Bryan's Extravagant Journal Update

Hi kids! It's all the news fit to print about NMR! You've paid for your whole seat but you'll only use the edge!!!

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Chemical Physics Vol: 344, Issue: 3, March 13, 2008, pp. 291-298

Dynamics of [Zn(D₂O)₆]^2^+ in [Zn(D₂O)₆][SiF₆] crystal as studied by 1D, 2D spectra and spin-lattice relaxation time of ^2H NMR
Araya, T.; Niwa, A.; Mizuno, M.; Endo, K.

Abstract: The dynamics of [Zn(D₂O)₆]^2^+ in [Zn(D₂O)₆][SiF₆] was investigated by ^2H NMR one-dimensional spectra, two-dimensional exchange spectra and spin-lattice relaxation time (T₁). The lineshapes of those spectra and T₁ were dominated by the 180^o flip of the water molecules and the reorientation of [Zn(D₂O)₆]^2^+ about the C₃ axis. The variation of lineshape of the one-dimensional spectrum below room temperature can be explained by only the 180^o flip of the water molecules. The spectrum at room temperature showed a typical shape due to the rapid 180^o flip of water molecules. The change in lineshape of the one-dimensional ^2H NMR spectrum is caused by the three-site jump of [Zn(D₂O)₆]^2^+ about its C₃ axis above 333K. Information of the reorientation of [Zn(D₂O)₆]^2^+ below 333K could not be obtained from the one-dimensional spectrum and T₁. In this temperature range, the two-dimensional exchange spectrum was effective for analysis of molecular motion. The effects of multiple motions, the 180^o flip of the water molecules and the reorientation of [Zn(D₂O)₆]^2^+ about the C₃ axis, on the lineshape of the two-dimensional exchange spectrum were studied using spectral simulation.

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Chemical Physics Vol: 344, Issue: 3, March 13, 2008, pp. 281-290

Inversion, internal rotation, and nitrogen nuclear quadrupole coupling of p-toluidine as obtained from microwave spectroscopy and ab initio calculations
Hellweg, A.

Abstract: A highly accurate combined experimental and theoretical investigation has been conducted on p-toluidine (4-methylaniline) in its vibrational and electronic ground state. Rotational transitions have been recorded using pulsed molecular beam Fourier transform microwave (MB-FTMW) spectroscopy in the frequency range 7-20GHz. The rotational spectrum of this molecule is complicated by the inversion of the amino group, the internal rotation of the methyl group, and the ^1^4N nuclear quadrupole hyperfine structure. Second-order Moller-Plesset perturbation theory and coupled-cluster singles-and-doubles with a perturbative correction for connected triples have been used in conjunction with high-level basis sets for the quantum chemical investigation. The torsional fine and quadrupole hyperfine structures of the spectra could be interpreted by means of these theoretical data.

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Chemical Physics Vol: 345, Issue: 1, April 3, 2008, pp. 116-118

The relationship between crystal structure and NMR relaxation in molecular solids with tert-butyl groups
Rheingold, A.L.; DiPasquale, A.G.; Beckmann, P.A.

Abstract: We correlate an X-ray determination of the molecular and crystal structures of 2-tert-butylanthracene and 2-tert-butylanthraquinone reported here with the previously reported dynamical nuclear magnetic resonance determination of the motions of the tert-butyl groups and their resident methyl groups in the solid state [P.A. Beckmann, K.S. Burbank, M.M.W. Lau, J.N. Ree, T.L. Weber, Chem. Phys. 290 (2003) 241]

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Chemical Physics Letters Vol: 451, Issue: 4-6, January 21, 2008, pp. 226-232

Solvent effects on zero-point vibrational corrections to optical rotations and nuclear magnetic resonance shielding constants
Kongsted, J.; Ruud, K.

Abstract: We present zero-point vibrational corrections to nuclear magnetic shielding constants and optical rotations of molecules in gas-phase and solution.

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Chemical Physics Letters Vol: 452, Issue: 4-6, February 11, 2008, pp. 233-238

Magic angle spinning (MAS) NMR linewidths in the presence of solid-state dynamics
Thrippleton, M.J.; Cutajar, M.; Wimperis, S.

Abstract: The failure of magic angle spinning (MAS) to achieve narrow NMR linewidths in the presence of solid-state dynamics is discussed.

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Chemical Physics Letters Vol: 454, Issue: 1-3, March 10, 2008, pp. 56-60

Orientational order of solutes in liquid crystals: The effect of distributed electric quadrupoles
Lee, J.S.J.; Sokolovskii, R.O.; Berardi, R.; Zannoni, C.; Burnell, E.E.

Abstract: The layout of electrical quadrupoles in acetylene, benzene, and 1,3,5-trifluorobenzene molecules.

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Chemical Physics Letters Vol: 454, Issue: 1-3, March 10, 2008, pp. 129-132

Density functionals for calculating NMR ^1J_CH coupling constants in electron-rich systems
Neto, A.C.; Santos, F.P.d.; Paula, A.S.; Tormena, C.F.; Rittner, R.

Abstract: Experimental and theoretically calculated ^1J_CH values, using several DFT exchange-correlation functionals, were obtained, compared and the results interpreted.

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Chem. Commun., 2008, 868 - 870, DOI: 10.1039/b716383e

Measuring nitrogen quadrupolar coupling with ¹³C detected wide-line ¹⁴N NMR under magic-angle spinning
Zhehong Gan

Abstract: A ¹³C-detected ¹⁴N wide-line NMR experiment is described for measuring nitrogen quadrupolar coupling under magic-angle spinning.

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Chem. Commun., 2008, 1621 - 1634, DOI: 10.1039/b711551b

Solid-state NMR studies of weak interactions in supramolecular systems
Michele R. Chierotti and Roberto Gobetto

Abstract: The field of application of solid-state NMR to the study of supramolecular systems is growing rapidly, with many research groups involved in the development of techniques for the study of crystalline and amorphous phases. This Feature Article aims to provide an overview of the recent contributions of our research group to this field, paying particular attention to the study of the weak interactions such as hydrogen bonds in supramolecular systems through solid-state NMR investigations. The structure and dynamic behaviour of selected host–guest systems will be also discussed. An overview of the characterization of supramolecular systems by means of solid-state NMR is presented: many parameters NMR have been discussed and particular attention has been given to the hydrogen-bond investigation and to the detection of molecular motion in the solid state.

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Dalton Trans., 2008, 1195 - 1202, DOI: 10.1039/b717390c

A benzene-core trinuclear Gd^III complex: towards the optimization of relaxivity for MRI contrast agent applications at high magnetic field
João Bruno Livramento, Lothar Helm, Angélique Sour, Conlin O'Neil, André E. Merbach and Éva Tóth

Abstract: A novel ligand, H₁₂L, based on a trimethylbenzene core bearing three methylenediethylenetriamine-N,N,N,N-tetraacetate moieties (–CH₂DTTA^4-) for Gd³⁺ chelation has been synthesized, and its trinuclear Gd³⁺ complex [Gd₃L(H₂O)₆]^3- investigated with respect to MRI contrast agent applications. A multiple-field, variable-temperature ¹⁷O NMR and proton relaxivity study on [Gd₃L(H₂O)₆]^3- yielded the parameters characterizing water exchange and rotational dynamics. On the basis of the ¹⁷O chemical shifts, bishydration of Gd³⁺ could be evidenced. The water exchange rate, k_ex²⁹⁸ = 9.0 ± 3.0 s^-1 is around twice as high as k_ex²⁹⁸ of the commercial [Gd(DTPA)(H₂O)]^2- and comparable to those on analogous Gd³⁺-DTTA chelates. Despite the relatively small size of the complex, the rotational dynamics had to be described with the Lipari–Szabo approach, by separating global and local motions. The difference between the local and global rotational correlation times, _lO²⁹⁸ = 170 ± 10 ps and _gO²⁹⁸ = 540 ± 100 ps respectively, shows that [Gd₃L(H₂O)₆]^3- is not fully rigid; its flexibility originates from the CH₂ linker between the benzene core and the poly(amino carboxylate) moiety. As a consequence of the two inner-sphere water molecules per Gd³⁺, their close to optimal exchange rate and the appropriate size and limited flexibility of the molecule, [Gd₃L(H₂O)₆]^3- has remarkable proton relaxivities when compared with commercial contrast agents, particularly at high magnetic fields (r₁ = 21.6, 17.0 and 10.7 mM^-1s^-1 at 60, 200 and 400 MHz respectively, at 25 °C; r₁ is the paramagnetic enhancement of the longitudinal water proton relaxation rate, referred to 1 mM concentration of Gd³⁺).

