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Solid State Nuclear Magnetic Resonance

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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
#1
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/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
#2
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...
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
#3
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
#4
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
#5
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
https://www.readbyqxmd.com/read/28237521/recoupling-dipolar-interactions-with-multiple-i-1-quadrupolar-nuclei-a-11-b-6-li-and-31-p-6-li-rotational-echo-double-resonance-study-of-lithium-borophosphate-glasses
#6
Lena Marie Funke, Henrik Bradtmüller, Hellmut Eckert
The case of rotational echo double resonance (REDOR) experiments on the observe nuclei (11)B and (31)P interacting with multiple I=1 quadrupolar nuclei is analyzed in detail by SIMPSON simulations and experimental studies. The simulations define the region within the parameter space spanned by nutation frequency, quadrupolar coupling constant and spinning frequency where the parabolic analysis of the initial REDOR curve in terms of dipolar second moments has validity. The predictions are tested by experimental studies on the crystalline model compounds lithium diborate and lithium pyrophosphate, which are subsequently extended to measure dipolar second moments M2((11)B{(6)Li}) and M2((31)P{(6)Li}) in three borophosphate glasses...
February 20, 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/28216036/-1-h-csa-parameters-by-ultrafast-mas-nmr-measurement-and-applications-to-structure-refinement
#7
Habeeba K Miah, Rosalie Cresswell, Dinu Iuga, Jeremy J Titman
A (1)H anisotropic-isotropic chemical shift correlation experiment which employs symmetry-based recoupling sequences to reintroduce the chemical shift anisotropy in ν1 and ultrafast MAS to resolve (1)H sites in ν2 is described. This experiment is used to measure (1)H shift parameters for L-ascorbic acid, a compound with a relatively complex hydrogen-bonding network in the solid. The (1)H CSAs of hydrogen-bonded sites with resolved isotropic shifts can be extracted directly from the recoupled lineshapes. In combination with DFT calculations, hydrogen positions in crystal structures obtained from X-ray and neutron diffraction are refined by comparison with simulations of the full two-dimensional NMR spectrum...
February 13, 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/28209384/non-homogeneous-distribution-of-al-3-in-doped-phosphate-glasses-revealed-by-27-al-31-p-solid-state-nmr
#8
G Tricot, B Doumert, B Revel, M Bria, J Trebosc, H Vezin
Solid state NMR is applied in this contribution on the xAl2O3-(50-x/2)Na2O-(50-x/2)P2O5 composition line (with 0<x<5mol%) in order to investigate the distribution of Al(3+) ions in Al2O3-doped sodium phosphate glasses. The structure was analysed by (i) (27)Al 1D-, 3Q-, DQ- MAS-NMR analysis and (ii) 1D (31)P, (27)Al((31)P) 2D D-HMQC MAS-NMR and 2D (31)P R-INADEQUATE technique. The (27)Al NMR results confirm the presence of six-coordinated aluminate as major aluminate species and indicate that Al(3+) ions are fully dissociated in the glass network...
February 9, 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/28187332/elimination-of-digital-and-analog-artefacts-from-time-domain-signals
#9
Günter Hempel
A method is described for the elimination of artefacts that arise in time-domain signals because of the presence of digital and analogous filters. Such artefacts are mostly located at the beginning of the free-induction decay (FID). The procedure introduced here is particularly important if at least one signal component decays rather quickly, i.e. if there is only a small number of data containing this component (as for solid-state (1)H or (2)H FIDs). The method is able to restore the original signal by deconvolution of the spectrometer output from the transfer function of the spectrometer console...
February 3, 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/28169117/composite-pulses-in-directly-and-indirectly-detected-14-n-mas-overtone-spectroscopy
#10
Ming Shen, Qun Chen, Bingwen Hu
(14)N MAS overtone spectroscopy is mainly limited by narrow excitation bandwidths owing to the use of very long pulses to get stronger signals. We previously reported the use of modified 90° composite pulses for broadband excitation in (1)H-{NOTDQ14}D-HMQC experiments at ultra-fast MAS. In this work, we modified the 180° composite pulses, which are originally designed for spin 1/2 nuclei, for both indirect detection in (1)H-{NOTDQ14}D-HMQC experiment and direct detection in one-pulse experiment, and found that the modified 180° composite pulses are useful for broadband excitation...
February 3, 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/28214103/tracking-the-evolution-and-differences-between-guest-induced-phases-of-ga-mil-53-via-ultra-wideline-69-71-ga-solid-state-nmr-spectroscopy
#11
Yue Zhang, Bryan E G Lucier, Victor V Terskikh, Renlong Zheng, Yining Huang
Ga-MIL-53 is a metal-organic framework (MOF) that exhibits a "breathing effect," in which the pore size and overall MOF topology can be influenced by temperature, pressure, and host-guest interactions. The phase control afforded by this flexible framework renders Ga-MIL-53 a promising material for guest storage and sensing applications. In this work, the structure and behavior of four Ga-MIL-53 phases (as, ht, enp and lt), along with CO2 adsorbed within Ga-MIL-53 at various loading levels, has been investigated using (69/71)Ga solid-state NMR (SSNMR) experiments at 21...
January 31, 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
#12
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...
