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Solid state NMR

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https://www.readbyqxmd.com/read/28107690/time-domain-nmr-as-a-new-process-monitoring-method-for-characterization-of-pharmaceutical-hydrates
#1
Stefanie Ulrike Schumacher, Benno Rothenhäusler, Alf Willmann, Jürgen Thun, Regina Moog, Martin Kuentz
Hydrates are of great pharmaceutical relevance and even though they have been characterized thoroughly by various analytical techniques, there is barely literature available on molecular mobility of the hydrate water studied by NMR relaxation in the time domain. The aim of this work was to examine the possibility of differentiating hydration states of drugs by (1)H time domain NMR (TD-NMR) regarding spin-spin and spin-lattice relaxation times (T2 and T1) using benchtop equipment. Caffeine and theophylline were selected as model compounds and binary mixtures of hydrate to anhydrate were analyzed for each drug using a spin echo and inversion recovery pulse sequence...
January 9, 2017: Journal of Pharmaceutical and Biomedical Analysis
https://www.readbyqxmd.com/read/28107633/binding-and-proton-blockage-by-amantadine-variants-of-the-influenza-m2wt-and-m2s31n-explained
#2
Christina Tzitzoglaki, Anna K Wright, Kathrin-Maria Freudenberger, Anja Hoffmann, Ian Tietjen, Ioannis Stylianakis, Felix Kolarov, David Fedida, Michaela Schmidtke, Guenter Gauglitz, Timothy A Cross, Antonios Kolocouris
While aminoadamantanes are well-established inhibitors of the influenza A M2 proton channel, the mechanisms by which they are rendered ineffective against M2S31N are unclear. Solid state NMR, isothermal titration calorimetry, electrophysiology, anti-viral assays and molecular dynamics simulations suggest stronger binding interactions for aminoadamantanes to M2WT compared to negligible or weak binding to M2S31N. This is due to reshaping of the M2pore when N31 is present, which in contrast to WT, leads: A) to the loss of the V27 pocket for the adamantyl cage and to a predominant orientation of the ligand's ammonium group toward the N-terminus and, B) to the lack of a helical kink upon ligand binding...
January 20, 2017: Journal of Medicinal Chemistry
https://www.readbyqxmd.com/read/28099024/surface-interactions-and-confinement-of-methane-a-high-pressure-magic-angle-spinning-nmr-and-computational-chemistry-study
#3
Salim Ok, David W Hoyt, Amity Andersen, Julie Sheets, Susan A Welch, David R Cole, Karl Todd Mueller, Nancy M Washton
Characterization and modeling of the molecular-level behavior of simple hydrocarbon gases, such as methane, in the presence of both nonporous and nano-porous mineral matrices allows for predictive understanding of important processes in engineered and natural systems. In this study, changes in local electromagnetic environments of the carbon atoms in methane under conditions of high pressure (up to 130 bar) and moderate temperature (up to 346 K) were observed with 13C magic-angle spinning (MAS) NMR spectroscopy while the methane gas was mixed with two model solid substrates: a fumed non-porous, 12 nm particle size silica and a mesoporous silica with 200 nm particle size and 4 nm average pore diameter...
January 18, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28099013/dynamic-nuclear-polarization-signal-enhancement-with-high-affinity-biradical-tags
#4
Rivkah Tamar Rogawski, Ivan V Sergeyev, Yongjun Li, Maria Francesca Ottaviani, Virginia W Cornish, Ann E McDermott
Dynamic nuclear polarization is an emerging technique for sensitizing solid state NMR experiments by transferring polarization from electrons to nuclei. Stable biradicals, the polarization source for the cross effect mechanism, are typically co-dissolved at millimolar concentrations with proteins of interest. Here we describe the high-affinity biradical tag TMP-T, created by covalently linking trimethoprim, a nanomolar affinity ligand of dihydrofolate reductase (DHFR), to the biradical polarizing agent TOTAPOL...
January 18, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28097775/breaking-the-tetra-coordinated-framework-rule-new-clathrate-ba8-m24-p28-%C3%AE-m-cu-zn
#5
Juli-Anna Dolyniuk, Julia V Zaikina, Derrick C Kaseman, Sabyasachi Sen, Kirill Kovnir
A new clathrate type has been discovered in the Ba/Cu/Zn/P system. The crystal structure of the Ba8 M24 P28+δ (M=Cu/Zn) clathrate is composed of the pentagonal dodecahedra common to clathrates along with a unique 22-vertex polyhedron with two hexagonal faces capped by additional partially occupied phosphorus sites. This is the first example of a clathrate compound where the framework atoms are not in tetrahedral or trigonal-pyramidal coordination. In Ba8 M24 P28+δ a majority of the framework atoms are five- and six-coordinated, a feature more common to electron-rich intermetallics...
