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https://www.readbyqxmd.com/read/28219822/ultrafast-acquisition-of-1-h-1-h-dipolar-correlation-experiments-in-spinning-elastomers
#1
Laetitia Rouger, Maxime Yon, Vincent Sarou-Kanian, Franck Fayon, Jean-Nicolas Dumez, Patrick Giraudeau
We show that two widely used 2D solid-state NMR (ssNMR) pulse sequences can be implemented in an ultrafast (UF) manner, and yield 2D spectra of elastomers in a single scan, under magic-angle spinning. UF 2D ssNMR provides an acceleration of one to several orders of magnitude for classic experiments.
February 9, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28217261/affinity-of-rimantadine-enantiomers-against-influenza-a-m2-protein-revisited
#2
Antonios Drakopoulos, Christina Tzitzoglaki, Chulong Ma, Kathrin Freudenberger, Anja Hoffmann, Yanmei Hu, Günter Gauglitz, Michaela Schmidtke, Jun Wang, Antonios Kolocouris
Recent findings from solid state NMR (ssNMR) studies suggested that the (R)-enantiomer of rimantadine binds to the full M2 protein with higher affinity than the (S)-enantiomer. Intrigued by these findings, we applied functional assays, such as antiviral assay and electrophysiology (EP), to evaluate the binding affinity of rimantadine enantiomers to the M2 protein channel. Unexpectedly, no significant difference was found between the two enantiomers. Our experimental data based on the full M2 protein function were further supported by alchemical free energy calculations and isothermal titration calorimetry (ITC) allowing an evaluation of the binding affinity of rimantadine enantiomers to the M2TM pore...
February 9, 2017: ACS Medicinal Chemistry Letters
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
#3
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/28195488/surface-sensitive-nmr-detection-of-the-sei-layer-on-reduced-graphene-oxide
#4
Michal Leskes, Gunwoo Kim, Tao Liu, Alison L Michan, Fabien Aussenac, Patrick Dorffer, Subhradip Paul, Clare P Grey
The solid electrolyte interphase (SEI) is detrimental for rechargeable batteries' performance and lifetime. Understanding its formation requires analytical techniques that provide molecular level insight. Here dynamic nuclear polarization (DNP) is utilized for the first time for enhancing the sensitivity of solid state NMR (ssNMR) spectroscopy to the SEI. The approach is demonstrated on reduced-graphene oxide (rGO) cycled in Li-ion cells in natural abundance and 13C-enriched electrolyte solvents. Our results indicate that DNP enhances the signal of outer SEI layers, enabling detection of natural abundance 13C spectra from this component of the SEI at reasonable timeframes...
February 14, 2017: Journal of Physical Chemistry Letters
https://www.readbyqxmd.com/read/28191584/sizable-dynamics-in-small-pores-co2-location-and-motion-in-the-%C3%AE-mg-formate-metal-organic-framework
#5
Yuanjun Lu, Bryan E G Lucier, Yue Zhang, Pengju Ren, Anmin Zheng, Yining Huang
Metal-organic frameworks (MOFs) are promising materials for carbon dioxide (CO2) adsorption and storage; however, many details regarding CO2 dynamics and specific adsorption site locations within MOFs remain unknown, restricting the practical uses of MOFs for CO2 capture. The intriguing α-magnesium formate (α-Mg3(HCOO)6) MOF can adsorb CO2 and features a small pore size. Using an intertwined approach of (13)C solid-state NMR (SSNMR) spectroscopy, (1)H-(13)C cross-polarization SSNMR, and computational molecular dynamics (MD) simulations, new physical insights and a rich variety of information have been uncovered regarding CO2 adsorption in this MOF, including the surprising suggestion that CO2 motion is restricted at elevated temperatures...
February 13, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28166408/characterization-of-the-particle-size-and-polydispersity-of-dicumarol-using-solid-state-nmr-spectroscopy
#6
Kassibla Elodie Dempah, Joseph W Lubach, Eric J Munson
A variety of particle sizes of a model compound, dicumarol, were prepared and characterized in order to investigate the correlation between particle size and solid-state NMR (SSNMR) proton spin-lattice relaxation ((1)H T1) times. Conventional laser diffraction and scanning electron microscopy were used as particle size measurement techniques and showed crystalline dicumarol samples with sizes ranging from tens of micrometers to a few micrometers. Dicumarol samples were prepared using both bottom-up and top-down particle size control approaches, via antisolvent microprecipitation and cryogrinding...
February 15, 2017: Molecular Pharmaceutics
https://www.readbyqxmd.com/read/28157561/indirect-detection-of-infinite-speed-mas-solid-state-nmr-spectra
#7
Frédéric A Perras, Amrit Venkatesh, Michael P Hanrahan, Tian Wei Goh, Wenyu Huang, Aaron J Rossini, Marek Pruski
Heavy spin-1/2 nuclides are known to possess very large chemical shift anisotropies that can challenge even the most advanced magic-angle-spinning (MAS) techniques. Wide manifolds of overlapping spinning sidebands and insufficient excitation bandwidths often obfuscate meaningful spectral information and force the use of static, low-resolution solid-state (SS)NMR methods for the characterization of materials. To address these issues, we have merged fast-magic-angle-turning (MAT) and dipolar heteronuclear multiple-quantum coherence (D-HMQC) experiments to obtain D-HMQC-MAT pulse sequences which enable the rapid acquisition of 2D SSNMR spectra that correlate isotropic (1)H chemical shifts to the indirectly detected isotropic "infinite-MAS" spectra of heavy spin-1/2 nuclides...
