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Solid State Nuclear Magnetic Resonance

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https://www.readbyqxmd.com/read/30508738/application-of-combined-solid-state-nmr-and-dft-calculations-for-the-study-of-piracetam-polymorphism
#1
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://www.readbyqxmd.com/read/30468954/elucidating-the-internal-structure-and-dynamics-of-%C3%AE-chitin-by-2dpass-mas-nmr-and-spin-lattice-relaxation-measurements
#2
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://www.readbyqxmd.com/read/30439542/nmr-study-of-microscopic-mechanism-of-water-molecules-diffusion-in-natrolite
#3
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://www.readbyqxmd.com/read/30322721/editorial-a-dynamic-journal
#4
EDITORIAL
David L Bryce
No abstract text is available yet for this article.
December 2018: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/30273904/accurate-13-c-and-15-n-molecular-crystal-chemical-shielding-tensors-from-fragment-based-electronic-structure-theory
#5
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://www.readbyqxmd.com/read/30253250/optorelaxers-achieving-real-time-control-of-nmr-relaxation
#6
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://www.readbyqxmd.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
#7
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://www.readbyqxmd.com/read/30125798/broadband-adiabatic-inversion-cross-polarization-phenomena-in-the-nmr-of-rotating-solids
#8
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
https://www.readbyqxmd.com/read/30125797/reduction-of-the-temperature-gradients-in-laser-assisted-high-temperature-mas-nmr
#9
Daniel Jardón-Álvarez, Jörn Schmedt Auf der Günne
Laser assisted magic angle spinning (MAS) solid state NMR experiments enable studying physicochemical properties at very high temperatures with high resolution. Large temperature gradients however, can degrade resolution and precision of this technique. Due to the strong temperature dependence of the 207 Pb chemical-shift in lead nitrate, a temperature difference along the sample leads to a broadening of the signal. A second moment analysis of the NMR spectra serves as an analytical method to quantify the temperature gradient...
October 2018: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/30125796/reduction-of-the-13-c-cross-polarization-experimental-time-for-pharmaceutical-samples-with-long-t-1-by-ball-milling-in-solid-state-nmr
#10
Xiaobing Lou, Ming Shen, Chao Li, Qun Chen, Bingwen Hu
Many pharmaceutical samples have notably long 1 H T1 (proton spin-lattice relaxation time), leading to lengthy experiments lasting several days in solid-state NMR studies. In this work, we propose the use of ball milling on the pharmaceutical samples to reduce the 1 H T1 , which also leads to enhanced sensitivity in {1 H}-13 C Cross-Polarization (CP) experiments due to reduced particle sizes and increased surface areas of the samples. Experimentally, we determined that depending on the substrates and milling time, the signal-to-noise ratio (S/N) of a 1D 13 C CP spectrum can be increased by a factor of 3-6, which means that the experimental time can be shortened by a factor of 9-36...
October 2018: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/30103084/observation-of-proximities-between-spin-1-2-and-quadrupolar-nuclei-in-solids-improved-robustness-to-chemical-shielding-using-adiabatic-symmetry-based-recoupling
#11
Hiroki Nagashima, Aany Sofia Lilly Thankamony, Julien Trébosc, Lionel Montagne, Gwendal Kerven, Jean-Paul Amoureux, Olivier Lafon
We introduce a novel heteronuclear dipolar recoupling based on the R21 -1 symmetry, which uses the tanh/tan (tt) shaped pulse as a basic inversion element and is denoted R21 -1 (tt). Using first-order average Hamiltonian theory, we show that this sequence is non-γ-encoded and that it reintroduces the |m| = 1 spatial component of the Chemical Shift Anisotropy (CSA) of the irradiated isotope and its heteronuclear dipolar interactions. Using numerical simulations and one-dimensional (1D) 27 Al-{31 P} through-space D-HMQC (Dipolar Heteronuclear Multiple-Quantum Correlation) experiments on VPI-5, we compare the performances of this recoupling to those of other non-γ-encoded |m| = 1 heteronuclear recoupling schemes: REDOR (Rotational-Echo DOuble Resonance), SFAM (Simultaneous Frequency and Amplitude Modulation) and R42 -1 (tt)...
October 2018: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/30096558/effects-of-chelator-lipids-paramagnetic-metal-ions-and-trehalose-on-liposomes-by-solid-state-nmr
#12
Dennis Lam, Jianqin Zhuang, Leah S Cohen, Boris Arshava, Fred R Naider, Ming Tang
The effects of various lipid bound paramagnetic metal ions on liposomes prepared in the presence of trehalose and chelator lipids are evaluated to observe site-specific signal changes on liposome samples with optimal resolution in solid-state NMR spectroscopy. We found that Mn2+ , Gd3+ and Dy3+ have different influences on the lipid 13 C sites depending on their penetration depths into the bilayer, which can be extracted as distance information. The trehalose-liposome mixture is efficiently packed into solid-state NMR rotors and provides optimal resolution at reasonable instrument temperatures (10-50 °C)...