January 18, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28094949/how-high-concentrations-of-proteins-stabilize-the-amorphous-state-of-calcium-orthophosphate-a-solid-state-nmr-study-of-the-casein-case
#6
Paulo De Sa Peixoto, Juliana Valle Costa Silva, Guillaume Pierre Laurent, Marc Schmutz, Daniel Thomas, Antoine Bouchoux, Genevieve Gesan-Guiziou
Understanding how proteins stabilize Amorphous Calcium ortho-Phosphate (ACP) phases is of great importance in biology and for pharmaceutical or food applications. Until now, most of the former investigations about ACP-protein stability and equilibrium were performed in conditions where ACP colloidal nanoclusters are surrounded by low to moderate concentrations of peptides or proteins (15-30 g.L-1). As a result, the question of ACP-protein interactions in highly concentrated protein systems has clearly been overlooked, whereas it corresponds to actual industrial conditions such as drying or membrane filtration in the dairy industry for instance...
January 17, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28094514/structural-model-of-the-tubular-assembly-of-the-rous-sarcoma-virus-capsid-protein
#7
Jaekyun Jeon, Xin Qiao, Ivan Hung, Alok K Mitra, Ambroise Desfosses, Daniel Huang, Peter L Gor'kov, Rebecca C Craven, Richard L Kingston, Zhehong Gan, Fangqiang Zhu, Bo Chen
The orthoretroviral capsid protein (CA) assembles into polymorphic capsids, whose architecture, assembly and stability are still being investigated. The N-terminal and C-terminal domains of CA (NTD and CTD, respectively) engage in both homotypic and heterotypic interactions to create the capsid. Hexameric turrets formed by the NTD decorate the majority of the capsid surface. We report nearly-complete solid-state NMR (ssNMR) resonance assignments of Rous sarcoma virus (RSV) CA, assembled into hexamer tubes that mimic the authentic capsid...
January 17, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28090725/non-aqueous-microwave-assisted-syntheses-of-deca-and-hexa-molybdovanadates
#8
Samuel Spillane, Rupali Sharma, Athanasios Zavras, Roger Mulder, C André Ohlin, Lars Goerigk, Richard A J O'Hair, Chris Ritchie
We report a new approach for the synthesis of heterohexa- and heterodecametalates via the use of non-aqueous, microwave-assisted reaction conditions. The two novel molybdovanadates have been isolated and characterized in the solid and solution states using single-crystal X-ray diffraction, FT-IR, UV/Vis, multinuclear NMR spectroscopy, and ESI-MS. The relative stabilities of the possible structural isomers were probed using dispersion-corrected DFT calculations for both polyoxometalate systems.
January 16, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28080040/insights-into-thiol-aromatic-interactions-a-stereoelectronic-basis-for-s-h-%C3%AF-interactions
#9
Christina R Forbes, Sudipta Kumar Sinha, Himal Kanti Ganguly, Shi Bai, Glenn P A Yap, Sandeep Patel, Neal J Zondlo
Thiols can engage favorably with aromatic rings in S-H/π interactions, within abiological systems and within proteins. However, the underlying bases for S-H/π interactions are not well understood. The crystal structure of Boc-L-4-thiolphenylalanine tert-butyl ester revealed crystal organization centered on the interaction of the thiol S-H with the aromatic ring of an adjacent molecule, with a through-space Hthiol...Caromatic distance of 2.71 Å, below the 2.90 Å sum of the van der Waals radii of H and C...
January 12, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28079219/internal-dynamics-in-helical-molecules-studied-by-x-ray-diffraction-nmr-spectroscopy-and-dft-calculations
#10
Martin Dračínský, Jan Storch, Vladimír Církva, Ivana Císařová, Jan Sýkora
The conformational behaviour of a prototype helical molecule, [6]helicene, and its derivatives was studied in solution and the solid state. Available crystal structures of [6]helicene revealed surprisingly large flexibility of this molecule and variable-temperature NMR experiments provided unusual temperature dependence of chemical shifts of hydrogen, carbon and fluorine atoms in the peripheral aromatic rings of [6]helicene and tetrafluoro[6]helicene. These chemical shift changes were interpreted as a consequence of the helicene 'pitch' opening with elevated temperature, and the experimental data were corroborated by DFT calculations of the chemical shift dependence on the helicene conformation and by variable-temperature DFT molecular dynamics simulations...