January 29, 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/28167375/orientation-dependent-proton-double-quantum-nmr-build-up-function-for-soft-materials-with-anisotropic-mobility
#13
Anna Naumova, Carsten Tschierske, Kay Saalwächter
In recent years, the analysis of proton double-quantum NMR build-up curves has become an important tool to quantify anisotropic mobility in different kinds of soft materials such as polymer networks or liquid crystals. In the former case, such data provides a measure of orientation-dependent residual (time-averaged) dipolar couplings arising from anisotropic segmental motions, informing about the length and the state of local stretching of the network chains. Previous studies of macroscopically ordered, i.e...
January 26, 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/28159455/application-of-1-h-and-27-al-magic-angle-spinning-solid-state-nmr-at-60khz-for-studies-of-au-and-au-ni-catalysts-supported-on-boehmite-alumina
#14
Piotr Paluch, Natalia Potrzebowska, Agnieszka M Ruppert, Marek J Potrzebowski
In this work for the first time we show the power of solid state NMR spectroscopy in structural analysis of alumina and catalysts supported on the alumina surface employing very fast (60kHz) magic angle spinning (MAS) technique. In the methodological part we demonstrate that under such MAS condition, cross-polarization (CP) from proton to aluminum is an efficient process when a very weak (27)Al RF field is applied. The mechanism of CP transfer and the Hartmann-Hahn (H-H) matching conditions were tested for (27)Al RF fields equal to 3...
January 26, 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/28159456/heteronuclear-correlation-experiments-of-23-na-27-al-in-rotating-solids
#15
Shaohui Xin, Qiang Wang, Jun Xu, Ningdong Feng, Wenzheng Li, Feng Deng
We demonstrated that the heteronuclear correlation experiments between two quadrupolar nuclei, (23)Na and (27)Al, with close Larmor frequencies can be achieved via D-HMQC and D-RINEPT approaches by using a diplexer connected to a conventional probe in magic-angle-spinning solid-state NMR. Low-power heteronuclear dipolar recoupling schemes can be applied on (23)Na or (27)Al to establish polarization transfers between the central transitions of (23)Na and (27)Al for a model compound, NaAlO2. Further, we showed a practical implementation of the two dimensional (23)Na-(27)Al dipolar-based heteronuclear correlation experiment on a heterogeneous catalyst, Na2CO3/γ-Al2O3...
January 21, 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/28131696/investigating-fam-n-pulses-for-signal-enhancement-in-mqmas-nmr-of-quadrupolar-nuclei
#16
Henri Colaux, Daniel M Dawson, Sharon E Ashbrook
Although a popular choice for obtaining high-resolution solid-state NMR spectra of quadrupolar nuclei, the inherently low sensitivity of the multiple-quantum magic-angle spinning (MQMAS) experiment has limited its application for nuclei with low receptivity or when the available sample volume is limited. A number of methods have been introduced in the literature to attempt to address this problem. Recently, we have introduced an alternative, automated approach, based on numerical simulations, for generating amplitude-modulated pulses (termed FAM-N pulses) to enhance the efficiency of the triple- to single-quantum conversion step within MQMAS...
January 18, 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/28089491/satellite-and-central-transitions-selective-1-h-27-al-d-hmqc-experiments-at-very-fast-mas-for-quadrupolar-couplings-determination
#17
Nghia Tuan Duong, Yusuke Nishiyama
Recent study has demonstrated the application of the proton-detected heteronuclear multi-quantum coherence (HMQC) at ultrafast Magic Angle Spinning (MAS) to probe quadrupolar nuclei including (14)N and (35)Cl. In addition, for half-integer quadrupolar nucleus like (35)Cl, the quadrupolar product can be calculated based on the shift difference between the center band of satellite transition (ST) and the central transition (CT) peaks. The applicability of this technique is further investigated on spin I=5/2, namely (27)Al nucleus, and kaolin is chosen as the testing sample...
January 4, 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/28081936/quadrupolar-solid-state-nmr-and-repetitive-experiments-some-aspects-in-the-liouville-space-application-to-spins-i-1
#18
Christophe Odin
The aim of this work is to generalize the Ernst-Anderson model developed to account of the steady-state regime of isolated spins I=1/2 subject to a train of strictly identical pulse sequences separated by free evolution periods of same duration. We generalize this model to the general case of spins I≥1 and general pulse sequence within the framework of the Liouville space. In particular, it is proved that under reasonable assumptions, a well defined steady-state regime is reached which is independent of the initial conditions...
December 29, 2016: 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
#19
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/27960099/study-of-cross-relaxation-and-molecular-dynamics-in-the-solid-3-trifluoromethyl-benzoic-acid-by-solid-state-nmr-off-resonance
#20
Aneta Woźniak-Braszak
Molecular dynamics of the solid 3-(trifluoromethyl) benzoic acid containing proton (1)H and fluorine (19)F nuclei was explored by the solid-state NMR off - resonance technique. Contrary to the previous experiments the proton nuclei system I relaxed in the off - resonance effective field B→e while fluorine nuclei system S was saturated for short time in comparison to the relaxation time T1I. New cross - relaxation solid - state NMR off - resonance experiments were conducted on a homebuilt pulse spectrometer operating at the on-resonance frequency of 30...
February 2017: Solid State Nuclear Magnetic Resonance
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