefore be close together in the lattice. In contrast, deuterium resonating at −68 ppm does not show deuterium exchange and thus appears to be located at more stable sites. The observed deuterium exchange and the reduced Knight shift compared to bulk TiD2 are explained using a model with TiD2 nanoslabs.<br /><br /><br /><span style="font-size:180%;">Towards Portable High-Resolution NMR Spectroscopy†<br /><br /></span><em>Angew. Chem. Int. Ed.</em> 2011, 50, 354 – 356<br /><br />Analysis on the go: Portable high-resolution NMR spectroscopy is of great interest for many applications. Recent advances in magnet design, spectrometer stability, and acquisition schemes have placed the realization of low-field spectrometers based on room-temperature permanent magnets and that can deliver chemical shift resolution within reach.<div class="blogger-post-footer">Recent articles and reviews featuring solid-state NMR.</div>superczarhttp://www.blogger.com/profile/07399861027764577975noreply@blogger.com0tag:blogger.com,1999:blog-19927787.post-4215518769854843282011-01-31T14:26:00.000-05:002011-01-31T14:27:16.521-05:00<h2 class="entry-title"><a class="entry-title-link" target="_blank" href="http://xlink.rsc.org/?DOI=c0jm00155d&RSS=1">Probing the local structures and protonic conduction pathways in scandium substituted BaZrO3 by multinuclear <b class="highlighted0">solid</b>-<b class="highlighted1">state</b> <b class="highlighted2">NMR</b> spectroscopy</a></h2><span class="entry-source-title-parent">from <a href="http://www.google.ca/reader/view/feed/http%3A%2F%2Fwww.rsc.org%2Fpublishing%2Fjournals%2Frssfeed.asp%3FFeedType%3DLatestArticles%26JournalCode%3DJM" class="entry-source-title" target="_blank">RSC - J. Mater. Chem. latest articles</a></span> <span class="entry-author-parent">by <span class="entry-author-name">Clare P. Grey<br /></span></span><div class="denialmessage_middleImage"> <div class="abstract_new"> <strong> <label id="lblAbstract"> Abstract</label></strong><br /> <label id="lblAbstractValue"> </label><p>A comprehensive multinuclear solid-state NMR study of scandium-substituted BaZrO<small><sub>3</sub></small> is reported. Static low field and MQMAS very high field <small><sup>45</sup></small>Sc NMR data revealed the presence of both 5- and 6-coordinated scandium atoms, 5-coordinated scandium arising from Sc nearby an oxygen vacancy. <small><sup>17</sup></small>O NMR spectra showed the presence of up to three different chemical oxygen environments assigned to Zr–O–Zr, Zr–O–Sc and Sc–O–Sc. From the ratios of these different oxygen sites, the distribution of the scandium cations was close to random but indicated that the maximum scandium incorporation was lower than expected, consistent with the observation of Sc<small><sub>2</sub></small>O<small><sub>3</sub></small> impurities at substitution levels of 30% Sc for Zr. <small><sup>1</sup></small>H and <small><sup>45</sup></small>Sc NMR data on the hydrated materials revealed the presence of scandium next to protonic defects. Finally, variable temperature <small><sup>1</sup></small>H NMR showed the presence of at least two different proton environments in between which proton transfer occurs at ambient temperatures (300 K).</p> <br /> <br /> <div class="abstract_new_img" align="center"> <img id="imgGALoader" style="" title="Graphical abstract" alt="Graphical abstract: Probing the local structures and protonic conduction pathways in scandium substituted BaZrO3 by multinuclear solid-state NMR spectroscopy" src="http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=C0JM00155D" /> </div> </div> </div> <div class="artcle_bott_img_s10"> </div><div class="blogger-post-footer">Recent articles and reviews featuring solid-state NMR.</div>Chris Mireaulthttp://www.blogger.com/profile/02994299709212098832noreply@blogger.com0tag:blogger.com,1999:blog-19927787.post-61650585927720287902011-01-31T14:24:00.000-05:002011-01-31T14:25:59.727-05:00<h2 class="entry-title"><a class="entry-title-link" target="_blank" href="http://xlink.rsc.org/?DOI=c0jm02828b&RSS=1"><b class="highlighted0">Solid</b> <b class="highlighted1">state</b> <b class="highlighted2">NMR</b> study on the thermal decomposition pathway of sodium amidoborane NaNH2BH3</a></h2><span class="entry-source-title-parent">from <a href="http://www.google.ca/reader/view/feed/http%3A%2F%2Fwww.rsc.org%2Fpublishing%2Fjournals%2Frssfeed.asp%3FFeedType%3DLatestArticles%26JournalCode%3DJM" class="entry-source-title" target="_blank">RSC - J. Mater. Chem. latest articles</a></span> <span class="entry-author-parent">by <span class="entry-author-name">Yoshitsugu Kojima<br /></span></span><strong><label id="lblAbstract">Abstract</label></strong><br /> <label id="lblAbstractValue"> </label><p>The thermal decomposition pathway of sodium amidoborane (NaAB; NaNH<small><sub>2</sub></small>BH<small><sub>3</sub></small>) has been investigated in detail by using solid state NMR spectroscopy. <small><sup>23</sup></small>Na MAS/3QMAS NMR spectra suggested that NaH and an amorphous Na–N–B–H phase started to be formed as decomposition products even at 79 °C, although NaAB was prepared from NaH and NH<small><sub>3</sub></small>BH<small><sub>3</sub></small> by ball milling at room temperature. Based on the quantitative analyses of the <small><sup>23</sup></small>Na MAS spectra, we proposed a decomposition reaction to 200 °C to be NaNH<small><sub>2</sub></small>BH<small><sub>3</sub></small> → Na<small><sub>0.5</sub></small>NBH<small><sub>0.5</sub></small> + 0.5NaH + 2.0H<small><sub>2</sub></small>. The hypothetical phase Na<small><sub>0.5</sub></small>NBH<small><sub>0.5</sub></small> is amorphous, where the basic molecular unit of the original NaAB is polymerized into a [–B<img src="http://www.rsc.org/images/entities/char_e001.gif" alt="[double bond, length as m-dash]" border="0" />N–]<small><sub><i>n</i></sub></small> network structure. It was also found that the diammoniate of diborane (DADB) and polyaminoborane (PAB) were not formed during the decomposition of NaAB, which are both key compounds on the pyrolysis of ammonia borane (AB).</p><div class="blogger-post-footer">Recent articles and reviews featuring solid-state NMR.</div>Chris Mireaulthttp://www.blogger.com/profile/02994299709212098832noreply@blogger.com0tag:blogger.com,1999:blog-19927787.post-52819400582995344542011-01-17T10:31:00.004-05:002011-01-17T10:37:39.692-05:0017O Central Transition NMR<span class="Apple-style-span" >A nice write-up of Gang Wu's solution 17O central transition NMR studies of biomolecules can be found in C&E News</span><div><span class="Apple-style-span" ><br /></span></div><div><a href="http://pubs.acs.org/cen/news/89/i01/8901notw4.html"><span class="Apple-style-span" >http://pubs.acs.org/cen/news/89/i01/8901notw4.html</span></a></div><div><span class="Apple-style-span" ><br /></span></div><div><span class="Apple-style-span" >The corresponding articles are:</span></div><div><span class="Apple-style-span" ><br /></span></div><div><span class="Apple-style-span" style="line-height: 18px; "><h1 class="articleTitle" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0.5em; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; font: normal normal bold 1.3em/normal 'Trebuchet MS', Arial, Helvetica, sans-serif; color: rgb(0, 0, 0) !important; line-height: 1.4em; "><span class="Apple-style-span" style="font-weight: normal; line-height: normal; " >Quadrupole Central Transition 17O NMR Spectroscopy of Biological Macromolecules in Aqueous Solution</span></h1></span></div><span class="Apple-style-span" ><br />Jianfeng Zhu and Gang Wu*<br /><br />J. Am. Chem. Soc., Article ASAP<br />DOI: 10.1021/ja1079207<br /><br />Abstract: We demonstrate a general nuclear magnetic resonance (NMR) spectroscopic approach in obtaining high-resolution 17O (spin-5/2) NMR spectra for biological macromolecules in aqueous solution. This approach, termed quadrupole central transition (QCT) NMR, is based on the multiexponential relaxation properties of half-integer quadrupolar nuclei in molecules undergoing slow isotropic tumbling motion. Under such a circumstance, Redfield’s relaxation theory predicts that the central transition, mI = +1/2 ↔ −1/2, can exhibit relatively long transverse relaxation time constants, thus giving rise to relatively narrow spectral lines. Using three robust protein−ligand complexes of size ranging from 65 to 240 kDa, we have obtained 17O QCT NMR spectra with unprecedented resolution, allowing the chemical environment around the targeted oxygen atoms to be directly probed for the first time. The new QCT approach increases the size limit of molecular systems previously attainable by solution 17O NMR by nearly 3 orders of magnitude (1000-fold). We have also shown that, when both quadrupole and shielding anisotropy interactions are operative, 17O QCT NMR spectra display an analogous transverse relaxation optimized spectroscopy type behavior in that the condition for optimal resolution depends on the applied magnetic field. We conclude that, with the currently available moderate and ultrahigh magnetic fields (14 T and higher), this 17O QCT NMR approach is applicable to a wide variety of biological macromolecules. The new 17O NMR parameters so obtained for biological molecules are complementary to those obtained from 1H, 13C, and 15N NMR studies.<br /><br /><br />Solid-State 17O NMR Spectroscopy of Large Protein–Ligand Complexes†<br />Dr. Jianfeng Zhu1, Dr. Eric Ye2, Dr. Victor Terskikh3, Prof. Dr. Gang Wu1<br />Article first published online: 29 OCT 2010<br /><br />DOI: 10.1002/anie.201002041<br /><br />Angewandte Chemie International Edition<br />Volume 49, Issue 45, pages 8399–8402, November 2, 2010<br /><br />Keywords:<br />oxygen-17;protein–ligand interactions;proteins;solid-state NMR spectroscopy;structure refinement<br /><br />Oxygen, oxygen, everywhere! Poor sensitivity has hindered the development of solid-state 17O NMR spectroscopy as a practical technique for the structural elucidation of protein complexes. However, this has now changed and it has been demonstrated that multinuclear 17O, 27Al, 13C NMR parameters can be used to aid structural refinement for a protein-bound ligand molecule (see picture).</span><div class="blogger-post-footer">Recent articles and reviews featuring solid-state NMR.</div>Aaronhttp://www.blogger.com/profile/10367130607577279623noreply@blogger.com0tag:blogger.com,1999:blog-19927787.post-91909768507102670622011-01-10T16:42:00.002-05:002011-01-10T17:47:35.668-05:00Solid-State NMR<meta charset="utf-8"><span class="Apple-style-span" style="font-family: arial, sans-serif; font-size: 13px; border-collapse: collapse; "><h2 class="entry-title" style="max-width: 650px; font-size: 18px; margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><a class="entry-title-link" target="_blank" href="http://www.sciencedirect.com/science?_ob=GatewayURL&_origin=IRSSCONTENT&_method=citationSearch&_piikey=S0926204010000731&_version=1&md5=49ff98b2f23bad4273e2471d78d6c04e" style="color: rgb(34, 68, 187); text-decoration: none; ">A practical guide for the setup of a 1H-31P-13C double cross-polarization (DCP) experiment<div class="entry-title-go-to" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 2px; display: inline; padding-left: 16px; height: 17px; background-image: url(http://www.google.ca/reader/ui/3607832474-entry-action-icons.png); background-attachment: initial; background-origin: initial; background-clip: initial; background-color: initial; background-position: 0% -416px; background-repeat: no-repeat no-repeat; "></div></a></h2><div class="entry-author" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; color: rgb(102, 102, 102); text-decoration: none; "><div class="entry-likers" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; background-color: rgb(255, 255, 255); max-width: 650px; "></div></div><div class="entry-debug" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "></div><div class="entry-annotations" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "></div><div class="entry-body" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; max-width: 650px; padding-top: 0.5em; "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><div class="item-body" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Publication year: 2010
<br /><b>Source:</b> Solid State Nuclear Magnetic Resonance, In Press, Accepted Manuscript, Available online 13 December 2010
<br />Wlodzimierz, Ciesielski , Hassan, Kassasir , Marek J., Potrzebowski</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><meta charset="utf-8"><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, verdana, helvetica, sans-serif; font-size: 12px; line-height: 18px; ">O-phospho-L-threonine is a convenient sample to setup a <sup>1</sup>H-<sup>31</sup>P-<sup>13</sup>C double cross-polarization (DCP) Hartmann-Hahn match. The <sup>1</sup>H-<sup>31</sup>P-<sup>13</sup>C technique is extremely sensitive to the rate of sample spinning. Both zero-quantum (ZQ) and double-quantum (DQ) cross-polarization operate at an average spinning rate (6–7 kHz). At higher spinning rates (10 kHz), the DQCP mechanism dominates and leads to a reduction of signal intensity, in particular for lower <sup>31</sup>P rf field strength. The application of two shape pulses during the second cross-polarization greatly improves the signal to noise ratio allowing the recording of better quality spectra. <sup>31</sup>P-<sup>13</sup>C SPECIFIC-CP (spectrally induced filtering in combination with cross-polarization) experiments can be carried out under ZQCP and DQCP condition if careful attention is paid to the choice of RF field amplitudes and carriers Ω. Application of 1D and 2D <sup>1</sup>H-<sup>31</sup>P-<sup>13</sup>C experiments is demonstrated on model samples; disodium ATP hydrate and O-phospho-L-tyrosine.</span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, verdana, helvetica, sans-serif; font-size: 12px; line-height: 18px; ">
<br /></span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, verdana, helvetica, sans-serif; font-size: 12px; line-height: 18px; ">
<br /></span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, verdana, helvetica, sans-serif; font-size: 12px; line-height: 18px; "><meta charset="utf-8"><span class="Apple-style-span" style="font-family: arial, sans-serif; font-size: 13px; line-height: normal; border-collapse: collapse; "><h2 class="entry-title" style="max-width: 650px; font-size: 18px; margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><a class="entry-title-link" target="_blank" href="http://www.sciencedirect.com/science?_ob=GatewayURL&_origin=IRSSCONTENT&_method=citationSearch&_piikey=S0926204010000743&_version=1&md5=a477fd4459674e3016799095243da85b" style="color: rgb(34, 68, 187); text-decoration: none; ">Multinuclear NMR study of silica fiberglass modified with zirconia<div class="entry-title-go-to" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 2px; display: inline; padding-left: 16px; height: 17px; background-image: url(http://www.google.ca/reader/ui/3607832474-entry-action-icons.png); background-attachment: initial; background-origin: initial; background-clip: initial; background-color: initial; background-position: 0% -416px; background-repeat: no-repeat no-repeat; "></div></a></h2><div class="entry-author" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; color: rgb(102, 102, 102); text-decoration: none; "><div class="entry-likers" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; background-color: rgb(255, 255, 255); max-width: 650px; "></div></div><div class="entry-debug" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "></div><div class="entry-annotations" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "></div><div class="entry-body" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; max-width: 650px; padding-top: 0.5em; color: rgb(0, 0, 0); "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><div class="item-body" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Publication year: 2010
<br /><b>Source:</b> Solid State Nuclear Magnetic Resonance, In Press, Accepted Manuscript, Available online 29 December 2010
<br />O.B., Lapina , D.F, Khabibulin , V.V., Terskikh</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><meta charset="utf-8"><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, verdana, helvetica, sans-serif; font-size: 12px; line-height: 18px; ">Silica fiberglass textiles are emerging as uniquely suited supports in catalysis which offer unprecedented flexibility in designing advanced catalytic systems for chemical and auto industries. During manufacturing fiberglass materials are often modified with additives of various nature to improve glass properties. Glass network formers, such as zirconia and alumina, are known to provide the glass fibers with higher strength and to slow down undesirable devitrification processes. In this work multinuclear <sup>1</sup>H, <sup>23</sup>Na, <sup>29</sup>Si, and <sup>91</sup>Zr NMR spectroscopy was used to characterize the effect of zirconia on the molecular-level fiberglass structure. <sup>29</sup>Si NMR results help in understanding why zirconia-modified fiberglass is more stable towards devitrification comparing with pure silica glass. Internal void spaces formed in zirconia-silica glass fibers after acidic leaching correlate with sodium and water distributions in the starting bulk glass as probed by <sup>23</sup>Na and <sup>1</sup>H NMR. These voids spaces are important for stabilization of catalytically active species in the supported catalysts. Potentials of high-field <sup>91</sup>Zr NMR spectroscopy to study zirconia-containing glasses and similarly disordered systems are illustrated.</span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, verdana, helvetica, sans-serif; font-size: 12px; line-height: 18px; ">
<br /></span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, verdana, helvetica, sans-serif; font-size: 12px; line-height: 18px; "><meta charset="utf-8"><span class="Apple-style-span" style="font-family: arial, sans-serif; font-size: 13px; line-height: normal; border-collapse: collapse; "><h2 class="entry-title" style="max-width: 650px; font-size: 18px; margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><a class="entry-title-link" target="_blank" href="http://www.sciencedirect.com/science?_ob=GatewayURL&_origin=IRSSCONTENT&_method=citationSearch&_piikey=S0926204010000755&_version=1&md5=319976a2c75423956a5b3819975c017c" style="color: rgb(34, 68, 187); text-decoration: none; ">Kinetics of 1H→13C NMR cross-polarization in polymorphs and solvates of the antipsychotic drug olanzapine<div class="entry-title-go-to" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 2px; display: inline; padding-left: 16px; height: 17px; background-image: url(http://www.google.ca/reader/ui/3607832474-entry-action-icons.png); background-attachment: initial; background-origin: initial; background-clip: initial; background-color: initial; background-position: 0% -416px; background-repeat: no-repeat no-repeat; "></div></a></h2><div class="entry-author" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; color: rgb(102, 102, 102); text-decoration: none; "><div class="entry-likers" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; background-color: rgb(255, 255, 255); max-width: 650px; "></div></div><div class="entry-debug" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "></div><div class="entry-annotations" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "></div><div class="entry-body" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; max-width: 650px; padding-top: 0.5em; color: rgb(0, 0, 0); "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><div class="item-body" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Publication year: 2011
<br /><b>Source:</b> Solid State Nuclear Magnetic Resonance, In Press, Accepted Manuscript, Available online 4 January 2011
<br />Waclaw, Kolodziejski , Joanna, Herold , Marzena, Kuras , Irena, Wawrzycka-Gorczyca , Anna E., Koziol</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><meta charset="utf-8"><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, verdana, helvetica, sans-serif; font-size: 12px; line-height: 18px; ">The <sup>1</sup>H→<sup>13</sup>C NMR cross-polarization (CP) was studied under magic-angle spinning at 7.5 kHz in various crystal forms of the antipsychotic drug olanzapine: two polymorphs (metastable I and stable II) and eight solvates containing organic solvent and water molecules. The CP kinetics followed the non-classical I-I<sup>*</sup>-S model, in which CP begins in a spin cluster of proximate abundant spins I<sup>*</sup> and rare spins S, then is controlled by spin diffusion of the abundant spins I from bulk to the I<sup>*</sup> spins of the spin cluster and finally is governed by spin-lattice relaxation of the abundant spins in the rotating frame. The corresponding CP kinetics parameters were determined and analyzed. It was demonstrated that the, λ and <i>T</i><sub><i>df</i></sub> values (the CP time constant, the cluster composition parameter and the <sup>1</sup>H spin-diffusion constant, respectively) were very useful to discriminate the functional groups, especially in the 3D parameter space. In order to conveniently analyze the large amount (1 7 5) of the collected CP parameters, the number of the observed variables was reduced using the principal component (PC) analysis. The 2D plot of PC2 vs. PC1 showed adequate separation of the CH<sub>3</sub>, CH<sub>2</sub>, CH and C cases (C stands for carbons without adjacent hydrogens). It was demonstrated that those cases were located along the PC1 axis in the order of increasing <sup>1</sup>H-<sup>13</sup>C dipolar couplings: C<ch<sub>3</sub><ch<ch<sub>2</sub>. Our study showed the I-I<sup>*</sup>-S model at work and established ranges of its parameters for various functional groups.</span></div></div></div></div></span></span></div></div></div></div></span></span></div></div></div></div></span><div class="blogger-post-footer">Recent articles and reviews featuring solid-state NMR.</div>Kris Harrishttp://www.blogger.com/profile/16401554771902373385noreply@blogger.com0tag:blogger.com,1999:blog-19927787.post-6496102597732026112011-01-10T10:47:00.001-05:002011-01-10T10:49:41.275-05:00Inorg. Chem.<h1 style="font-family: verdana;" class="articleTitle"><span style="font-size:85%;">Solvent Effects and Dynamic Averaging of <sup>195</sup>Pt NMR Shielding in Cisplatin Derivatives</span></h1><span style="font-size:85%;"><span style="font-family: verdana;">Lionel A. Truflandier, Kiplangat Sutter, and Jochen Autschbach*</span><br /></span><div style="font-family: verdana;" id="citation"> <span style="font-size:85%;"><a href="mailto:jochena@buffalo.edu">jochena@buffalo.edu</a><br /><cite><br />Inorg. Chem.</cite>, Article ASAP</span></div><div style="font-family: verdana;" id="doi"><span style="font-size:85%;"><strong>DOI: </strong>10.1021/ic102174b</span></div><div id="pubDate"><span style="font-size:85%;"><span style="font-family: verdana;">Publication Date (Web): January 4, 2011</span><br /><br /><span style="font-family: verdana;">The influences of solvent effects and dynamic averaging on the </span><sup style="font-family: verdana;">195</sup><span style="font-family: verdana;">Pt NMR shielding and chemical shifts of cisplatin and three cisplatin derivatives in aqueous solution were computed using explicit and implicit solvation models. Within the density functional theory framework, these simulations were carried out by combining ab initio molecular dynamics (aiMD) simulations for the phase space sampling with all-electron relativistic NMR shielding tensor calculations using the zeroth-order regular approximation. Structural analyses support the presence of a solvent-assisted “inverse” or “anionic” hydration previously observed in similar square-planar transition-metal complexes. Comparisons with computationally less demanding implicit solvent models show that error cancellation is ubiquitous when dealing with liquid-state NMR simulations. After aiMD averaging, the calculated chemical shifts for the four complexes are in good agreement with experiment, with relative deviations between theory and experiment of about 5% on average (1% of the Pt</span><sup style="font-family: verdana;">II</sup><span style="font-family: verdana;"> chemical shift range).</span></span><br /></div><div class="blogger-post-footer">Recent articles and reviews featuring solid-state NMR.</div>Stas Vhttp://www.blogger.com/profile/02184095866106646987noreply@blogger.com0tag:blogger.com,1999:blog-19927787.post-5285067654431316682011-01-10T10:20:00.002-05:002011-01-10T10:46:43.055-05:00J. Phys. Chem. A<h1 style="font-family: verdana;" class="articleTitle"><span style="font-size:85%;">Crystal Structure Based Design of Signal Enhancement Schemes for Solid-State NMR of Insensitive Half-Integer Quadrupolar Nuclei</span></h1><span style="font-size:85%;"><span style="font-family: verdana;">Luke A. O’Dell</span><span style="text-decoration: underline; font-family: verdana;"><span style="font-weight: bold;"></span></span><span style="font-family: verdana;">* and Christopher I. Ratcliffe </span><br /><a style="font-family: verdana;" href="mailto:luke.odell@nrc-cnrc.gc.ca">luke.odell@nrc-cnrc.gc.ca</a><br /><br /></span><div style="font-family: verdana;" id="citation"><span style="font-size:85%;"><cite>J. Phys. Chem. A</cite>, Article ASAP</span></div><div style="font-family: verdana;" id="doi"><span style="font-size:85%;"><strong>DOI: </strong>10.1021/jp111531e</span></div><div style="font-family: verdana;" id="pubDate"><span style="font-size:85%;">Publication Date (Web): December 21, 2010</span></div><div id="artCopyright"><span style="font-size:85%;"><br /><span style="font-family: verdana;">A combination of density functional and optimal control theory has been used to generate amplitude- and phase-modulated excitation pulses tailored specifically for the </span><sup style="font-family: verdana;">33</sup><span style="font-family: verdana;">S nuclei in taurine, based on one of several reported crystal structures. The pulses resulted in significant signal enhancement (stemming from population transfer from the satellite transitions) without the need for any experimental optimization. This allowed an accurate determination of the </span><sup style="font-family: verdana;">33</sup><span style="font-family: verdana;">S NMR interaction parameters at natural abundance and at a moderate magnetic field strength (11.7 T). The </span><sup style="font-family: verdana;">33</sup><span style="font-family: verdana;">S NMR parameters, along with those measured from </span><sup style="font-family: verdana;">14</sup><span style="font-family: verdana;">N using frequency-swept pulses, were then used to assess the accuracy of various proposed crystal structures.</span><br /><br /><span style="font-family: verdana;">___________________________________________________</span><br /></span><span style="font-size:85%;"><span style="font-weight: bold;"><br />Interactions of Volatile Organic Compounds with Syndiotactic Polystyrene Crystalline Nanocavities<br /></span></span><span style="font-size:85%;"><span style="font-family: verdana;">Alexandra<span style="font-weight: bold;"> </span>R. Albunia*, Patrizia Oliva, and Alfonso Grassi</span><br /><a style="font-family: verdana;" href="mailto:aalbunia@unisa.it">aalbunia@unisa.it</a><br /><br /></span> <div style="font-family: verdana;" id="citation"><span style="font-size:85%;"><cite>J. Phys. Chem. A</cite>, Article ASAP</span></div><div style="font-family: verdana;" id="doi"><span style="font-size:85%;"><strong>DOI: </strong>10.1021/jp1090608</span></div><div style="font-family: verdana;" id="pubDate"><span style="font-size:85%;">Publication Date (Web): December 17, 2010</span></div><div style="font-family: verdana;" id="artCopyright"><span style="font-size:85%;"><br />The interaction of some volatile organic compounds, namely, 1,2-dichloroethane, 1,2-dibromoethane, and 1,1,2,2-tetrachloroethane, included in the δ crystalline phase of syndiotactic polystyrene (sPS) has been studied in terms of conformation, orientation, and dynamical behavior. By combination of X-ray diffraction (XRD), Fourier-transform infrared (FTIR), and solid-state <sup>2</sup>H NMR analyses, it has been shown that despite the differences in guest molecular properties (mass, boiling temperature, and volume), stable sPS/guest δ-clathrate cocrystals are formed since the nanoporous δ crystalline form has a flexible structure able to adapt itself to the guest molecule. As a consequence of inclusion, it has been shown that the guest diffusivity is strongly reduced and the dynamical processes are constrained, particularly when these guests are in <i>trans</i><br />conformation. This suggests the nanoporous sPS δ form to be an efficient tool for water and air purification through volatile organic compound absorption.</span></div></div><div class="blogger-post-footer">Recent articles and reviews featuring solid-state NMR.</div>Stas Vhttp://www.blogger.com/profile/02184095866106646987noreply@blogger.com0tag:blogger.com,1999:blog-19927787.post-40336469495476636402011-01-07T16:39:00.001-05:002011-01-07T16:43:30.478-05:00J. Chem. Phys.