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Dalton Trans., 2008, 481 - 490, DOI: 10.1039/b712011g

A solid-state NMR investigation of single-source precursors for group 12 metal selenides; M[N(ⁱPr₂PSe)₂]₂ (M = Zn, Cd, Hg)
Bryan A. Demko and Roderick E. Wasylishen

Abstract: The first solid-state NMR investigation of dichalcogenoimidodiphosphinato complexes, M[N(R₂PE)₂]_n, is presented. The single-source precursors for metal-selenide materials, M[N(ⁱPr₂PSe)₂]₂ (M = Zn, Cd, Hg), were studied by solid-state ³¹P, ⁷⁷Se, ¹¹³Cd, and ¹⁹⁹Hg NMR at 4.7, 7.0, and 11.7 T, representing the only ⁷⁷Se NMR measurements, and in the case of Cd[N(ⁱPr₂PSe)₂]₂¹¹³Cd NMR measurements, to have been performed on these complexes. Residual dipolar coupling between ¹⁴N and ³¹P was observed in solid-state ³¹P NMR spectra at 4.7 and 7.0 T yielding average values of R(³¹P,¹⁴N)_eff = 880 Hz, C_Q(¹⁴N) = 3.0 MHz, ¹J(³¹P,¹⁴N)_iso = 15 Hz, = 90°, = 26°. The solid-state NMR spectra obtained were used to determine the respective phosphorus, selenium, cadmium, and mercury chemical shift tensors along with the indirect spin–spin coupling constants: ¹J(⁷⁷Se,³¹P)_iso, ¹J(^111/113Cd,⁷⁷Se)_iso, ¹J(¹⁹⁹Hg,⁷⁷Se)_iso, and ²J(¹⁹⁹Hg,³¹P)_iso. Density functional theory magnetic shielding tensor calculations were performed yielding the orientations of the corresponding chemical shift tensors. For this series of complexes the phosphorus magnetic shielding tensors are essentially identical, the selenium magnetic shielding tensors are also very similar with respect to each other, and the magnetic shielding tensors of the central metals, cadmium and mercury, display near axial symmetry demonstrating an expected deviation from local S₄ symmetry.

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J. Mater. Chem., 2008, 18, 894 - 904, DOI: 10.1039/b715319h

Preparation and photophysical characterisation of Zn–Al layered double hydroxides intercalated by anionic pyrene derivatives
Sandra Gago, Telma Costa, J. Seixas de Melo, Isabel S. Gonçalves and Martyn Pillinger

Abstract: Zn–Al hydrotalcite-like compounds intercalated by 1,3,6,8-pyrenetetrasulfonate (PTS), 1-pyrenesulfonate (PS) and 1-pyrenecarboxylate (PC) anions were synthesised by an ion-exchange procedure. The materials were characterised by powder X-ray diffraction at different temperatures, thermogravimetric analysis, FTIR, ¹³C{¹H} CP/MAS NMR and photoluminescence techniques. In the fully hydrated states, the interlayer distances are 13.7 Å for Zn–Al–PTS, 18.9 Å for Zn–Al–PS, and 24.8 Å for Zn–Al–PC. These can be ascribed to a monolayer arrangement for intercalated PTS anions and bilayer arrangements for the 1-pyrenyl derivatives. The samples exhibit different thermal decomposition pathways, and in the case of Zn–Al–PTS the removal of physisorbed and interlayer water leads to a change in the orientation of the organic anion with respect to the hydroxide layers. The structural transformation is fully reversible upon hydration. The photophysical characterisation of the bulk materials was based on the determination of their emission and fluorescence excitation spectra, and the fluorescence lifetimes. From the steady-state (monomer and excimer-like bands) and time-resolved (triple exponential decays) data, evidence for the presence of a structure with similar characteristics to pyrene dimer together with monomer (by comparison with the emission of dilute solutions of PS and PC), pre-associated and (possibly) dynamic excimer species could be presented.

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J. Mater. Chem., 2008, 18, 392 - 399, DOI: 10.1039/b714785f

Organosilicas based on purine–pyrimidine base pair assemblies: a solid state NMR point of view
Guilhem Arrachart, Carole Carcel, Joël J. E. Moreau, Geoffrey Hartmeyer, Bruno Alonso, Dominique Massiot, Gaëlle Creff, Jean-Louis Bantignies, Philippe Dieudonne, Michel Wong Chi Man, Gerhard Althoff, Florence Babonneau and Christian Bonhomme

Abstract: Organosilicas based on adenine (A) and thymine (T) assemblies have been synthesized. A surfactant-free route, based on specific molecular recognition between A and T entities, has been developed. The characterization of the H-bond networks, in both homo- and hetero-assemblies, has been emphasized by using ¹H solid state NMR (nuclear magnetic resonance). The latest experimental developments were implemented (i.e. very fast MAS (magic angle spinning) experiments at 750 MHz and 33 kHz), in order to enhance drastically the spectral resolution. Moreover, ¹H experiments at 67 kHz in 1.3 mm rotors were performed. Spatial connectivities between protons were established by using ¹H–¹H DQ (double quantum) MAS experiments, allowing the precise characterization of A/A, T/T and A/T associations.

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Joel's Journal Update

Not that much this time around. The following is not really SSNMR related, but it is an intriguing approach in determining shielding anisotropies.


An alternative NMR method to determine nuclear shielding anisotropies for molecules in liquid-crystalline solutions with 13C shielding anisotropy of methyl iodide as an example
Pekka Tallavaara and Jukka Jokisaari
PCCP(2008)10,1681.

Abstract:
An alternative NMR method for determining nuclear shielding anisotropies in molecules is proposed. The method is quite simple, linear and particularly applicable for heteronuclear spin systems. In the technique, molecules of interest are dissolved in a thermotropic liquid crystal (LC) which is confined in a mesoporous material, such as controlled pore glass (CPG) used in this study. CPG materials consist of roughly spherical particles with a randomly oriented and connected pore network inside. LC Merck Phase 4 was confined in the pores of average diameter from 81 to 375 and LC Merck ZLI 1115 in the pores of average diameter 81 . In order to demonstrate the functionality of the method, the 13C shielding anisotropy of 13C-enriched methyl iodide, 13CH3I, was determined as a function of temperature using one dimensional 13C NMR spectroscopy. Methane gas, 13CH4, was used as an internal chemical shift reference. It appeared that methyl iodide molecules experience on average an isotropic environment in LCs inside the smallest pores within the whole temperature range studied, ranging from bulk solid to isotropic phase. In contrast, in the spaces in between the particles, whose diameter is approximately 150 µm, LCs behave as in the bulk. Consequently, isotropic values of the shielding tensor can be determined from spectra arising from molecules inside the pores at exactly the same temperature as the anisotropic ones from molecules outside the pores. Thus, for the first time in the solution state, shielding anisotropies can easily be determined as a function of temperature. The effects of pore size as well as of different LC media on the shielding anisotropy are examined and discussed.

JMR - up to April 2008 - IUPAC NMR conventions

JMR - up to April 2008

Journal of Magnetic Resonance
Volume 191, Issue 2, April 2008, Pages 340-341

The only thing this month is another announcement on chemical shift tensor conventions from the IUPAC committee

doi:10.1016/j.jmr.2008.02.002
Copyright © 2008 Published by Elsevier Inc.

Announcement

Further conventions for NMR shielding and chemical shifts: IUPAC recommendations 2008

Full information can be found at:

http://www.iupac.org/publications/pac/80/1/0059/

Physical Review B – March 2008

Phys. Rev. B 77, 092103 (2008)
Ab initio investigation of intermolecular interactions in solid benzene
O. Bludský, M. Rubeš and P. Soldán

A computational strategy for the evaluation of the crystal lattice constants and cohesive energy of the weakly bound molecular solids is proposed. The strategy is based on the high level ab initio coupled-cluster determination of the pairwise additive contribution to the interaction energy. The zero-point-energy correction and nonadditive contributions to the interaction energy are treated using density functional methods. The experimental crystal lattice constants of the solid benzene are reproduced, and the value of 480 meV/molecule is calculated for its cohesive energy.


Phys. Rev. B 77, 094124 (2008)
Nuclear quadrupole interaction at 44Sc in the anatase and rutile modifications of TiO2: Time-differential perturbed-angular-correlation measurements and ab initio calculations
Seung-baek Ryu, Satyendra K. Das, Tilman Butz, Werner Schmitz, Christian Spiel, Peter Blaha, and Karlheinz Schwarz

The nuclear quadrupole interaction of the first excited I=1 state of 44Sc in the anatase and rutile modifications of bulk TiO2 was determined by time-differential perturbed-angular correlation of gamma rays. New LaBr3(Ce) scintillators with excellent energy resolution allowed us to separate the 68 and 78 keV lines of the gamma-gamma cascade. For anatase, an almost axially symmetric electric field gradient (EFG) with an asymmetry parameter of eta=0.10(1) and a nuclear quadrupole frequency of omega-Q=9.29(3) Mrad/s was obtained. For rutile, an almost antiaxial EFG with eta=0.94(1) and omega-Q=16.14(6) Mrad/s was obtained, which contradicts literature values. Ab initio calculations of the EFG using the WIEN2K code were performed for anatase and rutile for pure systems as well as for relevant impurities, such as Sc and Cd on Ti sites. The nuclear quadrupole moment of the I=1 state in 44Sc is redetermined with a sevenfold improved accuracy to be Q=±0.214(3) b.


