keyword
MENU ▼
Read by QxMD icon Read
search

Solid state NMR

keyword
https://www.readbyqxmd.com/read/28631929/-13-c-dynamic-nuclear-polarization-using-a-trimeric-gd-3-complex-as-an-additive
#1
Peter Niedbalski, Christopher Parish, Qing Wang, Andhika Kiswandhi, Zahra Hayati, Likai Song, Lloyd Laporca Lumata
Dissolution dynamic nuclear polarization (DNP) is one of the most successful techniques that resolves the insensitivity problem in liquid-state nuclear magnetic resonance (NMR) spectroscopy and imaging (MRI) by amplifying the signal by several thousand-fold. One way to further improve the DNP signal is the inclusion of trace amounts of lanthanides in DNP samples doped with trityl OX063 free radical as the polarizing agent. In practice, stable monomeric gadolinium complexes such as Gd-DOTA or Gd-HP-DO3A are used as beneficial additives in DNP samples, further boosting the DNP-enhanced solid-state 13C polarization by a factor of 2 or 3...
June 20, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28631856/tetrameric-and-dimeric-n%C3%A2-%C3%A2-%C3%A2-i-%C3%A2-%C3%A2-%C3%A2-n-halogen-bonded-supramolecular-cages
#2
Kari Rissanen, Lotta Turunen, Anssi Peuronen, Samu Forsblom, Elina Kalenius, Manu Lahtinen
Tripodal N-donor ligands are used to form halogen-bonded assemblies via structurally analogous Ag+-complexes. Selective formation of discrete tetrameric I6L4 and dimeric I3L2 halonium cages, wherein multiple [N∙∙∙I+∙∙∙N] halogen bonds are used in concert, can be achieved by using sterically rigidified cationic tris(1-methyl-1-azonia-4-azabicyclo[2.2.2]octane)-mesitylene ligand, L1(PF6)3, and flexible ligand 1,3,5-tris(imidazole-1-ylmethyl)-2,4,6-trimethylbenzene, L2, respectively. The iodonium cages, I6L14(PF6)18 and I3L22(PF6)3, were obtained through the [N∙∙∙Ag+∙∙∙N] → [N∙∙∙I+∙∙∙N] cation exchange reaction between the corresponding Ag6L14(PF6)18 and Ag3L22(PF6)3 coordination cages, prepared as intermediates, and I2...
June 20, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28631847/conjunction-of-pyrrole-and-amide-moieties-highly-anion-responsive-%C3%AF-electronic-molecules-forming-ion-free-and-ion-pairing-assemblies
#3
Atsuko Kuno, Norimitsu Tohnai, Nobuhiro Yasuda, Hiromitsu Maeda
Dipyrrolyldiketone BF2 complexes with amide units at pyrrole α-positions were synthesized in modest yields and showed extremely high anion-binding affinities due to multiple hydrogen-bonding interactions. The phenyl-amide-substituted derivative formed solid-state chiral helical structures, wherein π planes were oriented parallel to the helical directions. Examination of anion-binding behavior using 1H NMR combined with theoretical studies suggested fast pyrrole inversions, particularly, for the phenyl-amide-substituted derivative...
June 20, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28629215/unusual-interfacial-freezing-phenomena-in-hexacontane-silica-composites
#4
Xia Gao, Yunlan Su, Weiwei Zhao, Qingyun Qian, Xin Chen, Robert Wittenbrink, Dujin Wang
The crystallization behaviors of n-hexacontane (C60H122)/Stöber silica (SiO2) composites with various compositions were investigated by a combination of differential scanning calorimetry (DSC), solid-state (13)C nuclear magnetic resonance (solid-state (13)C NMR) and Proton NMR relaxation experiments. By means of DSC, C60H122 molecules in C60H122/silica composites were observed to be involved in the interfacial freezing not present in the free bulk C60H122. The orientation of C60H122 molecules, being preferentially normal to silica surface, was confirmed by grazing incidence X-ray diffraction experiments on thin n-hexacontane film adsorbed on the silicon wafer with a native SiO2 layer...