<meta charset="utf-8"><span class="Apple-style-span" style="font-family: arial, sans-serif; font-size: 13px; border-collapse: collapse; "><h2 class="entry-title" style="max-width: 650px; font-size: 18px; margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><a class="entry-title-link" target="_blank" href="http://link.aip.org/link/?JCP/133/234509/1&agg=rss" style="color: rgb(34, 68, 187); text-decoration: none; ">Electrical and ionic conductivity effects on magic-angle spinning nuclear magnetic resonance parameters of CuI<div class="entry-title-go-to" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 2px; display: inline; padding-left: 16px; height: 17px; background-image: url(http://www.google.ca/reader/ui/3607832474-entry-action-icons.png); background-attachment: initial; background-origin: initial; background-clip: initial; background-color: initial; background-position: 0% -416px; background-repeat: no-repeat no-repeat; "></div></a></h2><div class="entry-author" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; color: rgb(102, 102, 102); text-decoration: none; "><span class="entry-source-title-parent">from <a class="entry-source-title" target="_blank" href="http://www.google.ca/reader/view/feed/http%3A%2F%2Fscitation.aip.org%2Frss%2Fjcp1.xml" style="color: rgb(34, 68, 187); text-decoration: none; ">Journal of Chemical Physics: All Topics</a></span><div class="entry-likers" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; background-color: rgb(255, 255, 255); max-width: 650px; "></div></div><div class="entry-debug" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "></div><div class="entry-annotations" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "></div><div class="entry-body" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; max-width: 650px; padding-top: 0.5em; color: rgb(0, 0, 0); "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><div class="item-body" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">James P. Yesinowski, Harold D. Ladouceur, Andrew P. Purdy, and Joel B. Miller</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><meta charset="utf-8"><span class="Apple-style-span" style="border-collapse: separate; font-size: 12px; line-height: 21px; ">We investigate experimentally and theoretically the effects of two different types of conductivity, electrical and ionic, upon magic-angle spinning NMR spectra. The experimental demonstration of these effects involves <sup class="emphsuperior" style="vertical-align: super; font-size: 10px; line-height: 10px; ">63</sup>Cu, <sup class="emphsuperior" style="vertical-align: super; font-size: 10px; line-height: 10px; ">65</sup>Cu, and <sup class="emphsuperior" style="vertical-align: super; font-size: 10px; line-height: 10px; ">127</sup>I variable temperature MAS-NMR experiments on samples of γ-CuI, a Cu<sup class="emphsuperior" style="vertical-align: super; font-size: 10px; line-height: 10px; ">+</sup>-ion conductor at elevated temperatures as well as a wide bandgap semiconductor. We extend previous observations that the chemical shifts depend very strongly upon the square of the spinning-speed as well as the particular sample studied and the magnetic field strength. By using the <sup class="emphsuperior" style="vertical-align: super; font-size: 10px; line-height: 10px; ">207</sup>Pb resonance of lead nitrate mixed with the γ-CuI as an internal chemical shift thermometer we show that frictional heating effects of the rotor do not account for the observations. Instead, we find that spinning bulk CuI, a p-type semiconductor due to Cu<sup class="emphsuperior" style="vertical-align: super; font-size: 10px; line-height: 10px; ">+</sup>vacancies in nonstoichiometric samples, in a magnetic field generates induced AC electric currents from the Lorentz force that can resistively heat the sample by over 200 °C. These induced currents oscillate along the rotor spinning axis at the spinning speed. Their associated heating effects are disrupted in samples containing inert filler material, indicating the existence of macroscopic current pathways between micron-sized crystallites. Accurate measurements of the temperature-dependence of the <sup class="emphsuperior" style="vertical-align: super; font-size: 10px; line-height: 10px; ">63</sup>Cu and <sup class="emphsuperior" style="vertical-align: super; font-size: 10px; line-height: 10px; ">127</sup>I chemical shifts in such diluted samples reveal that they are of similar magnitude (ca. 0.27 ppm/K) but opposite sign (being negative for <sup class="emphsuperior" style="vertical-align: super; font-size: 10px; line-height: 10px; ">63</sup>Cu), and appear to depend slightly upon the particular sample. This relationship is identical to the corresponding slopes of the chemical shifts versus square of the spinning speed, again consistent with sample heating as the source of the observed large shift changes. Higher drive-gas pressures are required to spin samples that have higher effective electrical conductivities, indicating the presence of a braking effect arising from the induced currents produced by rotating a conductor in a homogeneous magnetic field. We present a theoretical analysis and finite-element simulations that account for the magnitude and rapid time-scale of the resistive heating effects and the quadratic spinning speed dependence of the chemical shift observed experimentally. Known thermophysical properties are used as inputs to the model, the sole adjustable parameter being a scaling of the bulk thermal conductivity of CuI in order to account for the effective thermal conductivity of the rotating powdered sample. In addition to the dramatic consequences of <em class="emphitalic" style="font-style: italic; ">electrical conductivity</em> in the sample,<em class="emphitalic" style="font-style: italic; ">ionic conductivity</em> also influences the spectra. All three nuclei exhibit quadrupolar satellite transitions extending over several hundred kilohertz that reflect defects perturbing the cubic symmetry of the zincblende lattice. Broadening of these satellite transitions with increasing temperature arises from the onset of Cu<sup class="emphsuperior" style="vertical-align: super; font-size: 10px; line-height: 10px; ">+</sup> ion jumps to sites with different electric field gradients, a process that interferes with the formation of rotational echoes. This broadening has been quantitatively analyzed for the <sup class="emphsuperior" style="vertical-align: super; font-size: 10px; line-height: 10px; ">63</sup>Cu and <sup class="emphsuperior" style="vertical-align: super; font-size: 10px; line-height: 10px; ">65</sup>Cu nuclei using a simple model in the literature to yield an activation barrier of 0.64 eV (61.7 kJ/mole) for the Cu<sup class="emphsuperior" style="vertical-align: super; font-size: 10px; line-height: 10px; ">+</sup> ion jumping motion responsible for the ionic conductivity that agrees with earlier results based on <sup class="emphsuperior" style="vertical-align: super; font-size: 10px; line-height: 10px; ">63</sup>Cu NMR relaxation times of static samples</span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-size: 12px; line-height: 21px; ">
<br /></span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-size: 12px; line-height: 21px; ">
<br /></span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-size: 12px; line-height: 21px; "><meta charset="utf-8"><span class="Apple-style-span" style="font-size: 13px; line-height: normal; border-collapse: collapse; "><h2 class="entry-title" style="max-width: 650px; font-size: 18px; margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><a class="entry-title-link" target="_blank" href="http://link.aip.org/link/?JCP/134/011102/1&agg=rss" style="color: rgb(34, 68, 187); text-decoration: none; ">Communication: Critical dynamics and nuclear relaxation in lipid bilayers<div class="entry-title-go-to" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 2px; display: inline; padding-left: 16px; height: 17px; background-image: url(http://www.google.ca/reader/ui/3607832474-entry-action-icons.png); background-attachment: initial; background-origin: initial; background-clip: initial; background-color: initial; background-position: 0% -416px; background-repeat: no-repeat no-repeat; "></div></a></h2><div class="entry-author" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; color: rgb(102, 102, 102); text-decoration: none; "><div class="entry-likers" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; background-color: rgb(255, 255, 255); max-width: 650px; "></div></div><div class="entry-debug" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "></div><div class="entry-annotations" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "></div><div class="entry-body" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; max-width: 650px; padding-top: 0.5em; color: rgb(0, 0, 0); "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><div class="item-body" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Harden McConnell</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><meta charset="utf-8"><span class="Apple-style-span" style="border-collapse: separate; font-size: 12px; line-height: 21px; ">Membrane composition fluctuations affect deuterium nuclear magnetic relaxation in lipid bilayers. The time dependence of the fluctuations depends on lipid diffusion. Near a miscibility critical point this diffusion involves an advective hydrodynamic coupling to the aqueous phase. The corresponding diffusion coefficient depends on both the critical length and the fluctuation wavelength. We calculate the effects of these dynamics on transverse deuterium nuclear relaxation in the 0.1<sup class="emphsuperior" style="vertical-align: super; font-size: 10px; line-height: 10px; ">o</sup>–10<sup class="emphsuperior" style="vertical-align: super; font-size: 10px; line-height: 10px; ">o</sup> range above the critical temperature.</span></div></div></div></div></span></span></div></div></div></div></span><div class="blogger-post-footer">Recent articles and reviews featuring solid-state NMR.</div>Kris Harrishttp://www.blogger.com/profile/16401554771902373385noreply@blogger.com0tag:blogger.com,1999:blog-19927787.post-25950144866956695322011-01-07T16:06:00.000-05:002011-01-07T16:07:43.006-05:00Phys. Rev. Lett.<meta charset="utf-8"><span class="Apple-style-span" style="font-family: arial, sans-serif; font-size: 13px; border-collapse: collapse; "><h2 class="entry-title" style="max-width: 650px; font-size: 18px; margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><a class="entry-title-link" target="_blank" href="http://link.aps.org/doi/10.1103/PhysRevLett.106.017801" style="color: rgb(34, 68, 187); text-decoration: none; ">Detection of Phase Biaxiality in Liquid Crystals by Use of the Quadrupole Shift in ^{131} Xe NMR Spectra<div class="entry-title-go-to" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 2px; display: inline; padding-left: 16px; height: 17px; background-image: url(http://www.google.ca/reader/ui/3607832474-entry-action-icons.png); background-attachment: initial; background-origin: initial; background-clip: initial; background-color: initial; background-position: 0% -416px; background-repeat: no-repeat no-repeat; "></div></a></h2><div class="entry-author" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; color: rgb(102, 102, 102); text-decoration: none; "><span class="entry-source-title-parent">from <a class="entry-source-title" target="_blank" href="http://www.google.ca/reader/view/feed/http%3A%2F%2Ffeeds.aps.org%2Frss%2Frecent%2Fprl.xml" style="color: rgb(34, 68, 187); text-decoration: none; ">Recent Articles in Phys. Rev. Lett.</a></span> <span class="entry-author-parent">by <span class="entry-author-name">Jukka P. Jokisaari, Anu M. Kantola, Juhani A. Lounila, and L. Petri Ingman</span></span></div><div class="entry-author" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; color: rgb(102, 102, 102); text-decoration: none; "><span class="entry-author-parent"><span class="entry-author-name"><meta charset="utf-8"><span class="Apple-style-span" style="border-collapse: separate; color: rgb(50, 50, 50); font-family: arial, helvetica, sans-serif; font-size: 12px; line-height: 18px; -webkit-border-horizontal-spacing: 2px; -webkit-border-vertical-spacing: 2px; ">An experimental method to unambiguously distinguish between uniaxial and biaxial liquid crystal phases is introduced. The method is based on the second order quadrupole shift (SOQS) observable in <span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; "><sup style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; font-size: 0.88em; vertical-align: 0.5em; line-height: 1em; ">131</sup>Xe</span> NMR spectra of xenon dissolved in liquid crystals. It is shown that besides revealing the biaxiality, the <span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; "><sup style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; font-size: 0.88em; vertical-align: 0.5em; line-height: 1em; ">131</sup>Xe</span> SOQS offers a novel method to determine the tilt angle in smectic <span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; "><span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; font-style: italic; ">C</span></span> phases. As an example, the <span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; "><sup style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; font-size: 0.88em; vertical-align: 0.5em; line-height: 1em; ">131</sup>Xe</span> SOQS in a ferroelectric liquid crystal is reported. It yields up a biaxial phase in between isotropic and smectic <span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; "><span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; font-style: italic; ">C</span></span> phases.</span></span></span></div></span><div class="blogger-post-footer">Recent articles and reviews featuring solid-state NMR.</div>Kris Harrishttp://www.blogger.com/profile/16401554771902373385noreply@blogger.com0tag:blogger.com,1999:blog-19927787.post-18139088633037241082010-12-17T15:40:00.002-05:002010-12-17T15:46:53.914-05:00Phys. Rev. B.<meta charset="utf-8"><span class="Apple-style-span" style="font-family: arial, sans-serif; font-size: 13px; border-collapse: collapse; "><h2 class="entry-title" style="max-width: 650px; font-size: 18px; margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><meta charset="utf-8"><span class="Apple-style-span" style="font-size: 13px; font-weight: normal; "><h2 class="entry-title" style="max-width: 650px; font-size: 18px; margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><a class="entry-title-link" target="_blank" href="http://link.aps.org/doi/10.1103/PhysRevB.82.214416" style="color: rgb(124, 140, 197); text-decoration: none; ">NMR and NQR study of the tetrahedral frustrated quantum spin system Cu_{2} Te_{2} O_{5} Br_{2} in its paramagnetic phase</a></h2><div class="entry-author" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; color: rgb(102, 102, 102); text-decoration: none; "><div class="entry-likers" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; background-color: rgb(255, 255, 255); max-width: 650px; "></div></div><div class="entry-debug" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "></div><div class="entry-annotations" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "></div><div class="entry-body" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; max-width: 650px; padding-top: 0.5em; color: rgb(34, 34, 34); "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><div class="item-body" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Author(s): Arnaud Comment, Hadrien Mayaffre, Vesna Mitrović, Mladen Horvatić, Claude Berthier, Béatrice Grenier, and Patrice Millet</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><meta charset="utf-8"><span class="Apple-style-span" style="border-collapse: separate; color: rgb(50, 50, 50); font-family: arial, helvetica, sans-serif; font-size: 12px; line-height: 18px; -webkit-border-horizontal-spacing: 2px; -webkit-border-vertical-spacing: 2px; ">The quantum antiferromagnet <span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; ">Cu<sub style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; ">2</sub>Te<sub style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; ">2</sub>O<sub style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; ">5</sub>Br<sub style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; ">2</sub></span> was investigated by NMR and nuclear quadrupole resonance (NQR). The <span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; "><sup style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; font-size: 0.88em; vertical-align: 0.5em; line-height: 1em; ">125</sup>Te</span> NMR investigation showed that there is a magnetic transition around 10.5 K at 9 T, in agreement with previous studies. From the divergence of the spin-lattice relaxation rate, we ruled out the possibility that the transition could be governed by a one-dimensional divergence of the spin-spin correlation function. The observed anisotropy of the <span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; "><sup style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; font-size: 0.88em; vertical-align: 0.5em; line-height: 1em; ">125</sup>Te</span> shift was shown to be due to a spin polarization of the <span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; ">5<span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; font-style: italic; ">s</span><sup style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; font-size: 0.88em; vertical-align: 0.5em; line-height: 1em; ">2</sup></span> “E” doublet of the<span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; ">[TeO<sub style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; ">3</sub>E]</span> tetrahedra, highlighting the importance of tellurium in the exchange paths. In the paramagnetic state, Br NQR and NMR measurements led to the determination of the Br hyperfine coupling and the electric field gradient tensor, and to the spin polarization of <span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; ">Br <span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; font-style: italic; ">p</span></span>orbitals. The results demonstrate the crucial role of bromine in the interaction paths between Cu spins.</span></div></div></div></div></span></h2><h2 class="entry-title" style="max-width: 650px; font-size: 18px; margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">
<br /></h2><div>
<br /></div><h2 class="entry-title" style="max-width: 650px; font-size: 18px; margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><a class="entry-title-link" target="_blank" href="http://link.aps.org/doi/10.1103/PhysRevB.82.195129" style="color: rgb(34, 68, 187); text-decoration: none; ">NMR evidence for the partially gapped state in CeOs_{2} Al_{10}</a></h2><div class="entry-author" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; color: rgb(102, 102, 102); text-decoration: none; "><div class="entry-likers" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; background-color: rgb(255, 255, 255); max-width: 650px; "></div></div><div class="entry-debug" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "></div><div class="entry-annotations" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "></div><div class="entry-body" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; max-width: 650px; padding-top: 0.5em; "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><div class="item-body" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Author(s): C. S. Lue, S. H. Yang, T. H. Su, and Ben-Li Young</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><meta charset="utf-8"><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, helvetica, sans-serif; font-size: 12px; color: rgb(50, 50, 50); line-height: 18px; -webkit-border-horizontal-spacing: 2px; -webkit-border-vertical-spacing: 2px; ">We report the results of a <span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; "><sup style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; font-size: 0.88em; vertical-align: 0.5em; line-height: 1em; ">27</sup>Al</span> nuclear magnetic resonance (NMR) study of <span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; ">CeOs<sub style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; ">2</sub>Al<sub style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; ">10</sub></span> at temperatures between 4 and 300 K. This material has been of current interest due to indications of hybridization gap behavior below the transition temperature <span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; "><span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; font-style: italic; ">T</span><sub style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; "><span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; font-style: italic; ">o</span></sub>≃29 K</span>. Five <span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; "><sup style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; font-size: 0.88em; vertical-align: 0.5em; line-height: 1em; ">27</sup>Al</span> NMR resonance lines that are associated with five nonequivalent crystallographic aluminum sites have been resolved. For each individual aluminum site, the low-temperature NMR Knight shift goes over a thermally activated response. The temperature-dependent spin-lattice-relaxation rate exhibits a rapid drop below <span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; "><span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; font-style: italic; ">T</span><sub style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; "><span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; font-style: italic; ">o</span></sub></span>, indicative of the formation of an energy gap in this material. We interpret the Knight shift and the relaxation-rate data in light of the presence of a pseudogap with residual electronic density of states at the Fermi level. Moreover, the magnitude of the pseudogap of 120 K is extracted from NMR results, in agreement with the value obtained from the inelastic neutron-scattering experiment.</span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, helvetica, sans-serif; font-size: 12px; color: rgb(50, 50, 50); line-height: 18px; -webkit-border-horizontal-spacing: 2px; -webkit-border-vertical-spacing: 2px; ">
<br /></span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, helvetica, sans-serif; font-size: 12px; color: rgb(50, 50, 50); line-height: 18px; -webkit-border-horizontal-spacing: 2px; -webkit-border-vertical-spacing: 2px; ">
<br /></span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, helvetica, sans-serif; font-size: 12px; line-height: 18px; -webkit-border-horizontal-spacing: 2px; -webkit-border-vertical-spacing: 2px; "><meta charset="utf-8"><span class="Apple-style-span" style="font-family: arial, sans-serif; font-size: 13px; line-height: normal; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; border-collapse: collapse; "><h2 class="entry-title" style="max-width: 650px; font-size: 18px; margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; color: rgb(0, 0, 0); "><a class="entry-title-link" target="_blank" href="http://link.aps.org/doi/10.1103/PhysRevB.82.235102" style="color: rgb(34, 68, 187); text-decoration: none; ">Spin order and lattice frustration in optimally doped manganites: A high-temperature NMR study</a></h2><h2 class="entry-title" style="max-width: 650px; font-size: 18px; margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; color: rgb(0, 0, 0); "><a class="entry-title-link" target="_blank" href="http://link.aps.org/doi/10.1103/PhysRevB.82.235102" style="color: rgb(34, 68, 187); text-decoration: none; "></a><span class="Apple-style-span" style="font-weight: normal; font-size: 13px; ">Author(s): N. Panopoulos, D. Koumoulis, G. Diamantopoulos, M. Belesi, M. Fardis, M. Pissas, and G. Papavassiliou</span></h2><div><span class="Apple-style-span" style="font-weight: normal; font-size: 13px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, helvetica, sans-serif; font-size: 12px; color: rgb(50, 50, 50); line-height: 18px; -webkit-border-horizontal-spacing: 2px; -webkit-border-vertical-spacing: 2px; ">Understanding the complex glassy phenomena, which accompany polaron formation in optimally doped manganites (ODMs) is a cumbersome issue with many unexplained perspectives. Here, on the basis of <span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; "><sup style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; font-size: 0.88em; vertical-align: 0.5em; line-height: 1em; ">139</sup>La</span> and <span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; "><sup style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; font-size: 0.88em; vertical-align: 0.5em; line-height: 1em; ">55</sup>Mn</span> nuclear magnetic resonance (NMR) measurements, performed in the temperature range 80–900 K we show that glass freezing, observed in the paramagnetic (PM) phase of ODM <span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; ">La<sub style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; ">0.67</sub>Ca<sub style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; ">0.33</sub>MnO<sub style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; ">3</sub></span>, is not a random uncorrelated process but the signature of the formation of a genuine spin-glass state, which for<span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; "><span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; font-style: italic; ">T</span><<span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; font-style: italic; ">T</span><sub style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; "><span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; font-style: italic; ">c</span></sub></span> consolidates with the ferromagnetic (FM) state into a single thermodynamic phase. Comparison with NMR measurements performed on<span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; ">La<sub style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; ">1−<span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; font-style: italic; ">x</span></sub>Ca<sub style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; "><span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; font-style: italic; ">x</span></sub>MnO<sub style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; ">3</sub></span> systems for <span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; ">0.0≤<span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; font-style: italic; ">x</span>≤0.41</span> and ODM <span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; ">La<sub style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; ">0.70</sub>Sr<sub style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; ">0.30</sub>MnO<sub style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; ">3</sub></span>, demonstrates the key role played by the local lattice distortions, which control (i) the stability of the spin-glass phase component and (ii) the kind (first or second order) of the PM-FM phase transition. The experimental results are in agreement with the predictions of the compressible random bond-random field Ising model, where consideration of a strain field induced by lattice distortions is shown to invoke at <span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; "><span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; font-style: italic; ">T</span><sub style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; "><span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; font-style: italic; ">c</span></sub></span> a discontinuous first-orderlike change in both the FM and the “glassy” Edwards-Anderson order parameters.</span></span></div><div><span class="Apple-style-span" style="font-weight: normal; font-size: 13px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, helvetica, sans-serif; font-size: 12px; color: rgb(50, 50, 50); line-height: 18px; -webkit-border-horizontal-spacing: 2px; -webkit-border-vertical-spacing: 2px; ">
<br /></span></span></div><div><span class="Apple-style-span" style="font-weight: normal; font-size: 13px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, helvetica, sans-serif; font-size: 12px; color: rgb(50, 50, 50); line-height: 18px; -webkit-border-horizontal-spacing: 2px; -webkit-border-vertical-spacing: 2px; ">
<br /></span></span></div></span></span></div></div></div></div></span><div class="blogger-post-footer">Recent articles and reviews featuring solid-state NMR.</div>Kris Harrishttp://www.blogger.com/profile/16401554771902373385noreply@blogger.com0tag:blogger.com,1999:blog-19927787.post-47863090597148951212010-12-16T18:07:00.001-05:002010-12-16T18:10:55.494-05:00Phys. Rev. Lett.<meta charset="utf-8"><span class="Apple-style-span" style="font-family: arial, sans-serif; font-size: 13px; border-collapse: collapse; "><h2 class="entry-title" style="max-width: 650px; font-size: 18px; margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><a class="entry-title-link" target="_blank" href="http://link.aps.org/doi/10.1103/PhysRevLett.105.226402" style="color: rgb(34, 68, 187); text-decoration: none; ">^{7} Li NMR Investigation of Li-Li Pair Ordering in the Paraelectric Phase of Weakly Substitutionally Disordered K_{1-x} Li_{x} TaO_{3}<div class="entry-title-go-to" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 2px; display: inline; padding-left: 16px; height: 17px; background-image: url(http://www.google.ca/reader/ui/3607832474-entry-action-icons.png); background-attachment: initial; background-origin: initial; background-clip: initial; background-color: initial; background-position: 0% -416px; background-repeat: no-repeat no-repeat; "></div></a></h2><div class="entry-author" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; color: rgb(102, 102, 102); text-decoration: none; "><span class="entry-author-parent">by <span class="entry-author-name">Boštjan Zalar, Andrija Lebar, David C. Ailion, R. O. Kuzian, I. V. Kondakova, and V. V. Laguta</span></span><div class="entry-likers" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; background-color: rgb(255, 255, 255); max-width: 650px; "></div></div><div class="entry-debug" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "></div><div class="entry-annotations" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "></div><div class="entry-body" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; max-width: 650px; padding-top: 0.5em; "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><div class="item-body" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Author(s): Boštjan Zalar, Andrija Lebar, David C. Ailion, R. O. Kuzian, I. V. Kondakova, and V. V. Laguta</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><meta charset="utf-8"><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, helvetica, sans-serif; font-size: 12px; color: rgb(50, 50, 50); line-height: 18px; -webkit-border-horizontal-spacing: 2px; -webkit-border-vertical-spacing: 2px; ">Breaking of the average cubic symmetry in Li-doped potassium tantalate was observed with quadrupole-perturbed <span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; "><sup style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; font-size: 0.88em; vertical-align: 0.5em; line-height: 1em; ">7</sup>Li</span> NMR at temperatures (150–400 K) far above the nominal glass transition temperature (<span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; ">≈50 K</span> for Li concentration <span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; "><span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; font-style: italic; ">x</span>=0.03</span>). The observed spectrum consists of contributions from both isolated Li ions (i.e., with no nearest-neighbor Li) and from Li-Li pairs. The isolated Li ions move among six equivalent off-center sites in a potential having cubic symmetry. These have zero average electric field gradient and, hence, exhibit no quadrupole splitting. In addition, very low intensity, but well resolved, quadrupole satellites having a temperature-dependent splitting were observed. This splitting indicates that the various Li-Li pair configurations are not all equally probable. These are the first direct observations of biased Li ion ordering that persists in the paraelectric phase at temperatures high above the glass phase.</span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, helvetica, sans-serif; font-size: 12px; color: rgb(50, 50, 50); line-height: 18px; -webkit-border-horizontal-spacing: 2px; -webkit-border-vertical-spacing: 2px; ">
