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Solid-state NMR

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https://www.readbyqxmd.com/read/29334394/substitution-of-the-laser-borane-anti-b18h22-with-pyridine-a-structural-and-photophysical-study-of-some-unusually-structured-macropolyhedral-boron-hydrides
#1
Michael G S Londesborough, Jiří Dolanský, Tomáš Jelínek, John D Kennedy, Ivana Císařová, Robert D Kennedy, Daniel Roca-Sanjuán, Antonio Francés-Monerris, Kamil Lang, William Clegg
Reaction of anti-B18H221 with pyridine in neutral solvents gives sparingly soluble B16H18-3',8'-Py23a as the major product (ca. 53%) and B18H20-6',9'-Py22 (ca. 15%) as the minor product, with small quantities of B18H20-8'-Py 4 (ca. 1%) also being formed. The three new compounds 2, 3a and 4 are characterized by single-crystal X-ray diffraction analyses and by multinuclear multiple-resonance NMR spectroscopy. Compound 2 is of ten-vertex nido:ten-vertex arachno two-atoms-in-common architecture, long postulated for a species with borons-only cluster constitution, but previously elusive...
January 15, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/29334381/the-molecular-basis-of-subtype-selectivity-of-human-kinin-g-protein-coupled-receptors
#2
Lisa Joedicke, Jiafei Mao, Georg Kuenze, Christoph Reinhart, Tejaswi Kalavacherla, Hendrik R A Jonker, Christian Richter, Harald Schwalbe, Jens Meiler, Julia Preu, Hartmut Michel, Clemens Glaubitz
G-protein-coupled receptors (GPCRs) are the most important signal transducers in higher eukaryotes. Despite considerable progress, the molecular basis of subtype-specific ligand selectivity, especially for peptide receptors, remains unknown. Here, by integrating DNP-enhanced solid-state NMR spectroscopy with advanced molecular modeling and docking, the mechanism of the subtype selectivity of human bradykinin receptors for their peptide agonists has been resolved. The conserved middle segments of the bound peptides show distinct conformations that result in different presentations of their N and C termini toward their receptors...
January 15, 2018: Nature Chemical Biology
https://www.readbyqxmd.com/read/29332384/structure-of-lipid-nanoparticles-containing-sirna-or-mrna-by-dynamic-nuclear-polarization-enhanced-nmr-spectroscopy
#3
Jasmine Viger-Gravel, Anna Schantz, Arthur C Pinon, Aaron J Rossini, Staffan Schantz, Lyndon Emsley
Here we show how dynamic nuclear polarization (DNP) nuclear magnetic resonance (NMR) spectroscopy experiments permit the atomic level structural characterization of loaded and empty lipid nanoparticles (LNPs). The LNPs used here were synthesized by microfluidic mixing technique and are composed of ionizable cationic lipid (DLin-MC3-DMA), a phospholipid (DSPC), cholesterol and PEG (DMPE-PEG 2000), as well as encapsulated cargoes which are either phosphorothioated-siRNA (50 or 100%) or mRNA. We show that LNPs form physically stable complexes with bioactive drug siRNA for a period of 94 days...
January 14, 2018: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/29330069/conformation-and-trimer-association-of-the-transmembrane-domain-of-the-parainfluenza-virus-fusion-protein-in-lipid-bilayers-from-solid-state-nmr-insights-into-the-sequence-determinants-of-trimer-structure-and-fusion-activity
#4
Myungwoon Lee, Hongwei Yao, Byungsu Kwon, Alan J Waring, Peter Ruchala, Chandan Singh, Mei Hong
Enveloped viruses enter cells by using their fusion proteins to merge the virus lipid envelope and the cell membrane. While crystal structures of the water-soluble ectodomains of many viral fusion proteins have been determined, the structure and assembly of the C-terminal transmembrane domain (TMD) remains poorly understood. Here we use solid-state NMR to determine the backbone conformation and oligomeric structure of the TMD of the parainfluenza virus 5 (PIV5) fusion protein. 13C chemical shifts indicate that the central leucine-rich segment of the TMD is α-helical in POPC/cholesterol membranes and POPE membranes, while the Ile- and Val-rich termini shift to the β-strand conformation in the POPE membrane...