June 19, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28628906/quadrupolar-nutation-nmr-to-discriminate-central-and-satellite-transitions-spectral-assignments-for-a-ziegler-natta-catalyst
#5
E S Merijn Blaakmeer, Wouter M J Franssen, Arno P M Kentgens
In this contribution we used solid state (35)Cl (I=3/2) quadrupolar NMR to study a MgCl2/2,2-dimethyl-1,3-dimethoxypropane (DMDOMe) adduct that serves as a model system for Ziegler-Natta catalysis. Employing large Radio-Frequency (RF) field strengths we observe three spectral features with strongly varying line widths. The assignment of the spectra is complicated because of the large difference in quadrupolar interactions experienced by the different sites in the system. The satellite transitions (ST) of relatively well-defined bulk Cl sites are partially excited and may overlap with the central transition (CT) resonances of more distorted surface sites...
June 7, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28628721/protonation-of-nitramines-where-does-the-proton-go
#6
Thomas Saal, Martin Rahm, Karl O Christe, Ralf Haiges
The reactions of nitramine, N-methyl nitramine and N,N-dimethyl nitramine with anhydrous HF and the superacids HF/MF5 (M = As, Sb) were investigated at temperatures below -40 °C. In solution, exclusive O-protonation was observed by multinuclear NMR spectroscopy. Whereas no solid product could be isolated from the neat HF solutions even at -78 °C, in the HF/MF5 systems, protonated nitramine MF6- salts were isolated for the first time as moisture-sensitive solids that decompose at temperatures above -40 °C...
June 19, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28628319/on-the-mechanism-of-phenol-alkylation-in-zeolite-h-bea-using-in-situ-solid-state-nmr-spectroscopy
#7
Zhenchao Zhao, Hui Shi, Chuan Wan, Mary Y Hu, Yuanshuai Liu, Donghai Mei, Donald M Camaioni, Jian Zhi Hu, Johannes A Lercher
The reaction mechanism of solid-acid-catalyzed phenol alkylation with cyclohexanol and cyclohexene in the apolar solvent decalin has been studied using in situ (13)C MAS NMR spectroscopy. Phenol alkylation with cyclohexanol sets in only after a majority of cyclohexanol is dehydrated to cyclohexene. As phenol and cyclohexanol show similar adsorption strength, this strict reaction sequence is not caused by the limited access of phenol to cyclohexanol, but is due to the absence of a reactive electrophile as long as a significant fraction of cyclohexanol is present...
June 19, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28623034/new-nmr-tools-for-protein-structure-and-function-spin-tags-for-dynamic-nuclear-polarization-solid-state-nmr
#8
Rivkah Rogawski, Ann McDermott
Magic angle spinning solid state NMR studies of biological macromolecules [1-3] have enabled exciting studies of membrane proteins [4,5], amyloid fibrils [6], viruses, and large macromolecular assemblies [7]. Dynamic nuclear polarization (DNP) provides a means to enhance detection sensitivity for NMR, particularly for solid state NMR, with many recent biological applications and considerable contemporary efforts towards elaboration and optimization of the DNP experiment. This review explores precedents and innovations in biological DNP experiments, especially highlighting novel chemical biology approaches to introduce the radicals that serve as a source of polarization in the DNP experiments...
June 13, 2017: Archives of Biochemistry and Biophysics
https://www.readbyqxmd.com/read/28621934/tqopen-n-n-n-n-tetrakis-2-quinolylmethyl-3-oxa-1-5-pentanediamine-family-as-heptadentate-fluorescent-cd-2-sensors
#9
Yuji Mikata, Asako Kizu, Kana Nozaki, Hideo Konno, Hiroshi Ono, Shunsuke Mizutani, Shin-Ichiro Sato