<br /></span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, helvetica, sans-serif; font-size: 12px; color: rgb(50, 50, 50); line-height: 18px; -webkit-border-horizontal-spacing: 2px; -webkit-border-vertical-spacing: 2px; "><meta charset="utf-8"><span class="Apple-style-span" style="color: rgb(0, 0, 0); font-family: arial, sans-serif; font-size: 13px; line-height: normal; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; border-collapse: collapse; "><h2 class="entry-title" style="max-width: 650px; font-size: 18px; margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><a class="entry-title-link" target="_blank" href="http://link.aps.org/doi/10.1103/PhysRevLett.105.217002" style="color: rgb(34, 68, 187); text-decoration: none; ">Anisotropic Spin Fluctuations and Superconductivity in “115” Heavy Fermion Compounds: ^{59} Co NMR Study in PuCoGa_{5}<div class="entry-title-go-to" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 2px; display: inline; padding-left: 16px; height: 17px; background-image: url(http://www.google.ca/reader/ui/3607832474-entry-action-icons.png); background-attachment: initial; background-origin: initial; background-clip: initial; background-color: initial; background-position: 0% -416px; background-repeat: no-repeat no-repeat; "></div></a></h2><div class="entry-author" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; color: rgb(102, 102, 102); text-decoration: none; "><span class="entry-source-title-parent">from <a class="entry-source-title" target="_blank" href="http://www.google.ca/reader/view/feed/http%3A%2F%2Ffeeds.aps.org%2Frss%2Frecent%2Fprl.xml" style="color: rgb(34, 68, 187); text-decoration: none; ">Recent Articles in Phys. Rev. Lett.</a></span> <span class="entry-author-parent">by <span class="entry-author-name">S.-H. Baek, H. Sakai, E. D. Bauer, J. N. Mitchell, J. A. Kennison, F. Ronning, and J. D. Thompson</span></span><div class="entry-likers" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; background-color: rgb(255, 255, 255); max-width: 650px; "></div></div><div class="entry-debug" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "></div><div class="entry-annotations" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "></div><div class="entry-body" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; max-width: 650px; padding-top: 0.5em; color: rgb(0, 0, 0); "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><div class="item-body" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Author(s): S.-H. Baek, H. Sakai, E. D. Bauer, J. N. Mitchell, J. A. Kennison, F. Ronning, and J. D. Thompson</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><meta charset="utf-8"><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, helvetica, sans-serif; font-size: 12px; color: rgb(50, 50, 50); line-height: 18px; -webkit-border-horizontal-spacing: 2px; -webkit-border-vertical-spacing: 2px; ">We report results of <span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; "><sup style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; font-size: 0.88em; vertical-align: 0.5em; line-height: 1em; ">59</sup>Co</span> nuclear magnetic resonance measurements on a single crystal of superconducting <span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; ">PuCoGa<sub style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; ">5</sub></span> in its normal state. The nuclear spin-lattice relaxation rates and the Knight shifts as a function of temperature reveal an anisotropy of spin fluctuations with finite wave vector <span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; "><span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; font-style: italic; ">q</span></span>. By comparison with the isostructural members, we conclude that antiferromagnetic <span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; "><span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; font-style: italic; ">X</span><span style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; padding-top: 0px; padding-right: 0px; padding-bottom: 0px; padding-left: 0px; border-top-width: 0px; border-right-width: 0px; border-bottom-width: 0px; border-left-width: 0px; border-style: initial; border-color: initial; font-style: italic; ">Y</span></span>-type anisotropy of spin fluctuations plays an important role in mediating superconductivity in these heavy fermion materials.</span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, helvetica, sans-serif; font-size: 12px; color: rgb(50, 50, 50); line-height: 18px; -webkit-border-horizontal-spacing: 2px; -webkit-border-vertical-spacing: 2px; ">
<br /></span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, helvetica, sans-serif; font-size: 12px; color: rgb(50, 50, 50); line-height: 18px; -webkit-border-horizontal-spacing: 2px; -webkit-border-vertical-spacing: 2px; ">
<br /></span></div></div></div></div></span></span></div></div></div></div></span><div class="blogger-post-footer">Recent articles and reviews featuring solid-state NMR.</div>Kris Harrishttp://www.blogger.com/profile/16401554771902373385noreply@blogger.com0tag:blogger.com,1999:blog-19927787.post-5881320556285955592010-12-16T17:47:00.001-05:002010-12-16T17:50:34.367-05:00Journal of chemical physics<span class="Apple-style-span" style="font-family: arial, sans-serif; font-size: 13px; border-collapse: collapse; "><h2 class="entry-title" style="max-width: 650px; font-size: 18px; margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="font-size: 13px; font-weight: normal; "><h2 class="entry-title" style="max-width: 650px; font-size: 18px; margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><a class="entry-title-link" target="_blank" href="http://link.aip.org/link/?JCP/133/194502/1&agg=rss" style="color: rgb(34, 68, 187); text-decoration: none; ">High resolution NMR study of T magnetic relaxation dispersion. II. Influence of spin-spin couplings on the longitudinal spin relaxation dispersion in multispin systems</a></h2><div class="entry-author" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; color: rgb(102, 102, 102); text-decoration: none; "><div class="entry-likers" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; background-color: rgb(255, 255, 255); max-width: 650px; "></div></div><div class="entry-debug" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "></div><div class="entry-annotations" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "></div><div class="entry-body" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; max-width: 650px; padding-top: 0.5em; "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><div class="item-body" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Sergey Korchak, Konstantin Ivanov, Alexandra Yurkovskaya, and Hans-Martin Vieth</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><meta charset="utf-8"><span class="Apple-style-span" style="border-collapse: separate; font-size: 12px; line-height: 21px; ">Effects of scalar spin-spin interactions on the nuclear magnetic relaxation dispersion (NMRD) of coupled multispin systems were analyzed. Taking spin systems of increasing complexity we demonstrated pronounced influence of the intramolecular spin-spin couplings on the NMRD of protons. First, at low magnetic fields where there is strong coupling of spins the apparent relaxation times of the coupled spins become equal. Second, there are new features, which appear at the positions of the nuclear spin level anticrossings. Finally, in coupled spin systems there can be a coherent contribution to the relaxation kinetics present at low magnetic fields. All these peculiarities caused by spin-spin interactions are superimposed on the features in NMRD, which are conditioned by changes of the motional regime. Neglecting the effects of couplings may lead to misinterpretation of the NMRD curves and significant errors in determining the correlation times of molecular motion. Experimental results presented are in good agreement with theoretical calculations.</span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-size: 12px; line-height: 21px; ">
<br /></span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-size: 12px; line-height: 21px; "><meta charset="utf-8"><span class="Apple-style-span" style="font-size: 13px; line-height: normal; border-collapse: collapse; "><h2 class="entry-title" style="max-width: 650px; font-size: 16px; margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; font-weight: normal; line-height: 19px; ">
<br /></h2></span></span></div></div></div></div></span></h2></span><div class="blogger-post-footer">Recent articles and reviews featuring solid-state NMR.</div>Kris Harrishttp://www.blogger.com/profile/16401554771902373385noreply@blogger.com0tag:blogger.com,1999:blog-19927787.post-28134489707471261162010-12-06T10:37:00.003-05:002010-12-06T10:48:12.546-05:00Proceedings of National Academy of Sciences, Early Edition<span style="font-family:verdana;font-size:85%;">Strongly bound citrate stabilizes the apatite nanocrystals in bone<br />Y.-Y. Hu, A. Rawal, and K. Schmidt-Rohr1<br />+ Author Affiliations<br /><br />Ames Laboratory and Department of Chemistry, Iowa State University, Ames, IA 50011<br />Edited by David A. Tirrell, California Institute of Technology, Pasadena, CA, and approved October 12, 2010 (received for review June 27, 2010)<br /><br />Published online before print December 2, 2010, doi: 10.1073/pnas.1009219107<br />PNAS December 2, 2010<br /><br />Abstract: Nanocrystals of apatitic calcium phosphate impart the organic-inorganic nanocomposite in bone with favorable mechanical properties. So far, the factors preventing crystal growth beyond the favorable thickness of ca. 3 nm have not been identified. Here we show that the apatite surfaces are studded with strongly bound citrate molecules, whose signals have been identified unambiguously by multinuclear magnetic resonance (NMR) analysis. NMR reveals that bound citrate accounts for 5.5 wt% of the organic matter in bone and covers apatite at a density of about 1 molecule per (2 nm)2, with its three carboxylate groups at distances of 0.3 to 0.45 nm from the apatite surface. Bound citrate is highly conserved, being found in fish, avian, and mammalian bone, which indicates its critical role in interfering with crystal thickening and stabilizing the apatite nanocrystals in bone.<br /><br /><br /><br />A nice summary of the article can also be found in C&E News.<br /><br />http://pubs.acs.org/isubscribe/journals/cen/88/i49/html/8849scic2.html</span><div class="blogger-post-footer">Recent articles and reviews featuring solid-state NMR.</div>Aaronhttp://www.blogger.com/profile/10367130607577279623noreply@blogger.com0tag:blogger.com,1999:blog-19927787.post-83466045531946825972010-12-02T14:29:00.003-05:002010-12-02T15:02:10.408-05:00J. Phys. Chem. B and C, vol. 114, Issues 37-42<span style="font-family:verdana;font-size:85%;">Accurate Determination of Interstrand Distances and Alignment in Amyloid Fibrils by Magic Angle Spinning NMR<br /><br />Marc A. Caporini†§, Vikram S. Bajaj†, Mikhail Veshtort†, Anthony Fitzpatrick‡, Cait E. MacPhee‡, Michele Vendruscolo‡, Christopher M. Dobson‡, and Robert G. Griffin*†<br /><br />J. Phys. Chem. B, 2010, 114 (42), pp 13555–13561<br />DOI: 10.1021/jp106675h<br />Publication Date (Web): October 6, 2010<br />Copyright © 2010 American Chemical Society<br /><br />Abstract: Amyloid fibrils are structurally ordered aggregates of proteins whose formation is associated with many neurodegenerative and other diseases. For that reason, their high-resolution structures are of considerable interest and have been studied using a wide range of techniques, notably electron microscopy, X-ray diffraction, and magic angle spinning (MAS) NMR. Because of the excellent resolution in the spectra, MAS NMR is uniquely capable of delivering site-specific, atomic resolution information about all levels of amyloid structure: (1) the monomer, which packs into several (2) protofilaments that in turn associate to form a (3) fibril. Building upon our high-resolution structure of the monomer of an amyloid-forming peptide from transthyretin (TTR105−115), we introduce single 1-13C labeled amino acids at seven different sites in the peptide and measure intermolecular carbonyl−carbonyl distances with an accuracy of 0.11 A. Our results conclusively establish a parallel, in register, topology for the packing of this peptide into a β-sheet and provide constraints essential for the determination of an atomic resolution structure of the fibril. Furthermore, the approach we employ, based on a combination of a double-quantum filtered variant of the DRAWS recoupling sequence and multispin numerical simulations in SPINEVOLUTION, is general and should be applicable to a wide range of systems.<br /><br /><br /><br /><br />Solid-State NMR Study of Cysteine on Gold Nanoparticles<br /><br />Anuji Abraham, Eugene Mihaliuk, Bharath Kumar, Justin Legleiter, and Terry Gullion*<br />Department of Chemistry, West Virginia University, Morgantown, West Virginia 26506, United States<br />J. Phys. Chem. C, 2010, 114 (42), pp 18109–18114<br />DOI: 10.1021/jp107112b<br />Publication Date (Web): September 30, 2010<br />Copyright © 2010 American Chemical Society<br /><br />Abstract: Solid-state NMR spectroscopy is used to characterize the interaction of l-cysteine with gold nanoparticles. The experiments show that there are two types of cysteine in the gold−cysteine complex, with nearly equal populations. We postulate that cysteine forms a two-layer boundary around the gold nanoparticles. The first layer is made of cysteine molecules forming a thiolate bond with the gold surface and having its charged amino and carboxyl groups oriented away from the gold surface. The second layer has its amino and carboxyl groups oriented toward the first layer and its sulfur group oriented away from the gold particles.<br /><br /><br /><br /><br />Pore Size Distribution Analysis of Mesoporous TiO2 Spheres by 1H Nuclear Magnetic Resonance (NMR) Cryoporometry<br /><br />Su-Yeol Ryu, Dong Suk Kim, Jae-Deok Jeon, and Seung-Yeop Kwak*<br /><br />J. Phys. Chem. C, 2010, 114 (41), pp 17440–17445<br />DOI: 10.1021/jp105496h<br />Publication Date (Web): September 21, 2010<br />Copyright © 2010 American Chemical Society<br /><br />Abstract: Mesoporous TiO2 spheres with various pore sizes were prepared by varying the calcination temperature in the range of 300−700 °C. Increasing calcination temperature was found to increase the crystal size, decrease the surface area, and increase the pore size. The morphologies of mesoporous TiO2 spheres consist of well-defined spherical shapes of monodisperse sizes near 0.8 μm. To determine the pore size distributions (PSDs) of these mesoporous TiO2 spheres, 1H nuclear magnetic resonance (NMR) cryoporometry and Barrett−Joyner−Halenda (BJH) analysis were conducted. NMR cryoporometry is based on the theory of the melting point depression (MPD) of a probe molecule confined within a pore, which is dependent on the pore diameter. MPD was determined by analyzing the variation of the NMR spin−echo intensity with temperature. From the resulting spin−echo intensity versus temperature (I−T) curves, it was found that the maximum MPD of a probe molecule confined within the pores of mesoporous TiO2 decreases with increasing calcination temperature; that is, the pore size increases with increasing calcination temperature. Because mesoporous TiO2 spheres consist of aggregates of nanocrystallite TiO2 and mesopores located at intercrystallites, an increase in the calcination temperature induces an increase in the crystallite size and, thus, in the pore size because the small pores collapse and the large pores increase in size. We also confirmed by BJH analysis that the pore size of mesoporous TiO2 increases with increasing calcination temperature. This trend is in agreement with our 1H NMR cryoporometry results. Overall, these findings indicate that NMR cryoporometry is a very effective method for determining the PSDs of mesoporous TiO2 spheres.<br /><br /><br /><br />Defect Functionalization of Hexagonal Boron Nitride Nanosheets<br /><br />Yi Lin*†, Tiffany V. Williams‡, Wei Cao§, Hani E. Elsayed-Ali§, and John W. Connell‡<br /><br />J. Phys. Chem. C, 2010, 114 (41), pp 17434–17439<br />DOI: 10.1021/jp105454w<br />Publication Date (Web): September 21, 2010<br />Copyright © 2010 American Chemical Society<br /><br />Abstract:A pristine hexagonal boron nitride (h-BN) powder sample with layered crystalline sheetlike particles of 1−10 μm in lateral sizes and a few hundred nanometers in thicknesses was mechanically treated using a ball-mill to intentionally introduce defect sites. The h-BN was ball-milled for various times and subsequently was functionalized with a long alkyl chain amine via Lewis acid−base interactions between the amino groups and the boron atoms of h-BN to obtain soluble amine-attached nanosheet samples as the products. The functionalized h-BN nanosheet samples were characterized via various microscopic and spectroscopic techniques. The results strongly support a direct correlation between increasing defect site concentrations of the h-BN nanosheet samples and improved reaction efficiency with the amine. This suggests the enhanced reactivity of defect boron atoms in comparison to conjugated ones on an unperturbed h-BN plane. NMR investigations provided the strongest evidence supporting the hypothesis that the amino groups reacted with the h-BN at specific defect sites induced by ball-milling. The mechanistic implications are discussed.<br /><br /><br /><br />Access to Well-Defined Ruthenium Mononuclear Species Grafted via a Si−Ru Bond on Silane Functionalized Silica†<br /><br />Fernando Rascn‡, Romain Berthoud‡, Raphal Wischert‡, Wayne Lukens§, and Christophe Copret*‡<br /><br />J. Phys. Chem. C, Article ASAP<br />DOI: 10.1021/jp1064962<br />Publication Date (Web): September 20, 2010<br />Copyright © 2010 American Chemical Society<br /><br />Abstract: A functionalized silica with T3 silane surface groups (i.e., (≡SiO)3Si−H) was prepared and interacted with Ru(cod)(cot), resulting in the formation of monometallic surface species attached to the surface via a Si−Ru bond, according to EXAFS spectroscopy, infrared spectroscopy, and solid-state NMR.<br /><br /><br /><br />Time-Resolved and Site-Specific Insights into Migration Pathways of Li+ in α-Li3VF6 by 6Li 2D Exchange MAS NMR<br /><br />M. Wilkening*†, E. E. Romanova†‡, S. Nakhal§, D. Weber§, M. Lerch§, and P. Heitjans†<br /><br />J. Phys. Chem. C, 2010, 114 (44), pp 19083–19088<br />DOI: 10.1021/jp103433h<br />Publication Date (Web): September 14, 2010<br />Copyright © 2010 American Chemical Society<br /><br />Abstract: Two-dimensional (2D) exchange nuclear magnetic resonance (NMR) spectroscopy carried out under magic angle spinning (MAS) conditions is ideally suited to study site-specific Li diffusion parameters of cathode materials required for the target-oriented development of so-called high-energy density 4 V-lithium-ion batteries. In the present study, we took advantage of Li NMR hyperfine shifts to record temperature-variable 1D and mixing-time dependent 2D exchange MAS 6Li NMR spectra on α-Li3VF6 serving as both a potential cathode material as well as an application-oriented model substance with three magnetically inequivalent Li sites. By comparing the NMR results with structural details of the material we were able to obtain detailed insights into the migration pathways and Li exchange rates which are of the order of some hundreds of Li jumps per second at approximately 340 K. Site-specific Li jump rates τ−1 reveal the electrochemically active sites and provide information how to modify the material in order to increase its relatively low Li diffusivity found at room temperature.<br /><br /><br /><br />Adsorbate Effect on AlO4(OH)2 Centers in the Metal−Organic Framework MIL-53 Investigated by Solid-State NMR Spectroscopy<br /><br />Christian Lieder, Sabine Opelt, Michael Dyballa, Harald Henning, Elias Klemm, and Michael Hunger*<br /><br />J. Phys. Chem. C, 2010, 114 (39), pp 16596–16602<br />DOI: 10.1021/jp105700b<br />Publication Date (Web): September 10, 2010<br />Copyright © 2010 American Chemical Society<br /><br />Abstract:1H and 27Al MAS NMR spectroscopies have been applied for studying the effect of water molecules, nitrogen bases, and o-xylene on the hydroxyl protons of bridging AlOH groups and framework aluminum atoms in the metal−organic framework (MOF) MIL-53. For water molecules adsorbed on the low-temperature form MIL-53lt, two 1H MAS NMR signals were found indicating the formation of different O−H···O hydrogen bonds to neighboring oxygen atoms, such as to carboxylic oxygens. Upon adsorption of the nitrogen bases acetonitrile, ammonia, and pyridine, a linear increase of the quadrupole coupling constant, CQ, of the framework aluminum atoms in dehydrated MIL-53 from CQ = 8.5 MHz (unloaded material) to maximum 10.8 MHz (pyridine-loaded material) as a function of the proton affinity of the adsorbates was observed. Adsorption of o-xylene led to three stepwise changes of the quadrupole coupling constants, CQ, of framework aluminum atoms in dehydrated MIL-53. While the first two stepwise changes of the CQ values (CQ = 8.0 and 8.7 MHz) occur for o-xylene loadings of lower than 4 molecules per unit cell and for all AlO4(OH)2 centers, the third change of the CQ value to 9.4 MHz was observed for o-xylene loadings higher than 4 o-xylene molecules per unit cell and for maximum 50% of the framework aluminum atoms. This third adsorbate-induced change of the CQ value of framework aluminum atoms in MIL-53 is accompanied by a significant decrease of the adsorbate mobility<br /><br /><br /><br />Impact of Controlling the Site Distribution of Al Atoms on Catalytic Properties in Ferrierite-Type Zeolites†<br /><br />Yuriy Romn-Leshkov, Manuel Moliner, and Mark E. Davis*<br />Chemical Engineering, California Institute of Technology, Pasadena, California 91125<br />J. Phys. Chem. C, Article ASAP<br />DOI: 10.1021/jp106247g<br />Publication Date (Web): September 9, 2010<br />Copyright © 2010 American Chemical Society<br /><br />Abstract: Zeolites with the ferrierite (FER) topology are synthesized using a combination of tetramethylammonium (TMA) cations with differently sized cyclic amines (pyrrolidine (Pyr), hexamethyleneimine (HMI), and 1,4-diazabicyclo[2.2.2]octane (DAB)). Using these organic structure-directing agents (SDAs), low Si/Al ratios and concentrated synthesis mixtures favor the crystallization of FER materials. Increasing the size of the cyclic amine or decreasing the aluminum content leads to the crystallization of other phases or the creation of excessive amounts of connectivity defects. TMA cations play a decisive role in the synthesis of the FER materials, and their presence allows the use of HMI to synthesize FER. Proton MAS NMR is used to quantify the accessibility of pyridine to acid sites in these FER samples, where it is found that the FER+HMI+TMA sample contains only 27% acid sites in the 8-MR channels, whereas FER+Pyr and FER+Pyr+TMA contain 89% and 84%, respectively. The constraint index (CI) test and the carbonylation of dimethyl ether (DME) with carbon monoxide are used as probe reactions to evaluate how changes in the aluminum distribution in these FER samples affect their catalytic behavior. Results show that the use of Pyr as an SDA results in the selective population of acid sites in the 8-MR channels, whereas the use of HMI generates FER zeolites with an increased concentration of acid sites in the 10-MR channels.</span><div class="blogger-post-footer">Recent articles and reviews featuring solid-state NMR.</div>Aaronhttp://www.blogger.com/profile/10367130607577279623noreply@blogger.com0tag:blogger.com,1999:blog-19927787.post-47009450401616920102010-12-01T15:25:00.006-05:002010-12-02T15:02:58.066-05:00J. Phys. Chem. B and C, volume 114, Issues 43 - 45 + November ASAPs<span style="font-family:verdana;font-size:85%;">Quantum Oscillations and Polarization of Nuclear Spins in Photoexcited Triplet States†<br /><br />Gerd Kothe*‡, Tomoaki Yago‡, Jrg-Ulrich Weidner‡, Gerhard Link‡, Michail Lukaschek‡, and Tien-Sung Lin§<br /><br />J. Phys. Chem. B, 2010, 114 (45), pp 14755–14762<br />DOI: 10.1021/jp103508t<br />Publication Date (Web): July 28, 2010<br />Copyright © 2010 American Chemical Society<br /><br />Abstract: The unique physical properties of photoexcited triplet states have been explored in numerous spectroscopic studies employing electron paramagnetic resonance (EPR). So far, however, no quantum interference effects were found in these systems in the presence of a magnetic field. In this study, we report the successful EPR detection of nuclear quantum oscillations in an organic triplet state subject to an external magnetic field. The observed quantum coherences can be rationalized using an analytical theory. Analysis suggests that the nuclear spins are actively involved in the intersystem crossing process. The novel mechanism also acts as a source of oscillatory nuclear spin polarization that gives rise to large signal enhancement in nuclear magnetic resonance (NMR). This opens new perspectives for the analysis of chemically induced dynamic nuclear polarization in mechanistic studies of photoactive proteins.<br /><br /><br /><br />W/Mo-Oxide Nanomaterials: Structure−Property Relationships and Ammonia-Sensing Studies†<br /><br />Ying Zhou‡, Kaibo Zheng§, Jan-Dierk Grunwaldt, Thomas Fox‡, Leilei Gu§, Xiaoliang Mo§, Guorong Chen§, and Greta R. Patzke*‡<br /><br />J. Phys. Chem. C, Article ASAP<br />DOI: 10.1021/jp106439n<br />Publication Date (Web): November 30, 2010<br />Copyright © 2010 American Chemical Society<br /><br />Abstract:W/Mo-oxides of the hexagonal tungsten bronze (HTB) type have been investigated by X-ray absorption spectroscopy to obtain detailed insight into the substitution process of W by Mo that leads to mixed HTB frameworks. Both the morphology of the nanostructured W/Mo-HTBs as well as the oxidation state of Mo are significantly influenced through the incorporation of different alkali cations into the hexagonal channels of this open structure. A variety of complementary analytical methods, including TG, in situ and ex situ XRD, SEM, and solid-state NMR analyses, were applied to determine the thermal stability of the obtained W/Mo-HTB materials with respect to their alkali cation and NH4+ contents. A strong correlation between composition and stability was found with the Rb-W/Mo-HTBs exhibiting the highest structural and morphological resistance among the series (up to 580 °C). The NH3-sensing properties of selected W/Mo-oxides in test atmospheres furthermore point to promising features of the Rb-stabilized hexagonal framework materials<br /><br /><br /><br /><br />Hydrogen Physisorption in a Cu(II) Metallacycle<br /><br />Tanja Pietraβ*†, Itza Cruz-Campa‡, Justine Kombarakkaran†, Suman Sirimulla§, Atta M. Arif§, and Juan C. Noveron*‡<br />J. Phys. Chem. C, Article ASAP<br />DOI: 10.1021/jp104544r<br />Publication Date (Web): November 19, 2010<br />Copyright © 2010 American Chemical Society<br /><br />Abstract: The interaction of molecular hydrogen with a novel microporous dinuclear Cu(II) complex, [bis-μ-di(4-pyridyl)methanol-1,4,7-triazacyclononane copper(II)] triflate (1), and its derivatives formed from oxidation and solvent removal was studied with 2H NMR and density functional theory (DFT). The Cu-complex 1 was characterized with X-ray diffraction methods and consists of a dinuclear macrocycle that forms one-dimensional channels of 9.55 Å in diameter. 2H NMR studies of deuterium gas adsorption by 1 suggest that physisorption condensation of D2 occurs within two distinct microenvironments: in the interior and in-between the microtubular structures. The assignment of NMR resonances to specific adsorption sites is supported by spectral decomposition and analysis of the line widths and integrated signal intensities of the components. The dynamics of the system are probed by spin−lattice relaxation time measurements and spectral hole-burn experiments as a function of temperature and pressure. NMR and DFT calculations suggest that hydrogen uptake is mediated through interactions with the Cu(II) centers via dipole−ion interactions.<br /><br /><br /><br /><br />Influence of Structure on the Spectroscopic Properties of the Polymorphs of Piroxicam<br /><br />Wei Liu†, Wei David Wang†, Wei Wang†, Shi Bai*†‡, and Cecil Dybowski‡<br /><br />J. Phys. Chem. B, ASAP<br />DOI: 10.1021/jp1084444<br />Publication Date (Web): November 18, 2010<br />Copyright © 2010 American Chemical Society<br /><br />Abstract: The complete 13C NMR chemical-shift tensors for the carbon sites of the two polymorphic forms (PI and PII) and the monohydrate form (PM) of the analgesic drug, piroxicam, are reported. The NMR parameters (isotropic chemical shifts, chemical-shielding anisotropies and asymmetries, and dipolar couplings), X-ray powder diffraction, and density functional calculations of piroxicam are analyzed in terms of hydrogen bonding and structure. The integration of all the data gives an improved model of the local solid-state structures of the polymorphs. In particular, the solid-state NMR spectra demonstrate that the asymmetric unit of the monohydrate, PM, contains two zwitterionic piroxicam molecules.