January 9, 2018: Journal of Molecular Biology
https://www.readbyqxmd.com/read/29329809/new-n-guanidinium-chitosan-silica-ionic-microhybrids-as-efficient-adsorbent-for-dye-removal-from-waste-water
#5
Ahmed Salama, Peter Hesemann
N-guanidinium chitosan acetate, a new chitosan derivative, was prepared via direct guanylation reaction between chitosan and cyanamide in the presence of scandium (III) triflate. Treatment of N-guanidinium chitosan acetate with 3-(trihydroxysilyl)-1-propanesulphonic acid followed by sol-gel reaction allowed accessing N-guanidinium chitosan silica hybrid material. The new ionic microhybrid was characterized using 13C and 29Si solid state NMR, IR spectroscopy, scanning electron microscopy and thermogravimetry...
January 9, 2018: International Journal of Biological Macromolecules
https://www.readbyqxmd.com/read/29327221/whole-cell-solid-state-nmr-study-of-chlamydomonas-reinhardtii-microalgae
#6
Alexandre A Arnold, Jean-Philippe Bourgouin, Bertrand Genard, Dror E Warschawski, Réjean Tremblay, Isabelle Marcotte
In vivo or whole-cell solid-state NMR is an emerging field which faces tremendous challenges. In most cases, cell biochemistry does not allow the labelling of specific molecules and an in vivo study is thus hindered by the inherent difficulty of identifying, among a formidable number of resonances, those arising from a given molecule. In this work we examined the possibility of studying, by solid-state NMR, the model organism Chlamydomonas reinhardtii fully and non-specifically 13C labelled. The extension of NMR-based dynamic filtering from one-dimensional to two-dimensional experiments enabled an enhanced selectivity which facilitated the assignment of cell constituents...
January 11, 2018: Journal of Biomolecular NMR
https://www.readbyqxmd.com/read/29324246/spin-echo-based-diagonal-peak-suppression-in-solid-state-mas-nmr-homonuclear-chemical-shift-correlation-spectra
#7
Kaiyu Wang, Zhiyong Zhang, Xiaoyan Ding, Fang Tian, Yuqing Huang, Zhong Chen, Riqiang Fu
The feasibility of using the spin-echo based diagonal peak suppression method in solid-state MAS NMR homonuclear chemical shift correlation experiments is demonstrated. A complete phase cycling is designed in such a way that in the indirect dimension only the spin diffused signals are evolved, while all signals not involved in polarization transfer are refocused for cancellation. A data processing procedure is further introduced to reconstruct this acquired spectrum into a conventional two-dimensional homonuclear chemical shift correlation spectrum...
December 28, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/29324182/recent-advances-in-solid-state-nuclear-magnetic-resonance-spectroscopy
#8
Sharon E Ashbrook, John M Griffin, Karen E Johnston
The sensitivity of nuclear magnetic resonance (NMR) spectroscopy to the local atomic-scale environment offers great potential for the characterization of a diverse range of solid materials. Despite offering more information than its solution-state counterpart, solid-state NMR has not yet achieved a similar level of recognition, owing to the anisotropic interactions that broaden the spectral lines and hinder the extraction of structural information. Here, we describe the methods available to improve the resolution of solid-state NMR spectra and the continuing research in this area...