January 18, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28130009/practical-considerations-for-the-acquisition-of-ultra-wideline-14-n-nmr-spectra
#8
Stanislav L Veinberg, Austin W Lindquist, Michael J Jaroszewicz, Robert W Schurko
Several considerations for the acquisition, processing, and analysis of high quality ultra-wideline (UW) (14)N solid-state NMR (SSNMR) powder patterns under static conditions are discussed. It is shown that the (14)N quadrupolar parameters may be determined accurately using the frequencies of only two discontinuities in (14)N NMR powder patterns that are dominated by the first-order quadrupolar interaction, thereby eliminating the need for the acquisition of the entire pattern and concomitantly reducing experimental time...
December 21, 2016: Solid State Nuclear Magnetic Resonance
https://www.readbyqxmd.com/read/28094949/how-high-concentrations-of-proteins-stabilize-the-amorphous-state-of-calcium-orthophosphate-a-solid-state-nuclear-magnetic-resonance-nmr-study-of-the-casein-case
#9
Paulo De Sa Peixoto, Juliana V C Silva, Guillaume Laurent, Marc Schmutz, Daniel Thomas, Antoine Bouchoux, Geneviève Gésan-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 under 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 30, 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
#10
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 27, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28068097/characterization-of-phase-separation-propensity-for-amorphous-spray-dried-dispersions
#11
Daniel McNamara, Shawn Yin, Duohai Pan, George Crull, Peter Timmins, Balvinder Vig
A generalized screening approach, applying isothermal calorimetry at 37 °C 100% RH, to formulations of spray dried dispersions (SDDs) for two active pharmaceutical ingredients (APIs) (BMS-903452 and BMS-986034) is demonstrated. APIs 452 and 034, with similar chemotypes, were synthesized and promoted during development for oral dosing. Both APIs were formulated as SDDs for animal exposure studies using the polymer hydroxypropylmethlycellulose acetyl succinate M grade (HPMCAS-M). 452 formulated at 30% (wt/wt %) was an extremely robust SDD that was able to withstand 40 °C 75% RH open storage conditions for 6 months with no physical evidence of crystallization or loss of dissolution performance...
January 20, 2017: Molecular Pharmaceutics
https://www.readbyqxmd.com/read/28063904/a-rational-approach-towards-development-of-amorphous-solid-dispersions-experimental-and-computational-techniques
#12
Paroma Chakravarty, Joseph W Lubach, Jonathan Hau, Karthik Nagapudi
The purpose of this study was to determine the drug-polymer miscibility of GENE-A, a Genentech molecule, and hydroxypropyl methylcellulose-acetate succinate (HPMC-AS), a polymer, using computational and experimental approaches. The Flory-Huggins interaction parameter,χ, was obtained by calculating the solubility parameters for GENE-A and HPMC-AS over the temperature range of 25-100°C to obtain the free energy of mixing at different drug loadings (0-100%) using the Materials Studio modeling and simulation platform (thermodynamic approach)...
January 4, 2017: International Journal of Pharmaceutics
https://www.readbyqxmd.com/read/28052060/structural-variation-in-amyloid-%C3%AE-fibrils-from-alzheimer-s-disease-clinical-subtypes
#13
Wei Qiang, Wai-Ming Yau, Jun-Xia Lu, John Collinge, Robert Tycko
Aggregation of amyloid-β peptides into fibrils or other self-assembled states is central to the pathogenesis of Alzheimer's disease. Fibrils formed in vitro by 40- and 42-residue amyloid-β peptides (Aβ40 and Aβ42) are polymorphic, with variations in molecular structure that depend on fibril growth conditions. Recent experiments suggest that variations in amyloid-β fibril structure in vivo may correlate with variations in Alzheimer's disease phenotype, in analogy to distinct prion strains that are associated with different clinical and pathological phenotypes...
January 12, 2017: Nature
https://www.readbyqxmd.com/read/28035627/supramolecular-cocrystals-of-gliclazide-synthesis-characterization-and-evaluation
#14
Renu Chadha, Dimpy Rani, Parnika Goyal
PURPOSE: To prepare the supramolecular cocrystals of gliclazide (GL, a BCS class II drug molecule) via mechanochemical route, with the goal of improving physicochemical and biopharmaceutical properties. METHODS: Two cocrystals of GL with GRAS status coformers, sebacic acid (GL-SB; 1:1) and α-hydroxyacetic acid (GL-HA; 1:1) were screened out using liquid assisted grinding. The prepared cocrystals were characterized using thermal and analytical techniques followed by evaluation of antidiabetic activity and pharmacokinetic parameters...
