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Solid State Nuclear Magnetic Resonance

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https://read.qxmd.com/read/30865870/methyl-dynamics-in-amino-acids-modulate-heteronuclear-cross-relaxation-in-the-solid-state-under-mas-dnp
#1
Victoria Aladin, Björn Corzilius
Dynamic Nuclear Polarization (DNP) is a wide-spread technique for sensitivity enhancement of MAS NMR. During a typical MAS DNP experiment, several mechanisms resulting in polarization transfer may be active at the same time. One such mechanism which is most commonly active but up to now mostly disregarded is SCREAM-DNP (Specific Cross Relaxation Enhancement by Active Motions under DNP). This effect is generally observed in direct DNP experiments if molecular dynamics are supporting heteronuclear cross relaxation similar to the nuclear Overhauser effect...
February 26, 2019: Solid State Nuclear Magnetic Resonance
https://read.qxmd.com/read/30836289/brute-force-solvent-suppression-for-dnp-studies-of-powders-at-natural-isotopic-abundance
#2
Pierre Thureau, Marie Juramy, Fabio Ziarelli, Stephane Viel, Giulia Mollica
A method based on highly concentrated radical solutions is investigated for the suppression of the NMR signals arising from solvents that are usually used for dynamic nuclear polarization experiments. The presented method is suitable in the case of powders, which are impregnated with a radical-containing solution. It is also demonstrated that the intensity and the resolution of the signals due to the sample of interest is not affected by the high concentration of radicals. The method proposed here is therefore valuable when sensitivity is of the utmost importance, namely samples at natural isotopic abundance...
February 23, 2019: Solid State Nuclear Magnetic Resonance
https://read.qxmd.com/read/30826711/the-effects-of-sample-conductivity-on-the-efficacy-of-dynamic-nuclear-polarization-for-sensitivity-enhancement-in-solid-state-nmr-spectroscopy
#3
Asya Svirinovsky-Arbeli, Dina Rosenberg, Daniel Krotkov, Ran Damari, Krishnendu Kundu, Akiva Feintuch, Lothar Houben, Sharly Fleischer, Michal Leskes
In recent years dynamic nuclear polarization (DNP) has greatly expanded the range of materials systems that can be studied by solid state NMR spectroscopy. To date, the majority of systems studied by DNP were insulating materials including organic and inorganic solids. However, many technologically-relevant materials used in energy conversion and storage systems are electrically conductive to some extent or are employed as composites containing conductive additives. Such materials introduce challenges in their study by DNP-NMR which include microwave absorption and sample heating that were not thoroughly investigated so far...
February 20, 2019: Solid State Nuclear Magnetic Resonance
https://read.qxmd.com/read/30849736/absolute-1-h-polarization-measurement-with-a-spin-correlated-component-of-magnetization-by-hyperpolarized-mas-dnp-solid-state-nmr
#4
Tomoaki Sugishita, Yoh Matsuki, Toshimichi Fujiwara
Sensitivity of magic-angle spinning (MAS) NMR spectroscopy has been dramatically improved by the advent of high-field dynamic nuclear polarization (DNP) technique and its rapid advances over the past decades. In this course, discussions on ways to improve the DNP enhancement factor or the overall sensitivity gain have been numerous, and led to a number of methodological and instrumental breakthroughs. Beyond the sensitivity gain, however, discussions on accurate quantification of the 1 H polarization amplitude achievable in a sample with DNP have been relatively rare...
February 18, 2019: Solid State Nuclear Magnetic Resonance
https://read.qxmd.com/read/30738232/dynamics-in-hydrophilic-and-hydrophobic-molecular-chains-tethered-to-mcm41-type-mesoporous-silica-upon-wetting-and-dehydration-processes
#5
Lee Ghindes-Azaria, Ofer Melamed, Merav Nadav-Tsubery, Esthy Levy, Keren Keinan-Adamsky, Gil Goobes
Surface modified mesoporous silica materials are important materials for heterogeneous catalysis and are attracting attention as potential drug carriers. The functionality of these materials relies on the physical and chemical properties of the tethers attached to MCM41 silica surface. These chemically linked tails act as molecular brushes, that can capture pollutant molecules, anchor points for catalysts and can host drug molecules. To utilize the full potential of the tailored silica surfaces, one should infer their properties at different levels of solvation...
