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Grégory Spataro, Yohan Champouret, Pierre Florian, Yannik Coppel, Myrtil L Kahn
Characterization of hybrid materials is crucial for gaining an in-depth understanding of nano-objects. Here, it is evidenced that the use of multinuclear 1H, 2H, 13C, 15N, 67Zn and 17O MAS NMR spectroscopy is a very powerful approach to acquire both structural and dynamic information on hybrid ZnO nanomaterials prepared from an organometallic approach. Not only is the coordination mode of the organic part onto the inorganic surface evidenced but also important information about the dynamics of the organic capping molecules and some particularities of the nanocrystal structure itself are obtained...
April 25, 2018: Physical Chemistry Chemical Physics: PCCP
Jiahui Shen, Victor V Terskikh, Xiaoling Wang, Ivan Hung, Zhehong Gan, Gang Wu
We have observed the 17O quadrupole-central-transition (QCT) NMR signal from [17O]nicotinamide (vitamin B3) dissolved in glycerol at different temperatures. Measurements were performed at five magnetic fields ranging from 9.4 to 35.2 T. We found that, in the ultraslow motion regime, cross correlation between the second-order quadrupole interaction and magnetic shielding anisotropy is an important contributor to the transverse relaxation process for the QCT signal of [17O]nicotinamide. While such a cross correlation effect has generally been predicted by relaxation theory, we report here the first experimental evidence for this phenomenon in solution-state NMR for quadrupolar nuclei...
April 23, 2018: Journal of Physical Chemistry. B
Frédéric A Perras, Kasuni C Boteju, Igor I Slowing, Aaron D Sadow, Marek Pruski
We utilize direct 17O DNP for the characterization of non-protonated oxygens in heterogeneous catalysts. The optimal sample preparation and population transfer approach for 17O direct DNP experiments performed on silica surfaces is determined and applied to the characterization of Zr- and Y-based mesoporous silica-supported single-site catalysts.
March 21, 2018: Chemical Communications: Chem Comm
Vincent J Huber, Hironaka Igarashi, Satoshi Ueki, Ingrid L Kwee, Tsutomu Nakada
The blood-brain barrier (BBB), which imposes significant water permeability restriction, effectively isolates the brain from the systemic circulation. Seemingly paradoxical, the abundance of aquaporin-4 (AQP-4) on the inside of the BBB strongly indicates the presence of unique water dynamics essential for brain function. On the basis of the highly specific localization of AQP-4, namely, astrocyte end feet at the glia limitans externa and pericapillary Virchow-Robin space, we hypothesized that the AQP-4 system serves as an interstitial fluid circulator, moving interstitial fluid from the glia limitans externa to pericapillary Virchow-Robin space to ensure proper glymphatic flow draining into the cerebrospinal fluid...
March 20, 2018: Neuroreport
Nathan J Beal, Thomas A Corry, Patrick J O'Malley
Broken symmetry density functional theory has been used to calculate g-tensor, 55 Mn, 14 N, and 17 O hyperfine couplings for active site models of superoxidized MnIII /MnIV manganese catalase both in its native and azide-inhibited form. While a good agreement is found between the calculated and experimental g-tensor and 55 Mn hyperfine couplings for all models, the active site geometry and Mn ion oxidation state can only be readily distinguished based on a comparison of the calculated and experimental 14 N azide and 17 O HFCs...
March 22, 2018: Journal of Physical Chemistry. B
Francesca La Cava, Alberto Fringuello Mingo, Luigi Miragoli, Enzo Terreno, Enrico Cappelletti, Luciano Lattuada, Luisa Poggi, Sonia Colombo Serra
A dinuclear gadolinium(III) chelate containing two moieties of diethylenetriaminepentaacetic acid (DTPA), covalently conjugated to an analogue of deoxycholic acid, was synthesized and thoroughly characterized. A full relaxometric analysis was carried out, consisting of 1) the acquisition of nuclear magnetic resonance dispersion (NMRD) profiles in various media; 2) the study of binding affinity to serum albumin; 3) the measurement of 17 O transverse relaxation rate versus temperature, and 4) a transmetallation assay...
