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Solid State Nuclear Magnetic Resonance

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https://www.readbyqxmd.com/read/28623770/energy-efficiency-increase-of-nqr-spectrometer-transmitter-at-pulse-resonance-excitation-with-noise-signals
#1
A Samila, V Khandozhko, L Politansky
The specific feature of NQR is expansion of spectral lines which is caused not only by dipole-dipole interaction of nuclei, but also by local field nonuniformity caused by the defects and deformation in crystal matrix. Considerable line expansion, which is typical of crystals, requires in pulsed NQR method the optimization of pulse shape and the reserve of transmitter power output. Parametric computer identification was used to study a dependence of parameters of the energy spectra of the output signal of pulsed NQR spectrometer transmitter on the duration of excitation pulses with sine and noise occupation...
June 8, 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/28624184/-31-p-mas-nmr-spectroscopy-with-93-nb-decoupling-and-dft-calculations-a%C3%A2-structural-characterization-of-defects-in-a-niobium-phosphate-phase
#2
Guillaume Girard, Filipe Vasconcelos, Lionel Montagne, Laurent Delevoye
The present study has investigated the structure of four niobium phosphates compounds using (31)P MAS NMR spectroscopy. Niobium (93)Nb decoupling, applied during (31)P NMR acquisition led to a resolution enhancement by a factor of 2-3, which allowed distinguish phosphorous sites separated by 1 ppm or less. The assignment of (31)P spectra has been completed by use of first-principles calculations derived from the original XRD structures. One of the compounds, Na3.04Nb7P4O29, contains a sodium vacancy, clearly revealed in the (31)P MAS spectrum obtained with (93)Nb decoupling...
June 2, 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/28602610/-1-h-31-p-cpvc-nmr-method-under-very-fast-magic-angle-spinning-for-analysis-of-dipolar-interactions-and-dynamics-processes-in-the-crystalline-phosphonium-tetrafluoroborate-salts
#3
Piotr Paluch, Julien Trébosc, Jean-Paul Amoureux, Marek J Potrzebowski
We present an NMR methodology which can be used to study the dynamical processes occurring in organophosphorus compounds that belong to the group of the organic ionic plastic crystals (OIPCs). As model samples we employed two phosphonium tetrafluoroborate salts; (t-Bu)3PH(+)BF4(-) (1) and (Me)3PH(+)BF4(-) (2). Both samples possess in their structures direct H-P bonds, and both undergo complex thermal processes in the solid state, forming below the melting point three or four phases, respectively. (1)H-(31)P CPVC (Cross-Polarization Variable Contact) measurements were performed under Very Fast Magic Angle Spinning with speed equal to 50 or 60 kHz, in order (i) to establish the hydrogen-phosphorus dipolar couplings, and (ii) to correlate the dipolar splitting values with molecular motions of the cation...
June 1, 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/28582643/identification-of-double-four-ring-units-in-germanosilicate-itq-13-zeolite-by-solid-state-nmr-spectroscopy
#4
Xiaolong Liu, Yueying Chu, Qiang Wang, Weiyu Wang, Chao Wang, Jun Xu, Feng Deng
Well-crystallized Ge-free and Ge-ITQ-13 were successfully obtained by solid state synthesis method. The Ge/Si ratio and the water content that are the two important factors in the synthesis of germanosilicate zeolites were explored for the formation of ITQ-13. The effect of the mineralizing agents (NH4F and NH4Cl) on the ITQ-13 synthesis was investigated as well. The obtained pure silica ITQ-13 and Ge-ITQ-13 were characterized by one- and two-dimensional solid- state NMR techniques. One-dimensional (1D) (19)F MAS, (1)H→(29)Si CP/MAS and (19)F→(29)Si CP/MAS NMR spectroscopy evidenced the formation of pure Si-D4R (double four ring) and Ge-D4R units, with the latter being generated by substitution of Si atom from the former units...