December 29, 2016: Pharmaceutical Research
https://www.readbyqxmd.com/read/28026949/atomic-level-structure-characterization-of-biomass-pre-and-post-lignin-treatment-by-dynamic-nuclear-polarization-enhanced-solid-state-nmr
#15
Frédéric A Perras, Hao Luo, Ximing Zhang, Nathan S Mosier, Marek Pruski, Mahdi M Abu-Omar
Lignocellulosic biomass is a promising sustainable feedstock for the production of biofuels, biomaterials, and biospecialty chemicals. However, efficient utilization of biomass has been limited by our poor understanding of its molecular structure. Here, we report a dynamic nuclear polarization (DNP)-enhanced solid-state (SS)NMR study of the molecular structure of biomass, both pre- and postcatalytic treatment. This technique enables the measurement of 2D homonuclear (13)C-(13)C correlation SSNMR spectra under natural abundance, yielding, for the first time, an atomic-level picture of the structure of raw and catalytically treated biomass samples...
January 17, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28003854/one-step-grafting-of-polymers-to-graphene-oxide
#16
Helen R Thomas, Daniel J Phillips, Neil R Wilson, Matthew I Gibson, Jonathan P Rourke
The direct grafting of poly(N-isopropylacrylamide) to the basal plane of graphene oxide has been achieved in a single step: cleavage of the terminal thiocarbonylthio group on RAFT grown poly(N-isopropylacrylamide) reveals a reactive thiol that attacks the epoxides present across the surface of graphene oxide. The new composite material was characterised by a combination of SSNMR, FTIR, Raman, EDX, XPS, TGA and contact angle measurement; it shows enhanced thermal stability and solubility in water.
December 28, 2015: Polymer Chemistry
https://www.readbyqxmd.com/read/27995257/supramolecular-organization-of-perfluorinated-1h-indazoles-in-the-solid-state-using-x-ray-crystallography-ssnmr-and-sensitive-vcd-and-non-sensitive-mir-fir-and-raman-to-chirality-vibrational-spectroscopies
#17
María M Quesada-Moreno, Juan Ramón Avilés-Moreno, Juan Jesús López-González, Kane Jacob, Laure Vendier, Michel Etienne, Ibon Alkorta, José Elguero, Rosa M Claramunt
1H-Indazole derivatives exhibit a remarkable property since some of them form chiral supramolecular structures starting from achiral monomers. The present work deals with the study of three perfluorinated 1H-indazoles that resolve spontaneously as conglomerates. These conglomerates can contain either a pure enantiomer (one helix) or a mixture of both enantiomers (both helices) with an enantiomeric excess (e.e.) of one of them. The difficulty of the structural analysis of these types of compounds is thus clear...
January 4, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/27992182/heparin-and-methionine-oxidation-promote-the-formation-of-apolipoprotein-a-i-amyloid-comprising-%C3%AE-helical-and-%C3%AE-sheet-structures
#18
David Townsend, Eleri Hughes, Rohanah Hussain, Giuliano Siligardi, Sara J Baldock, Jillian Madine, David A Middleton
Peptides derived from apolipoprotein A-I (apoA-I), the main component of high-density lipoprotein (HDL), constitute the main component of amyloid deposits that co-localise with atherosclerotic plaques. Here we investigate the molecular details of full-length, lipid-deprived apoA-I after assembly into insoluble aggregates under physiologically-relevant conditions known to induce aggregation in vitro. Unmodified apoA-I is shown to remain soluble at pH 7 for at least 3 days, retaining its native α-helical-rich structure...
December 19, 2016: Biochemistry
https://www.readbyqxmd.com/read/27951638/structure-of-chemisorbed-co2-species-in-amine-functionalized-mesoporous-silicas-studied-by-solid-state-nmr-and-computer-modeling
#19
Luís Mafra, Tomaž Čendak, Sarah Schneider, Paul V Wiper, João Pires, José R B Gomes, Moisés L Pinto
Two-dimensional (2D) solid-state nuclear magnetic resonance (SSNMR) experiments on samples loaded with (13)C-labeled CO2, "under controlled partial pressures", have been performed in this work, revealing unprecedented structural details about the formation of CO2 adducts from its reaction with various amine-functionalized SBA-15 containing amines having distinct steric hindrances (e.g., primary, secondary) and similar loadings. Three chemisorbed CO2 species were identified by NMR from distinct carbonyl environments resonating at δC ≈ 153, 160, and 164 ppm...
December 29, 2016: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/27938895/dispersive-raman-spectroscopy-for-quantifying-amorphous-drug-content-in-intact-tablets
#20
Busolo Wa Wabuyele, Sutthilug Sotthivirat, George X Zhou, Jason Ash, Sundeep S Dhareshwar
Process-induced inadvertent phase change of an active pharmaceutical ingredient in a drug product could impact chemical stability, physical stability, shelf life, and bioperformance. In this study, dispersive Raman spectroscopy is presented as an alternative method for the nondestructive, high-throughput, at-line quantification of amorphous conversion. A quantitative Raman method was developed using a multivariate partial least squares (PLS) regression calibration technique with solid-state nuclear magnetic resonance (ssNMR) spectroscopy as the reference method...
February 2017: Journal of Pharmaceutical Sciences
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