<br /><br /><br />Heterogeneities in Gelatin Film Formation Using Single-Sided NMR<br /><br />Sushanta Ghoshal*, Carlos Mattea, Paul Denner, and Siegfried Stapf<br /><br />J. Phys. Chem. B, Article ASAP<br />DOI: 10.1021/jp1068363<br />Publication Date (Web): November 18, 2010<br />Copyright © 2010 American Chemical Society<br /><br />Abstract: Gelatin solutions were prepared in D2O. The drying process of cast solutions was followed with a single-sided nuclear magnetic resonance (NMR) scanner until complete solidification occurred. Spin−spin relaxation times (T2) were measured at different layers with microscopic resolution and were correlated with the drying process during film formation. Additionally, the evaporation of the gelatin solution was observed optically from the reduction of the sample thickness, revealing that at the macroscopic level, the rate of evaporation is not uniform throughout the experiment. A crossover in the spatial evolution of the drying process is observed from the NMR results. At the early stages, the gel appears to be drier in the upper layers near the evaporation front, while this tendency is inverted at the later stages, when drying is faster from the bottom. XRD (X-ray diffraction) data showed that a structural heterogeneity persists in the final film.<br /><br /><br /><br />Understanding the Properties of the Coagel and Gel Phases: A 2H and 13C NMR Study of Amphiphilic Ascorbic Acid Derivatives<br /><br />Silvia Borsacchi†, Moira Ambrosi‡, Pierandrea Lo Nostro‡, and Marco Geppi*†<br /><br />J. Phys. Chem. B, Article ASAP<br />DOI: 10.1021/jp107324e<br />Publication Date (Web): November 15, 2010<br />Copyright © 2010 American Chemical Society<br /><br />Abstract: The coagel and gel phases formed by the d and l diastereoisomers of ascorbyl-dodecanoate (ASC12) in deuterated water were studied through solid-state NMR techniques. In particular, the dynamic properties of water and surfactant chains were investigated by 2H and 13C NMR static spectra, respectively. Two fractions of water with very different dynamics were found in the coagel phases, one solidlike and one liquidlike, assigned to water strongly bound to the surfactant polar heads and bulk water, respectively. Only one kind of “intermediate” water was instead detected in the gel phase suggesting that the merging of the two types of water in the interlayers between the surfactant lamellae occurs at the coagel-to-gel transition. Moreover, the surfactant chains, very rigid in the coagel phase, give rise to fast trans−gauche interconformational jumps in the gel phase, where almost isotropic reorientations of the whole aggregates also occur. A different dynamic behavior was found for the two diastereoisomers in particular for what concerns the surfactant molecules in the gel phase and the water molecules in the coagel presumably ascribable to different inter- and intramolecular interactions that involve the polar heads<br /><br /><br /><br />The “Alkyl” and “Carbenium” Pathways of Methane Activation on Ga-Modified Zeolite BEA: 13C Solid-State NMR and GC-MS Study of Methane Aromatization in the Presence of Higher Alkane<br /><br />Mikhail V. Luzgin, Anton A. Gabrienko, Vladimir A. Rogov, Alexander V. Toktarev, Valentin N. Parmon, and Alexander G. Stepanov*<br />J. Phys. Chem. C, Article ASAP<br />DOI: 10.1021/jp1078899<br />Publication Date (Web): November 11, 2010<br />Copyright © 2010 American Chemical Society<br /><br />Abstract:By using 13C solid-state NMR spectroscopy and GC-MS analysis, the activation of methane and coaromatization of methane and propane have been monitored on gallium-modified zeolite BEA at 573−823 K. A noticeable degree involvement of the 13C-label from methane-13C into the aromatic reaction products (benzene, toluene) has been demonstrated. The major intermediate of the methane activation represents gallium-methyl species, which are formed by methane dissociative adsorption on Ga2O3 species of the zeolite. The minor species of methane activation, Ga-methoxy groups, provide the involvement of methane into aromatics by the methylation of aromatic molecules, which are generated exclusively from propane, by the mechanism of electrophilic substitution. Ga-methyl species can serve as methylating nucleophilic agent for the reaction of nucleophilic substitution with participation of aromatic molecules, which contain the electron-withdrawing substitutes.<br /><br /><br /><br />Slow Exchange Model of Nonrigid Rotational Motion in RNA for Combined Solid-State and Solution NMR Studies<br /><br />Prashant S. Emani†, Gregory L. Olsen‡, Dorothy C. Echodu‡, Gabriele Varani‡§, and Gary P. Drobny*‡<br /><br />J. Phys. Chem. B, Article ASAP<br />DOI: 10.1021/jp107193z<br />Publication Date (Web): November 10, 2010<br />Copyright © 2010 American Chemical Society<br /><br />Abstract: Functional RNA molecules are conformationally dynamic and sample a multitude of dynamic modes over a wide range of frequencies. Thus, a comprehensive description of RNA dynamics requires the inclusion of a broad range of motions across multiple dynamic rates which must be derived from multiple spectroscopies. Here we describe a slow conformational exchange theoretical approach to combining the description of local motions in RNA that occur in the nanosecond to microsecond window and are detected by solid-state NMR with nonrigid rotational motion of the HIV-1 transactivation response element (TAR) RNA in solution as observed by solution NMR. This theoretical model unifies the experimental results generated by solution and solid-state NMR and provides a comprehensive view of the dynamics of HIV-1 TAR RNA, a well-known paradigm of an RNA where function requires extensive conformational rearrangements. This methodology provides a quantitative atomic level view of the amplitudes and rates of the local and collective displacements of the TAR RNA molecule and provides directly motional parameters for the conformational capture hypothesis of this classical RNA−ligand interaction.<br /><br /><br /><br />Molecular Dynamics of Amorphous Gentiobiose Studied by Solid-State NMR<br /><br />Teresa G. Nunes*†, Hermnio P. Diogo†, Susana S. Pinto†, and Joaquim J. Moura Ramos‡<br /><br />J. Phys. Chem. B, Article ASAP<br />DOI: 10.1021/jp106371w<br />Publication Date (Web): November 10, 2010<br />Copyright © 2010 American Chemical Society<br /><br />Abstract: A solid-state NMR (SSNMR) study is reported on the effect of temperature on the molecular mobility of amorphous gentiobiose, which is complemented with data obtained from crystalline samples. 13C cross-polarization/magic-angle-spinning (CPMAS) spectra and 1H MAS spectra were obtained for gentiobiose at natural abundance, in the amorphous state, from 293 K up to the glass transformation region (Tg = 359 K). Two well-defined molecular mobility regimes were observed, corresponding to different motional modes. NMR results on molecular dynamics are discussed and compared with those obtained by thermally stimulated depolarization currents (TSDC) and dielectric relaxation spectroscopy (DRS). SSNMR spectra presented evidence for a new polymorphic form of gentiobiose, not yet reported in the literature, which is obtained by slow heating of the amorphous solid up to 364 K inside the NMR zirconia rotor.<br /><br /><br /><br />73Ge Solid-State NMR of Germanium Oxide Materials: Experimental and Theoretical Studies<br /><br />Vladimir K. Michaelis and Scott Kroeker*<br /><br />J. Phys. Chem. C, Article ASAP<br />DOI: 10.1021/jp1071082<br />Publication Date (Web): November 10, 2010<br />Copyright © 2010 American Chemical Society<br /><br />Abstract: A comprehensive series of crystalline germanates has been studied by ultrahigh-field 73Ge NMR and quantum chemical calculations. Despite its low gyromagnetic ratio, low natural abundance and large quadrupole moment, interpretable spectra were obtained in almost all cases, demonstrating that 73Ge is an accessible NMR nucleus. The spectra yield a wide range of quadrupole coupling constants (CQ = 9 to 35 MHz), with calculations indicating a range twice that, which are rationalized principally in terms of the variation in Ge−O bond lengths. The isotropic chemical shifts appear to fall into distinct regions for four-, five-, and six-coordinate Ge, with increasing coordination number corresponding to lower frequencies. Both CASTEP and WIEN2k consistently underestimate the CQs, suggesting that the exchange-correlation functional is poorly optimized for these systems. 73Ge NMR spectra of alkali germanate glasses are broad and featureless, rendering them difficult to interpret in terms of specific structural elements, even with the well understood NMR parameters from the crystalline systems. This study represents the first systematic 73Ge NMR investigation of solids, and shows that valuable structural information can be obtained in favorable cases.<br /><br /><br /><br />NMR Study of LiBH4 with C60<br /><br />David T. Shane*†, Robert L. Corey‡, Laura H. Rayhel†, Matthew Wellons§, Joseph A. Teprovich, Jr.§, Ragaiy Zidan§, Son-Jong Hwang, Robert C. Bowman, Jr., and Mark S. Conradi†<br /><br />J. Phys. Chem. C, 2010, 114 (46), pp 19862–19866<br />DOI: 10.1021/jp107911u<br />Publication Date (Web): November 3, 2010<br />Copyright © 2010 American Chemical Society<br /><br />Abstract:LiBH4 doped with 1.6 mol % well-dispersed C60 is studied with solid-state nuclear magnetic resonance (NMR). Variable-temperature hydrogen NMR shows large changes between the data upon first heating and after exposure to 300 °C. After heating, a large fraction on the order of 50% of the hydrogen signal appears in a motionally narrowed peak, similar to a previous report of LiBH4 in a porous carbon aerogel nanoscaffold. Magic-angle spinning (MAS) NMR of 13C in a 13C-enriched sample finds the C60 has reacted already in the as-mixed (unheated) material. Dehydriding and rehydriding result in further 13C spectral changes, with nearly all intensity being found in a broad peak corresponding to aromatic carbons. It thus appears that the previously reported improved dehydriding and rehydriding kinetics of this material at least partially result from in situ formation of a carbon framework. The method may offer a new route to dispersal of hydrides in carbon support structures.<br /><br /><br /><br />Investigation of Si Atom Migration in the Framework of MSE-Type Zeolite YNU-2<br /><br />Takuji Ikeda*†, Satoshi Inagaki‡, Taka-aki Hanaoka†, and Yoshihiro Kubota‡<br /><br />J. Phys. Chem. C, 2010, 114 (46), pp 19641–19648<br />DOI: 10.1021/jp1079586<br />Publication Date (Web): November 2, 2010<br />Copyright © 2010 American Chemical Society<br /><br />Abstract: The change in distribution of Si atom defects in the framework of zeolite YNU-2 by steam treatment was investigated using powder X-ray diffraction and solid-state NMR spectroscopy. The precursor of zeolite YNU-2 (abbreviated to YNU-2P) with a three-dimensional pore system has a large number of Si atom defects (more than 10% of all T sites in a unit cell) around the supercage. These defect sites were confirmed by observation of a Q3 ((−SiO)3Si−OH) resonance peak by 29Si magic angle spinning NMR spectroscopy. We have shown that steam treatment of YNU-2P at 523 K for 24 h significantly decreases the relative intensity ratio of the observed Q3 resonance peak for the Q4((−SiO)4Si) peak. The Rietveld analysis of steam-treated YNU-2P (YNU-2PST) shows a marked increase in the site occupancies of the defective Si sites. Furthermore, the Si atom defects in YNU-2PST almost disappeared after calcination, yielding siliceous zeolite YNU-2. These results indicate that the defective framework structure was almost restored by steam treatment. Experimental results suggest that Si atom migration in the framework of YNU-2P takes place during steam treatment. The migrated Si atom fragment fills defect sites and is connected with adjacent silanol groups. In addition, the quantity of the half amount of structure-directing agent molecules was removed from the micropores in YNU-2PST by steam treatment.<br /><br /><br /><br />Ryan M. Ravenelle†, Florian Schüβler‡, Andrew D’Amico†, Nadiya Danilina§, Jeroen A. van Bokhoven§, Johannes A. Lercher‡, Christopher W. Jones†, and Carsten Sievers*†<br /><br />J. Phys. Chem. C, 2010, 114 (46), pp 19582–19595<br />DOI: 10.1021/jp104639e<br />Publication Date (Web): November 2, 2010<br />Copyright © 2010 American Chemical Society<br /><br />Abstract: Zeolites Y and ZSM-5 with varying Si/Al ratios are treated in liquid water at 150 and 200 °C under autogenic pressure to assess their hydrothermal stability. The changes in the structure are characterized by atomic absorption spectroscopy, X-ray diffraction, scanning electron microscopy, argon physisorption, 27Al and 29Si MAS NMR spectroscopy, temperature-programmed desorption of ammonia, and pyridine adsorption followed by IR spectroscopy. During treatment in hot water, zeolite Y with a Si/Al ratio of 14 or higher is transformed into an amorphous material, and the rate of this degradation increases with increasing Si/Al ratio. In contrast, ZSM-5 is not modified under the same conditions. The main degradation mechanism is suggested to be hydrolysis of the siloxane bonds (Si−O−Si) as opposed to dealumination, which dominates under steaming conditions. In the resulting amorphous phase, Al remains tetrahedrally coordinated, but the micropore volume and concentration of accessible acid sites is reduced dramatically. The results demonstrate that potential structural changes of zeolites have to be considered when these materials are used as catalysts for aqueous phase conversion of biomass.<br /><br /><br /><br />Structure and Characterization of KSc(BH4)4<br /><br />Radovan ern*†, Dorthe B. Ravnsbæk‡, Godwin Severa§, Yaroslav Filinchuk, Vincenza D’ Anna, Hans Hagemann, Drthe Haase#, Jørgen Skibsted‡, Craig M. Jensen*§, and Torben R. Jensen*‡<br /><br />J. Phys. Chem. C, 2010, 114 (45), pp 19540–19549<br />DOI: 10.1021/jp106280v<br />Publication Date (Web): October 25, 2010<br />Copyright © 2010 American Chemical Society<br /><br />Abstract: A new potassium scandium borohydride, KSc(BH4)4, is presented and characterized by a combination of in situ synchrotron radiation powder X-ray diffraction, thermal analysis, and vibrational and NMR spectroscopy. The title compound, KSc(BH4)4, forms at ambient conditions in ball milled mixtures of potassium borohydride and ScCl3 together with a new ternary chloride K3ScCl6, which is also structurally characterized. This indicates that the formation of KSc(BH4)4 differs from a simple metathesis reaction, and the highest scandium borohydride yield (31 mol %) can be obtained with a reactant ratio KBH4:ScCl3 of 2:1. KSc(BH4)4 crystallizes in the orthorhombic crystal system, a = 11.856(5), b = 7.800(3), c = 10.126(6) Å, V = 936.4(8) Å3 at RT, with the space group symmetry Pnma. KSc(BH4)4 has a BaSO4 type structure where the BH4 tetrahedra take the oxygen positions. Regarding the packing of cations, K+, and complex anions, [Sc(BH4)4]−, the structure of KSc(BH4)4 can be seen as a distorted variant of orthorhombic neptunium, Np, metal. Thermal expansion of KSc(BH4)4 in the temperature range RT to 405 K is anisotropic, and the lattice parameter b shows strong nonlinearity upon approaching the melting temperature. The vibrational and NMR spectra are consistent with the structural model, and previous investigations of the related compounds ASc(BH4)4 with A = Li, Na. KSc(BH4)4 is stable from RT up to 405 K, where the compound melts and then releases hydrogen in two rapid steps approximately at 460−500 K and 510−590 K. The hydrogen release involves the formation of KBH4, which reacts with K3ScCl6 and forms a solid solution, K(BH4)1−xClx. The ternary potassium scandium chloride K3ScCl6 observed in all samples has a monoclinic structure at room temperature, P21/a, a = 12.729(3), b = 7.367(2), c = 12.825(3) Å, β = 109.22(2)°, V = 1135.6(4) Å3, which is isostructural to K3MoCl6. The monoclinic polymorph transforms to cubic at 635 K, a = 10.694 Å (based on diffraction data measured at 769 K), which is isostructural to the high temperature phase of K3YCl6.<br /><br /><br /><br />Phase Behavior and 13C NMR Spectroscopic Analysis of the Mixed Methane + Ethane + Propane Hydrates in Mesoporous Silica Gels<br /><br />Seungmin Lee, Inuk Cha, and Yongwon Seo*<br /><br />J. Phys. Chem. B, 2010, 114 (46), pp 15079–15084<br />DOI: 10.1021/jp108037m<br />Publication Date (Web): October 21, 2010<br />Copyright © 2010 American Chemical Society<br /><br />Abstract: In this study, the phase behavior and quantitative determination of hydrate composition and cage occupancy for the mixed CH4 + C2H6 + C3H8 hydrates were closely investigated through the experimental measurement of three-phase hydrate (H)−water-rich liquid (LW)−vapor (V) equilibria and 13C NMR spectra. To examine the effect of pore size and salinity, we measured hydrate phase equilibria for the quaternary CH4 (90%) + C2H6 (7%) + C3H8 (3%) + water mixtures in silica gel pores of nominal diameters of 6.0, 15.0, and 30.0 nm and for the quinary CH4 (90%) + C2H6 (7%) + C3H8 (3%) + NaCl + water mixtures of two different NaCl concentrations (3 and 10 wt %) in silica gel pores of a nominal 30.0 nm diameter. The value of hydrate−water interfacial tension for the CH4 (90%) + C2H6 (7%) + C3H8 (3%) hydrate was found to be 47 ± 4 mJ/m2 from the relation of the dissociation temperature depression with the pore size of silica gels at a given pressure. At a specified temperature, three-phase H−LW−V equilibrium curves of pore hydrates were shifted to higher pressure regions depending on pore sizes and NaCl concentrations. From the cage-dependent 13C NMR chemical shifts of enclathrated guest molecules, the mixed CH4 (90%) + C2H6 (7%) + C3H8 (3%) gas hydrate was confirmed to be structure II. The cage occupancies of each guest molecule and the hydration number of the mixed gas hydrates were also estimated from the 13C NMR spectra.<br /><br /><br /><br /><br />Biomimetic Apatite Mineralization Mechanisms of Mesoporous Bioactive Glasses as Probed by Multinuclear 31P, 29Si, 23Na and 13C Solid-State NMR<br /><br />Philips N. Gunawidjaja†, Andy Y. H. Lo†, Isabel Izquierdo-Barba‡§, Ana Garca‡§, Daniel Arcos‡§, Baltzar Stevensson†, Jekabs Grins, Mara Vallet-Reg‡§, and Mattias Edn*†<br /><br />J. Phys. Chem. C, 2010, 114 (45), pp 19345–19356<br />DOI: 10.1021/jp105408c<br />Publication Date (Web): October 21, 2010<br />Copyright © 2010 American Chemical Society<br /><br />Abstract: An array of magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy experiments is applied to explore the surface reactions of a mesoporous bioactive glass (MBG) of composition Ca0.10Si0.85P0.04O1.90 when subjected to a simulated body fluid (SBF) for variable intervals. Powder X-ray diffraction and 31P NMR techniques are employed to quantitatively monitor the formation of an initially amorphous calcium phosphate surface layer and its subsequent crystallization into hydroxycarbonate apatite (HCA). Prior to the onset of HCA formation, 1H → 29Si cross-polarization (CP) NMR evidence dissolution of calcium ions; a slightly increased connectivity of the speciation of silicate ions is observed at the MBG surface over 1 week of SBF exposure. The incorporation of carbonate and sodium ions into the bioactive orthophosphate surface layer is explored by 1H → 13C CPMAS and 23Na NMR, respectively. We discuss similarities and distinctions in composition−bioactivity relationships established for traditional melt-prepared bioglasses compared to MBGs. The high bioactivity of phosphorus-bearing MBGs is rationalized to stem from an acceleration of their surface reactions due to presence of amorphous calcium orthophosphate clusters of the MBG pore wall.<br /><br /><br /><br /><br />Analysis of the 7Li NMR signals in the Monoclinic Li3Fe2(PO4)3 and Li3V2(PO4)3 Phases<br />A. Castets, D. Carlier*, K. Trad, C. Delmas, and M. Mntrier<br /><br />J. Phys. Chem. C, 2010, 114 (44), pp 19141–19150<br />DOI: 10.1021/jp106871z<br />Publication Date (Web): October 21, 2010<br />Copyright © 2010 American Chemical Society<br /><br />Abstract: The monoclinic Li3Fe2(PO4)3 and Li3V2(PO4)3 phosphates are materials for positive electrodes in Li-ion batteries. They also have interesting structures to test and improve the understanding of Li NMR signals in paramagnetic compounds. The position of such signals is governed by the transfer of electron spin density from the transition metal ion to the Li nucleus. These mechanisms are based on delocalization and polarization effects which induce positive and negative Fermi contact shifts, respectively. We have characterized Li3Fe2(PO4)3 by Li NMR. To understand the signals observed, we have analyzed the electron spin density transfer mechanisms (i) by considering the different Li environments, (ii) by using DFT calculations. We compare our analysis to the one very recently reported by Davis et al. These analyses have been extended to Li3V2(PO4)3 studied by NMR by Cahill et al.<br /><br /><br /><br />Mechanically, Magnetically, and “Rotationally Aligned” Membrane Proteins in Phospholipid Bilayers Give Equivalent Angular Constraints for NMR Structure Determination<br /><br />Sang Ho Park, Bibhuti B. Das, Anna A. De Angelis, Mario Scrima, and Stanley J. Opella*<br /><br />J. Phys. Chem. B, 2010, 114 (44), pp 13995–14003<br />DOI: 10.1021/jp106043w<br />Publication Date (Web): October 20, 2010<br />Copyright © 2010 American Chemical Society<br /><br />Abstract: The native environment for membrane proteins is the highly asymmetric phospholipid bilayer, and this has a large effect on both their structure and dynamics. Reproducing this environment in samples suitable for spectroscopic and diffraction experiments is a key issue, and flexibility in sample preparation is essential to accommodate the diverse size, shape, and other physical properties of membrane proteins. In most cases, to ensure that the biological activities are maintained, this means reconstituting the proteins in fully hydrated planar phospholipid bilayers. The asymmetric character of protein-containing bilayers means that it is possible to prepare either oriented or unoriented (powder) samples. Here we demonstrate the equivalence of mechanical, magnetic, and what we refer to as “rotational alignment” of membrane proteins in phospholipid bilayer samples for solid-state NMR spectroscopy. The trans-membrane domain of virus protein “u” (Vpu) from human immunodeficiency virus (HIV-1) and the full-length membrane-bound form of fd bacteriophage coat protein in phospholipid bilayers are used as examples. The equivalence of structural constraints from oriented and unoriented (powder) samples of membrane proteins is based on two concepts: (1) their alignment is defined by the direction of the bilayer normal relative to the magnetic field and (2) they undergo rapid rotational diffusion about the same bilayer normal in liquid crystalline membranes. The measurement of angular constraints relative to a common external axis system defined by the bilayer normal for all sites in the protein is an essential element of oriented sample (OS) solid-state NMR.<br /><br /><br /><br />Controlled Interactions between Anhydrous Keggin-Type Heteropolyacids and Silica Support: Preparation and Characterization of Well-Defined Silica-Supported Polyoxometalate Species<br /><br />Eva Grinenval†, Xavier Rozanska§, Anne Baudouin†, Elise Berrier‡, Franoise Delbecq§, Philippe Sautet§, Jean-Marie Basset†, and Frdric Lefebvre*†<br /><br />J. Phys. Chem. C, 2010, 114 (44), pp 19024–19034<br />DOI: 10.1021/jp107317s<br />Publication Date (Web): October 20, 2010<br />Copyright © 2010 American Chemical Society<br /><br />Abstract:Anhydrous Keggin-type phosphorus heteropolyacids were deposited on partially dehydroxylated silica by using the surface organometallic chemistry (SOMC) strategy. The resulting solids were characterized by a combination of physicochemical methods including IR, Raman, 1D and 2D 1H, and 31P MAS NMR, electron microscopy experiments and density functional theory (DFT) calculations. It is shown that the main surface species is [≡Si(OH...H+)]2[H+]1[PM12O403−] where the polyoxometalate is linked to the support by proton interaction with two silanols. Two other minor species (10% each) are formed by coordination of the polyoxometalate to the surface via the interaction between all three protons with three silanol groups or via three covalent bonds formed by dehydroxylation of the above species. Comparison of the reactivity of these solids and of compounds prepared by a classical way shows that the samples prepared by the SOMC approach contain ca. 7 times more acid sites<br /><br /><br /><br /><br />Thermal Spreading As an Alternative for the Wet Impregnation Method: Advantages and Downsides in the Preparation of MoO3/SiO2−Al2O3 Metathesis Catalysts<br /><br />Damien P. Debecker*†, Mariana Stoyanova‡, Uwe Rodemerck‡, Pierre Eloy†, Alexandre Lonard§, Bao-Lian Su§, and Eric M. Gaigneaux*†<br /><br />J. Phys. Chem. C, 2010, 114 (43), pp 18664–18673<br />DOI: 10.1021/jp1074994<br />Publication Date (Web): October 14, 2010<br />Copyright © 2010 American Chemical Society<br /><br />Abstract:Silica−alumina-supported MoO3 catalysts are classically prepared via impregnation of the support with a molybdenum salt solution, usually ammonium heptamolybdate, and subsequent drying and calcination (three steps). The downsides of such a route for the synthesis of heterogeneous metathesis catalysts are linked to the limited control on the nature of the MoOx stabilized at the surface, to the uneven distribution of the deposit in the pores of the support, and to the build up of inactive species that find their origin in the wet step of the preparation. In opposition, the direct thermal spreading of molybdenum oxide onto the support is a straightforward (one step) method involving no wet stage. It allows the conversion of bulk MoO3 crystals to amorphous molybdate species dispersed at the surface of the silica−alumina support. This contribution shows that the catalysts obtained via both methods exhibit similar performances in the self-metathesis of propene to butene and ethene. However, based on XRD, XPS, Raman spectroscopy, ICP-AES, N2 physisorption, TEM, and MAS-NMR spectroscopy, it is shown that the origin of active and inactive species in the two systems is different. Whereas the activity of wet-made catalysts is limited by the formation of bulky MoO3 crystals and of aluminum molybdate, the performances of dry-made catalysts are limited by the incomplete spreading of MoO3 nanocrystallites.<br /><br /><br /><br /><br />On the Performance of Spin Diffusion NMR Techniques in Oriented Solids: Prospects for Resonance Assignments and Distance Measurements from Separated Local Field Experiments<br /><br />Nathaniel J. Traaseth†, T. Gopinath†, and Gianluigi Veglia*†‡<br /><br />J. Phys. Chem. B, 2010, 114 (43), pp 13872–13880<br />DOI: 10.1021/jp105718r<br />Publication Date (Web): October 11, 2010<br />Copyright © 2010 American Chemical Society<br /><br />Abstract: NMR spin diffusion experiments have the potential to provide both resonance assignment and internuclear distances for protein structure determination in oriented solid-state NMR. In this paper, we compared the efficiencies of three spin diffusion experiments: proton-driven spin diffusion (PDSD), cross-relaxation-driven spin diffusion (CRDSD), and proton-mediated proton transfer (PMPT). As model systems for oriented proteins, we used single crystals of N-acetyl-L-15N-leucine (NAL) and N-acetyl-L-15N-valyl-L-15N-leucine (NAVL) to probe long and short distances, respectively. We demonstrate that, for short 15N/15N distances such as those found in NAVL (3.3 Å), the PDSD mechanism gives the most intense cross-peaks, while, for longer distances (>6.5 Å), the CRDSD and PMPT experiments are more efficient. The PDSD was highly inefficient for transferring magnetization across distances greater than 6.5 Å (NAL crystal sample), due to small 15N/15N dipolar couplings (<4.5> </span><div class="blogger-post-footer">Recent articles and reviews featuring solid-state NMR.</div>Aaronhttp://www.blogger.com/profile/10367130607577279623noreply@blogger.com0tag:blogger.com,1999:blog-19927787.post-65858142403793472052010-11-10T13:02:00.023-05:002010-11-10T17:40:03.953-05:00Bryan's Blog Update, Part IIHope you're ready for more SSNMR literature!<br /><br />***<br /><i><b>Chem. Commun.</b></i>, 2010, <b>46</b>, 4514-4516 <br /> <span class="DOILink" style="float: left;"><strong>DOI: </strong> 10.1039/B924936B , Communication</span><br /><br /><div class="title_text_s4_jrnls" style="width: auto; float: none;"> <a name="B924936B" href="http://pubs.rsc.org/en/Content/ArticleLanding/2010/CC/B924936B"> On-line monitoring of a microwave-assisted chemical reaction by nanolitre NMR-spectroscopy </a> </div> <span class="red_txt_s4" style="float: none;"> M. Victoria Gomez, Hein H. J. Verputten, Angel Díaz-Ortíz, Andres Moreno, Antonio de la Hoz and Aldrik H. Velders</span> <br /><br /><strong><label id="lblAbstract">Abstract</label></strong><br /> <label id="lblAbstractValue"> </label><p>We report the use of a nanolitre nuclear magnetic resonance (NMR) spectroscopy microfluidic chip hyphenated to a continuous-flow microlitre-microwave irradiation set-up, for on-line monitoring and rapid optimization of reaction conditions.</p><p>***<a name="C0CC00113A" href="http://pubs.rsc.org/en/Content/ArticleLanding/2010/CC/C0CC00113A"><br /></a></p><div class="red_txt_s4"> <i><b>Chem. Commun.</b></i>, 2010, <b>46</b>, 4532-4534</div> <span class="DOILink" style="float: left;"><strong>DOI: </strong> 10.1039/C0CC00113A , Communicatio</span>n<br /><br /><a name="C0CC00113A" href="http://pubs.rsc.org/en/Content/ArticleLanding/2010/CC/C0CC00113A">Rational synthesis, enrichment, and <small><sup>13</sup></small>C NMR spectra of endohedral C<small><sub>60</sub></small> and C<small><sub>70</sub></small> encapsulating a helium atom </a><div class="title_text_s4_jrnls" style="width: auto; float: none;"> </div> <span class="red_txt_s4" style="float: none;"> Yuta Morinaka, Fumiyuki Tanabe, Michihisa Murata, Yasujiro Murata and Koichi Komatsu</span> <br /><br /><strong><label id="lblAbstract">Abstract</label></strong><br /> <label id="lblAbstractValue"> </label><p>Endohedral fullerenes encapsulating a helium atom, <i>i.e.