April 23, 2018: ChemMedChem
Samira M Abozeid, Eric M Snyder, Timothy Y Tittiris, Charles M Steuerwald, Alexander Y Nazarenko, Janet R Morrow
High-spin Co(II) complexes are promising for development as paraCEST agents (paraCEST = paramagnetic chemical exchange saturation transfer) for magnetic resonance imaging applications. The first examples of Co(II) paraCEST agents with bound water ligands are presented here. Four Co(II) macrocyclic complexes based on 1,4,7-triazacyclononane and containing either pendent alcohol or pendent amide groups were prepared. Two of the macrocycles encapsulate the Co(II) and contain no water ligands as shown by X-ray crystallographic studies, and two complexes have macrocycles with only five ligand donor groups to leave an open coordination site for bound water...
February 19, 2018: Inorganic Chemistry
N Galamba, Benedito J C Cabral
The magnetic properties and the core and inner valence electron binding energies of liquid water are investigated. The adopted methodology relies on the combination of molecular dynamics and electronic structure calculations. Born-Oppenheimer molecular dynamics with the Becke and Lee-Yang-Parr functionals for exchange and correlation, respectively, and includes an empirical correction (BLYP-D3) functional and classical molecular dynamics with the TIP4P/2005-F model were carried out. The Keal-Tozer functional was applied for predicting magnetic shielding and spin-spin coupling constants...
January 28, 2018: Journal of Chemical Physics
Yi-Jung Tu, Zhijin Lin, Matthew J Allen, G Andrés Cisneros
We report a kinetic study of the water exchange on lanthanide ions in water/[1-ethyl-3-methylimidazolium][trifluoromethylsufate] (water/[EMIm][OTf]). The results from 17 O-NMR measurements show that the water-exchange rates in water/[EMIm][OTf] increase with decreasing size of the lanthanide ions. This trend for water-exchange is similar to the previously reported trend in water/1-ethyl-3-methylimidazolium ethyl sulfate (water/[EMIm][EtSO4 ]) but opposite to that in water. To gain atomic-level insight into these water-exchange reactions, molecular dynamics simulations for lanthanide ions in water/[EMIm][OTf] have been performed using the atomic-multipole-optimized-energetics-for-biomolecular-application polarizable force field...
January 14, 2018: Journal of Chemical Physics
Balamurugan Kandasamy, Peter G Bruce, William Clegg, Ross W Harrington, Antonio Rodríguez-Fortea, Magda Pascual-Borrás, R John Errington
Incorporation of {MX}n+ groups into polyoxometalates (POMs) provides the means not only to introduce reactivity and functionality but also to tune the electronic properties of the oxide framework by varying M, X and n. In order to elucidate the factors responsible for differences in reactivity between {TiW5 } and {SnW5 } Lindqvist-type hexametalates, a series of alkoxido- and aryloxido-tin substituted POMs (nBu4 N)3 [(RO)SnW5 O18 ] (R=Me, Et, iPr and tBu) and (nBu4 N)3 [(ArO)SnW5 O18 ] (Ar=C6 H5 , 4-MeC6 H5 , 4-tBuC6 H5 , 4-HOC6 H4 , 3-HOC6 H4 and 2-CHOC6 H4 ) has been structurally characterised and studied by multinuclear NMR (1 H, 13 C, 17 O, 119 Sn and 183 W) and FTIR spectroscopy...