May 17, 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/28583290/nmr-investigations-unveil-phase-composition-property-correlations-in-sr0-55na0-45sio2-775-fast-ion-conductor
#5
P Lokeswara Rao, Bholanath Pahari, M Shivanand, Tukaram Shet, K V Ramanathan
This paper reports results of (23)Na and (29)Si solid-state NMR investigations carried out on sodium strontium silicate ion conductor, Sr0.55Na0.45SiO2.775 and presents the first experimental evidence to show that different synthesis conditions induce multiple devitrified phases. Along with 1-dimensional NMR, (23)Na MQMAS spectra have been used to identify the phases corresponding to polymorphs of Na2Si2O5, in addition to the crystalline SrSiO3 and the glass/amorphous Na2Si2O5 phases. The surprising observation of about an order of magnitude higher ionic conductivity achieved in devitrified samples is attributed to the growth of the crystalline δ-Na2Si2O5 phase within the amorphous Na2Si2O5 phase domains, identified using NMR...
May 12, 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/28473217/saturation-capability-of-short-phase-modulated-pulses-facilitates-the-measurement-of-longitudinal-relaxation-times-of-quadrupolar-nuclei
#6
Maria Makrinich, Rupal Gupta, Tatyana Polenova, Amir Goldbourt
The ability of various pulse types, which are commonly applied for distance measurements, to saturate or invert quadrupolar spin polarization has been compared by observing their effect on magnetization recovery curves under magic-angle spinning. A selective central transition inversion pulse yields a bi-exponential recovery for a diamagnetic sample with a spin-3/2, consistent with the existence of two processes: the fluctuations of the electric field gradients with identical single (W1) and double (W2) quantum quadrupolar-driven relaxation rates, and spin exchange between the central transition of one spin and satellite transitions of a dipolar-coupled similar spin...
April 21, 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/28438365/protein-conformational-dynamics-studied-by-15-n-and-1-h-r1%C3%AF-relaxation-dispersion-application-to-wild-type-and-g53a-ubiquitin-crystals
#7
Diego F Gauto, Audrey Hessel, Petra Rovó, Vilius Kurauskas, Rasmus Linser, Paul Schanda
Solid-state NMR spectroscopy can provide site-resolved information about protein dynamics over many time scales. Here we combine protein deuteration, fast magic-angle spinning (~45-60kHz) and proton detection to study dynamics of ubiquitin in microcrystals, and in particular a mutant in a region that undergoes microsecond motions in a β-turn region in the wild-type protein. We use (15)N R1ρ relaxation measurements as a function of the radio-frequency (RF) field strength, i.e. relaxation dispersion, to probe how the G53A mutation alters these dynamics...
April 14, 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/28433479/modeling-short-range-substitution-order-and-disorder-in-crystals-application-to-the-ga-si-distribution-in-a-natrolite-zeolite
#8
Sylvian Cadars, Nak Ho Ahn, Kirill Okhotnikov, Jiho Shin, Aurélie Vicente, Suk Bong Hong, Christian Fernandez
Atomic substitutions are a central feature of the physicochemical properties of an increasing number of solid-state materials. The complexity that this chemical disorder locally generates in otherwise crystalline solids poses a major challenge to the understanding of the relationships between the structure and properties of materials at the atomic and molecular level. Strategies designed to efficiently explore the ensemble of local chemical environments present in disordered crystals and predict their signatures in local spectroscopies such as solid-state nuclear magnetic resonance (NMR) are therefore essential...
April 13, 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/28392024/proton-detection-of-mas-solid-state-nmr-spectra-of-half-integer-quadrupolar-nuclei
#9
Amrit Venkatesh, Michael P Hanrahan, Aaron J Rossini
Fast magic angle spinning (MAS) and proton detection has found widespread application to enhance the sensitivity of solid-state NMR experiments with spin-1/2 nuclei such as (13)C, (15)N and (29)Si, however, this approach is not yet routinely applied to half-integer quadrupolar nuclei. Here we have investigated the feasibility of using fast MAS and proton detection to enhance the sensitivity of solid-state NMR experiments with half-integer quadrupolar nuclei. The previously described dipolar hetero-nuclear multiple quantum correlation (D-HMQC) and dipolar refocused insensitive nuclei enhanced by polarization transfer (D-RINEPT) pulse sequences were used for proton detection of half-integer quadrupolar nuclei...
March 30, 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/28501714/determination-of-polymer-crystallinity-by-the-multivariable-curve-resolution-method-in-13-c-solid-nmr-spectrum
#10
Xiaoyue Zhou, Kaipin Xu, Pei Ni, Qun Chen, Shanmin Zhang
Most of the polymers are composed of a crystal part, an amorphous part, and a transitional interfacial part. These components present disparate physical and chemical characteristics. However, it always suffers from peak overlapping in solid NMR spectrum in order to acquire polymer's crystallinity. The polyethylene oxide (PEO) sample was tested using the Torchia pulse sequence combined with the Multivariate Curve Resolution (MCR) method. A two dimensional CP/MAS spectrum containing spin-lattice relaxation time (T1) information was acquired...