January 12, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28078892/dynamical-transitions-at-low-temperatures-in-the-nearest-hydration-shell-of-phospholipid-bilayers
#11
Victoria N Syryamina, Sergei Andreevich Dzuba
For the so-called dynamical transition from harmonic to anharmonic (or diffusive) motions in biological systems, the presence of hydration water is important. To explain the molecular mechanism of this transition, the information on molecular motions in the nearest hydration shell would be helpful. In this work, to study molecular motions in the nearest hydration shell of spin-labeled model biological membranes, a pulsed version of electron paramagnetic resonance (EPR)-electron spin echo envelope modulation (ESEEM) spectroscopy-is employed...
January 12, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28078416/poly-ethylene-glycol-functionalization-of-monolithic-poly-divinyl-benzene-for-improved-miniaturized-solid-phase-extraction-of-protein-rich-samples
#12
Esme Candish, Aminreza Khodabandeh, Marianne Gaborieau, Thomas Rodemann, Robert A Shellie, Andrew A Gooley, Emily F Hilder
Non-specific protein adsorption on hydrophobic solid phase extraction (SPE) adsorbents can reduce the efficacy of purification. To improve sample clean-up, poly(divinyl benzene) (PDVB) monoliths grafted with hydrophilic polyethylene glycol methacrylate (PEGMA) were developed. Residual vinyl groups (RVGs) of the PDVB were employed as anchor points for PEGMA grafting. Two PEGMA monomers, M n 360 and 950, were compared for graft solutions containing 5-20% monomer. Protein binding was qualitatively screened using fluorescently labeled human serum albumin (HSA) to determine optimal PEGMA concentration...
January 11, 2017: Analytical and Bioanalytical Chemistry
https://www.readbyqxmd.com/read/28076820/probing-conformational-changes-during-the-gating-cycle-of-a-potassium-channel-in-lipid-bilayers
#13
Elwin A W van der Cruijsen, Alexander V Prokofyev, Olaf Pongs, Marc Baldus
Ion conduction across the cellular membrane requires the simultaneous opening of activation and inactivation gates of the K(+) channel pore. The bacterial KcsA channel has served as a powerful system for dissecting the structural changes that are related to four major functional states associated with K(+) gating. Yet, the direct observation of the full gating cycle of KcsA has remained structurally elusive, and crystal structures mimicking these gating events require mutations in or stabilization of functionally relevant channel segments...
January 10, 2017: Biophysical Journal
https://www.readbyqxmd.com/read/28075583/amyloid-fibril-polymorphism-almost-identical-on-the-atomic-level-mesoscopically-very-different
#14
Carolin Seuring, Joeri Verasdonck, Philippe Ringler, Riccardo Cadalbert, Henning Stahlberg, Anja Böckmann, Beat H Meier, Roland Riek
Amyloid polymorphism of twisted and straight β-endorphin fibril was studied by negative-stain transmission electron microscopy, scanning transmission electron microscopy, and solid-state nuclear magnetic resonance spectroscopy. While fibrils assembled in the presence of salt form flat, striated ribbons, in the absence of salt they formed mainly twisted filaments. To get insights into their structural differences at the atomic level, 3D solid-state NMR spectra on both fibril types were acquired allowing the detection of the differences in chemical shifts of 13C and 15N atoms in both preparations...
January 11, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28075555/familial-mutations-may-switch-conformational-preferences-in-%C3%AE-synuclein-fibrils
#15
Liang Xu, Buyong Ma, Ruth Nussinov, Damien Thompson
The pathogenesis of Parkinson's disease is closely associated with the aggregation of the α-synuclein protein. Several familial mutants have been identified and shown to affect the aggregation kinetics of α-synuclein through distinct molecular mechanisms. Quantitative evaluation of the relative stabilities of the wild type and mutant fibrils is crucial for understanding the aggregation process and identifying the key component steps. In this work, we examined two topologically different α-synuclein fibril structures that are either determined by solid-state NMR method or modelled based on solid-state NMR data, and characterized their conformational properties and thermodynamic stabilities using molecular dynamics simulations...