October 2018: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/30243098/investigation-of-the-effects-of-sintering-and-indium-doping-of-zinc-oxide-using-67-zn-magic-angle-spinning-nmr-analysis
#13
Ryutaro Ohashi, Wataru Sato, Motohiro Mizuno, Shinobu Ohki, Kenzo Deguchi, Masataka Tansho, Tadashi Shimizu
Indium-doped zinc oxide, a potential alternative material to indium tin oxide, was analyzed in powder form via 67 Zn magic angle spinning nuclear magnetic resonance (MAS NMR). The 67 Zn MAS NMR results show that the line shapes of zinc oxide were broadened by sintering, which was also observed for indium-doped zinc oxide, in which the broadening also depended on the sintering time. Furthermore, the line shapes of indium-doped zinc oxide were significantly broader than those of the corresponding zinc oxide, and were independent of the degree of indium doping...
September 12, 2018: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/29803916/acetone-mobility-in-zeolite-cages-with-new-features-in-the-deuteron-nmr-spectra-and-relaxation
#14
E E Ylinen, M Punkkinen, A Birczyński, Z T Lalowicz
We studied deuteron NMR spectra and spin-lattice relaxation of deuterated acetone-d6 , adsorbed into zeolites NaX (1.3) and NaY(2.4) at 100% coverage of sodium cations. At temperatures roughly below 160 K the deuterons are localized and their NMR characteristics are determined by CD3 rotation and rotational oscillations of acetone molecules. In NaX the CD3 rotation and rotational oscillations about the twofold axis of acetone dominate the spectra below 100 K, while above it oscillations also about other axes become important...
September 2018: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/29803915/measurement-of-proton-chemical-shift-anisotropy-in-solid-state-nmr-spectroscopy
#15
REVIEW
Lixin Liang, Guangjin Hou, Xinhe Bao
Proton chemical shift anisotropy (CSA) is significantly important as it provides the information of the dynamics and local environmental structure of the proton. The measurement of proton CSA keeps drawing the attention of NMR researchers, and great efforts have been expended. In the early years, measuring proton CSA in solid-state NMR, especially with the strong 1 H-1 H dipolar network, was hampered by ineffective decoupling or selectively recoupling techniques, and the applications were only limited to those with sparse proton sites or single crystals...
September 2018: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/29758460/assessment-of-the-sensitivity-of-dqf-zqf-2-h-nmr-of-d-2-o-for-studying-modified-nafion-membranes-at-20-%C3%A2-c-and-80-%C3%A2-c
#16
Alyxandra N Thiessen, Wesley Verbeek, Kelsey Gritter, Kristopher J Ooms
Double and zero quantum filtered (ZQF/DQF) 2 H NMR spectroscopy was used to study D2 O in five different Nafion membranes, N117, N115, NR212, XL, and HP, in order to assess the effectiveness of the technique for monitoring differences in thickness, membrane reinforcement, and the addition of chemical stabilizers. Experiments were also carried out at 20 and 80 °C to understand if the ZQF/DQF technique could detect changes in the water environments and exchange dynamics as a function of temperature. For two of the membranes, significant decreases in the 1/T2 relaxation rates were observed at 80 °C...
September 2018: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/30189330/spin-orbit-effects-on-the-125-te-magnetic-shielding-tensor-a-cluster-based-zora-dft-investigation
#17
Fahri Alkan, Cecil Dybowski
Cluster-based calculations of 125 Te magnetic-shielding tensors demonstrate that inclusion of spin-orbit effects is necessary to obtain the best agreement of theoretical predictions with experiment. The spin-orbit contribution to shielding depends on the oxidation state and stereochemistry of the 125 Te site. Comparison of the performance of various density functionals indicates that GGA functionals behave similarly to each other in predicting NMR magnetic shielding. The use of hybrid functionals improves the predictive ability on average for a large set of 125 Te-containing materials...
August 28, 2018: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/29751342/pushing-the-limit-of-nmr-based-distance-measurements-retrieving-dipolar-couplings-to-spins-with-extensively-large-quadrupolar-frequencies
#18
M Makrinich, E Nimerovsky, A Goldbourt
Dipolar recoupling under magic-angle spinning allows to measure accurate inter-nuclear distances provided that the two interacting spins can be efficiently and uniformly excited. Alexander (Lex) Vega has shown that adiabatic transfers of populations in quadrupolar spins during the application of constant-wave (cw) radio-frequency pulses lead to efficient and quantifiable dipolar recoupling curves. Accurate distance determination within and beyond the adiabatic regime using cw pulses is limited by the size of the quadrupolar coupling constant...
August 2018: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/29729494/automated-detection-of-broad-nmr-spectra-19-f-nmr-of-paramagnetic-uf-4-and-195-pt-nmr-of-supported-pt-catalysts
#19
Christopher A Klug, Joel B Miller
The automated detection of broad NMR spectra via the controlled stepwise motion of the NMR probe along the field axis of the superconducting solenoid is demonstrated for the detection of 19 F NMR of paramagnetic UF4 and 195 Pt NMR of supported metal catalysts. The sensitivity advantages of performing these measurements at 2.3 T are discussed with reference to applying this methodology to room temperature in situ electrochemical 195 Pt NMR.
August 2018: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/29653371/foreword-special-issue-in-honor-of-alexander-j-lex-vega
#20
EDITORIAL
Clare P Grey, Tatyana Polenova, Shimon Vega
No abstract text is available yet for this article.
August 2018: Solid State Nuclear Magnetic Resonance
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