September 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/28472732/repetitive-experiments-of-one-or-two-pulse-sequences-in-nqr-of-spins-i-3-2-liouville-space-steady-state-ernst-angle-and-optimum-signal
#11
Christophe Odin
In NMR, the repetition of pulse sequences with a recycle time that does not allow the spin system to completely relax back to equilibrium is a well known and often used method to increase the signal to noise ratio at given total measuring time. For isolated spins I=1/2, the steady-state of a train of strictly identical pulse sequences separated by free evolution periods of same duration is described by the well known Ernst-Anderson model, and the optimum pulse angle is given by the Ernst angle. We showed recently that equivalent formula, but with super-operators in the Liouville space, can be obtained for general spins I...
September 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/28433869/community-based-barriers-to-the-wider-acceptance-of-solid-state-nmr
#12
Paul Jonsen
During August 2015, the author surveyed 76 solid state NMR scientists from materials science to biology, academic to industrial, based in North America, Europe, India, China, Japan and Australia. The subject concerned barriers to the wider acceptance of solid state NMR and included the various barriers based on experimental, funding, vendor based and community aspects. This survey was confidential. However, many of the survey participants requested that at least the results of the part of the survey relevant to our community be made public...
September 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/28342403/fitting-mas-nmr-spectra-in-crystals-with-local-disorder-czjzek-s-vs-maurer-s-model-for-11-b-and-71-ga-in-polycrystalline-gallium-borate
#13
K Seleznyova, N A Sergeev, M Olszewski, P Stępień, S V Yagupov, M B Strugatsky, J Kliava
A comparative analysis of the Czjzek's and Maurer's models of the joint distribution density of NMR quadrupole parameters has been carried out in view of their application to account for spectra broadening induced by local disorder in crystals. As an example of such an application, we have considered Magic Angle Spinning NMR of (11)B and (71)Ga isotopes in polycrystalline gallium borate. Computer simulations carried out using both models unambiguously show that in the case of low local disorder the Maurer's model, in contrast to the Czjzek's model, provides satisfactory fits to experimental NMR spectra...
September 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/28260612/monitoring-a-simple-hydrolysis-process-in-an-organic-solid-by-observing-methyl-group-rotation
#14
Peter A Beckmann, Joseph M Bohen, Jamie Ford, William P Malachowski, Clelia W Mallory, Frank B Mallory, Andrew R McGhie, Arnold L Rheingold, Gilbert J Sloan, Steven T Szewczyk, Xianlong Wang, Kraig A Wheeler
We report a variety of experiments and calculations and their interpretations regarding methyl group (CH3) rotation in samples of pure 3-methylglutaric anhydride (1), pure 3-methylglutaric acid (2), and samples where the anhydride is slowly absorbing water from the air and converting to the acid [C6H8O3(1) + H2O → C6H10O4(2)]. The techniques are solid state (1)H nuclear magnetic resonance (NMR) spin-lattice relaxation, single-crystal X-ray diffraction, electronic structure calculations in both isolated molecules and in clusters of molecules that mimic the crystal structure, field emission scanning electron microscopy, differential scanning calorimetry, and high resolution (1)H NMR spectroscopy...
September 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/28187333/localization-of-cl-35-nuclei-in-biological-solids-using-rotational-echo-double-resonance-experiments
#15
D Iuga, P Rossi, J Herzfeld, R G Griffin
Chloride ions play important roles in many chemical and biological processes. This paper investigates the possibility of localizing (35)Cl nuclei using solid-state NMR. It demonstrates that distances shorter than 3.8Å, between (13)C atoms and (35)Cl atoms in 10% uniformly labeled (13)C L-tyrosine·HCl and natural abundance Glycine·HCl can be measured using rotational-echo (adiabatic passage) double-resonance (RE(AP)DOR). Furthermore the effect of quadrupolar interaction on the REDOR/REAPDOR experiment is quantified...