</i>, He@C<small><sub>60</sub></small> and He@C<small><sub>70</sub></small>, at occupation levels of 30% were prepared by rational chemical synthesis. The existence of weak interactions between the inner helium and the outer fullerene cages was demonstrated by experimental and computational investigations.</p><p>***</p><p><a href="http://pubs.rsc.org/en/Journals/Journal/CC"><i><b>Chem. Commun.</b></i></a>, 2010, <b>46</b>, 4982-4984 <br /><strong>DOI: </strong>10.1039/C0CC01007C<br /></p><div class="title_text_s4_jrnls" style="width: auto; float: none;"> <a name="C0CC01007C" href="http://pubs.rsc.org/en/Content/ArticleLanding/2010/CC/C0CC01007C"> Direct observation of a transient polymorph during crystallization </a> </div> <span class="red_txt_s4" style="float: none;"> Colan E. Hughes and Kenneth D. M. Harris</span> <br /><strong><label id="lblAbstract"><br />Abstract</label></strong><br /> <label id="lblAbstractValue"> </label><p>Application of a technique developed for <i>in situ</i> solid-state <small><sup>13</sup></small>C NMR studies of crystallization processes reveals direct evidence that crystallization of glycine from a methanol/water solution involves the initial transient formation of the β polymorph, which then undergoes a solution-mediated polymorphic transformation to yield the more stable α polymorph.</p>***<br /><a href="http://pubs.rsc.org/en/Journals/Journal/CC"><i><b>Chem. Commun.</b></i></a>, 2010, <b>46</b>, 5879-5881 <br /><strong>DOI: </strong>10.1039/C0CC01271H <br /><br /><div class=""> <div class="title_text_s4_jrnls" style="width: auto; float: none;"> <a name="C0CC01271H" href="http://pubs.rsc.org/en/Content/ArticleLanding/2010/CC/C0CC01271H"> Probing heterocycle conformation with residual dipolar couplings </a> </div> <div style="width: auto; float: none;"> <span class="red_txt_s4" style="float: none;"> Chakicherla Gayathri, M. Carmen de la Fuente, Burkhard Luy, Roberto R. Gil and Armando Navarro-Vázquez</span> <br /> </div> </div> <br /><strong><label id="lblAbstract">Abstract</label></strong><br /> <label id="lblAbstractValue"> </label><p>Residual dipolar couplings (RDCs) obtained in a stretched polydimethylsiloxanegel are applied to determine the 7-membered ring conformation in a 2-phenyl-3-benzazepine derivative, and to simultaneously assign all methyleneproton pairs using only <small><sup>1</sup></small><i>D</i><small><sub>CH</sub></small> RDCs and DFT molecular modelling data.</p><p>***</p><p><a href="http://pubs.rsc.org/en/Journals/Journal/CC"><i><b>Chem. Commun.</b></i></a>, 2010, <b>46</b>, 6714-6716 <br /><strong>DOI: </strong>10.1039/C0CC00829J </p><div class=""> <div class="title_text_s4_jrnls" style="width: auto; float: none;"> <a name="C0CC00829J" href="http://pubs.rsc.org/en/Content/ArticleLanding/2010/CC/C0CC00829J"> Solid-state NMR evidence for elastin-like β-turn structure in spider dragline silk </a> </div> <div style="width: auto; float: none;"> <span class="red_txt_s4" style="float: none;"> Janelle E. Jenkins, Melinda S. Creager, Emily B. Butler, Randolph V. Lewis, Jeffery L. Yarger and Gregory P. Holland</span> <br /><br /><strong><label id="lblAbstract">Abstract</label></strong><br /> <label id="lblAbstractValue"> </label><p>Two-dimensional homo- and heteronuclear solid-state MAS NMR experiments on <small><sup>13</sup></small>C/<small><sup>15</sup></small>N-proline labeled <i>Argiope aurantia</i> dragline silk provide evidence for an elastin-like β-turn structure for the repetitive Gly-Pro-Gly-X-X motif prevalent in major ampullate spidroin 2 (MaSp2).</p>***<br /><a href="http://pubs.rsc.org/en/Journals/Journal/CC"><i><b>Chem. Commun.</b></i></a>, 2010, <b>46</b>, 6774-6776 <br /><strong>DOI: </strong>10.1039/C0CC01902J <br /><br /><div class=""> <div class="title_text_s4_jrnls" style="width: auto; float: none;"> <a name="C0CC01902J" href="http://pubs.rsc.org/en/Content/ArticleLanding/2010/CC/C0CC01902J"> Ultra-wideline <small><sup>14</sup></small>N NMR spectroscopy as a probe of molecular dynamics </a> </div> <div style="width: auto; float: none;"> <span class="red_txt_s4" style="float: none;"> Luke A. O'Dell and Christopher I. Ratcliffe</span> <br /> </div> </div> <br /><strong><label id="lblAbstract">Abstract</label></strong><br /> <label id="lblAbstractValue"> </label><p>We show that ultra-wideline solid-state <small><sup>14</sup></small>N NMR can be used as a quantitative probe of molecular dynamics. Jump rates for the molecular flipping mechanism in crystalline urea are determined at various temperatures and are shown to be in good agreement with other NMR techniques.</p><p>***</p><p><a href="http://pubs.rsc.org/en/Journals/Journal/CC"><i><b>Chem. Commun.</b></i></a>, 2010, <b>46</b>, 7533-7535 <br /><strong>DOI: </strong>10.1039/C0CC01846E </p><div class="title_text_s4_jrnls" style="width: auto; float: none;"> <a name="C0CC01846E" href="http://pubs.rsc.org/en/Content/ArticleLanding/2010/CC/C0CC01846E"> Two-dimensional heteronuclear saturation transfer difference NMR reveals detailed integrin αvβ6 protein–peptide interactions </a> </div> <span class="red_txt_s4" style="float: none;"> Jane L. Wagstaff, Sabari Vallath, John F. Marshall, Richard A. Williamson and Mark J. Howard</span> <br /><br /><strong><label id="lblAbstract">Abstract</label></strong><br /> <label id="lblAbstractValue"> </label><p>We report the first example of peptide–protein heteronuclear two-dimensional (2D) saturation transfer difference nuclear magnetic resonance (STD NMR). This method, resulting in dramatically reduced overlap, was applied to the interaction of the integrin αvβ6 with a known peptide ligand and highlights novel contact points between the substrate and target protein.</p><p>***</p><p><a href="http://pubs.rsc.org/en/Journals/Journal/CC"><i><b>Chem. Commun.</b></i></a>, 2010, <b>46</b>, 8192-8194 <br /><strong>DOI: </strong>10.1039/C0CC01953D </p><div class=""> <div class="title_text_s4_jrnls" style="width: auto; float: none;"> <a name="C0CC01953D" href="http://pubs.rsc.org/en/Content/ArticleLanding/2010/CC/C0CC01953D"> Proton hyperpolarisation preserved in long-lived states </a> </div> <div style="width: auto; float: none;"> <span class="red_txt_s4" style="float: none;"> Puneet Ahuja, Riddhiman Sarkar, Sami Jannin, Paul R. Vasos and Geoffrey Bodenhausen</span> <br /> </div> </div> <br /><strong><label id="lblAbstract">Abstract</label></strong><br /> <label id="lblAbstractValue"> </label><p>The polarisation of abundant protons, rather than dilute nuclei with low gyromagnetic ratios, can be enhanced in less than 10 min using <i>dissolution</i> DNP and converted into a long-lived state delocalised over an ensemble of three coupled protons. The process is more straightforward than the hyperpolarisation of heteronuclei followed by magnetisation transfer to protons.</p> ***<br /><a href="http://pubs.rsc.org/en/Journals/Journal/CC"><i><b>Chem. Commun.</b></i></a>, 2010, <b>46</b>, 8273-8275 <br /><strong>DOI: </strong>10.1039/C0CC02730H <br /><br /><div class=""> <div class="title_text_s4_jrnls" style="width: auto; float: none;"> <a name="C0CC02730H" href="http://pubs.rsc.org/en/Content/ArticleLanding/2010/CC/C0CC02730H"> Artifact-free measurement of residual dipolar couplings in DMSO by the use of cross-linked perdeuterated poly(acrylonitrile) as alignment medium </a> </div> <div style="width: auto; float: none;"> <span class="red_txt_s4" style="float: none;"> Grit Kummerlöwe, Marc Behl, Andreas Lendlein and Burkhard Luy</span> <br /> </div> </div> <br /><strong><label id="lblAbstract">Abstract</label></strong><br /> <label id="lblAbstractValue"> </label><p>Perdeuterated poly(acrylonitrile) is introduced as a practically proton-free alignment medium for the measurement of anisotropic NMR parameters; its use in conventional glass tubes and in a Kalrez® 8002 UP-based stretching device with resulting spectra of astonishing quality are demonstrated.</p><p>***</p><p><br /></p><br /> </div> </div> <span class="DOILink" style="float: left;"><br /></span><div class="blogger-post-footer">Recent articles and reviews featuring solid-state NMR.</div>Bryanhttp://www.blogger.com/profile/12367146554703676104noreply@blogger.com0tag:blogger.com,1999:blog-19927787.post-13369780214250436122010-11-09T11:01:00.036-05:002010-11-09T17:20:18.516-05:00Bryan's Blog Update, Part ITime for another update! Let's see what's happening in the world of SSNMR!<br /><br />***<br /><a id="ddJrnl" href="http://www.sciencedirect.com/science/journal/00092614"><b>Chemical Physics Letters</b></a><br /><a href="http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235231%232010%23995089998%231917709%23FLA%23&_cdi=5231&_pubType=J&view=c&_auth=y&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=12fd549efc5fe4a2ccb0b27ea958b9de"> Volume 491, Issues 1-3</a>, 7 May 2010, Pages 11-16 <br /><br /><a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TFN-4YMY73H-9&_user=1010624&_coverDate=05%2F07%2F2010&_rdoc=4&_fmt=high&_orig=browse&_origin=browse&_zone=rslt_list_item&_srch=doc-info%28%23toc%235231%232010%23995089998%231917709%23FLA%23display%23Volume%29&_cdi=5231&_sort=d&_docanchor=&_ct=22&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=0a2b913452ae6d62861544b859a70981&searchtype=a"><span style="font-weight: bold;">F–H···N hydrogen bonds: Influence of substituent and hybridization of nitrogen on H-bond properties and two-bond <sup>19</sup>F–<sup>15</sup>N spin–spin coupling constants (<sup><span style="font-style: italic;">2h</span></sup><span style="font-style: italic;">J</span><sub>F–N</sub>)</span></a><br /><i>Pages 11-16</i><br />Ali Ebrahimi, Mostafa Habibi-Khorassani, Masoome Doosti<br /><a id="ddDoi" href="http://dx.doi.org/10.1016/j.cplett.2010.03.051" target="doilink">doi:10.1016/j.cplett.2010.03.051</a><br /><br /><div style="display: inline;" class="articleText"><div class="articleText_indent"> <h3 class="h3">Abstract</h3><p>The effects of substituent and hybridization of nitrogen atom on hydrogen bonding in the F–H···N<img src="http://www.sciencedirect.com/scidirimg/entities/tbnd" alt="triple bond; length of mdash" title="triple bond; length of mdash" border="0" />CX, F–H···N(H)<img src="http://www.sciencedirect.com/scidirimg/entities/dbnd" alt="double bond; length as m-dash" title="double bond; length as m-dash" border="0" />CX, and F–H···N(H)<sub>2</sub>–CX complexes have theoretically been studied by MP2 and DFT methods with aug-cc-pVDZ and 6-311++G** basis sets. With respect to the hybridization of nitrogen, sp<sup>3</sup>-hybridized nitrogen forms the strongest bond, followed by sp<sup>2</sup> and then sp. In equilibrium structures, the trend in the two-bond <sup>19</sup>F–<sup>15</sup>N spin–spin coupling constants (<sup><i>2h</i></sup><i>J</i><sub>F–N</sub>) is sp <>3 <>2. The results of atoms in molecules (AIM) and natural bond orbital (NBO) analyses are in meaningful relationships with other characteristics of hydrogen bonds, especially with the <sup><i>2h</i></sup><i>J</i><sub>F–N</sub> values.</p><p>***</p><p><a id="ddJrnl" href="http://www.sciencedirect.com/science/journal/00092614"><b>Chemical Physics Letters</b></a><br /><a href="http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235231%232010%23995089998%231917709%23FLA%23&_cdi=5231&_pubType=J&view=c&_auth=y&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=12fd549efc5fe4a2ccb0b27ea958b9de"> Volume 491, Issues 1-3</a>, 7 May 2010, Pages 72-74 </p><p><a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TFN-4YPPR56-6&_user=1010624&_coverDate=05%2F07%2F2010&_rdoc=16&_fmt=high&_orig=browse&_origin=browse&_zone=rslt_list_item&_srch=doc-info%28%23toc%235231%232010%23995089998%231917709%23FLA%23display%23Volume%29&_cdi=5231&_sort=d&_docanchor=&_ct=22&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=db6516c4ba4e4c245645d556aef77bb7&searchtype=a"><span style="font-weight: bold;">Intactness and spatial proximity of acid–base groups in bifunctional SBA-15 as revealed by solid-state NMR</span></a><br /><i>Pages 72-74</i><br />Wanling Shen, Wujun Xu, Qiang Gao, Jun Xu, Hailu Zhang, Anmin Zheng, Yao Xu, Feng Deng<a id="ddDoi" href="http://dx.doi.org/10.1016/j.cplett.2010.03.067" target="doilink"><br /></a></p><p><a id="ddDoi" href="http://dx.doi.org/10.1016/j.cplett.2010.03.067" target="doilink">doi:10.1016/j.cplett.2010.03.067</a></p><div style="display: inline;" class="articleText"><div class="articleText_indent"> <h3 class="h3">Abstract</h3><p>The intactness and spatial proximity of acid and base groups in bifunctional mesoporous SBA-15 has been studied by various NMR techniques. The NMR results show that Brønsted acid and Lewis base groups coexist peacefully on the surface of the same support and maintain their acidity and basicity, respectively. Meanwhile, the acid groups and the base groups are in close proximity with suitable distance.</p><p>***</p><p><a id="ddJrnl" href="http://www.sciencedirect.com/science/journal/00092614"><b>Chemical Physics Letters</b></a><br /><a href="http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235231%232010%23995089995%231943689%23FLA%23&_cdi=5231&_pubType=J&view=c&_auth=y&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=814f6548910e2368185f2dad014ebd75"> Volume 491, Issues 4-6</a>, 17 May 2010, Pages 224-229 </p><p><a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TFN-4YRHCWK-4&_user=1010624&_coverDate=05%2F17%2F2010&_rdoc=24&_fmt=high&_orig=browse&_origin=browse&_zone=rslt_list_item&_srch=doc-info%28%23toc%235231%232010%23995089995%231943689%23FLA%23display%23Volume%29&_cdi=5231&_sort=d&_docanchor=&_ct=29&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=345cf1e164fb4664252460143fe41ced&searchtype=a"><span style="font-weight: bold;">Contributions from orbital–orbital interactions to nucleus-independent chemical shifts and their relation with aromaticity or antiaromaticity of conjugated molecules</span></a><br /><i>Pages 224-229</i><br />Ignacio Pérez-Juste, Marcos Mandado, Luis Carballeira<a id="ddDoi" href="http://dx.doi.org/10.1016/j.cplett.2010.03.077" target="doilink"><br /></a></p><p><a id="ddDoi" href="http://dx.doi.org/10.1016/j.cplett.2010.03.077" target="doilink">doi:10.1016/j.cplett.2010.03.077</a></p><div style="display: inline;" class="articleText"><div class="articleText_indent"> <h3 class="h3">Abstract</h3><p>The out-of-plane components of the nucleus-independent chemical shifts (NICS) for a group of aromatic and antiaromatic [<i>n</i>]-annulenes have been separated into several contributions on the basis of the gauge-including atomic orbital (GIAO) method. The analysis of the orbital interactions responsible of the NICS(π)<sub>zz</sub> values shows that the large and positive values found for antiaromatic compounds are due to the predominance of π → π * rotational transitions that overcome the diamagnetic and gauge contributions. However, NICS(π)<i><sub>zz</sub></i> for aromatic compounds are dominated by contributions arising from the gauge transformation and no significant contributions are found from occupied–unoccupied orbital mixing. This analysis has been compared with previous work about ring currents in the same compounds.</p><p>***</p><p><a id="ddJrnl" href="http://www.sciencedirect.com/science/journal/00092614"><b>Chemical Physics Letters</b></a><br /><a href="http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235231%232010%23995079998%231996691%23FLA%23&_cdi=5231&_pubType=J&view=c&_auth=y&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=20c913993f2c67845196c59a5975403f"> Volume 492, Issues 1-3</a>, 26 May 2010, Pages 174-178 </p><p><a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TFN-4YXK0GB-8&_user=1010624&_coverDate=05%2F26%2F2010&_rdoc=36&_fmt=high&_orig=browse&_origin=browse&_zone=rslt_list_item&_srch=doc-info%28%23toc%235231%232010%23995079998%231996691%23FLA%23display%23Volume%29&_cdi=5231&_sort=d&_docanchor=&_ct=40&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=087ea169d5069b2761dc219df633418c&searchtype=a"><span style="font-weight: bold;">Homonuclear decoupled proton NMR spectra in modest to severe inhomogeneous fields via distant dipolar interactions</span></a> <br /><i>Pages 174-178</i><br />Yuqing Huang, Wen Zhang, Shuhui Cai, Jianhui Zhong, Zhong Chen<a id="ddDoi" href="http://dx.doi.org/10.1016/j.cplett.2010.04.030" target="doilink"><br /></a></p><p><a id="ddDoi" href="http://dx.doi.org/10.1016/j.cplett.2010.04.030" target="doilink">doi:10.1016/j.cplett.2010.04.030</a></p><div style="display: inline;" class="articleText"><div class="articleText_indent"> <h3 class="h3">Abstract</h3><p>On the basis of distant dipolar interactions, two new pulse sequences were proposed to obtain homonuclear broadband-decoupled proton NMR spectra in modest to severe inhomogeneous fields with time efficient acquisitions. Theoretical expressions for signals were derived according to the distant dipolar field (DDF) treatment combined with the product operator formalism. The measurements under either moderate (<img src="http://www.sciencedirect.com/scidirimg/entities/223c.gif" alt="not, vert, similar" title="not, vert, similar" border="0" />0.4 ppm) or severe (<img src="http://www.sciencedirect.com/scidirimg/entities/223c.gif" alt="not, vert, similar" title="not, vert, similar" border="0" />7 ppm) field inhomogeneity in a 500 MHz spectrometer show that the new sequences are complementary to each other and provide an attractive way to eliminate the influences of field inhomogeneities on homonuclear decoupled proton spectra.</p><p>***</p><p><a id="ddJrnl" href="http://www.sciencedirect.com/science/journal/00092614"><b>Chemical Physics Letters</b></a><br /><a href="http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235231%232010%23995079995%232086777%23FLA%23&_cdi=5231&_pubType=J&view=c&_auth=y&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=61f1763c6efa9272ed496c86ae6c5cbf"> Volume 492, Issues 4-6</a>, 7 June 2010, Pages 302-308 </p><p><a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TFN-4YWYYYM-3&_user=1010624&_coverDate=06%2F07%2F2010&_rdoc=20&_fmt=high&_orig=browse&_origin=browse&_zone=rslt_list_item&_srch=doc-info%28%23toc%235231%232010%23995079995%232086777%23FLA%23display%23Volume%29&_cdi=5231&_sort=d&_docanchor=&_ct=22&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=5a03a99d66d744cca4e747c2da5d5725&searchtype=a"><span style="font-weight: bold;">Importance of the hybrid orbital operator derivative term for the energy gradient in the fragment molecular orbital method</span></a> <br /><i>Pages 302-308</i><br />Takeshi Nagata, Dmitri G. Fedorov, Kazuo Kitaura<a id="ddDoi" href="http://dx.doi.org/10.1016/j.cplett.2010.04.043" target="doilink"><br /></a></p><p><a id="ddDoi" href="http://dx.doi.org/10.1016/j.cplett.2010.04.043" target="doilink">doi:10.1016/j.cplett.2010.04.043</a></p><div style="display: inline;" class="articleText"><div class="articleText_indent"> <h3 class="h3">Abstract</h3><p>The hybrid orbital operator is crucial in the fragment molecular orbital (FMO) method for the fragmentation across covalent bonds, however, its gradients have not been properly derived. We show that these very substantial contributions are the cause of the major part of the gradient error in FMO, impeding geometry optimizations and molecular dynamics. Capped alanine decamer <a name="mml9"></a><a style="text-decoration: none; color: black;" href="http://www.sciencedirect.com/science?_ob=MathURL&_method=retrieve&_udi=B6TFN-4YWYYYM-3&_mathId=mml9&_user=1010624&_cdi=5231&_pii=S0009261410005816&_rdoc=20&_issn=00092614&_acct=C000050266&_version=1&_userid=1010624&md5=549428e041cd890f7b6392e7c00b89e0" title="Click to view the MathML source" alt="Click to view the MathML source">(ALA)<sub>10</sub></a> and chignolin (PDB: <a href="http://www.sciencedirect.com/science?_ob=RedirectURL&_method=externObjLink&_locator=pdb&_cdi=5231&_issn=00092614&_origin=article&_zone=art_page&_plusSign=%2B&_targetURL=http%253A%252F%252Fwww.rcsb.org%252Fpdb%252Fexplore.do%253FstructureId%253D1UAO" target="externObjLink">1UAO</a>) solvated by 157 water molecules are used to assess the accuracy of the energy gradients, and the errors are reduced by approximately one order of magnitude.</p><p>***</p><p><a id="ddJrnl" href="http://www.sciencedirect.com/science/journal/00092614"><b>Chemical Physics Letters</b></a><br /><a href="http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235231%232010%23995069998%232115738%23FLA%23&_cdi=5231&_pubType=J&view=c&_auth=y&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=f67f9b771b291d1c724e09e71ca82e9b"> Volume 493, Issues 1-3</a>, 17 June 2010, Pages 27-32 </p><p><a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TFN-4YYRMV1-1&_user=1010624&_coverDate=06%2F17%2F2010&_rdoc=7&_fmt=high&_orig=browse&_origin=browse&_zone=rslt_list_item&_srch=doc-info%28%23toc%235231%232010%23995069998%232115738%23FLA%23display%23Volume%29&_cdi=5231&_sort=d&_docanchor=&_ct=41&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=4b2fb5c31448df7949b612743c658a75&searchtype=a"><span style="font-weight: bold;">The role of cation–π interactions in ethylenic complexes: A theoretical NMR study</span></a><br /><i>Pages 27-32</i><br />Ali Ebrahimi, Mostafa Habibi Khorassani, Hamid Reza Masoodi<a id="ddDoi" href="http://dx.doi.org/10.1016/j.cplett.2010.04.064" target="doilink"><br /></a></p><p><a id="ddDoi" href="http://dx.doi.org/10.1016/j.cplett.2010.04.064" target="doilink">doi:10.1016/j.cplett.2010.04.064</a></p><div style="line-height: 150%;"><h3 class="h3">Abstract</h3>The effect of cation–π interactions on some NMR data of ethylenic complexes has been investigated by B97-1, PBE1KCIS and MPWKCIS1K methods using 6-311++G(3df,3pd) basis set. Unlike <img src="http://www.sciencedirect.com/cache/MiamiImageURL/B6TFN-4YYRMV1-1-14/0?wchp=dGLzVzz-zSkWA" class="charImg" alt="image" title="image" width="45" height="23" />3JH–H(cis), the chemical shift of ethylenic hydrogen (<span style="font-style: italic;">δ</span><sup>H</sup>) and <img src="http://www.sciencedirect.com/cache/MiamiImageURL/B6TFN-4YYRMV1-1-1X/0?wchp=dGLzVzz-zSkWA" class="charImg" alt="image" title="image" width="48" height="22" /> increases by cation–π interaction. The changes of NMR data have been considered with regard to geometry and direct electronic effects. Also, the distance dependence of NMR parameters has been studied in these complexes.<br />***<br /><a id="ddJrnl" href="http://www.sciencedirect.com/science/journal/00092614"><b>Chemical Physics Letters</b></a><br /> <a href="http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235231%232010%23995059998%232189787%23FLA%23&_cdi=5231&_pubType=J&view=c&_auth=y&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=1fabd41c516e25fecd30f6cc677cfedf"> Volume 494, Issues 1-3</a>, 9 July 2010, Pages 104-110 <br /><a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TFN-506RN3V-5&_user=1010624&_coverDate=07%2F09%2F2010&_rdoc=23&_fmt=high&_orig=browse&_origin=browse&_zone=rslt_list_item&_srch=doc-info%28%23toc%235231%232010%23995059998%232189787%23FLA%23display%23Volume%29&_cdi=5231&_sort=d&_docanchor=&_ct=25&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=e986c3b49e7c63642d584012b3b303bb&searchtype=a"><span style="font-weight: bold;">Improved resolution in dipolar NMR spectra using constant time evolution PISEMA experiment</span></a> <br /><i>Pages 104-110</i><br />T. Gopinath, Gianluigi Veglia<br /><a id="ddDoi" href="http://dx.doi.org/10.1016/j.cplett.2010.05.078" target="doilink">doi:10.1016/j.cplett.2010.05.078</a><br /><div style="display: inline;" class="articleText"><div class="articleText_indent"> <h3 class="h3">Abstract</h3><p>The atomic structure of small molecules and polypeptides can be attained from anisotropic NMR parameters such as dipolar couplings (DC) and chemical shifts (CS). Separated local field experiments resolve DC and CS correlations into two dimensions. However, crowded NMR spectra represent a significant obstacle for the complete resolution of these anisotropic parameters. Using the polarization inversion spin exchange at the magic angle (PISEMA) experiment as a foundation, we designed new pulse schemes that use a constant time evolution in the dipolar (indirect) dimension to measure DC and CS correlations at high resolution. We demonstrated this approach on a 4-pentyl-4′-cyanobiphenyl (5CB) liquid crystal sample, achieving a resolution enhancement ranging from 30% to 60% for the resonances in the dipolar dimension. These new experiments open the possibility of obtaining significant resolution enhancement for multidimensional NMR experiments carried out on oriented liquid crystalline samples as well as oriented membrane proteins.</p><p>***</p><p><a id="ddJrnl" href="http://www.sciencedirect.com/science/journal/00092614"><b>Chemical Physics Letters</b></a><br /> <a href="http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235231%232010%23995059995%232207739%23FLA%23&_cdi=5231&_pubType=J&view=c&_auth=y&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=099ae5f6a99c1b3660c6b4b7a3a25b2d"> Volume 494, Issues 4-6</a>, 19 July 2010, Pages 326-330<br /></p><p><a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TFN-508K84C-3&_user=1010624&_coverDate=07%2F19%2F2010&_rdoc=43&_fmt=high&_orig=browse&_origin=browse&_zone=rslt_list_item&_srch=doc-info%28%23toc%235231%232010%23995059995%232207739%23FLA%23display%23Volume%29&_cdi=5231&_sort=d&_docanchor=&_ct=45&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=91a4535fcb57d9d156d47ae9bc239847&searchtype=a"><span style="font-weight: bold;">Broadband heteronuclear dipolar recoupling without <sup>1</sup>H decoupling in solid-state NMR using simple cross-polarization methods</span></a> <span style="font-size: 0.92em; color: rgb(126, 126, 126); white-space: nowrap;"></span><br /><i>Pages 326-330</i><br />Morten Bjerring, Anders Bodholt Nielsen, Zdenek Tosner, Niels Chr. Nielsen</p><p><a id="ddDoi" href="http://dx.doi.org/10.1016/j.cplett.2010.06.018" target="doilink">doi:10.1016/j.cplett.2010.06.018</a></p><div style="display: inline;" class="articleText"><div class="articleText_indent"> <h3 class="h3">Abstract</h3><p>Heteronuclear dipolar recoupling experiments without <sup>1</sup>H decoupling based on simple cross polarization are introduced for applications in biological solid-state NMR. It is shown that standard or adiabatic variants of the cross-polarization experiment with irradiation on the low-γ (e.g., <sup>13</sup>C,<sup>15</sup>N) spins even at modest spinning frequencies enable efficient band-selective or broadband dipolar recoupling without the need for intense <sup>1</sup>H decoupling. This facilitates experiments on expensive isotope-labelled protein samples for which sample heating by intense <sup>1</sup>H decoupling may lead to sample detoriation. The principle is demonstrated numerically and experimentally on uniformly <sup>13</sup>C,<sup>15</sup>N-labelled samples of GB1 and fibrils of hIAPP <a name="bbib20"></a><a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TFN-508K84C-3&_user=1010624&_coverDate=07%2F19%2F2010&_rdoc=43&_fmt=high&_orig=browse&_origin=browse&_zone=rslt_list_item&_srch=doc-info%28%23toc%235231%232010%23995059995%232207739%23FLA%23display%23Volume%29&_cdi=5231&_sort=d&_docanchor=&_ct=45&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=91a4535fcb57d9d156d47ae9bc239847&searchtype=a#bib20">[20]</a>, <a name="bbib21"></a><a 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href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TFN-508K84C-3&_user=1010624&_coverDate=07%2F19%2F2010&_rdoc=43&_fmt=high&_orig=browse&_origin=browse&_zone=rslt_list_item&_srch=doc-info%28%23toc%235231%232010%23995059995%232207739%23FLA%23display%23Volume%29&_cdi=5231&_sort=d&_docanchor=&_ct=45&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=91a4535fcb57d9d156d47ae9bc239847&searchtype=a#bib25">[25]</a>, <a name="bbib26"></a><a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TFN-508K84C-3&_user=1010624&_coverDate=07%2F19%2F2010&_rdoc=43&_fmt=high&_orig=browse&_origin=browse&_zone=rslt_list_item&_srch=doc-info%28%23toc%235231%232010%23995059995%232207739%23FLA%23display%23Volume%29&_cdi=5231&_sort=d&_docanchor=&_ct=45&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=91a4535fcb57d9d156d47ae9bc239847&searchtype=a#bib26">[26]</a>, <a name="bbib27"></a><a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TFN-508K84C-3&_user=1010624&_coverDate=07%2F19%2F2010&_rdoc=43&_fmt=high&_orig=browse&_origin=browse&_zone=rslt_list_item&_srch=doc-info%28%23toc%235231%232010%23995059995%232207739%23FLA%23display%23Volume%29&_cdi=5231&_sort=d&_docanchor=&_ct=45&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=91a4535fcb57d9d156d47ae9bc239847&searchtype=a#bib27">[27]</a>, <a name="bbib28"></a><a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TFN-508K84C-3&_user=1010624&_coverDate=07%2F19%2F2010&_rdoc=43&_fmt=high&_orig=browse&_origin=browse&_zone=rslt_list_item&_srch=doc-info%28%23toc%235231%232010%23995059995%232207739%23FLA%23display%23Volume%29&_cdi=5231&_sort=d&_docanchor=&_ct=45&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=91a4535fcb57d9d156d47ae9bc239847&searchtype=a#bib28">[28]</a> and <a name="bbib29"></a><a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TFN-508K84C-3&_user=1010624&_coverDate=07%2F19%2F2010&_rdoc=43&_fmt=high&_orig=browse&_origin=browse&_zone=rslt_list_item&_srch=doc-info%28%23toc%235231%232010%23995059995%232207739%23FLA%23display%23Volume%29&_cdi=5231&_sort=d&_docanchor=&_ct=45&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=91a4535fcb57d9d156d47ae9bc239847&searchtype=a#bib29">[29]</a> from the human islet amyloid labelled on the FGAIL part.