January 11, 2018: Annual Review of Analytical Chemistry
https://www.readbyqxmd.com/read/29323443/dicationic-e4-chains-e-p-as-sb-bi-embedded-in-the-coordination-sphere-of-transition-metals
#9
Manfred Scheer, Luis Dütsch, Martin Fleischmann, Stefan Welsch, Gabor Balaszs, Werner Kremer
A comparison of the oxidation chemistry of the complexes [{CpMo(CO)2}2(µ,η2:η2-E2)] (E = P (A), As (B), Sb (C), Bi (D)) is presented. The oxidation of A-D with [Thia]+ (= [C12H8S2]+) results in the selective formation of the dicationic E4 complexes [{CpMo(CO)2}4(µ4,η2:η2:η2:η2-E4)]2+ (E = P (1), As (2), Sb (3), Bi (4)) stabilized by four [CpMo(CO)2] fragments. The formation of the corresponding monocations [A]+, [C]+ and [D]+ could not be detected by cyclovoltammetry, EPR or NMR spectroscopy. This suggests a fast dimerization and no dissociation in solution, which is also predicted by DFT calculations...
January 11, 2018: Angewandte Chemie
https://www.readbyqxmd.com/read/29323432/orthogonal-%C3%A2-%C3%A2-f-labeling-for-solid-state-nmr-reveals-the-conformation-and-orientation-of-short-peptaibols-in-membranes
#10
Stephan L Grage, Sezgin Kara, Andrea Bordessa, Véronique Doan, Fabio Rizzolo, Marina Putzu, Tomáš Kubař, Anna Maria Papini, Grégory Chaume, Thierry Brigaud, Sergii Afonin, Anne S Ulrich
Peptaibols are promising drug candidates in view of their interference with cellular membranes. Knowledge of their lipid interactions and membrane-bound structure is needed for understanding their activity and should be in principle accessible by solid-state NMR. However, their unusual amino acid composition and their non-canonical conformations make it very challenging to find suitable NMR labels. Especially in the case of short sequences, new strategies are required to maximize the structural information that can be obtained from each label...
January 11, 2018: Chemistry: a European Journal
https://www.readbyqxmd.com/read/29321596/high-resolution-31p-nmr-spectroscopy-generates-a-quantitative-evolution-profile-of-phosphorous-translocation-in-germinating-sesame-seed
#11
Honghao Cai, Wei-Gang Chuang, Xiaohong Cui, Ren-Hao Cheng, Kuohsun Chiu, Zhong Chen, Shangwu Ding
Phosphorus metabolism and circulation are essential bio-physicochemical processes during development of a plant and have been extensively studied and known to be affected by temperature, humidity, lighting, hormones etc. However, a quantitative description of how various phosphorous species evolve over time has not been reported. In this work, a combined 31P liquid and solid state NMR spectroscopic methodology is employed, supported by a new extraction scheme and data analysis method, to carry out a quantitative investigation of phosphorous circulation in germinating sesame seeds in dark and under illumination with and without adding a growth hormone...
January 10, 2018: Scientific Reports
https://www.readbyqxmd.com/read/29320170/synthesis-and-characterization-of-the-most-active-copper-atrp-catalyst-based-on-tris-4-dimethylaminopyridyl-methyl-amine
#12
Thomas G Ribelli, Marco Fantin, Jean-Claude Daran, Kyle F Augustine, Rinaldo Poli, Krzysztof Matyjaszewski
The synthesis and characterization of tris[(4-dimethylaminopyridyl)methyl]amine (TPMANMe2) as a ligand for copper catalyzed atom transfer radical polymerization (ATRP) is reported. In solution, the [CuI(TPMANMe2)Br] complex shows fluxionality by variable temperature NMR, indicating rapid ligand exchange. In the solid-state, the [CuII(TPMANMe2)Br][Br] complex exhibits a slightly distorted trigonal bipyramidal geometry (τ = 0.89). The UV-Vis spectrum of [CuII(TPMANMe2)Br]+ salts is similar to those of other pyridine-based ATRP catalysts...