January 11, 2017: ACS Chemical Neuroscience
https://www.readbyqxmd.com/read/28074945/solid-state-nmr-at-natural-isotopic-abundance-for-the-determination-of-conformational-polymorphism-the-case-of-designed-%C3%AE-turn-peptides-containing-di-prolines
#16
Jayasubba Reddy Yarava, Rajesh Sonti, K Kantharaju, S Raghothama, K V Ramanathan
The proton double quantum-carbon single quantum correlation experiment has been applied to designed peptides in the solid state in natural isotopic abundance. Analogous to nOe studies in solution, through-space double-quantum connectivities have been exploited to obtain the cis-trans conformational polymorphism of diproline residues occurring at β-turns in the peptides.
January 19, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28074361/partially-deuterated-samples-of-het-s-218-289-fibrils-assignment-and-deuterium-isotope-effect
#17
Albert A Smith, Francesco Ravotti, Emilie Testori, Riccardo Cadalbert, Matthias Ernst, Anja Böckmann, Beat H Meier
Fast magic-angle spinning and partial sample deuteration allows direct detection of (1)H in solid-state NMR, yielding significant gains in mass sensitivity. In order to further analyze the spectra, (1)H detection requires assignment of the (1)H resonances. In this work, resonance assignments of backbone H(N) and Hα are presented for HET-s(218-289) fibrils, based on the existing assignment of Cα, Cβ, C', and N resonances. The samples used are partially deuterated for higher spectral resolution, and the shifts in resonance frequencies of Cα and Cβ due to the deuterium isotope effect are investigated...
January 10, 2017: Journal of Biomolecular NMR
https://www.readbyqxmd.com/read/28071716/lytic-polysaccharide-monooxygenases-disrupt-the-cellulose-fibers-structure
#18
Ana Villares, Céline Moreau, Chloé Bennati-Granier, Sona Garajova, Loïc Foucat, Xavier Falourd, Bodo Saake, Jean-Guy Berrin, Bernard Cathala
Lytic polysaccharide monooxygenases (LPMOs) are a class of powerful oxidative enzymes that breakdown recalcitrant polysaccharides such as cellulose. Here we investigate the action of LPMOs on cellulose fibers. After enzymatic treatment and dispersion, LPMO-treated fibers show intense fibrillation. Cellulose structure modifications visualized at different scales indicate that LPMO creates nicking points that trigger the disintegration of the cellulose fibrillar structure with rupture of chains and release of elementary nanofibrils...
January 10, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28069412/influence-of-glutamic-acid-residues-and-ph-on-the-properties-of-transmembrane-helices
#19
Venkatesan Rajagopalan, Denise V Greathouse, Roger E Koeppe
Negatively charged side chains are important for the function of particular ion channels and certain other membrane proteins. To investigate the influence of single glutamic acid side chains on helices that span lipid-bilayer membranes, we have employed GWALP23 (acetyl-GGALW(5)LALALALALALALW(19)LAGA-amide) as a favorable host peptide framework. We substituted individual Leu residues with Glu residues (L12E or L14E or L16E) and incorporated specific (2)H-labeled alanine residues within the core helical region or near the ends of the sequence...
January 7, 2017: Biochimica et Biophysica Acta
https://www.readbyqxmd.com/read/28067501/cation-miscibility-and-lithium-mobility-in-nasicon-li1-xti2-xscx-po4-3-0-%C3%A2-x-%C3%A2-0-5-series-a-combined-nmr-and-impedance-study
#20
Radhouene Kahlaoui, Kamel Arbi, Isabel Sobrados, Ricardo Jimenez, Jesus Sanz, Riadh Ternane
Rhombohedral NASICON compounds with general formula Li1+xTi2-xScx(PO4)3 (0 ≤ x ≤ 0.5) have been prepared using a conventional solid-state reaction and characterized by X-ray diffraction (XRD), nuclear magnetic resonance (NMR), and impedance spectroscopy. The partial substitution of Ti(4+) by Sc(3+) and Li(+) in pristine LiTi2(PO4)3 increases unit-cell dimensions and the number of charge carriers. In Sc-rich samples, the analysis of XRD data and (6)Li/(7)Li, (31)P, and (45)Sc MAS NMR spectra confirms the presence of secondary LiScO2 and LiScP2O7 phases that reduce the amount of lithium incorporated in the NASICON phase...
January 9, 2017: Inorganic Chemistry
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