Phys. Rev. B 77, 104301 (2008)
6Li and 7Li NMR line-shape and stimulated-echo studies of lithium ionic hopping in LiPO3 glass
Sandra Faske, Hellmut Eckert, and Michael Vogel

6Li and 7Li NMRs are used to investigate the lithium ion dynamics in LiPO3 glass. In particular, 6Li NMR stimulated-echo experiments are used to provide straightforward access to two-time correlation functions characterizing the lithium ionic hopping motion in the millisecond regime in a glassy ion conductor. Temperature-dependent measurements serve to separate the spin diffusion contribution and the dynamic contribution to the stimulated-echo decays. The 6Li NMR correlation functions of LiPO3 glass describing the lithium ionic motion show pronounced nonexponential decays, which can be well described by a stretched exponential function with a temperature-independent small stretching parameter beta=0.27, indicating the complex nature of the lithium dynamics. The temperature dependence of the mean correlation times tau resulting from these stimulated-echo experiments is described by an activation energy Ea=0.66 eV. The values of tau are in good agreement with time constants from previous electrical and mechanical relaxation studies. At appropriate temperatures, the 6Li and 7Li NMR spectra are superpositions of a broad and a narrow spectral component, which result from slow and fast lithium ions, respectively, on the NMR time scale. A detailed analysis of the temperature dependence of these line shapes provides information about the distribution of correlation times.


Phys. Rev. B 77, 104433 (2008)
Origin of the magnetic-field dependence of the nuclear spin-lattice relaxation in iron
G. Seewald, E. Zech, H.-J. Körner, D. Borgmann, and M. Dietrich

The magnetic-field dependence of the nuclear spin-lattice relaxation at Ir impurities in Fe was measured for fields between 0 and 2 T parallel to the [100] direction. The reliability of the applied technique of nuclear magnetic resonance on oriented nuclei was demonstrated by measurements at different radio-frequency (rf) field strengths. The interpretation of the relaxation curves, which used transition rates to describe the excitation of the nuclear spins by a frequency-modulated rf field, was confirmed by model calculations. The magnetic-field dependence of the so-called enhancement factor for rf fields, which is closely related to the magnetic-field dependence of the spin-lattice relaxation, was also measured. For several magnetic-field-dependent relaxation mechanisms, the form and the magnitude of the field dependence were derived. Only the relaxation via eddy-current damping and Gilbert damping could explain the observed field dependence. Using reasonable values of the damping parameters, the field dependence could perfectly be described. This relaxation mechanism is, therefore, identified as the origin of the magnetic-field dependence of the spin-lattice relaxation in Fe. The detailed theory, as well as an approximate expression, is derived, and the dependences on the wave vector, the resonance frequency, the conductivity, the temperature, and the surface conditions are discussed. The theory is related to previous attempts to understand the field dependence of the relaxation, and it is used to reinterpret previous relaxation experiments in Fe. Moreover, it is predicted that the field dependences of the relaxation in Fe and Co, on one side, and in Ni, on the other side, differ substantially, and it is suggested that the literature values of the high-field limits of the relaxation constants in Fe are slightly too large.

Hiyam's Journal update

J. Am. Chem. Soc., 130 (10), 3095 -3105, 2008.

Probing Local Structure in Zeolite Frameworks: Ultrahigh-Field NMR Measurements and Accurate First-Principles Calculations of Zeolite 29Si Magnetic Shielding Tensors
Darren H. Brouwer and Gary D. Enright

Abstract:
The principal components of zeolite 29Si magnetic shielding tensors have been accurately measured and calculated for the first time. The experiments were performed at an ultrahigh magnetic field of 21.1 T in order to observe the small anisotropies of the 29Si shielding interactions that arise for Si atoms in near-tetrahedral geometries. A robust two-dimensional (2D) chemical shift anisotropy (CSA) recoupling pulse sequence was employed that enables quasi-static powder patterns to be resolved according to the isotropic chemical shifts. For the zeolites Sigma-2 and ZSM-12, it is demonstrated that the 29Si chemical shift (CS) tensor components measured by the recoupling experiment are in excellent agreement with those determined from spinning sidebands in slow magic-angle spinning (MAS) experiments. For the zeolite ZSM-5, the principal components of the 29Si CS tensors of 15 of the 24 Si sites were measured using the 2D CSA recoupling experiment, a feat that would not be possible with a slow MAS experiment due to the complexity of the spectrum. A simple empirical relationship between the 29Si CS tensors and local structural parameters could not be established. However, the 29Si magnetic shielding tensors calculated using Hartree-Fock ab initio calculations on clusters derived from the crystal structures are in excellent agreement with the experimental results. The accuracy of the calculations is strongly dependent on the quality of the crystal structure used in the calculation, indicating that the 29Si magnetic shielding interaction is extremely sensitive to the local structure around each Si atom. It is anticipated that the measurement and calculation of 29Si shielding tensors could be incorporated into the "NMR crystallography" of zeolites and other related silicate materials, possibly being used for structure refinements that may lead to crystal structures with very accurate Si and O atomic coordinates.



J. Am. Chem. Soc., 130 (10), 2896 -2897, 2008.

Solid-State Deuterium NMR Studies Reveal s-ns Motions in the HIV-1 Transactivation Response RNA Recognition Site

Greg L. Olsen, Dorothy C. Echodu, Zahra Shajani, Michael F. Bardaro, Jr., Gabriele Varani, and Gary P. Drobny

Abstract:
Solution and solid-state NMR measurements were used together to examine motion in three sites in the HIV-1 TAR RNA. We wished to investigate the dynamics facilitating the conformational rearrangements the TAR RNA must undergo for Tat binding and in particular to characterize the full range of motional time scales accessible to this RNA. Our results demonstrate that the dynamics in TAR involving residues essential to Tat binding include not only the faster motions detected by solution relaxation measurements but also a significant component in the s-ns time scale.


Phys. Rev. B 77, 075421 (2008) (6 pages)

Highly rotational C60 dynamics inside single-walled carbon nanotubes: NMR observations
K. Matsuda, Y. Maniwa, and H. Kataura

Abstract
Rotational dynamics of C60 molecules composing a one-dimensional (1D) linear array inside single-walled carbon nanotubes have been investigated by 13C NMR in a temperature range from 4.2 to 300 K. The temperature dependence of the NMR lineshape and spin-lattice relaxation time (T1) indicate that the encapsulated C60 molecules exhibit a quasi-free-rotation with correlation times of 5–10 ps at 300 K. With decreasing temperature, the large amplitude molecular rotation continues to 30 K with an activation energy of 467 K. It is suggested that the C60 linear array does not undergo an orientational phase transition, which is associated with its 1D nature. Furthermore, no evidence for the polymerization of C60 molecules is found from the 13C NMR line shape analysis.

Chem. Soc. Rev. - up to Iss 3, 2008

Tutorial Review

Chem. Soc. Rev., 2008, 37, 518 - 526, DOI: 10.1039/b612793m

High resolution solid state NMR spectroscopy in surface organometallic chemistry: access to molecular understanding of active sites of well-defined heterogeneous catalysts
Frédéric Blanc, Christophe Copéret, Anne Lesage and Lyndon Emsley

Recent advances in solid state NMR spectroscopy have made possible the understanding of surface species and active sites of heterogeneous catalysts at a molecular level. This tutorial review describes solid state NMR spectroscopy, what are the possible techniques to obtain high resolution and 2D spectra (structural information), and what are their applications in the context of well-defined heterogeneous catalysts prepared by surface organometallic chemistry.

MRC - Special Issue: Biological Solids (April 2008)

Magnetic Resonance in Chemistry: Special Issue: Biological Solids (April 2008)

Volume 46 Issue 4 (April 2008)
Special Issue: Biological Materials
Issue Edited by Mark E. Smith

Editorial (p 307)
Mark E. Smith
Published Online: Feb 27 2008 10:19AM
DOI: 10.1002/mrc.2208

A solid-state 23Na NMR study of monovalent cation binding to double-stranded DNA at low relative humidity (p 308-315)
Alan Wong, Zhimin Yan, Yining Huang, Gang Wu
Published Online: Feb 27 2008 10:19AM
DOI: 10.1002/mrc.2136

Structures of the chain metaphosphates NaM(PO3)3 (M = Ca or Sr) (p 316-322)
I. Abrahams, G. E. Hawkes, A. Ahmed, T. Di Cristina, D. Z. Demetriou, G. I. Ivanova
Published Online: Feb 27 2008 10:19AM
DOI: 10.1002/mrc.2161

Towards a model of the mineral-organic interface in bone: NMR of the structure of synthetic glycosaminoglycan- and polyaspartate-calcium phosphate composites (p 323-329)
Serena M. Best, Melinda J. Duer, David G. Reid, Erica R. Wise, Shuo Zou
Published Online: Feb 27 2008 10:19AM
DOI: 10.1002/mrc.2168

Solid-state P-31 NMR study of the formation of hydroxyapatite in the presence of glutaric acid (p 330-334)
Yao-Hung Tseng, Yun Mou, Peng-Huan Chen, Tim W. T. Tsai, Cheng-I. Hsieh, Chung-Yuan Mou, Jerry C. C. Chan
Published Online: Feb 27 2008 10:19AM
DOI: 10.1002/mrc.2096

Kinetics of 1H rarr 31P NMR cross-polarization in bone apatite and its mineral standards (p 335-341)
Agnieszka Kaflak, Waclaw Kolodziejski
Published Online: Feb 27 2008 10:19AM
DOI: 10.1002/mrc.2207

Revisiting silicate substituted hydroxyapatite by solid-state NMR (p 342-346)
G. Gasquères, C. Bonhomme, J. Maquet, F. Babonneau, S. Hayakawa, T. Kanaya, A. Osaka
Published Online: Feb 27 2008 10:19AM
DOI: 10.1002/mrc.2109