January 10, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/29319709/displacement-of-%C3%AE-5-cyclopentadienyl-ligands-from-half-sandwich-c-c-nhc-cyanoalkyl-nickel-ii-metallacycles-further-insight-into-the-structure-of-the-resulting-cp-free-nickelacycles-and-a-catalytic-activity-study
#13
Bernardo de P Cardoso, Jean-Marie Bernard-Schaaf, Saurabh Shahane, Luis F Veiros, Michael J Chetcuti, Vincent Ritleng
Four cationic C,C-(NHC-cyanoalkyl)-nickel(ii) metallacyclic complexes, [Ni{Me-NHC-CH2CH(CN)}(NCMe)](PF6) (2a), [Ni{Mes-NHC-CH2CH(CN)}(NCMe)](PF6) (2b), [Ni{Mes-NHC-(CH2)2CH(CN)}(NCMe)](PF6) (2c) and [Ni{DiPP-NHC-(CH2)2CH(CN)}(NCMe)](PF6) (2d), were prepared by the removal of the Cp ligand under acidic conditions at 0 °C from the corresponding half-sandwich nickelacycles [NiCp{R-NHC-(CH2)nCH(CN)}] (1a-1d; Cp = η5-C5H5; n = 1 or 2; R-NHC-(CH2)nCH(CN) = 1-R-3-[(CH2)nCH(CN)]-imidazol-2-ylidene). Full characterization of 2a-d by 1H and 13C{1H} NMR spectroscopy in CD3CN and pyridine-d5, ATR-FTIR spectroscopy, mass spectrometry, and CHN microanalyses established the presence of only one acetonitrile ligand per nickel atom in the solid state...
January 10, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/29318098/synthesis-and-liquid-crystalline-properties-of-unsymmetrically-substituted-naphthalenediimides-with-a-polar-headgroup-effect-of-amide-hydrogen-bonding-and-alkyl-chain-length
#14
Namdev V Ghule, Rajesh S Bhosale, Sidhanath V Bhosale, Turlapati Srikanth, Nandiraju V S Rao, Sheshanath V Bhosale
A series of new unsymmetrically substituted naphthalenediimide (NDI) moieties NDI-1 to NDI-6 were synthesized. The structures of these compounds were confirmed by means of FT-IR, 1H NMR, 13C NMR, ESI-mass and HRMS spectroscopic measurements. UV/Vis and fluorescence spectroscopy were employed to investigate the photophysical properties of the prepared compounds in solution and in the solid state. Using the onset of UV/Vis absorption, the optical band gaps were calculated. Cyclic voltammetry measurements were performed to study the electrochemical behavior and to calculate the LUMO energy levels...
January 2018: ChemistryOpen
https://www.readbyqxmd.com/read/29316473/host-guest-interaction-of-styrene-and-ethylbenzene-in-mil-53-studied-by-solid-state-nmr
#15
Shenhui Li, Jing Li, Jing Tang, Feng Deng
Solid-state NMR was utilized to explore the host-guest interaction between adsorbate and adsorbent at atomic level to understand the separation mechanism of styrene (St) and ethylbenzene (EB) in MIL-53(Al). 13C-27Al double-resonance NMR experiments revealed that the host-guest interaction between St and MIL-53 was much stronger than that of EB adsorption. In addition, 13C DIPSHIFT experiments suggested that the adsorbed St was less mobile than EB confined inside the MIL-53 pore. Furthermore, the host-guest interaction model between St, EB and MIL-53 was established on the basis of the spatial proximities information extracted from 2D 1H-1H homo-nuclear correlation NMR experiments...