February 21, 2018: Chemistry: a European Journal
Stuart James Elliott, Christian Bengs, Karel Kouril, Benno Meier, Shamim Alom, Richard John Whitby, Malcolm Harris Levitt
The17 O isotopomer of the water-endofullerene H2 O@C60 displays a remarkable proton NMR spectrum, with six well resolved peaks. These peaks are due to the J-coupling between the water protons and the17 O nucleus, which has spin-5/2. The resolution of these peaks is enabled by the suppression of water proton exchange by the fullerene cage. The six peaks display an unusual pattern of linewidths, which we model by a Liouville-space treatment of scalar relaxation due to quadrupolar relaxation of the17 O nuclei...
February 5, 2018: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Pieter Geysens, Vijay Shankar Rangasamy, Savitha Thayumanasundaram, Koen Robeyns, Luc Van Meervelt, Jean-Pierre Locquet, Jan Fransaer, Koen Binnemans
Electrolytes consisting of sodium bis(fluorosulfonyl)imide (NaFSI) dissolved in glymes (monoglyme, diglyme, and triglyme) were characterized by FT-Raman spectroscopy and13 C,17 O, and23 Na NMR spectroscopy. The glyme:NaFSI molar ratio was varied from 50:1 to 1:1, and it was observed that, in the dilute electrolytes, the sodium salt is completely dissociated into solvent separated ion pairs (SSIPs). However, contact ion pairs (CIPs) and aggregates (AGGs) become the predominant species in more concentrated solutions...
January 11, 2018: Journal of Physical Chemistry. B
Rui Zhou, Michihiro Hirata, Tao Wu, Igor Vinograd, Hadrien Mayaffre, Steffen Krämer, Arneil P Reyes, Philip L Kuhns, Ruixing Liang, W N Hardy, D A Bonn, Marc-Henri Julien
The value of the upper critical field H c 2 , a fundamental characteristic of the superconducting state, has been subject to strong controversy in high- T c copper oxides. Since the issue has been tackled almost exclusively by macroscopic techniques so far, there is a clear need for local-probe measurements. Here, we use17 O NMR to measure the spin susceptibility [Formula: see text] of the CuO2 planes at low temperature in charge-ordered YBa2 Cu3 O y We find that [Formula: see text] increases (most likely linearly) with magnetic field H and saturates above field values ranging from 20 T to 40 T...
December 12, 2017: Proceedings of the National Academy of Sciences of the United States of America
Nathan J Beal, Thomas A Corry, Patrick J O'Malley
A comparison between experimental and Broken Symmetry Density Functional theory (BS-DFT) calculated hyperfine couplings for the S2 state of the oxygen-evolving complex (OEC) has been performed. The effect of Ca substitution by Sr combined with the protonation state of two terminal hydroxo or aqua ligands, W1 and W2, on the calculated hyperfine couplings of55 Mn,13 C,14 N,17 O, and1 H nuclei has been investigated. Our findings show best agreement with experiment for OEC models which contain a hydroxide group at the W2 position and a water molecule at W1...
December 21, 2017: Journal of Physical Chemistry. B
Eric G Keeler, Vladimir K Michaelis, Michael T Colvin, Ivan Hung, Peter L Gor'kov, Timothy A Cross, Zhehong Gan, Robert G Griffin
The structure of two protected amino acids, FMOC-l-leucine and FMOC-l-valine, and a dipeptide, N-acetyl-l-valyl-l-leucine (N-Ac-VL), were studied via one- and two-dimensional solid-state nuclear magnetic resonance (NMR) spectroscopy. Utilizing17 O magic-angle spinning (MAS) NMR at multiple magnetic fields (17.6-35.2 T/750-1500 MHz for1 H) the17 O quadrupolar and chemical shift parameters were determined for the two oxygen sites of each FMOC-protected amino acids and the three distinct oxygen environments of the dipeptide...