</p><p>***</p><p><a id="ddJrnl" href="http://www.sciencedirect.com/science/journal/00092614"><b>Chemical Physics Letters</b></a><br /> <a href="http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235231%232010%23995059995%232207739%23FLA%23&_cdi=5231&_pubType=J&view=c&_auth=y&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=099ae5f6a99c1b3660c6b4b7a3a25b2d"> Volume 494, Issues 4-6</a>, 19 July 2010, Pages 331-336<br /></p><p><img src="http://www.sciencedirect.com/scidirimg/clear.gif" alt="" width="1" border="0" height="10" /><a id="ddDoi" href="http://dx.doi.org/10.1016/j.cplett.2010.06.019" target="doilink">doi:10.1016/j.cplett.2010.06.019</a></p><p><a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TFN-508PPVV-1&_user=1010624&_coverDate=07%2F19%2F2010&_rdoc=44&_fmt=high&_orig=browse&_origin=browse&_zone=rslt_list_item&_srch=doc-info%28%23toc%235231%232010%23995059995%232207739%23FLA%23display%23Volume%29&_cdi=5231&_sort=d&_docanchor=&_ct=45&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=55c2ba3e1132289255a5f4991138a081&searchtype=a"><span style="font-weight: bold;">Optimal control NMR differentiation between fast and slow sodium</span></a><br /><i>Pages 331-336</i><br />Jae-Seung Lee, Ravinder R. Regatte, Alexej Jerschow</p><div style="display: inline;" class="articleText"><div class="articleText_indent"> <h3 class="h3">Abstract</h3><p><span class="nbApiHighlight">Sodium</span> ions in tissues and organs may experience motion on a variety of timescales, leading to NMR relaxation effects with quadrupolar coupling as the primary mechanism. The various effects that this fluctuating interaction has on spin dynamics can be exploited for distinguishing slow <span class="nbApiHighlight">sodium</span> ions from fast ones. Techniques such as triple-quantum filtering have been used for this purpose in the past. In this work we present optimal pulses which significantly improve the selectivity towards slow-tumbling <span class="nbApiHighlight">sodium</span>. These pulses can also be modified for robustness against magnetic field inhomogeneities, and could hence also become useful as MRI contrast methods.</p><p>***</p><p><a id="ddJrnl" href="http://www.sciencedirect.com/science/journal/00092614"><b>Chemical Physics Letters</b></a><br /> <a href="http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235231%232010%23995049995%232240893%23FLA%23&_cdi=5231&_pubType=J&view=c&_auth=y&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=3688a1796ba24ac93ee062f28a6b9f19"> Volume 495, Issues 4-6</a>, 10 August 2010, Pages 287-291<br /></p><p><img src="http://www.sciencedirect.com/scidirimg/clear.gif" alt="" width="1" border="0" height="10" /><a id="ddDoi" href="http://dx.doi.org/10.1016/j.cplett.2010.06.064" target="doilink">doi:10.1016/j.cplett.2010.06.064</a></p><p><a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TFN-50CDSPR-H&_user=1010624&_coverDate=08%2F10%2F2010&_rdoc=29&_fmt=high&_orig=browse&_origin=browse&_zone=rslt_list_item&_srch=doc-info%28%23toc%235231%232010%23995049995%232240893%23FLA%23display%23Volume%29&_cdi=5231&_sort=d&_docanchor=&_ct=30&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=ab003d28b9fa4eb17f838ac76b7216b7&searchtype=a"><span style="font-weight: bold;">NMR relaxometry: Spin lattice relaxation times in the laboratory frame versus spin lattice relaxation times in the rotating frame</span></a> <span style="font-size: 0.92em; color: rgb(126, 126, 126); white-space: nowrap;"></span><br /><i>Pages 287-291</i><br />Emilie Steiner, Mehdi Yemloul, Laouès Guendouz, Sébastien Leclerc, Anthony Robert, Daniel Canet</p><div style="display: inline;" class="articleText"><div class="articleText_indent"> <h3 class="h3">Abstract</h3><p>Relaxometry dispersion curves display the spin lattice relaxation rate as a function of the measurement frequency. However, as far as proton NMR is considered, dispersion curves usually start around 5 kHz and thus miss the very low frequency region. This gap can be filled by the measurement of the spin–lattice relaxation rate in the rotating frame. The issue of connecting both relaxation rates is considered for two relaxation mechanisms: (i) randomly varying magnetic fields, (ii) dipolar interaction within a system of two equivalent spins. Appropriate data processing is presented and the random field mechanism turns out to be adequate.</p><p>***</p><p><a id="ddJrnl" href="http://www.sciencedirect.com/science/journal/00092614"><b>Chemical Physics Letters</b></a><br /> <a href="http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235231%232010%23995039998%232258740%23FLA%23&_cdi=5231&_pubType=J&view=c&_auth=y&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=11a7f62e8c36ff7cf4c9a7a08527387a"> Volume 496, Issues 1-3</a>, 20 August 2010, Pages 148-151 </p><p><img src="http://www.sciencedirect.com/scidirimg/clear.gif" alt="" width="1" border="0" height="10" /><a id="ddDoi" href="http://dx.doi.org/10.1016/j.cplett.2010.07.063" target="doilink">doi:10.1016/j.cplett.2010.07.063</a></p><p><a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TFN-50KC6TJ-B&_user=1010624&_coverDate=08%2F20%2F2010&_rdoc=32&_fmt=high&_orig=browse&_origin=browse&_zone=rslt_list_item&_srch=doc-info%28%23toc%235231%232010%23995039998%232258740%23FLA%23display%23Volume%29&_cdi=5231&_sort=d&_docanchor=&_ct=46&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=bc09ab44b767fb7d810330c36dc4241e&searchtype=a"><span style="font-weight: bold;">Metal-alkyl species are formed on interaction of small alkanes with gallium oxide: Evidence from solid-state NMR</span></a> <span style="font-size: 0.92em; color: rgb(126, 126, 126); white-space: nowrap;"></span><br /><i>Pages 148-151</i><br />Anton A. Gabrienko, Sergei S. Arzumanov, Alexander V. Toktarev, Alexander G. Stepanov</p> </div></div> </div></div> </div></div> </div></div><br /><div style="line-height: 150%;"><h3 class="h3">Abstract</h3><sup>13</sup>C CP MAS NMR analysis of the products of the interaction of methane, ethane and propane with α-Ga<sub>2</sub>O<sub>3</sub> or Ga-modified zeolite BEA at 523–623 K shows that dissociative adsorption of C<sub>1</sub>–C<sub>3</sub> alkanes on the surface of gallium oxide or Ga-modified zeolite BEA results to the formation of Ga-methyl, Ga-ethyl and Ga-propyl species. This observation allows one to conclude that Ga-alkyls, rather than earlier suggested alkoxy species, could be the intermediates in small alkane dehydrogenation and aromatization on these catalysts.<br />***<br /><a id="ddJrnl" href="http://www.sciencedirect.com/science/journal/00092614"><b>Chemical Physics Letters</b></a><br /> <a href="http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235231%232010%23995039998%232258740%23FLA%23&_cdi=5231&_pubType=J&view=c&_auth=y&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=11a7f62e8c36ff7cf4c9a7a08527387a"> Volume 496, Issues 1-3</a>, 20 August 2010, Pages 162-166 <br /><a id="ddDoi" href="http://dx.doi.org/10.1016/j.cplett.2010.07.016" target="doilink">doi:10.1016/j.cplett.2010.07.016</a><br /><a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TFN-50GWNB4-6&_user=1010624&_coverDate=08%2F20%2F2010&_rdoc=35&_fmt=high&_orig=browse&_origin=browse&_zone=rslt_list_item&_srch=doc-info%28%23toc%235231%232010%23995039998%232258740%23FLA%23display%23Volume%29&_cdi=5231&_sort=d&_docanchor=&_ct=46&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=68608286ab9f1db383d861e325c9e9a0&searchtype=a"><span style="font-weight: bold;">A magic-angle turning NMR experiment for separating spinning sidebands of half-integer quadrupolar nuclei</span></a><br /><i>Pages 162-166</i><br />Ivan Hung, Zhehong Gan<br /><div style="display: inline;" class="articleText"><div class="articleText_indent"> <h3 class="h3">Abstract</h3><p>A two-dimensional magic-angle turning NMR experiment is described for separating spinning sidebands of half-integer quadrupolar nuclei. The experiment is an alternative to quadrupolar phase-adjusted sideband separation (QPASS) [Chem. Phys. Lett. 272 (1997) 295] that yields infinite speed spectra in one dimension and spinning sideband manifolds in the other dimension. A shear transformation is introduced for processing of quadrupolar magic-angle turning (QMAT) data with time evolution of only one rotor period. The QMAT experiment has the advantages of averaging the first-order modulation of the pulse sequence efficiencies giving smaller residual spinning sidebands, linearly incrementing pulse timings for convenient practical implementation, and easily adjustable pulse spacings suitable for higher spinning frequencies.</p><p>***</p><p><a id="ddJrnl" href="http://www.sciencedirect.com/science/journal/00092614"><b>Chemical Physics Letters</b></a><br /> <a href="http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235231%232010%23995039998%232258740%23FLA%23&_cdi=5231&_pubType=J&view=c&_auth=y&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=11a7f62e8c36ff7cf4c9a7a08527387a"> Volume 496, Issues 1-3</a>, 20 August 2010, Pages 175-182 </p><p><a id="ddDoi" href="http://dx.doi.org/10.1016/j.cplett.2010.07.027" target="doilink">doi:10.1016/j.cplett.2010.07.027</a></p><p><a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TFN-50GWNB4-K&_user=1010624&_coverDate=08%2F20%2F2010&_rdoc=38&_fmt=high&_orig=browse&_origin=browse&_zone=rslt_list_item&_srch=doc-info%28%23toc%235231%232010%23995039998%232258740%23FLA%23display%23Volume%29&_cdi=5231&_sort=d&_docanchor=&_ct=46&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=a51d9cde45366066b3f4132bdd78e19e&searchtype=a"><span style="font-weight: bold;">Enantiodiscrimination and extraction of short and long range homo- and hetero-nuclear residual dipolar couplings by a spin selective correlation experiment</span></a><br /><i>Pages 175-182</i><br />Nilamoni Nath, N. Suryaprakash</p><div style="line-height: 150%;"><h3 class="h3">Abstract</h3>A two dimensional correlation experiment for the measurement of short and long range homo- and hetero- nuclear residual dipolar couplings (RDCs) from the broad and featureless proton NMR spectra including <sup>13</sup>C satellites is proposed. The method employs a single natural abundant <sup>13</sup>C spin as a spy nucleus to probe all the coupled protons and permits the determination of RDCs of negligible strengths. The technique has been demonstrated for the study of organic chiral molecules aligned in chiral liquid crystal, where additional challenge is to unravel the overlapped spectrum of enantiomers. The significant advantage of the method is demonstrated in better chiral discrimination using homonuclear RDCs as additional parameters.<br />***<br /><br /><a id="ddJrnl" href="http://www.sciencedirect.com/science/journal/00092614"><b>Chemical Physics Letters</b></a><br /> <a href="http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235231%232010%23995039998%232258740%23FLA%23&_cdi=5231&_pubType=J&view=c&_auth=y&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=11a7f62e8c36ff7cf4c9a7a08527387a"> Volume 496, Issues 1-3</a>, 20 August 2010, Pages 201-207 <br /><a id="ddDoi" href="http://dx.doi.org/10.1016/j.cplett.2010.07.037" target="doilink">doi:10.1016/j.cplett.2010.07.037</a><br /><a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TFN-50J9H3R-2&_user=1010624&_coverDate=08%2F20%2F2010&_rdoc=42&_fmt=high&_orig=browse&_origin=browse&_zone=rslt_list_item&_srch=doc-info%28%23toc%235231%232010%23995039998%232258740%23FLA%23display%23Volume%29&_cdi=5231&_sort=d&_docanchor=&_ct=46&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=838a657682ef091fcf7d086020afa088&searchtype=a"><span style="font-weight: bold;">Indirect high-resolution detection for quadrupolar spin-3/2 nuclei in dipolar HMQC solid-state NMR experiments</span></a> <span style="font-size: 0.92em; color: rgb(126, 126, 126); white-space: nowrap;"></span><br /><i>Pages 201-207</i><br />Julien Trébosc, Olivier Lafon, Bingwen Hu, Jean-Paul Amoureux<br /><div style="display: inline;" class="articleText"><div class="articleText_indent"> <h3 class="h3">Abstract</h3><p>We present a new kind of NMR pulse sequences to observe heteronuclear correlation (HETCOR) specifically between spin-1/2 and spin-3/2 nuclei with isotropic resolution on the quadrupolar channel. These methods, called HMQC-ST, feature a STMAS filter during the evolution period of the HMQC scheme. Compared to existing HETCOR techniques involving quadrupolar nuclei, the HMQC-ST combines high-resolution and high efficiency and allows indirect detection of spin-3/2 nuclei via sensitive nuclei. We study analytically and using simulations how through-bond and through-space HMQC-ST perform compared to regular HMQC sequence. HMQC-ST potential is demonstrated experimentally by recording through-space HETCOR 2D spectra of <a name="mml54"></a><a style="text-decoration: none; color: black;" href="http://www.sciencedirect.com/science?_ob=MathURL&_method=retrieve&_udi=B6TFN-50J9H3R-2&_mathId=mml54&_user=1010624&_cdi=5231&_pii=S0009261410009693&_rdoc=42&_issn=00092614&_acct=C000050266&_version=1&_userid=1010624&md5=745b128f57b8f62f945a0ded00343896" title="Click to view the MathML source" alt="Click to view the MathML source">Na<sub>2</sub>HPO<sub>4</sub></a> and <a name="mml55"></a><a style="text-decoration: none; color: black;" href="http://www.sciencedirect.com/science?_ob=MathURL&_method=retrieve&_udi=B6TFN-50J9H3R-2&_mathId=mml55&_user=1010624&_cdi=5231&_pii=S0009261410009693&_rdoc=42&_issn=00092614&_acct=C000050266&_version=1&_userid=1010624&md5=02da58862eaf08e029ea528477dfa3f2" title="Click to view the MathML source" alt="Click to view the MathML source">NaH<sub>2</sub>PO<sub>4</sub></a>.</p><p>***</p><p><a id="ddJrnl" href="http://www.sciencedirect.com/science/journal/00092614"><b>Chemical Physics Letters</b></a><br /> <a href="http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235231%232010%23995039998%232258740%23FLA%23&_cdi=5231&_pubType=J&view=c&_auth=y&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=11a7f62e8c36ff7cf4c9a7a08527387a"> Volume 496, Issues 1-3</a>, 20 August 2010, Pages 223-226<br /></p><p><a id="ddDoi" href="http://dx.doi.org/10.1016/j.cplett.2010.07.051" target="doilink">doi:10.1016/j.cplett.2010.07.05</a></p><p><a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TFN-50JHBYM-3&_user=1010624&_coverDate=08%2F20%2F2010&_rdoc=46&_fmt=high&_orig=browse&_origin=browse&_zone=rslt_list_item&_srch=doc-info%28%23toc%235231%232010%23995039998%232258740%23FLA%23display%23Volume%29&_cdi=5231&_sort=d&_docanchor=&_ct=46&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=5b5b3f4389cb37ec7069d15870b0a2c1&searchtype=a"><span style="font-weight: bold;">Detection of magnetic environments in porous media by low-field 2D NMR relaxometry</span></a> <span style="font-size: 0.92em; color: rgb(126, 126, 126); white-space: nowrap;"></span><br /><i>Pages 223-226</i><br />Cinzia Casieri, Francesco De Luca, Luca Nodari, Umberto Russo, Camilla Terenzi</p><div style="display: inline;" class="articleText"><div class="articleText_indent"> <h3 class="h3">Abstract</h3><p>The 2D <sup>1</sup>H NMR correlation maps of longitudinal (<i>T</i><sub>1</sub>) and transverse (<i>T</i><sub>2</sub>) relaxation times prove sensitive in monitoring the distribution of magnetic pore environments in porous systems. The comparison with Mössbauer data establishes a direct correspondence between the susceptibility-induced effects observed in the <i>T</i><sub>1</sub>–<i>T</i><sub>2</sub> maps for pore–filling water and the Fe(III)-bearing magnetic compounds.</p><p>***</p><p><a id="ddJrnl" href="http://www.sciencedirect.com/science/journal/00092614"><b>Chemical Physics Letters</b></a><br /> <a href="http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235231%232010%23995019998%232411738%23FLA%23&_cdi=5231&_pubType=J&view=c&_auth=y&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=b1abe8e87813fe60befaabcc127b4b59"> Volume 498, Issues 1-3</a>, 30 September 2010, Pages 10-13<br /></p><p><a id="ddDoi" href="http://dx.doi.org/10.1016/j.cplett.2010.08.040" target="doilink">doi:10.1016/j.cplett.2010.08.040</a></p><p><a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TFN-50TRX9C-H&_user=1010624&_coverDate=09%2F30%2F2010&_rdoc=4&_fmt=high&_orig=browse&_origin=browse&_zone=rslt_list_item&_srch=doc-info%28%23toc%235231%232010%23995019998%232411738%23FLA%23display%23Volume%29&_cdi=5231&_sort=d&_docanchor=&_ct=46&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=ea3d5a0a5def5cf0dfa8b19354a9b6a5&searchtype=a"><span style="font-weight: bold;">The quadrupole moment of the As nucleus from molecular microwave data and calculated relativistic electric field gradients</span></a> <span style="font-size: 0.92em; color: rgb(126, 126, 126); white-space: nowrap;"></span><br /><i>Pages 10-13</i><br />Lukáš Demovič, Vladimir Kellö, Andrzej J. Sadlej</p><div style="line-height: 150%;"><h3 class="h3">Abstract</h3>The ‘molecular’ value of the nuclear quadrupole moment of the <sup>75</sup>As nucleus is determined combining the experimental data for quadrupole coupling constant and the calculated electric field gradient in the AsP molecule. The accurate calculations have been carried out at the CCSD(T) level. The relativistic effects were accounted for using the infinite-order two-component method in the scalar approximation. The new recommended value of the nuclear quadrupole moment of <sup>75</sup>As obtained in this work is 311(2) mb and is more precise than the previous ‘muonic’ value.<br />***<br /><a id="ddJrnl" href="http://www.sciencedirect.com/science/journal/00092614"><b>Chemical Physics Letters</b></a><br /> <a href="http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235231%232010%23995019998%232411738%23FLA%23&_cdi=5231&_pubType=J&view=c&_auth=y&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=b1abe8e87813fe60befaabcc127b4b59"> Volume 498, Issues 1-3</a>, 30 September 2010, Pages 42-44 <br /><a id="ddDoi" href="http://dx.doi.org/10.1016/j.cplett.2010.08.054" target="doilink">doi:10.1016/j.cplett.2010.08.054</a><br /><a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TFN-50V5NMF-2&_user=1010624&_coverDate=09%2F30%2F2010&_rdoc=11&_fmt=high&_orig=browse&_origin=browse&_zone=rslt_list_item&_srch=doc-info%28%23toc%235231%232010%23995019998%232411738%23FLA%23display%23Volume%29&_cdi=5231&_sort=d&_docanchor=&_ct=46&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=f5731840daf64d07d58319b62284a44c&searchtype=a"><span style="font-weight: bold;">Determination of chemical shift of gas-phase hydrogen molecules by <sup>1</sup>H nuclear magnetic resonance</span></a> <span style="font-size: 0.92em; color: rgb(126, 126, 126); white-space: nowrap;"></span><br /><i>Pages 42-44</i><br />Hirotada Fujiwara, Junichiro Yamabe, Shin Nishimura<br /><div style="display: inline;" class="articleText"><div class="articleText_indent"> <h3 class="h3">Abstract</h3><a name="sp005"></a><p>The precise and detailed chemical shift of gas-phase hydrogen molecules was successfully determined by <sup>1</sup>H nuclear magnetic resonance (NMR), avoiding the intervention of neighboring molecules such as in hydrogen occluding materials (free hydrogen). The measurement was conducted with double walled NMR sample tube taking into consideration the change of hydrogen pressure. The inner tube was filled with standard substance (DHO in D<sub>2</sub>O at 4.8 ppm). The chemical shift of free hydrogen molecules was determined to be 7.40 ± 0.01 ppm at 0.18 MPa, 25 °C, which is different from previously reported chemical shifts of hydrogen gas with intervention of neighboring molecules.</p><p>***</p><p><a id="ddJrnl" href="http://www.sciencedirect.com/science/journal/00092614"><b>Chemical Physics Letters</b></a><br /> <a href="http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235231%232010%23995019998%232411738%23FLA%23&_cdi=5231&_pubType=J&view=c&_auth=y&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=b1abe8e87813fe60befaabcc127b4b59"> Volume 498, Issues 1-3</a>, 30 September 2010, Pages 214-220<br /></p><p><a id="ddDoi" href="http://dx.doi.org/10.1016/j.cplett.2010.08.038" target="doilink">doi:10.1016/j.cplett.2010.08.038</a></p><p><a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TFN-50TRX9C-G&_user=1010624&_coverDate=09%2F30%2F2010&_rdoc=44&_fmt=high&_orig=browse&_origin=browse&_zone=rslt_list_item&_srch=doc-info%28%23toc%235231%232010%23995019998%232411738%23FLA%23display%23Volume%29&_cdi=5231&_sort=d&_docanchor=&_ct=46&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=a94e47983111e99149377a8974d18342&searchtype=a"><span style="font-weight: bold;">Homonuclear dipolar decoupling with very large scaling factors for high-resolution ultrafast magic angle spinning <sup>1</sup>H solid-state NMR spectroscopy</span></a><br /><i>Pages 214-220</i><br />Elodie Salager, Jean-Nicolas Dumez, Robin S. Stein, Stefan Steuernagel, Anne Lesage, Bénédicte Elena-Herrmann, Lyndon Emsley</p><div style="display: inline;" class="articleText"><div class="articleText_indent"> <h3 class="h3">Abstract</h3><a name="sp015"></a><p>We present a new phase modulated radio-frequency pulse sequence for homonuclear dipolar decoupling in proton solid-state NMR spectroscopy, eDUMBO-PLUS-1, with a chemical shift scaling factor of 0.73. This sequence was determined by screening random sequences, and experimentally optimizing the best candidates directly on <sup>1</sup>H NMR spectra with 60 kHz magic angle spinning. It yields efficient decoupling with linewidths as little as 150 Hz for 1.3 mm MAS probes on different spectrometers. Experiments and calculations support the hypothesis of a radio-frequency and MAS joint averaging regime, in which the large scaling factor contributes significantly to the overall performance of the decoupling sequence.</p><p>***</p><p><a id="ddJrnl" href="http://www.sciencedirect.com/science/journal/00092614"><b>Chemical Physics Letters</b></a><br /> <a href="http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235231%232010%23995019995%232452739%23FLA%23&_cdi=5231&_pubType=J&view=c&_auth=y&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=ab49a03d46921c22cc9582b258f65ff3"> Volume 498, Issues 4-6</a>, 8 October 2010, Pages 270-276<br /></p><p><a id="ddDoi" href="http://dx.doi.org/10.1016/j.cplett.2010.08.077" target="doilink">doi:10.1016/j.cplett.2010.08.077</a></p><p><a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TFN-50XV9DK-2&_user=1010624&_coverDate=10%2F08%2F2010&_rdoc=11&_fmt=high&_orig=browse&_origin=browse&_zone=rslt_list_item&_srch=doc-info%28%23toc%235231%232010%23995019995%232452739%23FLA%23display%23Volume%29&_cdi=5231&_sort=d&_docanchor=&_ct=30&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=0090286b3ca1f81dd37f965282ec7394&searchtype=a"><span style="font-weight: bold;">Distinguishing hydrogen bonding networks in <span style="font-style: italic;">α</span>-<span style="font-variant: small-caps;">d</span>-galactose using NMR experiments and first principles calculations</span></a><br /><i>Pages 270-276</i><br />Mikhail Kibalchenko, Daniel Lee, Limin Shao, Mike C. Payne, Jeremy J. Titman, Jonathan R. Yates</p><div style="display: inline;" class="articleText"><div class="articleText_indent"> <h3 class="h3">Abstract</h3><a name="sp015"></a><p>First principles calculations and solid-state NMR experiments are used to distinguish between possible hydrogen bonding networks in <i>α</i>-<span class="smCaps">d</span>-galactose. In contrast to <sup>13</sup>C, the <sup>1</sup>H chemical shift parameters show differences which are sufficient to allow the correct network to be identified by comparison with experiments which make use of modern homonuclear decoupling schemes. In addition, clear linear correlations are established between both <sup>1</sup>H chemical shift and chemical shift anisotropy, and hydrogen bond length.</p><p>***</p><p><a id="ddJrnl" href="http://www.sciencedirect.com/science/journal/00092614"><b>Chemical Physics Letters</b></a><br /> <a href="http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235231%232010%23994999998%232581739%23FLA%23&_cdi=5231&_pubType=J&view=c&_auth=y&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=926f9d69bae25e8aaa3de3c193793b0d"> Volume 500, Issues 1-3</a>, 10 November 2010, Pages 54-58<br /></p><p><a id="ddDoi" href="http://dx.doi.org/10.1016/j.cplett.2010.09.061" target="doilink">doi:10.1016/j.cplett.2010.09.061</a></p> </div></div> </div></div> </div></div><a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TFN-513VRHH-1&_user=1010624&_coverDate=11%2F10%2F2010&_rdoc=13&_fmt=high&_orig=browse&_origin=browse&_zone=rslt_list_item&_srch=doc-info%28%23toc%235231%232010%23994999998%232581739%23FLA%23display%23Volume%29&_cdi=5231&_sort=d&_docanchor=&_ct=36&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=fdaf0fcdebf7daf61529b76549ec413b&searchtype=a"><span style="font-weight: bold;">Assignment of the He@C<sub>84</sub> isomers in experimental NMR spectra using density functional calculations</span></a><br /><i>Pages 54-58</i><br />Petr Štěpánek, Petr Bouř, Michal Straka<br /><div style="display: inline;" class="articleText"><div class="articleText_indent"> <h3 class="h3">Abstract</h3><a name="sp005"></a><p>The <sup>3</sup>He chemical shifts were calculated for He<i><sub>n</sub></i>@C<sub>84</sub> (<i>n</i> = 1, 2) fullerenes to obtain characteristic NMR patterns for distinguishing their isomers in a mixture. The density functional methods were calibrated on experimental data. Accuracy within 1 ppm could be reached without further fitting of individual shifts. Such precision allows for a semi-quantitative assignment of <sup>3</sup>He NMR spectra. Additional criteria in the identification are discussed, such as the relative energies of the isomers, positions of the satellite di-helium peaks, and the differential <sup>3</sup>He shifts in the fullerenes reduced to anions. Endohedral <sup>3</sup>He shifts are predicted for so far experimentally unknown He@C<sub>84</sub> and <a name="mml4"></a><span class="inlMMLBox"><a href="http://www.sciencedirect.com/science?_ob=MathURL&_method=retrieve&_udi=B6TFN-513VRHH-1&_mathId=mml4&_user=1010624&_cdi=5231&_pii=S0009261410013084&_rdoc=13&_issn=00092614&_acct=C000050266&_version=1&_userid=1010624&md5=dd560491ad667641941bfdb54776fb0e"><img src="http://www.sciencedirect.com/cache/MiamiImageURL/B6TFN-513VRHH-1-N/0?wchp=dGLzVlb-zSkWb" alt="View the MathML source" title="View the MathML source" style="vertical-align: bottom;" width="60" border="0" height="21" /></a></span> isomers.</p><p>***<br /></p> </div></div><br /></div> </div></div> </div></div><br /></div> </div></div><br /></div></div><p></p></div></div> </div></div> </div></div> </div></div> </div></div><div class="blogger-post-footer">Recent articles and reviews featuring solid-state NMR.</div>Bryanhttp://www.blogger.com/profile/12367146554703676104noreply@blogger.com0tag:blogger.com,1999:blog-19927787.post-27714054412065508702010-10-20T11:27:00.002-04:002010-10-20T11:33:22.500-04:00Journal updatesJ. Am. Chem. Soc., 2010, 132 (40), pp 13984–13987<br /><br /><strong>High Resolution Measurement of Methyl 13Cm−13C and 1Hm−13Cm Residual Dipolar Couplings in Large Proteins</strong><br />Chenyun Guo, Raquel Godoy-Ruiz, and Vitali Tugarinov*<br /><br /><strong>Abstract</strong><br />NMR methodology is developed for high-resolution, accurate measurements of methyl 1Hm−13Cm (1DCH) and 13Cm−13C (1DCC) residual dipolar couplings (RDCs) in ILV-methyl-protonated high-molecular-weight proteins. Both types of RDCs are measured in a three-dimensional (3D) mode that allows dispersion of correlations to the third (13Cβ/γ) dimension, alleviating the problem of overlap of methyl resonances in highly complex and methyl-abundant protein structures. The methodology is applied to selectively ILV-protonated 82-kDa monomeric enzyme malate synthase G (MSG) that contains 273 ILV methyl groups with substantial overlap of methyl resonances in 2D methyl 1H−13C correlation maps. A good agreement is observed between the measured RDCs of both types and those calculated from the crystallographic coordinates of MSG for the residues with low-amplitude internal dynamics. Although the measurement of 1DCH RDCs from the acquisition dimension of NMR spectra imposes certain limitations on the accuracy of obtained 1DCH values, 1DCH couplings can be approximately corrected for cross-correlated relaxation effects. The ratios of 1DCH and 1DCC <br />couplings (1DCH/1DCC) are independent of methyl axis dynamics and the details of residual alignment [Ottiger, M.; Bax, A. J. Am. Chem. Soc. 1999, 121, 4690.]. <br />The 1DCH/1DCC ratios obtained in MSG can therefore validate the employed correction scheme.<br /><br /><strong>J. Am. Chem. Soc., 2010, 132 (40), pp 14015–14017<br /><br />The Structure of Formaldehyde-Inhibited Xanthine Oxidase Determined by 35 GHz 2H ENDOR Spectroscopy</strong><br />Muralidharan Shanmugam†, Bo Zhang‡, Rebecca L. McNaughton†, R. Adam Kinney†, Russ Hille*‡, and Brian M. Hoffman*† <br /><br /><br /><strong>Abstract</strong><br />The formaldehyde-inhibited Mo(V) state of xanthine oxidase (I) has been studied for four decades, yet it has not proven possible to distinguish unequivocally among the several structures proposed for this form. The uniquely large isotropic hyperfine coupling for 13C from CH2O led to the intriguing suggestion of a direct Mo−C bond for the active site of I. This suggestion was supported by the recent crystal structures of glycol- and glycerol-inhibited forms of aldehyde oxidoreductase, a member of the xanthine oxidase family. 1H and 2H ENDOR spectra of I(C1,2H2O) in H2O/D2O buffer now have unambiguously revealed that the active-site structure of I contains a CH2O adduct of Mo(V) in the form of a four-membered ring with S and O linking the C to Mo and have ruled out a direct Mo−C bond. Density functional theory computations are consistent with this conclusion. We interpret the large 13C coupling as resulting from a “transannular hyperfine interaction”.<br /><br /><br /><strong>J. Phys. Chem. A, 2010, 114 (24), pp 6622–6629</strong><br /><strong>Solid-State NMR Spectra and Long, Intra-Dimer Bonding in the π-[TTF]22+ (TTF = Tetrathiafulvalene) Dication</strong><br />Merrill D. Halling, Joshua D. Bell, Ronald J. Pugmire, David M. Grant* and Joel S. Miller*<br /><br /><strong><br />Abstract</strong><br />The 13C chemical-shift tensor principal values for TTF and π-[TTF]22+ (TTF = tetrathiafulvalene) dimer dications have been measured in order to better understand the electronic structure and long intradimer bonding of these TTF-based dimer structures. The structure of π-[TTF]22+ is abnormal due to its two C−C and four S−S ca. 3.4 Å intradimer separations, which is less than the sum of the sulfur van der Waals radii, and has a singlet 1A1g electronic ground state. This study of TTF and [TTF]22+ was conducted to determine how the NMR chemical-shift tensor principal values change as a function of electronic structure. This study also establishes a better understanding of the interactions that lead to spin-pairing of the monomeric radical units. The density functional theory (DFT) calculated nuclear shielding tensors are correlated with the experimentally determined principal chemical-shift values. The embedded ion method (EIM) was used to investigate the electrostatic lattice potential in [TTF]22+. These theoretical methods provide information on the tensor magnitudes and orientations of their tensor principal values with respect to the molecular frame. The experimental chemical-shift principal values agree with the calculated quantum mechanical chemical-shielding principal values, within typical errors commonly seen for this class of molecular system. Relatively weak Wiberg bond orders between the two [TTF]+ components of the dimer dication correlate with the long bonds linking the two [TTF]+ monomers and substantiate the claim that there is weak multicenter bonding present.