Natural abundance 43Ca solid-state NMR characterisation of hydroxyapatite: identification of the two calcium sites (p 347-350)
Danielle Laurencin, Alan Wong, Ray Dupree, Mark E. Smith
Published Online: Feb 27 2008 10:19AM
DOI: 10.1002/mrc.2117

Variable angle spinning (VAS) experiments for strongly oriented systems: methods development and preliminary results (p 351-355)
Chunqi Qian, Pierre Thureau, Rachel W. Martin
Published Online: Feb 27 2008 10:19AM
DOI: 10.1002/mrc.2170

A computational study of 2JHH(gem) indirect spin-spin coupling constants in simple hydrides of the second and third periods (p 356-361)
Ibon Alkorta, Patricio F. Provasi, Gustavo A. Aucar, José Elguero
Published Online: Feb 13 2008 10:18AM
DOI: 10.1002/mrc.2181

Investigation of the dynamic stereochemistry of dimesityl-2,4,6-trimethoxyphenylmethane by complete lineshape analysis and 2D EXSY NMR spectroscopy (p 362-369)
Pavletta Denkova, Nikolay Vassilev, Luk Van Lokeren, Rudolph Willem
Published Online: Feb 13 2008 10:17AM
DOI: 10.1002/mrc.2183

Theoretical 13C chemical shift, 14N, and 2H quadrupole coupling- constant studies of hydrogen bonding in L-alanylglycine dipeptide (p 370-376)
M. Tafazzoli, S. K. Amini
Published Online: Feb 13 2008 10:17AM
DOI: 10.1002/mrc.2185


HSQC pulse sequences for 19F (p 377-380)
Bruce Adams
Published Online: Jan 28 2008 11:14AM
DOI: 10.1002

MRC - up to March 2008

Magnetic Resonance in Chemistry - up to March 2008

Magnetic Resonance in Chemistry
Volume 46, Issue 3 , Pages 206 - 214
A solid-state 53Cr NMR study of chromate and dichromate salts
Michelle A. M. Forgeron, Roderick E. Wasylishen *
Department of Chemistry, Gunning/Lemieux Chemistry Centre, University of Alberta, Edmonton, Alberta, T6G 2G2, Canada
Keywords solid-state NMR • low-gamma nuclei • quadrupolar nuclei • Cr-53 • electric field gradient (EFG) • magnetic shielding

Abstract
Solid-state 53Cr NMR spectra of a series of chromate (CrO42-) and dichromate (Cr2O72-) salts have been examined by employing the stepped-frequency quadrupolar Carr-Purcell Meiboom-Gill (QCPMG) experiment and high applied magnetic field strengths, 11.75 and 18.8 T. Cr-53 nuclear quadrupolar coupling constants, CQ(53Cr), ranging from 1.23 to 5.01 MHz for the CrO42- salts and 7.25 to 8.14 MHz for the Cr2O72- salts have been measured. For the dichromate salts, this corresponds to central transition 53Cr NMR lineshapes of 200-250 kHz at 18.8 T. The use of hyperbolic secant (HS) pulses in combination with the Hahn-echo (HE) or QCPMG experiment results in significant sensitivity enhancements when acquiring 53Cr NMR spectra of magic-angle spinning (MAS) samples, provided the MAS rate is fast with respect to the second-order quadrupolar interaction. For the CrO42- and Cr2O72- salts, the anisotropic chromium magnetic shielding interaction is generally negligible compared to the second-order 53Cr nuclear quadrupolar interaction. No simple correlation between the structure of the CrO42- and Cr2O72- anions and the observed CQ(53Cr) values has been found.
Digital Object Identifier (DOI) 10.1002/mrc.2164 About DOI

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Magnetic Resonance in Chemistry
Volume 46, Issue 3 , Pages 226 - 234
A solid-state 17O NMR study of L -phenylalanine and L -valine hydrochlorides
Kazuhiko Yamada 1 2 *, Tadashi Shimizu 1, Shinobu Ohki 1, Toshio Yamazaki 2
1National Institute for Materials Science, 3-13 Sakura, Tsukuba, Ibaraki 305-0003, Japan
2Protein Research Group, Genomic Sciences Center, Yokohama Institute, RIKEN
Keywords NMR • 17O • electric-field-gradient tensor • chemical-shielding tensor • amino acid hydrochloride • hydrogen bonds

Abstract
We have presented an experimental investigation of the oxygen-17 chemical shielding (CS) and electric-field-gradient (EFG) tensors for -COOH groups in polycrystalline amino acid hydrochlorides. The 17O CS and EFG tensors including the relative orientations between the two NMR tensors are determined in [17O]-L-phenylalanine hydrochloride and [17O]-L-valine hydrochloride by the analysis of the 17O magic-angle-spinning (MAS) and stationary NMR spectra obtained at 9.4, 11.7, 16.4, and 21.8 T. The quadrupole coupling constants (CQ) and the span of the CS tensors are found to be 8.41-8.55 MHz and 7.35-7.41MHz, and 548-570 ppm and 225-231 ppm, for carbonyl and hydroxyl oxygen atoms, respectively. Extensive quantum chemical calculations using density functional theory (DFT) have been also carried out for a hydrogen-bonding model. It is demonstrated that the behavior of the dependence of hydrogen-bond distances on 17O NMR tensors for the halogen ions is different from those for the water molecule.
Digital Object Identifier (DOI) - 10.1002/mrc.2167 About DOI

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Progress in NMR - up to Feb. 4, 2008

Progress in NMR - up to Feb. 4, 2008

An article by Gang Wu all about 17O SSNMR in organic and biomolecules: both experimental results and ab initio calculations are discussed.

Progress in Nuclear Magnetic Resonance Spectroscopy
Vol: 52, Issue: 2-3, February 4, 2008 pp. 118-169

Title: Solid-state 17O NMR studies of organic and biological molecules
Author: Wu, G.
# Item Identifier: S0079-6565(07)00062-3
Publication Type: Miscellaneous
ISSN: 0079-6565

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Concepts in NMR - up to 32A, 2008

Concepts in NMR - up to 32A, 2008

More on line broadening and uncertainty by Szántay, and a discussion on measurement of internuclear distances by Khitrin.

Concepts Magn Reson Part A 32A: 1-33, 2008.
NMR and the uncertainty principle: How to and how not to interpret homogeneous line broadening and pulse nonselectivity. II. The Fourier connection
Csaba Szántay Jr. *
Spectroscopic Research Division, Gedeon Richter Plc., H-1475 Budapest, 10, POB 27, Hungary
email: Csaba Szántay (cs.szantay@richter.hu)

Keywords uncertainty principle • Fourier analysis • Fourier transform

Abstract
By building on the nomenclature introduced and the fundamental ideas discussed in Part I, I now continue my preliminary review of the basic concepts we need for exploring the issues surrounding the uncertainty principles in the context of our Two NMR Problems (namely: both the essense of homogeneous NMR line broadening, as well as the fact that a short monochromatic RF pulse exhibits a polychromatic spectral bandwidth, and consequently gives a broad off-resonance NMR excitation band, are often rationalized in terms of a superficial and/or misguided use of the uncertainty principle). To that end, in Part II, I discuss Fourier theory in a way that is hoped to offer a number of delicate, important, and interesting insights that are usually not readily available from more conventional texts. © 2008 Wiley Periodicals, Inc.

Digital Object Identifier (DOI) 10.1002/cmr.a.20102

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Concepts Magn Reson Part A 32A: 56-67, 2008.
High-precision measurement of internuclear distances using solid-state NMR
Jae-Seung Lee *, Anatoly K. Khitrin
Department of Chemistry, Kent State University, Kent, OH 44242-0001
email: Jae-Seung Lee (jlee2@kent.edu)
Keywords heteronuclei • adiabatic cross-polarization • dipolar coupling • static solid • internuclear distance

Abstract
Today, nuclear magnetic resonance (NMR) is among the most efficient tools in structural studies. Measurement of interatomic distances is the most common way of determining high-resolution structures of molecules using NMR techniques. In this article, we describe NMR techniques for static powder samples, based on a two-dimensional single-echo scheme, enhanced with adiabatic cross-polarization. They can significantly increase the accuracy of measuring internuclear distances and turn NMR into a high-precision crystallographic technique, complementing the X-ray, and neutron-scattering methods. Experimental examples are presented for intramolecular CN and CC distances in -crystalline form of glycine. © 2008 Wiley Periodicals, Inc.
Received: 1 June 2007; Revised: 16 August 2007; Accepted: 20 August 2007
Digital Object Identifier (DOI) - 10.1002/cmr.a.20101 About DOI

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JMR - March 2008

Journal of Magnetic Resonance - up to March 2008

Includes two articles on 19F MAS NMR of amino acids by Anne Ulrich, effectiveness of 1H decoupling in 13C MAS NMR spectra of paramagnetic solids by Willans and Wasylishen, NMR expeirments using hybrid magnetic fields by Gan and co-workers, and Malcolm Levitt's ideas about singlet state NMR.