A quinoline-based heptadentate ligand, N,N,N',N'-tetrakis(2-quinolylmethyl)-3-oxa-1,5-pentanediamine (TQOPEN), exhibits a fluorescence increase (ICd/I0 = 25, ϕCd = 0.017) at 428 nm upon addition of 1 equiv of Cd(2+). In contrast, 1 equiv of Zn(2+) induces a negligible fluorescence change due to weak interaction (IZn/I0 = 2.5, IZn/ICd = 10%). In comparison with TQOPEN, the thia and aza derivatives TQSPEN and TQNPEN exhibit improved Cd(2+)/Zn(2+) selectivity and higher Cd(2+)-binding affinity, respectively. The solid-state structures of mononuclear Cd(2+) and hydroxide-bridged dinuclear Zn(2+) complexes of TQOPEN were elucidated by X-ray crystallography...
June 16, 2017: Inorganic Chemistry
https://www.readbyqxmd.com/read/28621522/formation-and-structure-of-wild-type-huntingtin-exon-1-fibrils
#10
J Mario Isas, Andreas Langen, Myles C Isas, Nitin Kumar Pandey, Ansgar B Siemer
The fact that the heritable neurodegenerative disorder Huntington's Disease (HD) is autosomal dominant means that there is one wild type and one mutant allele in most HD patients. The CAG repeat expansion in the exon 1 of the protein huntingtin (HTTex1) that causes the disease, leads to the formation of HTT fibrils in vitro and vivo. An important question for understanding the molecular mechanism of HD is which role wild type HTT plays for the formation, propagation, and structure of these HTT fibrils. Here we report that fibrils of mutant HTTex1 are able to seed the aggregation of wild type HTTex1 into amyloid fibrils which in turn can seed the fibril formation of mutant HTTex1...
June 16, 2017: Biochemistry
https://www.readbyqxmd.com/read/28621371/does-z-equal-1-or-2-enhanced-powder-nmr-crystallography-verification-of-a-disordered-room-temperature-crystal-structure-of-a-p38-inhibitor-for-chronic-obstructive-pulmonary-disease
#11
Cory M Widdifield, Sten O Nilsson Lill, Anders Broo, Maria Lindkvist, Anna Pettersen, Anna Svensk Ankarberg, Peter Aldred, Staffan Schantz, Lyndon Emsley
The crystal structure of the Form A polymorph of N-cyclopropyl-3-fluoro-4-methyl-5-[3-[[1-[2-[2-(methylamino)ethoxy]phenyl]cyclopropyl]amino]-2-oxo-pyrazin-1-yl]benzamide (i.e., AZD7624), determined using single-crystal X-ray diffraction (scXRD) at 100 K, contains two molecules in the asymmetric unit (Z' = 2) and has regions of local static disorder. This substance has been in phase IIa drug development trials for the treatment of chronic obstructive pulmonary disease, a disease which affects over 300 million people and contributes to nearly 3 million deaths annually...
June 16, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28621361/single-site-silica-supported-tetramethyl-niobium-by-the-somc-strategy-synthesis-characterization-and-structure-activity-relationship-in-the-ethylene-oligomerization-reaction
#12
Ali Hamieh, Raju Dey, Bijan Nekoueishahraki, Manoja K Samantaray, Yin Chen, Edy Abou-Hamad, Jean-Marie Basset
A silica supported tetramethyl niobium complex [([triple bond, length as m-dash]SiO)NbMe4] 2 has been isolated by the surface alkylation of [([triple bond, length as m-dash]SiO-)NbCl3Me] 1 with dimethyl zinc in pentane. 1 can be easily synthesized by grafting NbCl3Me2 onto the surface of partially dehydroxylated silica by the SOMC strategy. Precise structural analysis was carried out using FTIR, advanced solid state NMR, elemental analysis and mass balance techniques (gas quantification after treating 2 with degassed water)...
June 16, 2017: Chemical Communications: Chem Comm
https://www.readbyqxmd.com/read/28619057/polysaccharide-compositions-of-collenchyma-cell-walls-from-celery-apium-graveolens-l-petioles
#13
Da Chen, Philip J Harris, Ian M Sims, Zoran Zujovic, Laurence D Melton