January 21, 2019: Solid State Nuclear Magnetic Resonance
https://read.qxmd.com/read/30690321/ion-exchange-and-binding-in-selenium-remediation-materials-using-dnp-enhanced-solid-state-nmr-spectroscopy
#6
Marco Mais, Javier Torroba, Nathan S Barrow, Subhradip Paul, Jeremy J Titman
Selenate-loaded selenium water remediation materials based on polymer fibres have been investigated by dynamic nuclear polarization (DNP) enhanced solid-state NMR. For carbon-13 a significant reduction in experiment time is obtained with DNP even when compared with conventional carbon-13 NMR spectra recorded using larger samples. For the selenium remediation materials studied here this reduction allows efficient acquisition of {1 H}-77 Se heteronuclear correlation spectra which give information about the nature of the binding of the remediated selenate ions with the grafted side chains which provide the required ion exchange functionality...
January 20, 2019: Solid State Nuclear Magnetic Resonance
https://read.qxmd.com/read/30772677/exploiting-in-situ-solid-state-nmr-spectroscopy-to-probe-the-early-stages-of-hydration-of-calcium-aluminate-cement
#7
Colan E Hughes, Brant Walkley, Laura J Gardner, Samuel A Walling, Susan A Bernal, Dinu Iuga, John L Provis, Kenneth D M Harris
We report a high-field in-situ solid-state NMR study of the hydration of CaAl2 O4 (the most important hydraulic phase in calcium aluminate cement), based on time-resolved measurements of solid-state 27 Al NMR spectra during the early stages of the reaction. A variant of the CLASSIC NMR methodology, involving alternate recording of direct-excitation and MQMAS 27 Al NMR spectra, was used to monitor the 27 Al species present in both the solid and liquid phases as a function of time. Our results provide quantitative information on the changes in the relative amounts of 27 Al sites with tetrahedral coordination (the anhydrous reactant phase) and octahedral coordination (the hydrated product phases) as a function of time, and reveal significantly different kinetic and mechanistic behaviour of the hydration reaction at the different temperatures (20 °C and 60 °C) studied...
January 14, 2019: Solid State Nuclear Magnetic Resonance
https://read.qxmd.com/read/30669006/enhanced-1-h-x-d-hmqc-performance-through-improved-1-h-homonuclear-decoupling
#8
Frédéric A Perras, Tian Wei Goh, Lin-Lin Wang, Wenyu Huang, Marek Pruski
The sensitivity of solid-state NMR experiments that utilize 1 H zero-quantum heteronuclear dipolar recoupling, such as D-HMQC, is compromised by poor homonuclear decoupling. This leads to a rapid decay of recoupled magnetization and an inefficient recoupling of long-range dipolar interactions, especially for nuclides with low gyromagnetic ratios. We investigated the use, in symmetry-based 1 H heteronuclear recoupling sequences, of a basic R element that was principally designed for efficient homonuclear decoupling...
January 10, 2019: Solid State Nuclear Magnetic Resonance
https://read.qxmd.com/read/30641444/hyperpolarized-mas-nmr-of-unfolded-and-misfolded-proteins
#9
REVIEW
Anna König, Daniel Schölzel, Boran Uluca, Thibault Viennet, Ümit Akbey, Henrike Heise
In this article we give an overview over the use of DNP-enhanced solid-state NMR spectroscopy for the investigation of unfolded, disordered and misfolded proteins. We first provide an overview over studies in which DNP spectroscopy has successfully been applied for the structural investigation of well-folded amyloid fibrils formed by short peptides as well as full-length proteins. Sample cooling to cryogenic temperatures often leads to severe line broadening of resonance signals and thus a loss in resolution...
January 3, 2019: Solid State Nuclear Magnetic Resonance
https://read.qxmd.com/read/30623800/proton-detected-3d-1-h-anisotropic-14-n-1-h-isotropic-chemical-shifts-correlation-nmr-under-fast-magic-angle-spinning-on-solid-samples-without-isotopic-enrichment
#10
Manoj Kumar Pandey, Joshua T Damron, Ayyalusamy Ramamoorthy, Yusuke Nishiyama
The chemical shift anisotropy (CSA) interaction of a nucleus is an important indicator of the local electronic environment particularly for the contributions arising from hydrogen (H)-bonding, electrostatic and π-π interactions. CSAs of protons bonded to nitrogen atoms are of significant interest due to their common role as H-bonding partners in many chemical, pharmaceutical and biological systems. Although very fast (∼100 kHz) magic angle sample spinning (MAS) experiments have enabled the measurement of proton CSAs directly from solids, due to a narrow chemical shift (CS) distribution, overlapping NH proton resonances are common and necessitate the introduction of an additional frequency dimension to the regular 2D 1 H CSA/1 H CS correlation method to achieve sufficient resolution...
