SSNMR update: up to Volume 35, Issue 4, July 2009, Pages 208-213

SSNMR update: up to Volume 35, Issue 4, July 2009, Pages 208-213
Highlights include:
- deconvolution of CP/MAS NMR data sets
- using polyethylene glycol to prevent sample decomposition during MAS
- Ram's review of antimicrobial peptides
- some new 25Mg NMR of metals from T.J. Bastow
- QUADFIT, a new program from M.E. Smith's group
- 13C MAS NMR of surgical sutures
- an XML program for designing cogwheel phase cycles

Solid State Nuclear Magnetic Resonance
Volume 35, Issue 4, July 2009, Pages 208-213
doi:10.1016/j.ssnmr.2009.04.001

Spectral deconvolution of NMR cross polarization data sets

Niklas Hedin, Jovice B.S. Ng and Peter Stilbs

Abstract
The COmponent-REsolved (CORE) strategy has been employed, for the first time to solid state NMR spectroscopy. CORE was used to extract two time-dependent spectral components in 24 29Si{1H} NMR spectra, recorded on a meso-structured silica material under conditions of cross polarization evolution. No prior assumptions were made about the component bandshapes, which were both found to be skewed to higher chemical shifts. For the silica fragments close to protons this skewness could be rationalized by a distribution of the degree of condensation in the silica network; however, for the other component the non-Gaussian shape was unexpected. We expect that the same strategy could be applied to a range of experiments in solid-state NMR spectroscopy, where spectral distributions or kinetic parameters need to be accurately extracted.

Keywords: Multivariate analysis; Cross polarization; Deconvolution; Si-29; Mesoporous

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Solid State Nuclear Magnetic Resonance
Volume 35, Issue 4, July 2009, Pages 214-216
doi:10.1016/j.ssnmr.2009.03.002

Zhen Wu and Shangwu Ding

Abstract
A simple solution is proposed to prevent a solid state polycrystalline sample from deterioration during long time high speed spinning experiments in solid state NMR. It is found that if a certain percentage (not, vert, similar40% volume) of polyethylene glycol (PEG, (HO–CH2–(CH2–O–CH2–)n–CH2–OH)n) is mixed with the sample that are subject to deterioration, the quality of the sample can be maintained for a long time under high speed spinning for a few days or longer, sufficient for multi-dimensional and/or low-sensitivity experiments. Both 1D and 2D experimental results are shown to support this idea.

Keywords: Magic angle spinning; Sample deterioration; Quadrupolar nuclei; Multiple quantum magic angle spinning; Polyethylene glycol

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Solid State Nuclear Magnetic Resonance
Volume 35, Issue 4, July 2009, Pages 201-207

Review
Beyond NMR spectra of antimicrobial peptides: Dynamical images at atomic resolution and functional insights

Ayyalusamy Ramamoorthy

Abstract
There is a considerable current interest in understanding the function of antimicrobial peptides for the development of potent novel antibiotic compounds with a very high selectivity. Since their interaction with the cell membrane is the major driving force for their function, solid-state NMR spectroscopy is the unique method of choice to study these insoluble, non-crystalline, membrane-peptide complexes. Here I discuss solid-state NMR studies of antimicrobial peptides that have reported high-resolution structure, dynamics, orientation, and oligomeric states of antimicrobial peptides in a membrane environment, and also address important questions about the mechanism of action at atomic-level resolution. Increasing number of solid-state NMR applications to antimicrobial peptides are expected in the near future, as these compounds are promising candidates to overcome ever-increasing antibiotic resistance problem and are well suited for the development and applications of solid-state NMR techniques.