<br /><br /><br /><strong>Inorg. Chem., 2010, 49 (12), pp 5522–5529</strong><br /><strong>Incorporation of Phosphorus Guest Ions in the Calcium Silicate Phases of Portland Cement from 31P MAS NMR Spectroscopy</strong>Søren L. Poulsen, Hans J. Jakobsen and Jørgen Skibsted*<br /><br /><strong>Abstract</strong><br />Portland cements may contain small quantities of phosphorus (typically below 0.5 wt % P2O5), originating from either the raw materials or alternative sources of fuel used to heat the cement kilns. This work reports the first 31P MAS NMR study of anhydrous and hydrated Portland cements that focuses on the phase and site preferences of the (PO4)3− guest ions in the main clinker phases and hydration products. The observed 31P chemical shifts (10 to −2 ppm), the 31P chemical shift anisotropy, and the resemblance of the lineshapes in the 31P and 29Si MAS NMR spectra strongly suggest that (PO4)3− units are incorporated in the calcium silicate <br />phases, alite (Ca3SiO5) and belite (Ca2SiO4), by substitution for (SiO4)4−tetrahedra. This assignment is further supported by a determination of the spin−lattice relaxation times for 31P in alite and belite, which exhibit the same ratio as observed for the corresponding 29Si relaxation times. From simulations of the intensities, observed in inversion−recovery spectra for a white Portland cement, it is deduced that 1.3% and 2.1% of the Si sites in alite and belite, respectively, are replaced by phosphorus. Charge balance may potentially be achieved to some extent by a coupled substitution mechanism where Ca2+ is replaced by Fe3+ ions, which may account for the interaction of the 31P spins with paramagnetic Fe3+ ions as observed for the ordinary Portland cements. A minor fraction of phosphorus may also be present in the separate phase Ca3(PO4)2, as indicated by the observation of a narrow resonance at δ(31P) = 3.0 ppm for two of the studied cements. 31P{1H} CP/MAS NMR spectra following the hydration of a white Portland cement show that the resonances from the hydrous phosphate species fall in the same spectral range as observed for (PO4)3− incorporated in alite. This similarity and the absence of a large 31P chemical shift ansitropy indicate that the hydrous (PO4)3− species are incorporated in the interlayers of the calcium−silicate−hydrate (C−S−H) phase, the principal phase formed upon hydration of alite and belite.<br /><br /><br /><strong>Inorg. Chem., 2010, 49 (12), pp 5573–5583</strong><br /><strong>Basic Coordination Chemistry Relevant to DNA Adducts Formed by the Cisplatin Anticancer Drug. NMR Studies on Compounds with Sterically Crowded Chiral Ligands</strong>Jamil S. Saad*†§, Michele Benedetti‡, Giovanni Natile‡ and Luigi G. Marzilli*† <br /><br /><strong>Abstract</strong><br />Me4DABPtG2 adducts with the bulky C2-symmetric chiral diamine, Me4DAB (N,N,N′,N′-tetramethyl-2,3-diaminobutane with R,R and S,S configurations at the chelate ring C atom, G = guanine derivative), exhibit slow conformer interchange and are amenable to characterization by NMR methods. The investigation of the cis-PtA2G2 adducts formed by clinically widely used anticancer drugs [A2 = diaminocyclohexane, (NH3)2] is impeded by the rapid conformer interchange permitted by the low A2 bulk near the inner coordination sphere. Me4DABPtG2 adducts exist as a mixture of exclusively head-to-tail (HT) conformers. No head-to-head (HH) conformer was observed. The Me4DAB chirality significantly influences which HT chirality is favored (ΔHT for S,S and ΛHT for R,R). For simple G ligands, the ratio of favored HT conformer to less favored HT conformer is 2:1. For guanosine monophosphate (GMP) ligands, the phosphate group cis G N1H hydrogen bonding favors the ΛHT and the ΔHT conformers for 5′-GMP and 3′-GMP adducts, respectively. For both HT conformers of cis-PtA2G2 adducts, the G nucleobase plane normally cants with respect to the coordination plane in the same direction, left or right, for a given A2 chirality. In contrast, the results for Me4DABPtG2 adducts provide the first examples of a change in the canting direction between the two HT conformers; this unusual behavior is attributed to the fact that canting always gives long G O6 to N−Me distances and that these Me4DAB ligands have bulk both above and below the coordination plane. These results and ongoing preliminary studies of Me4DABPt adducts with G residues linked by a phosphodiester backbone, which normally favors HH conformers, all indicate that a high percentage of HT conformer is present. Collectively, these findings advance fundamental concepts in Pt-DNA chemistry and may eventually help define the role of the carrier-ligand steric effects on anticancer activity.<div class="blogger-post-footer">Recent articles and reviews featuring solid-state NMR.</div>Hiyamhttp://www.blogger.com/profile/02777402614902251884noreply@blogger.com0tag:blogger.com,1999:blog-19927787.post-30648965285268702192010-10-07T10:57:00.002-04:002010-10-07T11:56:04.966-04:00Journal of magnetic resonance<meta charset="utf-8"><span class="Apple-style-span" style="font-family: arial, sans-serif; font-size: 13px; border-collapse: collapse; "><h2 class="entry-title" style="max-width: 650px; font-size: 18px; margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><a class="entry-title-link" target="_blank" href="http://www.sciencedirect.com/science?_ob=GatewayURL&_origin=IRSSCONTENT&_method=citationSearch&_piikey=S109078071000279X&_version=1&md5=1496f6da387c2f2a4ce554c7ddbb3592" style="color: rgb(34, 68, 187); text-decoration: none; ">On the choice of heteronuclear dipolar decoupling scheme in solid-state NMR<div class="entry-title-go-to" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 2px; display: inline; padding-left: 16px; height: 17px; background-image: url(http://www.google.ca/reader/ui/3607832474-entry-action-icons.png); background-attachment: initial; background-origin: initial; background-clip: initial; background-color: initial; background-position: 0% -416px; background-repeat: no-repeat no-repeat; "></div></a></h2><div class="entry-author" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; color: rgb(102, 102, 102); text-decoration: none; "><div class="entry-likers" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; background-color: rgb(255, 255, 255); max-width: 650px; "></div></div><div class="entry-debug" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "></div><div class="entry-annotations" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "></div><div class="entry-body" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; max-width: 650px; padding-top: 0.5em; color: rgb(0, 0, 0); "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><div class="item-body" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Publication year: 2010
<br /><b>Source:</b> Journal of Magnetic Resonance, In Press, Accepted Manuscript, Available online 9 September 2010
<br />Subhradip, Paul , N.D., Kurur , P.K., Madhu</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, verdana, helvetica, sans-serif; font-size: 12px; line-height: 18px; ">We present here a comparison of different heteronuclear dipolar decoupling sequences at the moderate magic-angle spinning (MAS) frequency (<i>ν</i><sub><i>r</i></sub>) of 30 kHz. The radio-frequency (RF) amplitude (<i>ν</i><sub>1</sub>) ranges from the low power (<i>ν</i><sub>1</sub> < <i>ν</i><sub><i>r</i></sub>) to the high power regime (<i>ν</i><sub>1</sub> > 2<i>ν</i><sub><i>r</i></sub>) and includes the rotary resonance conditions (<i>ν</i><sub>1</sub> = <i>nν</i><sub><i>r</i></sub>) where<i>n</i> = 1, 2. For decoupling at the rotary resonance condition, we recently introduced a modification of TPPM, namely high-phase TPPM, whose properties will be discussed here. Finally, based on earlier published and current experimental results we suggest the optimal sequence for heteronuclear dipolar decoupling at any RF amplitude and MAS frequencies up to 35 kHz.</span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, verdana, helvetica, sans-serif; font-size: 12px; line-height: 18px; ">
<br /></span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, verdana, helvetica, sans-serif; font-size: 12px; line-height: 18px; "><span class="Apple-style-span" style="font-family: arial, sans-serif; font-size: 13px; line-height: normal; border-collapse: collapse; "><h2 class="entry-title" style="max-width: 650px; font-size: 18px; margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><a class="entry-title-link" target="_blank" href="http://www.sciencedirect.com/science?_ob=GatewayURL&_origin=IRSSCONTENT&_method=citationSearch&_piikey=S1090780710002831&_version=1&md5=1126c9830f25764f65ff5ac3ff7f4f5d" style="color: rgb(34, 68, 187); text-decoration: none; ">Z-spectroscopy with Alternating Phase Irradiation<div class="entry-title-go-to" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 2px; display: inline; padding-left: 16px; height: 17px; background-image: url(http://www.google.ca/reader/ui/3607832474-entry-action-icons.png); background-attachment: initial; background-origin: initial; background-clip: initial; background-color: initial; background-position: 0% -416px; background-repeat: no-repeat no-repeat; "></div></a></h2><div class="entry-author" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; color: rgb(102, 102, 102); text-decoration: none; "><div class="entry-likers" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; background-color: rgb(255, 255, 255); max-width: 650px; "></div></div><div class="entry-debug" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "></div><div class="entry-annotations" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "></div><div class="entry-body" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; max-width: 650px; padding-top: 0.5em; color: rgb(0, 0, 0); "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><div class="item-body" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Publication year: 2010
<br /><b>Source:</b> Journal of Magnetic Resonance, In Press, Accepted Manuscript, Available online 15 September 2010
<br />Johanna, Närväinen , Penny L., Hubbard , Risto A., Kauppinen , Gareth A., Morris</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, verdana, helvetica, sans-serif; font-size: 12px; line-height: 18px; ">Magnetization transfer (MT) MRI and Z-spectroscopy are tools to study both water–macromolecule interactions and pH-sensitive exchange dynamics between water and the protons of mobile chemical groups within these macromolecules. Both rely on saturation of frequencies offset from water and observation of the on-resonance water signal. In this work, an RF saturation method called Z-spectroscopy with Alternating-Phase Irradiation (ZAPI) is introduced. Based on the <i>T</i><sub>2</sub>-selectivity of the irradiation pulse, ZAPI can be used to separate the different contributions to a Z-spectrum, as well as to study the <i>T</i><sub>2</sub> distribution of the macromolecules contributing to the MT signal. ZAPI can be run at resonance for water and with low power, thus minimizing problems with specific absorption rate (SAR) limits in clinical applications. In this paper, physical and practical aspects of ZAPI are discussed and the sequence is applied <i>in vitro</i> to sample systems and <i>in vivo</i> to rat head to demonstrate the method.</span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, verdana, helvetica, sans-serif; font-size: 12px; line-height: 18px; ">
<br /></span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, verdana, helvetica, sans-serif; font-size: 12px; line-height: 18px; ">
<br /></span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, verdana, helvetica, sans-serif; font-size: 12px; line-height: 18px; "><span class="Apple-style-span" style="font-family: arial, sans-serif; font-size: 13px; line-height: normal; border-collapse: collapse; "><h2 class="entry-title" style="max-width: 650px; font-size: 18px; margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><a class="entry-title-link" target="_blank" href="http://www.sciencedirect.com/science?_ob=GatewayURL&_origin=IRSSCONTENT&_method=citationSearch&_piikey=S109078071000282X&_version=1&md5=84c447569ae69b33fb4b70a39709f5c6" style="color: rgb(34, 68, 187); text-decoration: none; ">Application of Optimal Control to CPMG Refocusing Pulse Design<div class="entry-title-go-to" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 2px; display: inline; padding-left: 16px; height: 17px; background-image: url(http://www.google.ca/reader/ui/3607832474-entry-action-icons.png); background-attachment: initial; background-origin: initial; background-clip: initial; background-color: initial; background-position: 0% -416px; background-repeat: no-repeat no-repeat; "></div></a></h2><div class="entry-author" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; color: rgb(102, 102, 102); text-decoration: none; "><div class="entry-likers" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; background-color: rgb(255, 255, 255); max-width: 650px; "></div></div><div class="entry-debug" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "></div><div class="entry-annotations" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "></div><div class="entry-body" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; max-width: 650px; padding-top: 0.5em; color: rgb(0, 0, 0); "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><div class="item-body" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Publication year: 2010
<br /><b>Source:</b> Journal of Magnetic Resonance, In Press, Accepted Manuscript, Available online 15 September 2010
<br />Troy W., Borneman , Martin D., Hürlimann , David G., Cory</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, verdana, helvetica, sans-serif; font-size: 12px; line-height: 18px; ">We apply optimal control theory (OCT) to the design of refocusing pulses suitable for the CPMG sequence that are robust over a wide range of B<sub>0</sub> and B<sub>1</sub> offsets. We also introduce a model, based on recent progress in the analysis of unitary dynamics in the field of quantum information processing (QIP), that describes the multiple refocusing dynamics of the CPMG sequence as a dephasing Pauli channel. This model provides a compact characterization of the consequences and severity of residual pulse errors. We illustrate the methods by considering a specific example of designing and analyzing broadband OCT refocusing pulses of length 10 t<sub>180</sub>that are constrained by the maximum instantaneous pulse power. We show that with this refocusing pulse, the CPMG sequence can refocus over 98% of magnetization for resonance offsets up to 3.2 times the maximum RF amplitude, even in the presence of ±10% RF inhomogeneity.</span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, verdana, helvetica, sans-serif; font-size: 12px; line-height: 18px; ">
<br /></span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, verdana, helvetica, sans-serif; font-size: 12px; line-height: 18px; "><span class="Apple-style-span" style="font-family: arial, sans-serif; font-size: 13px; line-height: normal; border-collapse: collapse; "><h2 class="entry-title" style="max-width: 650px; font-size: 18px; margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><a class="entry-title-link" target="_blank" href="http://www.sciencedirect.com/science?_ob=GatewayURL&_origin=IRSSCONTENT&_method=citationSearch&_piikey=S1090780710002879&_version=1&md5=bcc7eec9d33d93b527a7f1c95fa7e674" style="color: rgb(34, 68, 187); text-decoration: none; ">A simple one-dimensional method of chemical shift anisotropy determination under MAS conditions<div class="entry-title-go-to" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 2px; display: inline; padding-left: 16px; height: 17px; background-image: url(http://www.google.ca/reader/ui/3607832474-entry-action-icons.png); background-attachment: initial; background-origin: initial; background-clip: initial; background-color: initial; background-position: 0% -416px; background-repeat: no-repeat no-repeat; "></div></a></h2><div class="entry-author" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; color: rgb(102, 102, 102); text-decoration: none; "><div class="entry-likers" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; background-color: rgb(255, 255, 255); max-width: 650px; "></div></div><div class="entry-debug" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "></div><div class="entry-annotations" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "></div><div class="entry-body" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; max-width: 650px; padding-top: 0.5em; color: rgb(0, 0, 0); "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><div class="item-body" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Publication year: 2010
<br /><b>Source:</b> Journal of Magnetic Resonance, In Press, Accepted Manuscript, Available online 18 September 2010
<br />Piotr, Bernatowicz</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">A method of determination of chemical shift anisotropy (CSA) tensor principal components under MAS condition is presented. It is a simple, one-dimensional, and robust alternative to the commonly exploited, but more complicated 2D-PASS. The required CSA components are delivered by simultaneous numerical analysis of a few regular MAS spectra acquired under different spinning rates.</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">
<br /></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><h2 class="entry-title" style="max-width: 650px; font-size: 18px; margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><a class="entry-title-link" target="_blank" href="http://www.sciencedirect.com/science?_ob=GatewayURL&_origin=IRSSCONTENT&_method=citationSearch&_piikey=S1090780710002934&_version=1&md5=6ff428ff415dcbc8063f646f3b49e2da" style="color: rgb(34, 68, 187); text-decoration: none; ">On the measurement of 15N-{1H} nuclear Overhauser effects. 2. Effects of the saturation scheme and water signal suppression<div class="entry-title-go-to" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 2px; display: inline; padding-left: 16px; height: 17px; background-image: url(http://www.google.ca/reader/ui/3607832474-entry-action-icons.png); background-attachment: initial; background-origin: initial; background-clip: initial; background-color: initial; background-position: 0% -416px; background-repeat: no-repeat no-repeat; "></div></a></h2><div class="entry-author" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; color: rgb(102, 102, 102); text-decoration: none; "><div class="entry-likers" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; background-color: rgb(255, 255, 255); max-width: 650px; "></div></div><div class="entry-debug" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "></div><div class="entry-annotations" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "></div><div class="entry-body" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; max-width: 650px; padding-top: 0.5em; color: rgb(0, 0, 0); "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><div class="item-body" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Publication year: 2010
<br /><b>Source:</b> Journal of Magnetic Resonance, In Press, Accepted Manuscript, Available online 24 September 2010
<br />Fabien, Ferrage , Amy, Reichel , Shibani, Battacharya , David, Cowburn , Ranajeet, Ghose</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, verdana, helvetica, sans-serif; font-size: 12px; line-height: 18px; ">Measurement of steady-state <sup>15</sup>N-{<sup>1</sup>H} nuclear Overhauser effects forms a cornerstone of most methods to determine protein backbone dynamics from spin-relaxation data, since it is the most reliable probe of very fast motions on the ps-ns timescale. We have, in two previous publications (J. Magn. Reson. 192 (2008), 302-313; J. Am. Chem. Soc. 131 (2009), 6048-6049) reevaluated spin-dynamics during steady-state (or “saturated”) and reference experiments, both of which are required to determine the NOE ratio. Here we assess the performance of several windowed and windowless sequences to achieve effective saturation of protons in steady-state experiments. We also evaluate the influence of the residual water signal due to radiation damping on the NOE ratio. We suggest a recipe that allows one to determine steady-state <sup>15</sup>N-{<sup>1</sup>H} NOE’s without artifacts and with the highest possible accuracy.</span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, verdana, helvetica, sans-serif; font-size: 12px; line-height: 18px; ">
<br /></span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, verdana, helvetica, sans-serif; font-size: 12px; line-height: 18px; "><span class="Apple-style-span" style="font-family: arial, sans-serif; font-size: 13px; line-height: normal; border-collapse: collapse; "><h2 class="entry-title" style="max-width: 650px; font-size: 18px; margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><a class="entry-title-link" target="_blank" href="http://www.sciencedirect.com/science?_ob=GatewayURL&_origin=IRSSCONTENT&_method=citationSearch&_piikey=S1090780710002910&_version=1&md5=f15d6b47d332dd078475cc2f55e7baca" style="color: rgb(34, 68, 187); text-decoration: none; ">Hydration Water Dynamics in Biopolymers from NMR Relaxation in the Rotating Frame<div class="entry-title-go-to" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 2px; display: inline; padding-left: 16px; height: 17px; background-image: url(http://www.google.ca/reader/ui/3607832474-entry-action-icons.png); background-attachment: initial; background-origin: initial; background-clip: initial; background-color: initial; background-position: 0% -416px; background-repeat: no-repeat no-repeat; "></div></a></h2><div class="entry-author" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; color: rgb(102, 102, 102); text-decoration: none; "><div class="entry-likers" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; background-color: rgb(255, 255, 255); max-width: 650px; "></div></div><div class="entry-debug" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "></div><div class="entry-annotations" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "></div><div class="entry-body" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; max-width: 650px; padding-top: 0.5em; color: rgb(0, 0, 0); "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><div class="item-body" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Publication year: 2010
<br /><b>Source:</b> Journal of Magnetic Resonance, In Press, Accepted Manuscript, Available online 24 September 2010
<br />Barbara, Blicharska , Hartwig, Peemoeller , Magdalena, Witek</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, verdana, helvetica, sans-serif; font-size: 12px; line-height: 18px; ">Assuming dipole-dipole interaction as the dominant relaxation mechanism of protons of water molecules adsorbed onto macromolecule (biopolymer) surfaces we have been able to model the dependences of relaxation rates on temperature and frequency. For adsorbed water molecules the correlation times are of the order of 10<sup>-5</sup> s, for which the dispersion region of spin-lattice relaxation rates in the rotating frame R<sub>1</sub>ρ = 1/T<sub>1</sub>ρ appears over a range of easily accessible B<sub>1</sub> values. Measurements of T<sub>1</sub>ρ at constant temperature and different B<sub>1</sub> values then give the “dispersion profiles” for biopolymers. Fitting a theoretical relaxation model to these profiles allows for the estimation of correlation times. This way of obtaining the correlation time is easier and faster than approaches involving measurements of the temperature dependence of R<sub>1</sub> = 1/T<sub>1</sub>. The T<sub>1</sub>ρ dispersion approach, as a tool for molecular dynamics study, has been demonstrated for several hydrated biopolymer systems including crystalline cellulose, starch of different origins (potato, corn, oat, wheat), paper (modern, old) and lyophilized proteins (albumin, lysozyme).</span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, verdana, helvetica, sans-serif; font-size: 12px; line-height: 18px; ">
<br /></span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, verdana, helvetica, sans-serif; font-size: 12px; line-height: 18px; "><span class="Apple-style-span" style="font-family: arial, sans-serif; font-size: 13px; line-height: normal; border-collapse: collapse; "><h2 class="entry-title" style="max-width: 650px; font-size: 18px; margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><a class="entry-title-link" target="_blank" href="http://www.sciencedirect.com/science?_ob=GatewayURL&_origin=IRSSCONTENT&_method=citationSearch&_piikey=S109078071000296X&_version=1&md5=236a6473074e8782153caa08da5e6197" style="color: rgb(34, 68, 187); text-decoration: none; ">IPAP- HSQMBC: Measurement of Long-Range Heteronuclear Coupling Constants from Spin-State Selective Multiplets<div class="entry-title-go-to" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 2px; display: inline; padding-left: 16px; height: 17px; background-image: url(http://www.google.ca/reader/ui/3607832474-entry-action-icons.png); background-attachment: initial; background-origin: initial; background-clip: initial; background-color: initial; background-position: 0% -416px; background-repeat: no-repeat no-repeat; "></div></a></h2><div class="entry-author" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; color: rgb(102, 102, 102); text-decoration: none; "><div class="entry-likers" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; background-color: rgb(255, 255, 255); max-width: 650px; "></div></div><div class="entry-debug" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "></div><div class="entry-annotations" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "></div><div class="entry-body" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; max-width: 650px; padding-top: 0.5em; color: rgb(0, 0, 0); "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><div class="item-body" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; ">Publication year: 2010
<br /><b>Source:</b> Journal of Magnetic Resonance, In Press, Accepted Manuscript, Available online 29 September 2010
<br />Sergi, Gil , Juan Félix, Espinosa , Teodor, Parella</div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, verdana, helvetica, sans-serif; font-size: 12px; line-height: 18px; ">A new NMR approach is proposed for the measurement of long-range heteronuclear coupling constants (<sup>n</sup>J<sub>XH</sub>, n>1) in natural abundance molecules. Two complementary in-phase (IP) and anti-phase (AP) data are separately recorded from a modified HSQMBC experiment and then added/subtracted to provide spin-state-selective α/β-HSQMBC spectra. The magnitude of <sup>n</sup><i>J</i><sub>XH</sub>can be directly determined by simple analysis of the relative displacement between α- and β-cross-peaks. The robustness of this IPAP-HSQMBC experiment is evaluated experimentally and by simulation using a variety of different conditions. Important aspects such as signal intensity dependence and presence of unwanted cross-talk effects are discussed and examples on the measurement of small proton-carbon (<sup>n</sup>J<sub>CH</sub>) and proton-nitrogen (<sup>n</sup>J<sub>NH</sub>) coupling constants are provided.</span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, verdana, helvetica, sans-serif; font-size: 12px; line-height: 18px; ">
<br /></span></div></div></div></div></span></span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, verdana, helvetica, sans-serif; font-size: 12px; line-height: 18px; ">