December 28, 2018: Solid State Nuclear Magnetic Resonance
https://read.qxmd.com/read/30597399/solid-state-23-na-nmr-spectroscopy-studies-of-ordered-and-disordered-cellulose-nanocrystal-films
#11
Ryutaro Ohashi, Carl A Michal, Wadood Y Hamad, Thanh-Dinh Nguyen, Motohiro Mizuno, Mark J MacLachlan
Cellulose nanocrystal films with either disordered or chiral nematic structures of varying helical pitch were investigated using 23 Na solid-state nuclear magnetic resonance (NMR) spectroscopy. Spin lattice relaxation of 1 H correlated with 23 Na analyzed by indirect observation using polarization transfer from 1 H nuclei to 23 Na nuclei showed that the Na+ cations are well hydrated in the cellulose nanocrystal films. Linewidth analysis in solid-state 23 Na NMR showed that the Na+ cations move in confined spaces, and that the Na+ cations in the film having disordered structure are more dynamic than in the films having ordered structure...
December 14, 2018: Solid State Nuclear Magnetic Resonance
https://read.qxmd.com/read/30583084/constancy-of-the-quadrupolar-interaction-product-in-nanocrystalline-gallium-nitride-revealed-by-71-ga-mas-nmr-shift-distribution
#12
Masataka Tansho, Takayuki Suehiro, Tadashi Shimizu
The question of whether the broad 71,69 Ga nuclear magnetic resonance (NMR) signal of hexagonal gallium nitride (h-GaN) at 530-330 ppm is related to the Knight shift (caused by the presence of carriers in semiconductors) is the subject of intense debate. The intensity increase observed for the narrower 71 Ga magic angle spinning (MAS) NMR signals above 1050 °C suggests that the broader signals do not reflect the decomposition of h-GaN. Herein, we utilized 71 Ga multi-quantum (MQ) MAS NMR spectroscopy to reveal that the quadrupolar interaction products for the broad signal of nanocrystalline h-GaN are almost constant in the entire shift range that we investigated, equaling 1...
December 14, 2018: Solid State Nuclear Magnetic Resonance
https://read.qxmd.com/read/30322721/editorial-a-dynamic-journal
#13
EDITORIAL
David L Bryce
No abstract text is available yet for this article.
December 2018: Solid State Nuclear Magnetic Resonance
https://read.qxmd.com/read/30273904/accurate-13-c-and-15-n-molecular-crystal-chemical-shielding-tensors-from-fragment-based-electronic-structure-theory
#14
Joshua D Hartman, Gregory J O Beran
Standard nuclear magnetic resonance (NMR) spectroscopy experiments measure isotropic chemical shifts, but measuring the chemical shielding anisotropy (CSA) tensor can provide additional insights into solid state chemical structures. Interpreting the principal components of these tensors is facilitated by first-principles chemical shielding tensor predictions. Here, the ability to predict molecular crystal CSA tensor components for 13 C and 15 N nuclei with fragment-based electronic structure techniques is explored...
December 2018: Solid State Nuclear Magnetic Resonance
https://read.qxmd.com/read/30253250/optorelaxers-achieving-real-time-control-of-nmr-relaxation
#15
James P Yesinowski, Joel B Miller, Christopher A Klug, Holly L Ricks-Laskoski
We present an approach to increase the detection sensitivity of NMR by shortening the spin-lattice relaxation time using transient paramagnetic species created by light irradiation of "optorelaxer" molecules. In the ultimate implementation of this concept, not yet realized here, these transient species are absent during the detection period, thereby avoiding the loss of spectral resolution caused by inhomogeneous broadening from paramagnetic species. Real-time control of NMR relaxation by visible light is demonstrated with Fe(II)(ptz)6 (BF4 )2 , (ptz = 1-propyltetrazole), abbreviated FePTZ...