Journal of Magnetic Resonance
Vol: 191, Issue: 1, March, 2008 pp. 7-15

Title: Solid state 19F NMR parameters of fluorine-labeled amino acids. Part I: Aromatic substituents
Authors: Durr, U.H.N.; Grage, S.L.; Witter, R.; Ulrich, A.S.
Keywords: Fluorine; Solid state NMR; Amino acid; 19F chemical shift anisotropy
Abstract (English): Structural parameters of peptides and proteins in biomembranes can be directly measured by solid state NMR of selectively labeled amino acids. The ^1^9F nucleus is a promising label to overcome the low sensitivity of 2H, 13C or 15N, and to serve as a background-free reporter group in biological compounds. To make the advantages of solid state 19F NMR fully available for structural studies of polypeptides, we have systematically measured the chemical shift anisotropies and relaxation properties of the most relevant aromatic and aliphatic 19F-labeled amino acids. In this first part of two consecutive contributions, six different 19F-substituents on representative aromatic side chains were characterized as polycrystalline powders by static and MAS experiments. The data are also compared with results on the same amino acids incorporated in synthetic peptides. The spectra show a wide variety of lineshapes, from which the principal values of the CSA tensors were extracted. In addition, temperature-dependent T1 and T2 relaxation times were determined by 19F NMR in the solid state, and isotropic chemical shifts and scalar couplings were obtained in solution.
# Item Identifier: S1090-7807(07)00357-6
ISSN: 1090-7807

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Journal of Magnetic Resonance
Vol: 191, Issue: 1, March, 2008 pp. 16-23

Title: Solid state 19F NMR parameters of fluorine-labeled amino acids. Part II: Aliphatic substituents
Authors: Grage, S.L.; Durr, U.H.N.; Afonin, S.; Mikhailiuk, P.K.; Komarov, I.V.; Ulrich, A.S.
Keywords: Flourine; Solid state NMR; Amino acid; 19F chemical shift anisotropy
Abstract (English): A representative set of amino acids with aliphatic 19F-labels has been characterized here, following up our previous compilation of NMR parameters for single 19F-substituents on aromatic side chains. Their isotropic chemical shifts, chemical shift tensor parameters, intra-molecular 19F dipole-dipole couplings and temperature-dependent T1 and T2 relaxation times were determined by solid state NMR on twelve polycrystalline amino acid samples, and the corresponding isotropic 19F chemical shifts and scalar couplings were obtained in solution. Of particular interest are amino acids carrying a trifluoromethyl-group, because not only the 19F chemical shift but also the intra-CF3 homonuclear dipolar coupling can be used for structural studies of 19F-labeled peptides and proteins. The CF3-groups are further compared with CH2F-, CD2F-, and CD3-groups, using both 19F and 2H NMR to describe their motional behavior and to examine the respective linebroadening effects of the protonated and deuterated neighbors. We have also characterized two unnatural amino acids in which a CF3-label is rigidly connected to the backbone by a phenyl or bicyclopentyl moiety, and which are particularly well suited for structure analysis of membrane-bound polypeptides. The 19F NMR parameters of the polycrystalline amino acids are compared with data from the correspondingly labeled side chains in synthetic peptides.
# Item Identifier: S1090-7807(07)00356-4
ISSN: 1090-7807

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Journal of Magnetic Resonance
Vol: 191, Issue: 1, March, 2008 pp. 31-46

Title: The effectiveness of 1H decoupling in the 13C MAS NMR of paramagnetic solids: An experimental case study incorporating copper(II) amino acid complexes
Authors: Willans, M.J.; Sears, D.N.; Wasylishen, R.E.
Keywords: Heteronuclear decoupling; 13C solid-state NMR spectroscopy; Paramagnetic metal-organic complexes; Copper; Amino acids
Abstract (English): The use of continuous-wave (CW) 1H decoupling has generally provided little improvement in the 13C MAS NMR spectroscopy of paramagnetic organic solids. Recent solid-state 13C NMR studies have demonstrated that at rapid magic-angle spinning rates CW decoupling can result in reductions in signal-to-noise and that 1H decoupling should be omitted when acquiring 13C MAS NMR spectra of paramagnetic solids. However, studies of the effectiveness of modern 1H decoupling sequences are lacking, and the performance of such sequences over a variety of experimental conditions must be investigated before 1H decoupling is discounted altogether. We have studied the performance of several commonly used advanced decoupling pulse sequences, namely the TPPM, SPINAL-64, XiX, and eDROOPY sequences, in 13C MAS NMR experiments performed under four combinations of the magnetic field strength (7.05 or 11.75T), rotor frequency (15 or 30kHz), and 1H rf-field strength (71, 100, or 140kHz). The effectiveness of these sequences has been evaluated by comparing the 13C signal intensity, linewidth at half-height, LWHH, and coherence lifetimes, T2', of the methine carbon of copper(II) bis(dl-alanine) monohydrate, Cu(ala)2.H2O, and methylene carbon of copper(II) bis(dl-2-aminobutyrate), Cu(ambut)2, obtained with the advanced sequences to those obtained without 1H decoupling, with CW decoupling, and for fully deuterium labelled samples. The latter have been used as model compounds with perfect 1H decoupling and provide a measure of the efficiency of the 1H decoupling sequence. Overall, the effectiveness of 1H decoupling depends strongly on the decoupling sequence utilized, the experimental conditions and the sample studied. Of the decoupling sequences studied, the XiX sequence consistently yielded the best results, although any of the advanced decoupling sequences strongly outperformed the CW sequence and provided improvements over no 1H decoupling. Experiments performed at 7.05T demonstrate that the XiX decoupling sequence is the least sensitive to changes in the 1H transmitter frequency and may explain the superior performance of this decoupling sequence. Overall, the most important factor in the effectiveness of 1H decoupling was the carbon type studied, with the methylene carbon of Cu(ambut)2 being substantially more sensitive to 1H decoupling than the methine carbon of Cu(ala)2.H2O. An analysis of the various broadening mechanisms contributing to 13C linewidths has been performed in order to rationalize the different sensitivities of the two carbon sites under the four experimental conditions.
# Item Identifier: S1090-7807(07)00350-3
ISSN: 1090-7807

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Journal of Magnetic Resonance
Vol: 191, Issue: 1, March, 2008 pp. 135-140

Title: High-field NMR using resistive and hybrid magnets
Authors: Gan, Z.; Kwak, H.T.; Bird, M.; Cross, T.; Gor'kov, P.; Brey, W.; Shetty, K.
Keywords: High field; High resolution; MAS; Ferromagnetic shim; Field homogeneity; Stability; HENPEC; NHMFL; Resistive; Hybrid magnet
Abstract (English): Resistive and resistive-superconducting hybrid magnets can generate dc magnetic fields much higher than conventional superconducting NMR magnets but the field spatial homogeneity and temporal stability are usually not sufficient for high-resolution NMR experiments. Hardware and technique development addressing these issues are presented for high-resolution NMR at magnetic fields up to 40T. Passive ferromagnetic shimming and magic-angle spinning are used effectively to reduce the broadening from inhomogeneous magnetic field. A phase correction technique based on simultaneous heteronuclear detection is developed to compensate magnetic field fluctuations to achieve high spectral resolution.
# Item Identifier: S1090-7807(07)00373-4
ISSN: 1090-7807

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Journal of Magnetic Resonance
Vol: 191, Issue: 1, March, 2008 pp. 148-155

Title: Isotropic filtering using polyhedral phase cycles: Application to singlet state NMR
Authors: Pileio, G.; Levitt, M.H.
Keywords: Isotropic filtering; Singlet states; Long-lived spin states; Spherical tensor operators; Phase cycling
Abstract (English): A technique is described for filtering out the components of an NMR signal that have passed through an isotropic spin order term. The method involves a coordinated cycle of three radiofrequency phase angles, where two of the phases correspond to the polar angles describing the vertices of a regular polyhedron, and the third angle is stepped around a circle. The most economical isotropic filtering scheme involves a 12-step phase cycle based on tetrahedral symmetry. The method is used to filter out NMR signals that have passed through singlet populations in a solution NMR experiment.
# Item Identifier: S1090-7807(07)00361-8
ISSN: 1090-7807

Solid-State NMR - up to February 2008

Solid-State NMR - up to February 2008

Includes work on glasses by Brunet and Charpentier, 31P-Tl interactions in inorganic solids by Weliky, a multinuclear SSNMR study of sol-gels by O'Dell and Smith, and an evaluation of 17O EFG tensor parameters in L-alanine by Yamada.

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Solid State Nuclear Magnetic Resonance
Volume 33, Issues 1-2, January-February 2008, Pages 1-11
doi:10.1016/j.ssnmr.2007.12.001

Solid-state NMR characterization of a controlled-pore glass and of the effects of electron irradiation
F. Brunet, T. Charpentier, S. Le Caër and J.-P. Renault
a Laboratoire de Structure et de Dynamique par Résonance Magnétique CEA/Saclay, DSM/DRECAM/SCM URA 331 CNRS, F-91191 Gif-sur-Yvette, France
b Laboratoire de Radiolyse CEA/Saclay, DSM/DRECAM/SCM URA 331 CNRS, F-91191 Gif-sur-Yvette, France

Abstract
Controlled-pore glasses (CPGs) are silica-based materials which provide an adequate model system for a better understanding of the radiation chemistry of glasses, especially under nanoscopic confinement. This paper presents a characterization of a nanoporous CPG before and after electron irradiation using multinuclear solid-state magnetic resonance (NMR). 1H MAS NMR has been used for studying the surface proton sites and it is observed that the irradiation leads to a dehydration of the material. Accordingly, concerning the silicon sites near the surface, the observed variation of the Q4, Q3 and Q2 species from 1H–29Si CPMAS spectra shows an increase of the surface polymerization under irradiation, implying in majority a Q2 to Q3/Q4 conversion mechanism. Similarly, 1H–17O CPMAS measurements exhibit an increase of Si–O–Si groups at the expenses of Si–OH groups. In addition, modifications of the environment of the residual boron atoms are also put in evidence from 11B MAS and MQMAS NMR These data show that MAS NMR methods provide sensitive tools for the characterization of these porous glasses and of the tiny modifications occurring under electron irradiation.