April 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/28351540/3d-correlation-nmr-spectrum-between-three-distinct-heteronuclei-for-the-characterization-of-inorganic-samples-application-on-sodium-alumino-phosphate-materials
#16
Hiroki Nagashima, Grégory Tricot, Julien Trébosc, Olivier Lafon, Jean-Paul Amoureux, Frédérique Pourpoint
We report here an original NMR sequence allowing the acquisition of 3D correlation NMR spectra between three distinct heteronuclei, among which two are half-integer spin quadrupolar nuclei. Furthermore, as two of them exhibit close Larmor frequency, this experiment was acquired using a standard triple-resonance probe equipped with a commercial frequency splitter. This NMR technique was tested and applied to sodium alumino-phosphate compounds with (31)P as the spin-1/2 nucleus and (23)Na and (27)Al as the close Larmor frequencies isotopes...
March 22, 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/28342732/hydrogen-bond-strength-in-membrane-proteins-probed-by-time-resolved-1-h-detected-solid-state-nmr-and-md-simulations
#17
João Medeiros-Silva, Shehrazade Jekhmane, Marc Baldus, Markus Weingarth
(1)H-detected solid-state NMR in combination with (1)H/(2)D exchange steps allows for the direct identification of very strong hydrogen bonds in membrane proteins. On the example of the membrane-embedded potassium channel KcsA, we quantify the longevity of such very strong hydrogen bonds by combining time-resolved (1)H-detected solid-state NMR experiments and molecular dynamics simulations. In particular, we show that the carboxyl-side chain of the highly conserved residue Glu51 is involved in ultra-strong hydrogen bonds, which are fully-water-exposed and yet stable for weeks...
March 18, 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/28283343/structural-roles-of-calcium-in-alkaline-and-alkaline-earth-aluminosilicate-glasses-by-solid-state-43-ca-17-o-and-27-al-nmr
#18
Koji Kanehashi
Structural roles of Ca in aluminosilicate glasses have been investigated by solid-state (43)Ca, (17)O, and (27)Al NMR spectroscopy. In 15Al2O3-55SiO2-15CaO-15RO (R=Mg, Ca, Sr, and Na2) (mol%) glass systems wherein half of the alkaline plus alkaline-earth cations charge-compensate (AlO4)(‒) tetrahedra and the other half modify the glass network, with decreasing cation field strength (CFS) in the order of Mg(2+)>Ca(2+)>Sr(2+)>Na(+), the isotropic chemical shift (δiso) of (43)Ca moves to a higher frequency and the quadrupolar coupling constant (PQ) of (43)Ca decreases...
March 3, 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/28342733/probing-intermolecular-interactions-in-a-diethylcarbamazine-citrate-salt-by-fast-mas-1-h-solid-state-nmr-spectroscopy-and-gipaw-calculations
#19
Tiago Venâncio, Lyege Magalhaes Oliveira, Javier Ellena, Nubia Boechat, Steven P Brown
Fast magic-angle spinning (MAS) NMR is used to probe intermolecular interactions in a diethylcarbamazine salt, that is widely used as a treatment against adult worms of Wuchereria bancrofti which cause a common disease in tropical countries named filariasis. Specifically, a dihydrogen citrate salt that has improved thermal stability and solubility as compared to the free form is studied. One-dimensional (1)H, (13)C and (15)N and two-dimensional (1)H-(13)C and (14)N-(1)H heteronuclear correlation NMR experiments under moderate and fast MAS together with GIPAW (CASTEP) calculations enable the assignment of the (1)H, (13)C and (14)N/(15)N resonances...
March 2, 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/28258809/solid-state-nmr-and-computational-insights-into-the-crystal-structure-of-silicocarnotite-based-bioceramic-materials-synthesized-mechanochemically
#20
A S Andreev, N V Bulina, M V Chaikina, I Yu Prosanov, V V Terskikh, O B Lapina
In this work, we report the results of a detailed structural study of a promising bioceramic material silicocarnotite Ca5(PO4)2SiO4 (SC) synthesized from mechanochemically treated nanosized silicon-substituted hydroxyapatite by annealing at 1000°C. This novel synthetic approach represents an attractive and efficient route towards large-scale manufacturing of the silicocarnotite-based bioceramics. A combination of solid-state nuclear magnetic resonance (NMR), powder X-ray crystallography and density function theory (DFT) calculations has been implemented to characterize the phase composition of the prepared composite materials and to gain insight into the crystal structure of silicocarnotite...
February 22, 2017: Solid State Nuclear Magnetic Resonance
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