December 2018: Solid State Nuclear Magnetic Resonance
https://read.qxmd.com/read/30508738/application-of-combined-solid-state-nmr-and-dft-calculations-for-the-study-of-piracetam-polymorphism
#16
Łukasz Szeleszczuk, Dariusz Maciej Pisklak, Tomasz Gubica, Klaudia Matjakowska, Sławomir Kaźmierski, Monika Zielińska-Pisklak
Piracetam, a popular nootropic drug, widely used in the treatment of age-associated mental decline and disorders of the nervous system such as Alzheimer's disease and dementia exists under normal pressure in three polymorphic forms (P1, P2 and P3) of different stability. In this work the relative stability of piracetam polymorphs depending on the temperature was studied using the ssNMR spectroscopy combined with ab initio DFT calculations. The ssNMR spectroscopy enabled the analysis of polymorphic phase transition in the case of pure active substance as well as polymorphic form identification in the analysis of the commercial solid dosage formulations...
November 22, 2018: Solid State Nuclear Magnetic Resonance
https://read.qxmd.com/read/30468954/elucidating-the-internal-structure-and-dynamics-of-%C3%AE-chitin-by-2dpass-mas-nmr-and-spin-lattice-relaxation-measurements
#17
Manasi Ghosh, Sourav Sadhukhan, Krishna Kishor Dey
The structure and dynamics of the second most abundant biopolymer α-chitin were studied by high resolution solid state 13 C cross-polarization magic angle spinning nuclear magnetic resonance (CP-MAS-NMR) spectral analysis, 13 C relaxation measurements at eight chemically different carbon sites and chemical shift anisotropy measurement by two-dimensional phase-adjusted spinning sidebands (2DPASS) magic angle spinning (MAS) solid state NMR method.13 C spin-lattice relaxation time was measured by high resolution Torchia CP method...
November 14, 2018: Solid State Nuclear Magnetic Resonance
https://read.qxmd.com/read/30439542/nmr-study-of-microscopic-mechanism-of-water-molecules-diffusion-in-natrolite
#18
A V Sapiga, N A Sergeev
The mineral natrolite is a good object for studying the features of the molecular mobility of water molecules in spatially restricted structures by NMR techniques. The microscopic mechanisms of water molecule mobility in channels of monocrystal natural zeolite natrolite (Na16 Al16 Si24 O80 ·16H2 O) have been investigated by broad-line (CW) NMR method. The CW NMR method, which accurately reproduces the shape of a Pake doublets of water molecules, has made it possible to trace diffusion of individual water molecules between specific positions in the crystal lattice as a function of temperature, which is important in understanding diffusion mechanisms in narrow channels of natrolite, where a diameter of the channel is smaller than the diameter of the water molecule...
November 2, 2018: Solid State Nuclear Magnetic Resonance
https://read.qxmd.com/read/30170130/solid-state-nmr-an-indispensable-tool-in-organic-inorganic-biocomposite-characterization-refining-the-structure-of-octacalcium-phosphate-composites-with-the-linear-metabolic-di-acids-succinate-and-adipate
#19
Yang Li, David G Reid, Melinda J Duer, Jerry C C Chan
Octacalcium phosphate (OCP; Ca8 (HPO4 )2 (PO4 )4 . 5H2 O) is a plausible precursor phase of biological hydroxyapatite, which composites with a number of biologically relevant organic metabolites. Widely used material science physicochemical structure determination techniques successfully characterize the mineral component of these composites but leave details of the structure, and interactions with mineral, of the organic component almost completely obscure. The metabolic linear di-acids succinate (SUC) and adipate (ADI) differentially expand the hydrated (100) layer of OCP...
November 2018: Solid State Nuclear Magnetic Resonance
https://read.qxmd.com/read/30125798/broadband-adiabatic-inversion-cross-polarization-phenomena-in-the-nmr-of-rotating-solids
#20
REVIEW
Sungsool Wi, Robert W Schurko, Lucio Frydman
We explore the use of cross-polarization magic-angle spinning (CPMAS) methods incorporating an adiabatic frequency sweep in a standard Hartman-Hahn CPMAS pulse scheme, to achieve signal enhancements in solid-state NMR spectra of rare spins under fast MAS spinning rates, including spin-1/2, integer spin, and half-integer spin nuclides. These experiments, dubbed Broadband Adiabatic INversion Cross-Polarization Magic-Angle Spinning (BRAIN-CPMAS) experiments, involve an adiabatic inversion pulse on the S-channel of a rare spin nuclide while simultaneously applying a conventional spin-locking pulse on the I-channel (1 H)...
October 2018: Solid State Nuclear Magnetic Resonance
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