December 29, 2017: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/29316398/probing-interactions-of-n-donor-molecules-with-open-metal-sites-within-paramagnetic-cr-mil-101-a-solid-state-nmr-spectroscopic-and-dft-study
#16
Thomas Wittmann, Arobendo Mondal, Carsten B L Tschense, Johannes J Wittmann, Ottokar Klimm, Renée Siegel, Björn Corzilius, Birgit Weber, Martin Kaupp, Jürgen Senker
Understanding host-guest interactions is one of the key-requirements for adjusting properties in metal-organic frameworks. In particular, systems with coordinatively unsaturated Lewis acidic metal sites feature highly selective adsorption processes. This is attributed to strong interactions with Lewis basic guest molecules. Here we show, that a combination of 13C MAS NMR spectroscopy with state-of-the-art DFT calculations allows to unravel the interactions of water, 2‑aminopyridine, 3-aminopyridine and diethylamine with the open metal sites in Cr-MIL-101...
January 9, 2018: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/29316053/templated-growth-of-inp-nanocrystals-with-a-polytwistane-structure
#17
Andrew Ritchhart, Brandi Cossairt
We have synthesized InP nanocrystals of an unprecedented crystal phase at low temperature (35 - 100 °C) by templated growth of InP magic-sized clusters. With the addition of stoichiometric equivalents of P(SiMe3)3 to the starting cluster, we demonstrate nanocrystal growth mediated through a partial dissolution and recrystallization pathway. This growth process was monitored using a combination of in situ UV-Vis and 31P NMR spectroscopy, revealing the intermediacy of smaller cluster species of higher symmetry...
January 5, 2018: Angewandte Chemie
https://www.readbyqxmd.com/read/29315751/does-the-choice-of-the-crystal-structure-influence-the-results-of-the-periodic-dft-calculations-a-case-of-glycine-alpha-polymorph-gipaw-nmr-parameters-computations
#18
Łukasz Szeleszczuk, Dariusz Maciej Pisklak, Monika Zielińska-Pisklak
Glycine is a common amino acid with relatively complex chemistry in solid state. Although several polymorphs (α, β, δ, γ, ε) of crystalline glycine are known, for NMR spectroscopy the most important is a polymorph, which is used as a standard for calibration of spectrometer performance and therefore it is intensively studied by both experimental methods and theoretical computation. The great scientific interest in a glycine results in a large number of crystallographic information files (CIFs) deposited in Cambridge Structural Database (CSD)...
January 5, 2018: Journal of Computational Chemistry
https://www.readbyqxmd.com/read/29315238/on-the-tautomerism-of-n-substituted-pyrazolones-1-2-dihydro-3h-pyrazol-3-ones-versus-1h-pyrazol-3-ols
#19
Eglė Arbačiauskienė, Sonata Krikštolaitytė, Aiva Mitrulevičienė, Aurimas Bieliauskas, Vytas Martynaitis, Matthias Bechmann, Alexander Roller, Algirdas Šačkus, Wolfgang Holzer
The tautomerism of 1-phenyl-1,2-dihydro-3H-pyrazol-3-One was investigated. An X-ray crystal structure analysis exhibits dimers of 1-phenyl-1H-pyrazol-3-ol units. Comparison of NMR (nuclear magnetic resonance) spectra in liquid state (¹H, 13C, 15N) with those of "fixed" derivatives, as well as with the corresponding solid state NMR spectra reveal this compound to exist predominantly as 1H-pyrazol-3-ol molecule pairs in nonpolar solvents like CDCl₃ or C₆D₆, whereas in DMSO-d₆ the corresponding monomers are at hand...
January 9, 2018: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/29314316/efficient-synthesis-of-ditopic-polyamide-receptors-for-cooperative-ion-pair-recognition-in-solution-and-solid-states
#20
Sumit Kumar Ray, Alexandre Homberg, Mahesh Vishe, Céline Besnard, Jerome Lacour
Following a late-stage functionalization strategy, a series of heteroditopic cryptand receptors were prepared - in three steps only from 1,4-dioxane. As evidenced by 1H-NMR spectroscopic and solid state analyses, these polyamide-crown ether conjugates present general ion pair binding capacity towards salts of monovalent cations and linear triatomic anions.
January 4, 2018: Chemistry: a European Journal
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