Keywords: Solid-state NMR; Nanoporous controlled-pore glass; 1H; 29Si; 17O; 11B; Radiolysis

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Solid State Nuclear Magnetic Resonance
Volume 33, Issues 1-2, January-February 2008, Pages 12-15
doi:10.1016/j.ssnmr.2007.11.002
Improved resolution and detection of 31P–Tl J-couplings at 21 T in 31P magic angle spinning NMR spectra of inorganic compounds containing Tl/Bi/P/S
Matthew A. Gave, Kermit M. Johnson, Mercouri G. Kanatzidis and David P. Weliky
a Department of Chemistry, Michigan State University, East Lansing, MI 48824, USA
b Department of Chemistry, Northwestern University, Evanston, IL 60208, USA
Received 8 August 2007; revised 31 October 2007. Available online 13 November 2007.

Abstract
For crystalline compounds containing Tl, Bi, P, and S, greatly improved chemical shift resolution was observed in 31P magic angle spinning spectra obtained at 21 T relative to spectra obtained at 9.4 T. In Hz units, the spectral linewidths were not strongly dependent on the applied field, which may be a result of a significant contribution to the linewidths from transverse relaxation. Comparison of the spectra at the two different fields confirmed that spectral splittings were due to two-bond phosphorus–thallium J-coupling. These results suggest that ultra-high field may be a useful tool to improve spectral resolution of spin Click to view the MathML source nuclei in crystalline inorganic compounds.

Keywords: 31P; Solid state NMR; High field NMR; Ultra-high field NMR; 900 MHz; J-coupling; Inorganic; Resolution; Chalcophosphate; Thiophosphate

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Solid State Nuclear Magnetic Resonance
Volume 33, Issues 1-2, January-February 2008, Pages 16-24
doi:10.1016/j.ssnmr.2007.11.001

Characterisation of sol–gel prepared (HfO2)x(SiO2)1-x (x=0.1, 0.2 and 0.4) by 1H, 13C, 17O and 29Si MAS NMR, FTIR and TGA
Luke A. O'Dell, Philips N. Gunawidjaja, Mark A. Holland, Gavin Mountjoy, Dave M. Pickup, Robert J. Newport and Mark E. Smith, Corresponding Author Contact Information, E-mail The Corresponding Author
a Department of Physics, University of Warwick, Coventry CV4 7AL, UK
b School of Physical Sciences, University of Kent, Canterbury CT2 7NH, UK

Abstract
The HfO2–SiO2 system is attracting interest as a possible new dielectric material in semiconductor devices. Knowledge of the location of hafnium within the silica network and the effect hafnium has on the structure will be central to the successful use of this material system in this application. Here, sol–gel techniques have been used to manufacture (HfO2)x(SiO2)1-x samples (x=0.1, 0.2 and 0.4, each heat treated at 250, 500 and 750 °C) and these have been characterised by magic angle spinning (MAS) NMR (1H, 13C, 17O, 29Si), Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis. 29Si MAS NMR showed that increasing the hafnia content decreases the connectivity of the silicate network, i.e. increases the range of differently connected SiO4 (Qn) units with more having increased numbers of non-bridging oxygens (i.e. lower n). FTIR and 17O MAS NMR showed unequivocally that the x=0.4 sample phase-separated at higher temperatures, while in the x=0.1 sample the hafnium was homogeneously mixed into the SiO2 phase without any phase separation.

Keywords: 17O NMR; Sol–gel; Nanoscale phase separation; Inorganic materials

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Solid State Nuclear Magnetic Resonance
Volume 33, Issues 1-2, January-February 2008, Pages 25-30
doi:10.1016/j.ssnmr.2007.10.006

Experimental determination of orientations for the 17O electric-field-gradient and chemical shielding tensors in l-alanine
Kazuhiko Yamada, Tadashi Shimizu, Miwako Asanuma, Toshio Yamazaki and Shigeyuki Yokoyama
a Tsukuba Magnet Laboratory, National Institute for Materials Science, 3-13 Sakura, Tsukuba 305-0003, Japan
b Protein Research Group, Genomic Sciences Center, Yokohama Institute, RIKEN, 1-7-22 Suehiro, Tsurumi, Yokohama 230-0045, Japan
c Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan

Abstract
We have presented a solid-state 17O NMR study of [13C, 17O]-l-alanine. Using the experimental results for the 13C–17O dipolar vector and Euler angles, the absolute orientations of 17O chemical shielding (CS) and electric-field-gradient (EFG) tensors with respect to the molecular frame can be determined for l-alanine. The present results suggest that the intermediate EFG tensor components, VYY, lie in the carboxylate plane and parallel to the C–O bond directions, while the least shielded components, ?11, and the intermediate CS tensor components, ?22, roughly lie in the molecular plane and the direction of ?22 components are approximately 38° and 25° off the C–O bonds for O1 and O2, respectively. These results are in reasonable agreement with those of our quantum chemical calculations reported previously.

Keywords: Solid-state 17O NMR; Electric-field-gradient tensor; Chemical shielding tensor; 13C–17O dipolar vector

Hiyam's Journal update

Phys. Rev. Lett. 100, 087202 (2008)

17O NMR Study of the Intrinsic Magnetic Susceptibility and Spin Dynamics of the Quantum Kagome Antiferromagnet ZnCu3(OH)6Cl2
A. Olariu,1 P. Mendels,1 F. Bert,1 F. Duc,2 J. C. Trombe,2 M. A. de Vries,3 and A. Harrison3,4

We report, through 17O NMR, an unambiguous local determination of the intrinsic kagome lattice spin susceptibility as well as that created around nonmagnetic defects arising from natural Zn/Cu exchange in the S=1/2 (Cu2+) herbertsmithite ZnCu3(OH)6Cl2 compound. The issue of a singlet–triplet gap is addressed. The magnetic response around a defect is found to markedly differ from that observed in nonfrustrated antiferromagnets. Finally, we discuss our relaxation measurements in the light of Cu and Cl NMR data and suggest a flat q dependence of the excitations.




Phys. Rev. Lett. 100, 077203 (2008)

63Cu, 35Cl, and 1H NMR in the S= Kagome Lattice ZnCu3(OH)6Cl2
T. Imai,1,2 E. A. Nytko,3 B. M. Bartlett,3 M. P. Shores,3 and D. G. Nocera3

ZnCu3(OH)6Cl2 (S=) is a promising new candidate for an ideal Kagome Heisenberg antiferromagnet, because there is no magnetic phase transition down to ~50 mK. We investigated its local magnetic and lattice environments with NMR techniques. We demonstrate that the intrinsic local spin susceptibility decreases toward T=0, but that slow freezing of the lattice near ~50 K, presumably associated with OH bonds, contributes to a large increase of local spin susceptibility and its distribution. Spin dynamics near T=0 obey a power-law behavior in high magnetic fields.



J. Am. Chem. Soc., 130 (7), 2202 -2212, 2008. 10.1021/ja074244w S0002-7863(07)04244-8 Web Determination of Peptide Backbone Torsion Angles Using Double-Quantum Dipolar Recoupling Solid-State NMR Spectroscopy
Manish A. Mehta,* Matthew T. Eddy, Seth A. McNeill, Frank D. Mills, and Joanna R. Long*

Abstract:
Several approaches for utilizing dipolar recoupling solid-state NMR (ssNMR) techniques to determine local structure at high resolution in peptides and proteins have been developed. However, many of these techniques measure only one torsion angle or are accurate for only certain classes of secondary structure. Additionally, the efficiency with which these dipolar recoupling experiments suppress the deleterious effects of chemical shift anisotropy (CSA) at high magnetic field strengths varies. Dipolar recoupling with a windowless sequence (DRAWS) has proven to be an effective pulse sequence for exciting double-quantum (DQ) coherences between adjacent carbonyl carbons along the peptide backbone. By allowing this DQ coherence to evolve, it is possible to measure the relative orientations of the CSA tensors and subsequently use this information to determine the Ramachandran torsion angles and . Here, we explore the accuracies of the assumptions made in interpreting DQ-DRAWS data and demonstrate their fidelity in measuring torsion angles corresponding to a variety of secondary structures irrespective of hydrogen-bonding patterns. It is shown how a simple choice of isotopic labels and experimental conditions allows accurate measurement of backbone secondary structures without any prior knowledge. This approach is considerably more sensitive for determining structure in helices and has comparable accuracy for -sheet and extended conformations relative to other methods. We also illustrate the ability of DQ-DRAWS to distinguish between structures in heterogeneous samples.