BACKGROUND: Collenchyma serves as a mechanical support tissue for many herbaceous plants. Previous work based on solid-state NMR and immunomicroscopy suggested collenchyma cell walls (CWs) may have similar polysaccharide compositions to those commonly found in eudicotyledon parenchyma walls, but no detailed chemical analysis was available. In this study, compositions and structures of cell wall polysaccharides of peripheral collenchyma from celery petioles were investigated. RESULTS: This is the first detailed investigation of the cell wall composition of collenchyma from any plant...
June 15, 2017: BMC Plant Biology
https://www.readbyqxmd.com/read/28618387/two-pulse-recoupling
#14
Navin Khaneja, Ashutosh Kumar
The paper describes a family of novel recoupling pulse sequences in magic angle spinning (MAS) solid state NMR, called two pulse recoupling. These pulse sequences can be employed for both homonuclear and heteronuclear recoupling experiments and are robust to dispersion in chemical shifts and rf-inhomogeneity. The homonuclear pulse sequence consists of a building block (π)ϕ(π)-ϕ where ϕ=π4n, and n is number of blocks in a rotor period. The recoupling block is made robust to rf-inhomogeneity by extending it to (π)ϕ(π)-ϕ(π)π+ϕ(π)π-ϕ...
June 12, 2017: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28616128/establishing-hierarchy-the-chain-of-events-leading-to-the-formation-of-silicalite-1-nanosheets
#15
Xiaochun Zhu, Maarten G Goesten, Arjan J J Koekkoek, Brahim Mezari, Nikolay Kosinov, Georgy Filonenko, Heiner Friedrich, Roderigh Rohling, Bartłomiej M Szyja, Jorge Gascon, Freek Kapteijn, Emiel J M Hensen
In applying a multi-scale spectroscopic and computational approach, we demonstrate that the synthesis of stacked zeolite silicalite-1 nanosheets, in the presence of a long-tail diquaternary ammonium salt surfactant, proceeds through a pre-organised phase in the condensed state. In situ small-angle X-ray scattering, coupled to paracrystalline theory, and backed by electron microscopy, shows that this phase establishes its meso-scale order within the first five hours of hydrothermal synthesis. Quasi in situ vibrational and solid-state NMR spectroscopy reveal that this meso-shaped architecture already contains some elementary zeolitic features...
October 1, 2016: Chemical Science
https://www.readbyqxmd.com/read/28613900/solid-state-nmr-provides-evidence-for-small-amplitude-slow-domain-motions-in-a-multi-spanning-transmembrane-%C3%AE-helical-protein
#16
Daryl Good, Charlie Pham, Jacob Jagas, Józef R Lewandowski, Vladimir Ladizhansky
Proteins are dynamic entities and populate ensembles of conformations. Transitions between states within a conformational ensemble occur over a broad spectrum of amplitude and time scales, and are often related to biological function. Whereas solid-state NMR (SSNMR) spectroscopy has recently been used to characterize conformational ensembles of proteins in the microcrystalline states, its applications to membrane proteins remain limited. Here we use SSNMR to study conformational dynamics of a seven-helical transmembrane (TM) protein, Anabaena Sensory Rhodopsin (ASR) reconstituted in lipids...
June 14, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28612457/soluble-platinum-nanoparticles-ligated-by-long-chain-n-heterocyclic-carbenes-as-catalysts
#17
Luis M Martínez-Prieto, Lena Rakers, Angela M López-Vinasco, Israel Cano, Yannick Coppel, Karine Philippot, Frank Glorius, Bruno Chaudret, Piet W N M van Leeuwen