<br /></span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, verdana, helvetica, sans-serif; font-size: 12px; line-height: 18px; "><span class="Apple-style-span" style="font-family: arial, sans-serif; font-size: 13px; line-height: normal; border-collapse: collapse; "><h2 class="entry-title" style="max-width: 650px; font-size: 18px; margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><a class="entry-title-link" target="_blank" href="http://www.sciencedirect.com/science?_ob=GatewayURL&_origin=IRSSCONTENT&_method=citationSearch&_piikey=S1090780710003009&_version=1&md5=54cdf90579a9f5e2ab45aa9874c1270f" style="color: rgb(34, 68, 187); text-decoration: none; ">Characterization of a 3D MEMS fabricated micro solenoid at 9.4T<div class="entry-title-go-to" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 2px; display: inline; padding-left: 16px; height: 17px; background-image: url(http://www.google.ca/reader/ui/3607832474-entry-action-icons.png); background-attachment: initial; background-origin: initial; background-clip: initial; background-color: initial; background-position: 0% -416px; background-repeat: no-repeat no-repeat; "></div></a></h2><div class="entry-author" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; color: rgb(102, 102, 102); text-decoration: none; "><div class="entry-likers" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; background-color: rgb(255, 255, 255); max-width: 650px; "></div></div><div class="entry-debug" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "></div><div class="entry-annotations" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "></div><div class="entry-body" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; max-width: 650px; padding-top: 0.5em; color: rgb(0, 0, 0); "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><div class="item-body" style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, verdana, helvetica, sans-serif; font-size: 12px; line-height: 18px; "><strong>M. Mohmmadzadeh<a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WJX-515SRMV-2&_user=1010624&_coverDate=10%2F06%2F2010&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=000801c03e5d86c9557d8d9c67e741f1&searchtype=a#aff1" style="color: rgb(1, 86, 170); text-decoration: none; "><sup>a</sup></a><sup>,</sup>, N. Baxan<a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WJX-515SRMV-2&_user=1010624&_coverDate=10%2F06%2F2010&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=000801c03e5d86c9557d8d9c67e741f1&searchtype=a#aff1" style="color: rgb(1, 86, 170); text-decoration: none; "><sup>a</sup></a>, V. Badilita<a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WJX-515SRMV-2&_user=1010624&_coverDate=10%2F06%2F2010&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=000801c03e5d86c9557d8d9c67e741f1&searchtype=a#aff2" style="color: rgb(1, 86, 170); text-decoration: none; "><sup>b</sup></a>, K. Kratt<a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WJX-515SRMV-2&_user=1010624&_coverDate=10%2F06%2F2010&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=000801c03e5d86c9557d8d9c67e741f1&searchtype=a#aff2" style="color: rgb(1, 86, 170); text-decoration: none; "><sup>b</sup></a>, H. Weber<a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WJX-515SRMV-2&_user=1010624&_coverDate=10%2F06%2F2010&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=000801c03e5d86c9557d8d9c67e741f1&searchtype=a#aff1" style="color: rgb(1, 86, 170); text-decoration: none; "><sup>a</sup></a>, J.G. Korvink<a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WJX-515SRMV-2&_user=1010624&_coverDate=10%2F06%2F2010&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=000801c03e5d86c9557d8d9c67e741f1&searchtype=a#aff3" style="color: rgb(1, 86, 170); text-decoration: none; "><sup>c</sup></a><sup>, </sup><a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WJX-515SRMV-2&_user=1010624&_coverDate=10%2F06%2F2010&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=000801c03e5d86c9557d8d9c67e741f1&searchtype=a#aff4" style="color: rgb(1, 86, 170); text-decoration: none; "><sup>d</sup></a>, U. Wallrabe<a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WJX-515SRMV-2&_user=1010624&_coverDate=10%2F06%2F2010&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=000801c03e5d86c9557d8d9c67e741f1&searchtype=a#aff2" style="color: rgb(1, 86, 170); text-decoration: none; "><sup>b</sup></a><sup>, </sup><a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WJX-515SRMV-2&_user=1010624&_coverDate=10%2F06%2F2010&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=000801c03e5d86c9557d8d9c67e741f1&searchtype=a#aff4" style="color: rgb(1, 86, 170); text-decoration: none; "><sup>d</sup></a>, J. Hennig<a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WJX-515SRMV-2&_user=1010624&_coverDate=10%2F06%2F2010&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=000801c03e5d86c9557d8d9c67e741f1&searchtype=a#aff1" style="color: rgb(1, 86, 170); text-decoration: none; "><sup>a</sup></a> and D. von Elverfeldt<sup><a href="http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WJX-515SRMV-2&_user=1010624&_coverDate=10%2F06%2F2010&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_acct=C000050266&_version=1&_urlVersion=0&_userid=1010624&md5=000801c03e5d86c9557d8d9c67e741f1&searchtype=a#aff1" style="color: rgb(1, 86, 170); text-decoration: none; ">a</a></sup></strong></span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, verdana, helvetica, sans-serif; font-size: 12px; line-height: 18px; "><strong><span class="Apple-style-span" style="font-weight: normal; ">We present for the first time a complete characterization of a micro-solenoid for high resolution MR imaging of mass- and volume-limited samples based on three-dimensional <i>B<sub>0</sub></i>, <i>B<sub>1</sub></i> per unit current (<i>B<sub>1unit</sub></i>) and <i>SNR</i> maps. The micro-solenoids are fabricated using a fully micro-electromechanical systems (MEMS) compatible process in conjunction with an automatic wire-bonder. We present 15 μm isotropic resolution 3D <i>B<sub>0</sub></i> maps performed using the phase difference method. The resulting <i>B<sub>0</sub></i> variation in the range of [-0.07 ppm-0.157 ppm] around the coil center, compares favorably with the 0.5 ppm limit accepted for MR microscopy. 3D <i>B<sub>1unit</sub></i> maps of 40 μm isotropic voxel size were acquired according to the extended multi flip angle (ExMFA) method. The results demonstrate that the characterized microcoil provides a high and uniform sensitivity distribution around its center (<i>B<sub>1unit</sub></i> = 3.4 mT/A ± 3.86%) which is in agreement with the corresponding 1D theoretical data computed along the coil axis. The 3D <i>SNR</i> maps reveal a rather uniform signal distribution around the coil center with a mean value of 53.69 ± 19%, in good agreement with the analytical 1D data along coil axis in the axial slice. Finally, we prove the microcoil capabilities for MR microscopy by imaging Eremosphaera Viridis cells with 18 μm isotropic resolution.</span></strong></span></div></div></div></div></span></span></div></div></div></div></span></span></div></div></div></div></div></div></div></div></span></span></div></div></div></div></span></span></div></div></div></div></span></span></div><div style="margin-top: 0px; margin-right: 0px; margin-bottom: 0px; margin-left: 0px; "><span class="Apple-style-span" style="border-collapse: separate; font-family: arial, verdana, helvetica, sans-serif; font-size: 12px; line-height: 18px; ">
<br /></span></div></div></div></div></span><div class="blogger-post-footer">Recent articles and reviews featuring solid-state NMR.</div>Kris Harrishttp://www.blogger.com/profile/16401554771902373385noreply@blogger.com0tag:blogger.com,1999:blog-19927787.post-68380884790683049542010-09-20T17:28:00.003-04:002010-09-20T17:34:58.015-04:00Surface Enhanced NMR Spectroscopy by Dynamic Nuclear PolarizationA nice write-up in C&E News about DNP SSNMR of molecules bound to silica surfaces. <br /><br />http://pubs.acs.org/cen/news/88/i38/8838notw6.html<br /><br />The corresponding JACS communication can be found at:<br /><br />http://pubs.acs.org/doi/abs/10.1021%2Fja104771z<br /><br />Surface Enhanced NMR Spectroscopy by Dynamic Nuclear Polarization<br /><br />Anne Lesage†, Moreno Lelli†, David Gajan‡, Marc A. Caporini§, Veronika Vitzthum§, Pascal Miville§, Johan Alauzun, Arthur Roussey‡, Chlo Thieuleux‡, Ahmad Medhi, Geoffrey Bodenhausen§, Christophe Copret‡, and Lyndon Emsley*† <br /><br />J. Am. Chem. Soc., Article ASAP<br />DOI: 10.1021/ja104771z<br />Publication Date (Web): September 10, 2010<br />Copyright © 2010 American Chemical Society<br /><br />Abstract: It is shown that surface NMR spectra can be greatly enhanced using dynamic nuclear polarization. Polarization is transferred from the protons of the solvent to the rare nuclei (here carbon-13 at natural isotopic abundance) at the surface, yielding at least a 50-fold signal enhancement for surface species covalently incorporated into a silica framework<div class="blogger-post-footer">Recent articles and reviews featuring solid-state NMR.</div>Aaronhttp://www.blogger.com/profile/10367130607577279623noreply@blogger.com0tag:blogger.com,1999:blog-19927787.post-41078461719235372452010-09-20T11:34:00.002-04:002010-09-20T11:50:20.831-04:00J. Chem. Phys.<h2 class="entry-title"><a class="entry-title-link" target="_blank" href="http://link.aip.org/link/?JCP/133/114503/1&agg=rss">Internal symmetry of basic elements in symmetry-based recoupling sequences under magic-angle spinning</a></h2><div class="entry-author"><span class="entry-source-title-parent">from <a href="http://www.google.ca/reader/view/feed/http%3A%2F%2Fscitation.aip.org%2Frss%2Fjcp1.xml" class="entry-source-title" target="_blank">Journal of Chemical Physics: All Topics</a></span> </div>Fang-Chieh Chou, Hsin-Kuan Lee, and Jerry C. C. Chan<br /><br />In solid-state NMR, many powerful pulse sequences under the condition of magic-angle spinning can be analyzed on the basis of the <span class="formula"><em class="emphitalic">C</em></span>- and <span class="formula"><em class="emphitalic">R</em></span>-sequences developed by Levitt and co-workers. It has been speculated for some years that the basic elements commonly used in symmetry-based recoupling pulse sequences have certain kind of internal symmetries. We show by a detailed analysis that a set of internal selection rules does exist for many basic elements. These internal selection rules may allow a more versatile design of <span class="formula"><em class="emphitalic">C</em><em class="emphitalic">N</em><span class="emphinferior"><em class="emphitalic">n</em></span><span class="emphsuperior"><em class="emphitalic">ν</em></span></span> or <span class="formula"><em class="emphitalic">R</em><em class="emphitalic">N</em><span class="emphinferior"><em class="emphitalic">n</em></span><span class="emphsuperior"><em class="emphitalic">ν</em></span></span> sequences when <span class="formula"><em class="emphitalic">n</em></span> is an integer or half-integer multiple of <span class="formula"><em class="emphitalic">N</em></span>. As an illustration, we have derived the symmetry arguments to rationalize the observation that the C-REDOR pulse sequence can suppress homonuclear dipole-dipole interaction, leading to the design of new windowed basic elements usable for heteronuclear dipolar recoupling with active suppression of homonuclear dipole-dipole interaction. Numerical simulations and experiments measured for <span class="formula">[U–<sup class="emphsuperior">13</sup>C,<sup class="emphsuperior">15</sup>N]-L</span>-alanine have been used to validate our approach. On a more general note, the symmetry rules discussed in this work can also be applied for the design of supercycles.<br /><br /><h2 class="entry-title"><a class="entry-title-link" target="_blank" href="http://link.aip.org/link/?JCP/133/095104/1&agg=rss">Puckering free energy of pyranoses: A NMR and metadynamics-umbrella sampling investigation</a></h2><div class="entry-author"><span class="entry-source-title-parent">from <a href="http://www.google.ca/reader/view/feed/http%3A%2F%2Fscitation.aip.org%2Frss%2Fjcp1.xml" class="entry-source-title" target="_blank">Journal of Chemical Physics: All Topics</a></span> <div class="entry-likers"><div class="entry-likers-n"><span class="number-of-likers more-likers-link link">1 person liked this</span></div></div></div>E. Autieri, M. Sega, F. Pederiva, and G. Guella<br /><br />We present the results of a combined metadynamics-umbrella sampling investigation of the puckered conformers of pyranoses described using the <span class="emphsmallcaps">GROMOS</span> 45a4 force field. The free energy landscape of Cremer–Pople puckering coordinates has been calculated for the whole series of <span class="formula"><em class="emphitalic">α</em></span> and <span class="formula"><em class="emphitalic">β</em></span> aldohexoses, showing that the current force field parameters fail in reproducing proper puckering free energy differences between chair conformers. We suggest a modification to the <span class="emphsmallcaps">GROMOS</span> 45a4 parameter set which improves considerably the agreement of simulation results with theoretical and experimental estimates of puckering free energies. We also report on the experimental measurement of altrose conformer populations by means of NMR spectroscopy, which show good agreement with the predictions of current theoretical models.<div class="blogger-post-footer">Recent articles and reviews featuring solid-state NMR.</div>Kris Harrishttp://www.blogger.com/profile/16401554771902373385noreply@blogger.com0tag:blogger.com,1999:blog-19927787.post-34125926213169710362010-09-14T15:28:00.001-04:002010-09-14T15:29:43.629-04:00J. Phys. Chem. B and C, vol. 114, Issues 36Combined Solid-State NMR and Theoretical Calculation Studies of Brønsted Acid Properties in Anhydrous 12-Molybdophosphoric Acid<br /><br />Ningdong Feng†, Anmin Zheng*†, Shing-Jong Huang‡, Hailu Zhang§, Ningya Yu‡, Chih-Yi Yang‡, Shang-Bin Liu*‡, and Feng Deng*† <br /><br />J. Phys. Chem. C, 2010, 114 (36), pp 15464–15472<br />DOI: 10.1021/jp105683y<br />Publication Date (Web): August 20, 2010<br />Copyright © 2010 American Chemical Society<br /><br />Abstract: The strength and distribution of Brønsted acidic protons in anhydrous phosphomolybdic acid (H3PMo12O40, HPMo) have been studied by solid-state magic-angle-spinning (MAS) NMR, using trimethylphosphine oxide (TMPO) as the probe molecule in conjunction with density functional theory (DFT) calculations. Brønsted acid sties with strengths exceeding the threshold of superacidity (Zheng, A. et al. J. Phys. Chem. B 2008, 112, 4496) were observed for HPMo. In addition, the locations and adsorption structures of Brønsted protons on various oxygen sites in HPMo were also identified. The preferred location of the acidic proton was found to follow the trend: corner-sharing (Ob) > edge-sharing (Oc) terminal (Od) sites. Moreover, a tendency of hybridization among Brønsted protons residing at Ob and Oc sites of HPMo was inferred by experimental as well as theoretical 31P chemical shifts of the adsorbed TMPO.<div class="blogger-post-footer">Recent articles and reviews featuring solid-state NMR.</div>Aaronhttp://www.blogger.com/profile/10367130607577279623noreply@blogger.com0tag:blogger.com,1999:blog-19927787.post-68932976519506345332010-09-07T12:19:00.004-04:002010-09-14T15:14:25.255-04:00J. Phys. Chem. B and C, v114, Issues 32 - 35Structure and Disorder in Amorphous Alumina Thin Films: Insights from High-Resolution Solid-State NMR<br /><br />Sung Keun Lee*†, Sun Young Park†, Yoo Soo Yi† and Jaehyun Moon‡<br /><br />J. Phys. Chem. C, 2010, 114 (32), pp 13890–13894<br />Publication Date (Web): July 28, 2010<br /><br />Abstract:Revealing the extent of disorder in amorphous oxides is one of the remaining puzzles in physical chemistry, glass sciences, and geochemistry. Here, we report the 27Al NMR results for amorphous Al2O3 thin films obtained from two different deposition methods (i.e., physical vapor-deposition and atomic layer-deposition), revealing two distinct amorphous states defined by a fraction of five-coordinated Al ([5]Al). The fractions of [4]Al and [5]Al are dominant (92−95%) in both films. While the overall similarity between these two states suggests a narrow stability of available amorphous states, the fraction of [5]Al in atomic layer-deposited thin films is apparently larger and thus more disordered than that in physical vapor-deposited films. Such results require that varying extents of disorder exist in the amorphous oxides prepared under different processing conditions. As the [5]Al site (<1%) in crystalline Al2O3 is known to control its catalytic ability over [4]Al and [6]Al, the significant fractions (40%) of [5]Al in our amorphous thin films suggest that amorphous Al2O3 may be potentially useful as a new class of catalysts.<br /><br /><br /><br />X-ray Diffraction, FT-IR, and 13C CP/MAS NMR Structural Studies of Solvated and Desolvated C-Methylcalix[4]resorcinarene<br /><br />Rafal Kuzmicz†, Violetta Kowalska†, Sławomir Domagała‡, Marcin Stachowicz‡, Krzysztof Woniak‡ and Waclaw Kolodziejski*†<br /><br />J. Phys. Chem. B, 2010, 114 (32), pp 10311–10320<br />DOI: 10.1021/jp1015565<br />Publication Date (Web): July 26, 2010<br /><br />Abstract: Solid C-methylcalix[4]resorcinarene solvated by acetonitrile and water (CAL-Me) and then modified by slow solvent evaporation (CAL-Me*) was studied using single-crystal and powder X-ray diffraction, FT-IR, and 13C CP/MAS NMR. The CAL-Me solvate crystallizes in the monoclinic P21/n space group with three CH3CN and two H2O molecules in the asymmetric part of the unit cell. The CAL-Me molecules adopt a typical crown conformation with all of the hydroxyl groups of the aryl rings oriented up and all of the methyl groups disposed down (the rccc isomeric form). The crystalline network is formed by resorcinarene, CH3CN, and H2O molecules and assembled by intermolecular hydrogen bonds and weak C−H···A or C−H···π interactions. The desolvated CAL-Me* loses its crystalline character and becomes partly amorphous. It is devoid of CH3CN and deficient in water. However, the resorcinarene molecules still remain in the crown conformation supported by intramolecular hydrogen bonds, while intermolecular hydrogen bonds are considerably disintegrated. The work directs general attention to the problem of stability and polymorphism of resorcinarene solvates. It shows that the joint use of diffractometric and spectroscopic methods is advantageous in the structural studies of complex crystalline macromolecular systems. On the other hand, the solid-state IR and NMR spectroscopic analyses applied in tandem have been found highly beneficial to elucidate the disordered structure of poorly crystalline, desolvated resorcinarene<br /><br /><br /><br />Conformational Changes at Mesophase Transitions in a Ferroelectric Liquid Crystal by Comparative DFT Computational and 13C NMR Study<br /><br />Alberto Marini* and Valentina Domenici<br /><br />J. Phys. Chem. B, 2010, 114 (32), pp 10391–10400<br />DOI: 10.1021/jp105095m<br />Publication Date (Web): July 26, 2010<br /><br />Abstract: In this work, we report a detailed investigation on both the conformational and the orientational ordering properties of a ferroelectric liquid crystal mesogen, namely, M10/**, through the combination of high resolution solid state 13C NMR and density functional theory (DFT) computational methods. The trends of the observed 13C chemical shift in the blue, cholesteric, and ferroelectric SmC* phases of M10/** were analyzed in terms of conformational changes occurring in the flexible parts of the molecule. In particular, we focused on the aliphatic alpha methylenoxy carbons because of their high sensitivity to mesophase environment, as evidenced by experimental 13C chemical shift anisotropy (CSA). DFT computation of the chemical shift tensors as a function of geometrical parameters, such as dihedral angles, put in evidence significant changes in the average conformation at the mesophase transitions. The conformations predicted by DFT have been validated by comparing the calculated 13C chemical shifts with those experimentally observed for the alkoxylic carbons, whose relative orientation plays a key role in establishing the overall conformation of the molecule in each liquid crystalline phase. Furthermore, the orientational order parameters of the relevant flexible fragments were calculated and found to be in good agreement with those characterizing similar systems, thus validating our approach.<br /><br /><br /><br />Glass-to-Vitroceramic Transition in the Yttrium Aluminoborate System: Structural Studies by Solid-State NMR<br /><br />Heinz Deters†‡, Andrea S. S. de Camargo†§, Cristiane N. Santos§ and Hellmut Eckert*†<br /><br />J. Phys. Chem. C, 2010, 114 (34), pp 14618–14626<br />Publication Date (Web): August 6, 2010<br /><br />Abstract: The crystallization of laser glasses in the system (B2O3)0.6{(Al2O3)0.4−y(Y2O3)y} (0.1 ≤ y ≤ 0.25) doped with different levels of ytterbium oxide has been investigated by X-ray powder diffraction, differential thermal analysis, and various solid-state NMR techniques. The homogeneous glasses undergo major phase segregation processes resulting in crystalline YBO3, crystalline YAl3(BO3)4, and residual glassy B2O3 as the major products. This process can be analyzed in a quantitative fashion by solid-state 11B, 27Al, and 89Y NMR spectroscopies as well as 11B{27Al} rotational echo double resonance (REDOR) experiments. The Yb dopants end up in both of the crystalline components, producing increased line widths of the corresponding 11B, 27Al, and 89Y NMR resonances that depend linearly on the Yb/Y substitution ratio. A preliminary analysis of the composition dependence suggests that the Yb3+ dopant is not perfectly equipartitioned between both crystalline phases, suggesting a moderate preference of Yb to substitute in the crystalline YBO3 component<br /><br /><br /><br /><br />Chemical Degradation of Nafion Membranes under Mimic Fuel Cell Conditions as Investigated by Solid-State NMR Spectroscopy<br /><br />Lida Ghassemzadeh†‡, Klaus-Dieter Kreuer†, Joachim Maier† and Klaus Mller*§<br /><br />J. Phys. Chem. C, 2010, 114 (34), pp 14635–14645<br />Publication Date (Web): August 5, 2010<br /><br />Abstract: A new ex situ method has been developed to mimic the degradation of the polymer membranes in polymer electrolyte membrane fuel cells (PEMFCs), caused by the cross-leakage of H2 and O2. In this ex situ setup, it is possible to expose membranes to flows of different gases with a controlled temperature and humidity. H+-form Nafion films with and without an electrode layer (Pt) have been treated in the presence of different gases in order to simulate the anode and cathode side of a PEMFC. The changes of the chemical structure occurring during the degradation tests were primarily examined by solid-state 19F NMR spectroscopy. For completion, liquid-state NMR studies and ion-exchange capacity measurements were performed. The molecular mobility changes of the ionomer membrane upon degradation were examined for the first time by variable-temperature 19F NMR line-shape, T1 and T1ρ relaxation experiments. It was found that degradation occurs only when both H2 and O2 are present (condition of gas cross-leakage) and when the membrane is coated with a Pt catalyst. The chemical degradation rate is found to be highest for H2-rich mixtures of H2 and O2, which corresponds to the anode under OCV conditions. It is further shown that side-chain disintegration is very important for chemical degradation, although backbone decomposition also takes place. The temperature-dependent line-width and spectral anisotropy alterations were explained by the reduction of static disorder in the Nafion membrane. From the relaxation data, there is evidence for structural annealing, which is independent of the chemical degradation. Chemical degradation is considered to reduce the chain flexibility, as expressed by smaller motional amplitudes, most probably due to chain cross-linking.<br /><br /><br /><br /><br />Activation of Ammonia Borane Hybridized with Alkaline−Metal Hydrides: A Low-Temperature and High-Purity Hydrogen Generation Material<br /><br />Yu Zhang, Keiji Shimoda, Takayuki Ichikawa* and Yoshitsugu Kojima<br />J. Phys. Chem. C, 2010, 114 (34), pp 14662–14664<br />Publication Date (Web): August 5, 2010<br /><br />Abstract: Recently, alkali−metal amidoborane complexes have been highlighted as materials that satisfy many of the criteria required to make hydrogen-storage media. In this paper, ammonia borane was successfully activated by the existence of hybrid alkaline−metal hydrides. The desorption results showed that this activation strategy can significantly decrease the dehydrogenation temperature and, furthermore, can successfully suppress ammonia gas release and volume expansion. These results will be helpful for the design of future hydrogen-storage media.<br /><br /><br /><br />Solid-State 2H NMR and MD Simulations of Positional Isomers of a Monounsaturated Phospholipid Membrane: Structural Implications of Double Bond Location<br /><br />Stephen R. Wassall*†, M. Alan McCabe†, Cynthia D. Wassall†, Richard O. Adlof‡ and Scott E. Feller§ <br /><br />J. Phys. Chem. B, 2010, 114 (35), pp 11474–11483<br />DOI: 10.1021/jp105068g<br />Publication Date (Web): August 13, 2010<br />Copyright © 2010 American Chemical Society<br /><br />Abstract: The impact that the position of double bonds has upon the properties of membranes is investigated using solid-state 2H NMR and MD simulations to compare positional isomers of 1-palmitoyl-2-octadecenoylphosphatidylcholine (16:0-18:1PC) bilayers that are otherwise identical apart from the location of a single cis double bond at the Δ6, Δ9, Δ12, or Δ15 position in the 18:1 sn-2 chain. Moment analysis of 2H NMR spectra recorded for isomers perdeuterated in the 16:0 sn-1 chain reveals that average order parameters CD change by more than 35% and that the temperature for chain melting Tm varies by 40 °C. At equal temperature, the CD values exhibit a minimum, as do Tm values, when the double bond is in the middle of the 18:1 sn-2 chain and increase as it is shifted toward each end. Order parameter profiles generated from depaked (“dePaked”) spectra for the 16:0 sn-1 chain all possess the same shape with a characteristic “plateau” region of slowly decreasing order in the upper portion before progressively decreasing more in the lower portion. The NMR results are interpreted on the basis of MD simulation results obtained on each of the four systems. The simulations support the idea that the order parameter changes reflect differences in molecular surface areas, and furthermore that the molecular areas are a function of the strength of the acyl chain attractions.<br /><br /><br /><br />A Solid-State 17O NMR Study of l-Tyrosine in Different Ionization States: Implications for Probing Tyrosine Side Chains in Proteins<br /><br />Jianfeng Zhu, Justin Y. C. Lau and Gang Wu*<br />J. Phys. Chem. B, 2010, 114 (35), pp 11681–11688<br />DOI: 10.1021/jp1055123<br />Publication Date (Web): August 16, 2010<br />Copyright © 2010 American Chemical Society<br /><br />Abstract: We report experimental characterization of 17O quadrupole coupling (QC) and chemical shift (CS) tensors for the phenolic oxygen in three l-tyrosine (l-Tyr) compounds: l-Tyr, l-Tyr·HCl, and Na2(l-Tyr). This is the first time that these fundamental 17O NMR tensors are completely determined for phenolic oxygens in different ionization states. We find that, while the 17O QC tensor changes very little upon phenol ionization, the 17O CS tensor displays a remarkable sensitivity. In particular, the isotropic 17O chemical shift increases by approximately 60 ppm upon phenol ionization, which is 6 times larger than the corresponding change in the isotropic 13C chemical shift for the Cζ nucleus of the same phenol group. By examining the CS tensor orientation in the molecular frame of reference, we discover a “cross-over” effect between δ11 and δ22 components for both 17O and 13C CS tensors. We demonstrate that the knowledge of such “cross-over” effects is crucial for understanding the relationship between the observed CS tensor components and chemical bonding. Our results suggest that solid-state 17O NMR can potentially be used to probe the ionization state of tyrosine side chains in proteins.<div class="blogger-post-footer">Recent articles and reviews featuring solid-state NMR.</div>Aaronhttp://www.blogger.com/profile/10367130607577279623noreply@blogger.com0tag:blogger.com,1999:blog-19927787.post-17953252931209841682010-09-07T11:32:00.002-04:002010-09-07T11:43:06.898-04:00J. Chem. Phys.<a class="entry-title-link" target="_blank" href="http://link.aip.org/link/?JCP/133/094903/1&agg=rss">Self-diffusion of poly(propylene glycol) in nanoporous glasses studied by pulsed field gradient NMR: A study of molecular dynamics and surface interactions</a><br />A. Schonhals, F. Rittig, and J. Karger<br />Pulsed field gradient NMR is applied to investigate the self-diffusion of poly(proypylene glycol) in nanoporous glasses (nominal pore sizes of 2.5–7.5 nm). In general, the diffusion is slowed down by the confinement compared to the bulk. For native pore surfaces covered by hydroxyl groups the spin echo attenuation <span class="formula">Ψ</span> displays a bimodal behavior versus <span class="formula"><em class="emphitalic">q</em><sup class="emphsuperior">2</sup><em class="emphitalic">t</em></span> (<span class="formula"><em class="emphitalic">q</em></span>-norm of a generalized scattering vector). This was explained assuming spatial regions of different diffusivities in a two-phase model. The slow component is assigned to segments forming a surface layer close to the pore walls in which the segments have a lower mobility than those located in the center of the pores. By variation of observation time it was concluded that time constant for the dynamic exchange of segments between these two regions is around 100 ms at room temperature. For silanized pores, the bimodal behavior in the spin echo attenuation <span class="formula">Ψ</span> shows a stretched exponential decay versus <span class="formula"><em class="emphitalic">q</em><sup class="emphsuperior">2</sup><em class="emphitalic">t</em></span>. The estimated diffusion coefficients decrease strongly with decreasing pore size. The temperature dependence of the diffusion coefficient can be approximated by an Arrhenius law where the activation energy increases with decreasing pore size. The observed pore size dependence for the diffusion of poly(propylene glycol) in silanized nanoporous glasses can be discussed assuming interaction and confining size effects.<br /><br /><h2 class="entry-title"><a class="entry-title-link" target="_blank" href="http://link.aip.org/link/?JCP/133/084109/1&agg=rss">Dynamical effects in ab initio NMR calculations: Classical force fields fitted to quantum forces</a></h2>Mark Robinson and Peter D. Haynes<br />NMR chemical shifts for an <span class="emphsmallcaps">L</span>-alanine molecular crystal are calculated using <em class="emphitalic">ab initio</em> plane wave density functional theory. Dynamical effects including anharmonicity may be included by averaging chemical shifts over an ensemble of structural configurations generated using molecular dynamics (MD). The time scales required mean that <em class="emphitalic">ab initio</em> MD is prohibitively expensive. Yet the sensitivity of chemical shifts to structural details requires that the methodologies for performing MD and calculating NMR shifts be consistent. This work resolves these previously competing requirements by fitting classical force fields to reproduce <em class="emphitalic">ab initio</em> forces. This methodology is first validated by reproducing the averaged chemical shifts found using <em class="emphitalic">ab initio</em> molecular dynamics. Study of a supercell of <span class="emphsmallcaps">L</span>-alanine demonstrates that finite size effects can be significant when accounting for dynamics.<br /><br />s<div class="blogger-post-footer">Recent articles and reviews featuring solid-state NMR.</div>Kris Harrishttp://www.blogger.com/profile/16401554771902373385noreply@blogger.com0