Hiyam's Journal update

ASAP Chem. Mater., ASAP Article, 10.1021/cm702523d Web Release Date: February 29, 2008 Copyright © 2008 American Chemical Society
Determination and Quantification of the Local Environments in Stoichiometric and Defect Jarosite by Solid-State 2H NMR Spectroscopy

Ulla Gro Nielsen,†‡ Juraj Majzlan,§ and Clare P. Grey*†

Abstract:
The nature and concentrations of the local environments in a series of deuterated jarosite (nominally AFe3(SO4)2(OD)6 with A = K, Na, and D3O) samples with different levels of iron and cation vacancies have been determined by 2H MAS NMR spectroscopy at ambient temperatures. Three different local deuteron environments, Fe2OD, FeOD2, and D2O/D3O+, can be separated based on their very different Fermi contact shifts of δ ≈ 237, 70, and 0 ppm, respectively. The FeOD2 group arises from the charge compensation of the Fe3+ vacancies, allowing the concentrations of the vacancies to be readily determined. Analysis of the 2H quadrupole interaction indicates that the FeOD2 groups are mobile, undergoing rapid 180° flips on the NMR time scale; the D2O/D3O+ species (located on the A sites) undergo close to isotropic motion, whereas the Fe2OD groups are rigid and are hydrogen-bonded to nearby sulfate O atoms, with a (Fe)OD−O(S) distance of 2.79(4) Å. No evidence for the intrinsic protonation reaction Fe2OH + H3O+ → Fe2OH2 + H2O is found in the hydronium jarosite, suggesting that this mechanism is not the cause of the anomalous magnetic behavior of this material. The results illustrate that 2H MAS NMR spectroscopy is an excellent probe of the local environments and defects, on the atomic/molecular level, providing information that is complementary to diffraction techniques and that will help to rationalize the magnetic properties of these materials.

J. Am. Chem. Soc., ASAP Article 10.1021/ja709975z S0002-7863(70)09975-4 Web Release Date: February 23, 2008 Copyright © 2008 American Chemical Society
Direct NMR Detection of Alkali Metal Ions Bound to G-Quadruplex DNA
Ramsey Ida and Gang Wu*

Abstract:
We describe a general multinuclear (1H, 23Na, 87Rb) NMR approach for direct detection of alkali metal ions bound to G-quadruplex DNA. This study is motivated by our recent discovery that alkali metal ions (Na+, K+, Rb+) tightly bound to G-quadruplex DNA are actually "NMR visible" in solution (Wong, A.; Ida, R.; Wu, G. Biochem. Biophys. Res. Commun. 2005, 337, 363). Here solution and solid-state NMR methods are developed for studying ion binding to the classic G-quadruplex structures formed by three DNA oligomers: d(TG4T), d(G4T3G4), and d(G4T4G4). The present study yields the following major findings. (1) Alkali metal ions tightly bound to G-quadruplex DNA can be directly observed by NMR in solution. (2) Competitive ion binding to the G-quadruplex channel site can be directly monitored by simultaneous NMR detection of the two competing ions. (3) Na+ ions are found to locate in the diagonal T4 loop region of the G-quadruplex formed by two strands of d(G4T4G4). This is the first time that direct NMR evidence has been found for alkali metal ion binding to the diagonal T4 loop in solution. We propose that the loop Na+ ion is located above the terminal G-quartet, coordinating to four guanine O6 atoms from the terminal G-quartet and one O2 atom from a loop thymine base and one water molecule. This Na+ ion coordination is supported by quantum chemical calculations on 23Na chemical shifts. Variable-temperature 23Na NMR results have revealed that the channel and loop Na+ ions in d(G4T4G4) exhibit very different ion mobilities. The loop Na+ ions have a residence lifetime of 220 s at 15 C, whereas the residence lifetime of Na+ ions residing inside the G-quadruplex channel is 2 orders of magnitude longer. (4) We have found direct 23Na NMR evidence that mixed K+ and Na+ ions occupy the d(G4T4G4) G-quadruplex channel when both Na+ and K+ ions are present in solution. (5) The high spectral resolution observed in this study is unprecedented in solution 23Na NMR studies of biological macromolecules. Our results strongly suggest that multinuclear NMR is a viable technique for studying ion binding to G-quadruplex DNA.

Joel's Journal Update

Spin-counting NMR experiments for the spectral editing of structural motifs in solids
Michaël Deschamps, Franck Fayon, Julien Hiet, Geoffroy Ferru, Marc Derieppe, Nadia Pellerin and Dominique Massiot
PCCP(2008)10,1298.
Abstract:
Scalar couplings, recoupled or full dipolar interactions can be used to characterize multinuclear structural molecular motifs in solids, by counting the neighbouring spins in solid-state NMR, opening new ways for the differentiation of overlapping spectral responses which is a limiting factor in many high resolution experiments carried out on disordered systems.

Experimental and Computational Characterization of the 17O Quadrupole Coupling and Magnetic Shielding Tensors or p-Nitrobenzaldehyde and Formaldehyde.
Gang Wu, Peter Mason, Xin Mo, and Victor Terskikh
JPCA(2008)112,1024.
Abstract:
We have used solid-state 17O NMR experiments to determine the 17O quadrupole coupling (QC) tensor and chemical shift (CS) tensor for the carbonyl oxygen in p-nitro-[1-17O]benzaldehyde. Analyses of solid-state 17O NMR spectra obtained at 11.75 and 21.15 T under both magic-angle spinning (MAS) and stationary conditions yield the magnitude and relative orientation of these two tensors: CQ = 10.7 ± 0.2 MHz, Q = 0.45 ± 0.10, 11 = 1050 ± 10, 22 = 620 ± 10, 33 = -35 ± 10, = 90 ± 10, = 90 ± 2, = 90 ± 10. The principal component of the 17O CS tensor with the most shielding, 33, is perpendicular to the H-C=O plane, and the tensor component with the least shielding, 11, lies along the C=O bond. For the 17O QC tensor, the largest (zz) and smallest (xx) components are both in the H-C=O plane being perpendicular and parallel to the C=O bond, respectively. This study represents the first time that these two fundamental 17O NMR tensors have been simultaneously determined for the carbonyl oxygen of an aldehyde functional group by solid-state 17O NMR. The reported experimental solid-state 17O NMR results provide the first set of reliable data to allow evaluation of the effect of electron correlation on individual CS tensor components. We found that the electron correlation effect exhibits significant influence on 17O chemical shielding in directions within the H-C=O plane. We have also carefully re-examined the existing experimental data on the 17O spin-rotation tensor for formaldehyde and proposed a new set of best "experimental" 17O chemical shielding tensor components: 11 = -1139 ± 80, 22 = -533 ± 80, 33 = 431 ± 5, and iso = -414 ± 60 ppm. Using this new set of data, we have evaluated the accuracy of quantum chemical calculations of the 17O CS tensors for formaldehyde at the Hartree-Fock (HF), density-functional theory (DFT), Mller-Plesset second-order perturbation (MP2), and coupled-cluster singles and doubles (CCSD) levels of theory. The conclusion is that, while results from HF and DFT tend to underestimate the electron correlation effect, the MP2 method overestimates its contribution. The CCSD results are in good agreement with the experimental data.

Proton Spin Diffusion in Polyethylene as a Function of Magic-Angle Spinning Rate. A Phenomenological Approach.
Zhenlong Jia, Lili Zhang, Qun Chen, and E. W. Hansen
JPCA(2008)112,1228.
Abstract:
Starting from the phenomenological Bloembergen-Purcell-Pound equation a relation between magic-angle spinning (MAS) rate and spin diffusion is derived. The resulting model equation was fitted to observed spin diffusion versus MAS rate data obtained at 298 K on an high-density polyethylene sample, revealing a reduction in the effective spin diffusivity by (65 + 5)% when increasing the MAS rate from 2 to 12 kHz. The same model equation enabled the rigid-lattice diffusivity to be estimated and was found to be only slightly higher, by approximately 10%, compared to the spin diffusivity observed at the lowest MAS rate applied (2 kHz). Moreover, the model equation predicts a reduction in the effective spin diffusivity by more than 90% when increasing the MAS rate to more than 30 kHz.

Hiyam's Journal Update

Low-lying excitations at the rare-earth site due to the rattling motion in the filled skutterudite LaOs4Sb12 revealed by 139La NMR and 121/123Sb NQR
Yusuke Nakai,1 Kenji Ishida,1 Hitoshi Sugawara,2 Daisuke Kikuchi,3 and Hideyuki Sato3

Abstract
We report experimental results of nuclear magnetic resonance (NMR) at the La site and nuclear quadrupole resonance (NQR) at the Sb site in the filled skutterudite LaOs4Sb12. We found that the nuclear spin-lattice relaxation rate divided by temperature 1/T1T at the La site exhibits a different temperature dependence from that at the Sb site. Although 1/T1T at the Sb site is explained by the Korringa mechanism, 1/T1T at the La site exhibits a broad maximum around 50 K, showing the presence of an additional contribution at the La site. The additional low-lying excitations observed at the La site can be understood with the relaxation from anharmonic phonons due to the rattling motion of the La atoms.