Soluble platinum nanoparticles (Pt NPs) ligated by two different long-chain N-Heterocyclic Carbenes (LC-IPr and LC-IMe) were synthesized and fully characterized by TEM, HRTEM, WAXS, XPS and solution NMR. The surface chemistry of these NPs (Pt@LC-IPr and Pt@LC-IMe) was investigated by FT-IR and solid state NMR using CO as a probe molecule. A clear influence of the bulkiness of the N-substituents was observed on the size, surface state and catalytic activity of these Pt NPs. While Pt@LC-IMe showed no activity in the hydroboration of phenylacetylene, Pt@LC-IPr revealed good selectivity for the trans-isomer which might be supported by a homogeneous species...
June 14, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28611402/dynamic-nuclear-polarization-nmr-as-a-new-tool-to-investigate-the-nature-of-organic-compounds-occluded-in-plant-silica-particles
#18
Armand Masion, Anne Alexandre, Fabio Ziarelli, Stéphane Viel, Guaciara M Santos
The determination of the chemical nature of the organic matter associated with phytoliths remains a challenge. This difficulty mainly stems from amounts of organic carbon (C) that are often well below the detection limit of traditional spectroscopic tools. Conventional solid-state (13)C Nuclear Magnetic Resonance (NMR) is widely used to examine the nature and structure of organic molecules, but its inherent low sensitivity prohibits the observation of diluted samples. The recent advent of commercial microwave source in the terahertz range triggered a renewed interest in the Dynamic Nuclear Polarization (DNP) technique to improve the signal to noise ratio of solid-state NMR experiments...
June 13, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28608690/conformational-plasticity-of-the-cell-penetrating-peptide-sap-as-revealed-by-solid-state-19-f-nmr-and-circular-dichroism-spectroscopies
#19
Sergii Afonin, Vladimir Kubyshkin, Pavel K Mykhailiuk, Igor V Komarov, Anne S Ulrich
The cell-penetrating peptide SAP, which was designed as an amphipathic poly-L-proline helix II (PPII), was suggested to self-assemble into regular fibrils that are relevant for its internalization. Herein we have analyzed the structure of SAP in the membrane-bound state by solid-state (19)F-NMR, which revealed other structural states, in addition to the expected surface-aligned PPII. (2S)-2-Amino-2-[3-(trifluoromethyl)bicyclo[1.1.1]pent-1-yl]ethanoic acid and two rigid isomers of trifluoromethyl-4,5-methanoprolines (CF3-MePro) were used as labels for (19)F-NMR analysis...
June 13, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28607961/potential-of-polymethacrylate-pseudo-crown-ethers-as-solid-state-polymer-electrolytes
#20
S Moins, J C Martins, A Krumpmann, V Lemaur, J Cornil, N Delbosc, A Decroly, Ph Dubois, R Lazzaroni, J-F Gohy, O Coulembier
The association of kinetic studies, DFT calculations and (1)H-(7)Li NMR analyses allowed the control of the cyclo-ATRP of PEG9DMA and the production of polymethacrylate pseudo crown-ethers of various molar masses. Their potential to act as a solid-state polymer electrolyte in Li-ion batteries has been highlighted and may come from the supramolecular organization of the cyclo-PEG forming a Li(+) diffusion channel.
June 13, 2017: Chemical Communications: Chem Comm
keyword
keyword
98018
1
2
Fetch more papers »
Fetching more papers... Fetching...
Read by QxMD. Sign in or create an account to discover new knowledge that matter to you.
Remove bar
Read by QxMD icon Read
×

Search Tips

Use Boolean operators: AND/OR

diabetic AND foot
diabetes OR diabetic

Exclude a word using the 'minus' sign

Virchow -triad

Use Parentheses

water AND (cup OR glass)

Add an asterisk (*) at end of a word to include word stems

Neuro* will search for Neurology, Neuroscientist, Neurological, and so on

Use quotes to search for an exact phrase

"primary prevention of cancer"
(heart or cardiac or cardio*) AND arrest -"American Heart Association"