December 13, 2017: Journal of the American Chemical Society
Caroline A Yao, Thomas Imahiyerobo, Jordan Swanson, Allyn Auslander, Diego De Cardenas, Jane C Figueiredo, Meghan McCullough, Melinda Costa, Richard Vanderburg, William P Magee
BACKGROUND: Unilateral cleft lip has a spectrum of disease morphology, but severity classifications are difficult given the absence of accessible, objective assessment tools or reference data. The authors characterize the spectrum of cleft morphology before and after surgical repair for a large, multi-ethnic population using easily identifiable facial landmarks collected through a novel smart phone-based application. METHODS: Anthropometric measurements and standardized photographs were prospectively collected in Morocco, Bolivia, Vietnam, and Madagascar during medical missions in 2015 using an application designed specifically for the study...
January 2018: Plastic and Reconstructive Surgery
Tomáš Magna, Karel Žák, Andreas Pack, Frédéric Moynier, Bérengère Mougel, Stefan Peters, Roman Skála, Šárka Jonášová, Jiří Mizera, Zdeněk Řanda
Chemical fingerprints of impacts are usually compromised by extreme conditions in the impact plume, and the contribution of projectile matter to impactites does not often exceed a fraction of per cent. Here we use chromium and oxygen isotopes to identify the impactor and impact-plume processes for Zhamanshin astrobleme, Kazakhstan. ε(54)Cr values up to 1.54 in irghizites, part of the fallback ejecta, represent the (54)Cr-rich extremity of the Solar System range and suggest a CI-like chondrite impactor. Δ(17)O values as low as -0...
August 9, 2017: Nature Communications
Philipp Roesch, Ulrike Warzok, Martin Enke, Robert Müller, Caspar Schattenberg, Christoph A Schalley, Martin Kaupp, Thomas Braun, Philipp Wittwer
A series of isotopologues of the siloxanediol Mes2 Si(OH)(μ-O)Si(OH)Mes2 (3 a) (Mes=2,4,6-trimethylphenyl) were synthesized by reactions of the corresponding disiloxane precursors Mes2 Si(μ-O)2 SiMes2 (2 a), Mes2 Si(μ-17 O)2 SiMes2 (2 b) or Mes2 Si(μ-18 O)2 SiMes2 (2 c) with an excess of H2 O, H2 17 O or H2 18 O. NMR and IR signal assignments for the siloxanediols in benzene are supported by quantum-chemical calculations, which indicate small energy differences between trans and cis conformers, the latter of which exhibits an intramolecular hydrogen bond...
October 9, 2017: Chemistry: a European Journal
Chamika U Lenora, Fabio Carniato, Yimin Shen, Zahid Latif, E Mark Haacke, Philip D Martin, Mauro Botta, Matthew J Allen
EuII -containing complexes were studied with respect to properties relevant to their use as contrast agents for magnetic resonance imaging. The influences of molecular parameters and field strength on relaxivity were studied for a series of EuII -containing cryptates and their adducts with β-cyclodextrins, poly-β-cyclodextrins, and human serum albumin. Solid- and solution-phase characterization of EuII -containing complexes is presented that demonstrates the presence of inner-sphere molecules of water. Additionally, relaxivity, water-exchange rate, rotational correlation time, and electronic relaxation times were determined using variable-temperature17 O NMR, nuclear magnetic relaxation dispersion, and electron paramagnetic resonance spectroscopic techniques...
November 2, 2017: Chemistry: a European Journal
Yin Gao, Yizhe Dai, Gang Wu
We report a solid-state (15)N and (17)O NMR study of two representative S-nitrosothiols (RSNO): S-nitroso N-acetylpenicillamine (SNAP) and S-nitrosoglutathione (GSNO). The (15)N and (17)O NMR tensors are experimentally determined for the first time for this important class of nitric-oxide (NO)-related compounds. The observed NMR characteristics for RSNO include large (15)N and (17)O chemical shift anisotropies and large (17)O quadrupole coupling constants. Quantum chemical calculations are also performed for the (15)N and (17)O NMR tensors in two simple RSNO models: t-BuSNO and MeSNO...
July 20, 2017: Journal of Physical Chemistry. B
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