Keywords: Antimicrobial peptides; Membrane; Bilayers; Solid-state NMR

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Solid State Nuclear Magnetic Resonance
Volume 35, Issue 4, July 2009, Pages 217-222
doi:10.1016/j.ssnmr.2009.02.002

25Mg NMR site analysis in metals and intermetallics

T.J. Bastow and S. Celotto

Abstract
Nuclear magnetic resonance (NMR) of the low abundance and low gyromagnetic ratio isotope 25Mg, I=5/2, 2.606 MHz/T, 10% abundant, is shown here to provide an informative probe for phase identification, site symmetry and site multiplicity of the intermetallic compounds which occur as strengthening precipitate phases in lightweight alloys. The intermetallics discussed here, Mg17Al12, MgZn2, Mg2Al3 and Al2CuMg, are the final equilibrium precipitate phases in a number of Mg- and Al-based heat-treatable alloys. The 25Mg spectra of Mg in Al–10 at%Mg alloy show the progressive precipitation of Mg2Al3 from Mg in solid solution as a function of annealing time at 150 °C. Also reported are 25Mg spectra for CuMg2, Mg44Al15Zn41 and Mg2Sn, along with the counter atom 67Zn and 63Cu NMR spectra for MgZn2 and CuMg2. All spectra are simulated to determine nuclear interaction parameters and confirm site occupancy.

Keywords: A. Metals; C. Crystal structure and symmetry; E. Nuclear magnetic resonance; E. Hyperfine interactions

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Solid State Nuclear Magnetic Resonance
Volume 35, Issue 4, July 2009, Pages 223-229
doi:10.1016/j.ssnmr.2009.01.003

Determination of NMR cogwheel phase cycle with XML

Yannick Millot, Redouane Hajjar and Pascal P. Man

Abstract
The selection of correct coherence transfer pathways is an essential component of an NMR pulse sequence. This article describes a new method based on the use of web tools (eXtensible Markup Language and eXtensible Stylesheet Language Transformation) to generate a cogwheel phase cycle for selecting coherence transfer pathways. We illustrate this method with the three-pulse phase-modulated shifted-echo or split-t1 MQMAS sequences for triple-quantum spin-3/2 systems. After generalization to the different half-integer quadrupole spins, we use the SIMPSON program to confirm our results. Finally, we apply our method to the case of the z-filter 3QMAS sequence for I=3/2 systems.

Keywords: NMR; Cogwheel phase cycling; Coherence transfer pathways; XML; XSLT; SIMPSON; MQMAS; z-filter

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Solid State Nuclear Magnetic Resonance
Volume 35, Issue 4, July 2009, Pages 230-234
doi:10.1016/j.ssnmr.2009.01.001

Kinetics of solid-state NMR cross-polarization from protons to carbon-13 in surgical sutures

Marcin Sobczak, Tadeusz Chreptowicz, Joanna Kolmas and Waclaw Kolodziejski

Abstract
Commercial Dexon surgical sutures, made of polyglycolide (PGA), were examined using 13C CP/MAS NMR. The study shows that detailed analysis of the cross-polarization (CP) process is useful in the peak assignments and in the assessment of molecular mobility in the polymer domains. Crystallinity of PGA in the sutures was estimated at ca. 55%.

Keywords: Biodegradable polymers; Polyglicolide; Surgical sutures; 13C NMR; Cross-polarization

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Solid State Nuclear Magnetic Resonance
Volume 35, Issue 4, July 2009, Pages 243-252
doi:10.1016/j.ssnmr.2008.12.003

QuadFit—A new cross-platform computer program for simulation of NMR line shapes from solids with distributions of interaction parameters

T.F. Kemp and M.E. Smith

Abstract
A new Java computer program called QuadFit has been written to simulate NMR line shapes from solid materials. The program takes into account the major interactions, with a key feature that distributions of isotropic chemical shift and quadrupolar interaction parameters can be calculated, which are often encountered in amorphous and disordered materials. The quadrupolar interaction can be simulated for all the transitions for both half-integer and integer spins. The utility of the program is demonstrated with examples of 27Al (nuclear spin View the MathML source) in an atomically disordered aluminoborate mullite, 65Cu (View the MathML source) in CuInSe2 and 10B (I=3) in amorphous B2O3. The program has good cross-platform compatibility and is written for high stability. The program has been designed with an easy to use graphical interface. It can be run efficiently on any reasonably powerful PC and is freely available from the Warwick website (http://go.warwick.ac.uk/quadfit).

Keywords: NMR line shape simulation; Computer program; Interaction distribution; Amorphous materials