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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...
February 23, 2018: Neuroreport
Nathan J Beal, Thomas A Corry, Patrick J O'Malley
Broken Symmetry Density Functional Theory (BS-DFT) g-tensor, 55Mn, 14N, and 17O hyperfine couplings have been calculated for active site models of superoxidised Mn(III)/Mn(IV) manganese catalase both in its native and azide inhibited form. While good agreement is found between calculated and experimental g-tensor and 55Mn hyperfine couplings for all models, the active site geometry and Mn ion oxidation state can only be readily distinguished based on comparison of calculated and experimental 14N azide and 17O HFCs...
February 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 has been synthesized and widely characterized. A full relaxometric analysis was carried out, consisting of (i) the acquisition of nuclear magnetic resonance dispersion (NMRD) profiles in different media; (ii) the study of binding affinity to serum albumin; (iii) the measurement of 17O transverse relaxation rate vs temperature and (iv) a transmetallation assay...
February 14, 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 7, 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 17O-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 Rodriguez Fortea, Magda Pascual Borras, 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 (nBu4N)3[(RO)SnW5O18] (R = Me, Et, iPr and tBu) and (nBu4N)3[(ArO)SnW5O18] (Ar = C6H5, 4-MeC6H5, 4-tBuC6H5, 4-HOC6H4, 3-HOC6H4 and 2-CHOC6H4) has been structurally characterised and studied by multinuclear NMR (1H, 13C, 17O, 119Sn and 183W) and FTIR spectroscopy...
January 5, 2018: Chemistry: a European Journal
Stuart J Elliott, Christian Bengs, Karel Kouril, Benno Meier, Shamim Alom, Richard J Whitby, Malcolm Harris Levitt
The 17O isotopomer of the water-endofullerene H2O@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 the 17O 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 the 17O nuclei. The data are consistent with rotational diffusion of the water molecule on the sub-picosecond timescale...
December 13, 2017: 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 assessments are difficult given the absence of an accessible, objective assessment tools or reference data. We 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 utilizing an application designed specifically for the study...
September 14, 2017: 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...
July 29, 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
Eu(II) -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 Eu(II) -containing cryptates and their adducts with β-cyclodextrins, poly-β-cyclodextrins, and human serum albumin. Solid- and solution-phase characterization of Eu(II) -containing complexes is presented that demonstrates the presence of inner-sphere molecules of water...
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
Keith M Haynes, Narges Abdali, Varsha Jhawar, Helen I Zgurskaya, Jerry M Parks, Adam T Green, Jerome Baudry, Valentin V Rybenkov, Jeremy C Smith, John K Walker
In Gram-negative bacteria, efflux pumps are able to prevent effective cellular concentrations from being achieved for a number of antibiotics. Small molecule adjuvants that act as efflux pump inhibitors (EPIs) have the potential to reinvigorate existing antibiotics that are currently ineffective due to efflux mechanisms. Through a combination of rigorous experimental screening and in silico virtual screening, we recently identified novel classes of EPIs that interact with the membrane fusion protein AcrA, a critical component of the AcrAB-TolC efflux pump in Escherichia coli...
July 27, 2017: Journal of Medicinal Chemistry
Frédéric A Perras, Zhuoran Wang, Pranjali Naik, Igor I Slowing, Marek Pruski
Heterogeneous Brønsted acid catalysts are tremendously important in industry, particularly in catalytic cracking processes. Here we show that these Brønsted acid sites can be directly observed at natural abundance by (17) O DNP surface-enhanced NMR spectroscopy (SENS). We additionally show that the O-H bond length in these catalysts can be measured with sub-picometer precision, to enable a direct structural gauge of the lability of protons in a given material, which is correlated with the pH of the zero point of charge of the material...
May 12, 2017: Angewandte Chemie
Sohei Sukenaga, Pierre Florian, Koji Kanehashi, Hiroyuki Shibata, Noritaka Saito, Kunihiko Nakashima, Dominique Massiot
The description of the structure of aluminosilicate glasses is more often centered on its cationic constituents, and oxygen ions determine their connectivity, directly impacting the physical properties of those disordered materials. A very powerful approach to ascertain this short- to medium-range order is to use (17)O NMR, but up to now the speciation of the chemical bonds was only ambiguously achieved for multicomponent glasses. Here, we propose to directly probe the very scarcely explored through-bond correlations using (17)O{(27)Al} and (17)O{(23)Na} solid-state nuclear magnetic resonance (NMR) double-resonance experiments...
May 8, 2017: Journal of Physical Chemistry Letters
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