Phys. Rev. B 77, 014412 (2008) (10 pages)

17O and 51V NMR for the zigzag spin-1 chain compound CaV2O4
X. Zong,1,2 B. J. Suh,1 A. Niazi,1 J. Q. Yan,1 D. L. Schlagel,3 T. A. Lograsso,3 and D. C. Johnston1,2
1Ames Laboratory, Ames, Iowa 50011, USA

Abstract
51V NMR studies on CaV2O4 single crystals and 17O NMR studies on 17O-enriched powder samples are reported. The temperature dependences of the 17O NMR linewidth and nuclear spin-lattice relaxation rate give strong evidence for a long-range antiferromagnetic transition at TN=78 K in the powder. Magnetic susceptibility measurements show that TN=69 K in the crystals. A zero-field 51V NMR signal was observed at low temperatures (f237 MHz at 4.2 K) in the crystals. The field-swept spectra with the field in different directions suggest the presence of two antiferromagnetic substructures. Each substructure is collinear, with the easy axes of the two substructures separated by an angle of 19(1)°, and with their average direction pointing approximately along the b axis of the crystal structure. The two spin substructures contain equal numbers of spins. The temperature dependence of the ordered moment, measured up to 45 K, shows the presence of an energy gap EG in the antiferromagnetic spin wave excitation spectrum. Antiferromagnetic spin wave theory suggests that EG/kB lies between 64 and 98 K.


J. Am. Chem. Soc., ASAP Article 10.1021/ja0778803 S0002-7863(07)07880-8 Web Release

Solid-State Deuterium NMR Studies Reveal s-ns Motions in the HIV-1 Transactivation Response RNA Recognition Site
Greg L. Olsen, Dorothy C. Echodu, Zahra Shajani, Michael F. Bardaro, Jr., Gabriele Varani, and Gary P. Drobny*

Abstract:
Solution and solid-state NMR measurements were used together to examine motion in three sites in the HIV-1 TAR RNA. We wished to investigate the dynamics facilitating the conformational rearrangements the TAR RNA must undergo for Tat binding and in particular to characterize the full range of motional time scales accessible to this RNA. Our results demonstrate that the dynamics in TAR involving residues essential to Tat binding include not only the faster motions detected by solution relaxation measurements but also a significant component in the s-ns time scale.


J. Am. Chem. Soc., 130 (8), 2667 -2675, 2008. 10.1021/ja078337p S0002-7863(07)08337-0 Web Release Date: February 1, 2008 Copyright © 2008 American Chemical Society

Probing Chemical Shifts of Invisible States of Proteins with Relaxation Dispersion NMR Spectroscopy: How Well Can We Do?
D. Flemming Hansen, Pramodh Vallurupalli, Patrik Lundström, Philipp Neudecker, and Lewis E. Kay*

Abstract:
Carr-Purcell-Meiboom-Gill relaxation dispersion NMR spectroscopy has evolved into a powerful approach for the study of low populated, invisible conformations of biological molecules. One of the powerful features of the experiment is that chemical shift differences between the exchanging conformers can be obtained, providing structural information about invisible excited states. Through the development of new labeling approaches and NMR experiments it is now possible to measure backbone 13C and 13CO relaxation dispersion profiles in proteins without complications from 13C-13C couplings. Such measurements are presented here, along with those that probe exchange using 15N and 1HN nuclei. A key experimental design has been the choice of an exchanging system where excited-state chemical shifts were known from independent measurement. Thus it is possible to evaluate quantitatively the accuracy of chemical shift differences obtained in dispersion experiments and to establish that in general very accurate values can be obtained. The experimental work is supplemented by computations that suggest that similarly accurate shifts can be measured in many cases for systems with exchange rates and populations that fall within the range of those that can be quantified by relaxation dispersion. The accuracy of the extracted chemical shifts opens up the possibility of obtaining quantitative structural information of invisible states of the sort that is now available from chemical shifts recorded on ground states of proteins.

J. Am. Chem. Soc., 130 (8), 2432 -2433, 2008. 10.1021/ja710477h S0002-7863(71)00477-3 Web Release Date: February 5, 2008 Copyright © 2008 American Chemical Society
Accurately Probing Slow Motions on Millisecond Timescales with a Robust NMR Relaxation Experiment
Dong Long, Maili Liu, and Daiwen Yang*

Abstract:
A new pulse scheme is proposed for the accurate measurement of relaxation dispersion, which cycles the phases of CPMG pulses. Numerical simulations show that systematic errors in the measured relaxation rates mainly result from off-resonance and radio frequency inhomogeneity effects and they can be significantly suppressed with the method proposed here. The method has been demonstrated on human liver fatty acid binding protein. It allows the reliable identification of residues undergoing conformational exchange on millisecond timescales and accurate extraction of kinetics parameters. The relaxation dispersion data indicate that human liver fatty acid binding protein is highly flexible on millisecond timescales.



J. Am. Chem. Soc., 130 (8), 2412 -2413, 2008. 10.1021/ja710557t S0002-7863(71)00557-2 Web Release Date: February 1, 2008 Copyright © 2008 American Chemical Society
A High-Resolution 43Ca Solid-State NMR Study of the Calcium Sites of Hydroxyapatite

Danielle Laurencin, Alan Wong, John V. Hanna, Ray Dupree, and Mark E. Smith*

Abstract:
High resolution 43Ca solid-state NMR studies of hydroxyapatite (Ca10(PO4)6(OH)2) were performed at 14.1 T. The two crystallographically distinct calcium sites were unequivocally resolved by a triple-quantum magic angle spinning experiment, and the unambiguous assignment of the signals was possible using 1H-43Ca rotational echo double resonance and 1H-43Ca cross polarization magic angle spinning experiments.


J. Am. Chem. Soc., ASAP Article 10.1021/

Probing Local Structure in Zeolite Frameworks: Ultrahigh-Field NMR Measurements and Accurate First-Principles Calculations of Zeolite 29Si Magnetic Shielding Tensors
Darren H. Brouwer* and Gary D. Enright

Abstract:
The principal components of zeolite 29Si magnetic shielding tensors have been accurately measured and calculated for the first time. The experiments were performed at an ultrahigh magnetic field of 21.1 T in order to observe the small anisotropies of the 29Si shielding interactions that arise for Si atoms in near-tetrahedral geometries. A robust two-dimensional (2D) chemical shift anisotropy (CSA) recoupling pulse sequence was employed that enables quasi-static powder patterns to be resolved according to the isotropic chemical shifts. For the zeolites Sigma-2 and ZSM-12, it is demonstrated that the 29Si chemical shift (CS) tensor components measured by the recoupling experiment are in excellent agreement with those determined from spinning sidebands in slow magic-angle spinning (MAS) experiments. For the zeolite ZSM-5, the principal components of the 29Si CS tensors of 15 of the 24 Si sites were measured using the 2D CSA recoupling experiment, a feat that would not be possible with a slow MAS experiment due to the complexity of the spectrum. A simple empirical relationship between the 29Si CS tensors and local structural parameters could not be established. However, the 29Si magnetic shielding tensors calculated using Hartree-Fock ab initio calculations on clusters derived from the crystal structures are in excellent agreement with the experimental results. The accuracy of the calculations is strongly dependent on the quality of the crystal structure used in the calculation, indicating that the 29Si magnetic shielding interaction is extremely sensitive to the local structure around each Si atom. It is anticipated that the measurement and calculation of 29Si shielding tensors could be incorporated into the "NMR crystallography" of zeolites and other related silicate materials, possibly being used for structure refinements that may lead to crystal structures with very accurate Si and O atomic coordinates.


ASAP Chem. Mater., ASAP Article, 10.1021/cm0717763 Web Release Date: February 16, 2008 Copyright © 2008 American Chemical Society
A Solid-State NMR, X-ray Diffraction, and Ab Initio Investigation into the Structures of Novel Tantalum Oxyfluoride Clusters

Todd M. Alam,*† Jacalyn S. Clawson,†‡ François Bonhomme,† Steven G. Thoma,† Mark A. Rodriguez,† Shaohui Zheng,§ and Jochen Autschbach§

Abstract:
A series of tantalum oxyfluoride materials containing the [Ta4F16O4]4− and [Ta8F24O12]8− anion clusters have been synthesized and characterized using X-ray diffraction (XRD) and solid-state nuclear magnetic resonance (SSNMR) spectroscopy. The structure of both tantalum oxyfluoride materials display octahedrally bonded tantalum atoms with bridging oxygen and terminal fluoride atoms. The [Ta4F16O4]4− cluster is an eight-membered ring, whereas the [Ta8F24O12]8- cluster forms a cagelike structure. Solid-state dynamics of these clusters were explored by monitoring the impact of temperature on the one-dimensional (1D) 19F magic angle spinning (MAS) NMR, 13C cross-polarization (CP) MAS NMR, and two-dimensional (2D) double quantum (DQ) 19F MAS NMR spectra. The DQ 19F NMR correlation experiments allowed the through space connectivity between the different resolved fluorine environments to be determined, thus aiding in the spectral assignment and structural refinement of these materials. Ab initio 19F NMR chemical shift calculations were used to assist in the interpretation of the 19F NMR spectra. The influence of scalar relativistic and Ta−F spin–orbit coupling on the 19F NMR shielding calculation arising from bonding to tantalum atoms is also addressed.