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proton density

Chiara Caratelli, Julianna Hajek, Sven M J Rogge, Steven Vandenbrande, Evert Jan Meijer, Michel Waroquier, Veronique Van Speybroeck
UiO-66, composed of Zr-oxide bricks and terephthalate linkers, is currently one of the most studied metal-organic frameworks due to its exceptional stability. Defects can be introduced in the structure, creating undercoordinated Zr atoms which are Lewis acid sites. Here, additional Brønsted sites can be generated by coordinated protic species from the solvent. In this contribution, a multilevel modeling approach was applied to unravel the effect of a confined methanol solvent on the active sites in UiO-66...
December 14, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Li Xu, Yangyang Duanmu, Glen M Blake, Chenxin Zhang, Yong Zhang, Keenan Brown, Xiaoqi Wang, Peng Wang, Xingang Zhou, Manling Zhang, Chao Wang, Zhe Guo, Giuseppe Guglielmi, Xiaoguang Cheng
OBJECTIVES: This study aimed to validate the accuracy and reliability of quantitative computed tomography (QCT) and chemical shift encoded magnetic resonance imaging (CSE-MRI) to assess hepatic steatosis. METHODS: Twenty-two geese with a wide range of hepatic steatosis were collected. After QCT and CSE-MRI examinations, the liver of each goose was removed and samples were taken from the left lobe, upper and lower half of the right lobe for biochemical measurement and histology...
December 13, 2017: European Radiology
Nungnit Wattanavichean, Ella Casey, Richard J Nichols, Heike Arnolds
We investigate the surface-enhanced Raman spectra of 4-mercaptopyridine on gold in a variety of acids. 4-Mercaptopyridine is a known pH sensor which exhibits characteristic spectral changes when the pH is changed. Here we show with the help of experiment and density functional calculations that the ring breathing mode is also highly sensitive to hydrogen bonding. Its spectral signature is a broad band with up to three contributions from free, protonated and hydrogen-bonded 4-mercaptopyridine. Unlike pyridine in solution, where protonation leads to a higher ring breathing frequency than hydrogen-bonding, we find that protonated adsorbed 4-mercaptopyridine possesses a frequency which is lower than the corresponding hydrogen-bonded species...
December 13, 2017: Physical Chemistry Chemical Physics: PCCP
Xinlin Li, Richard Selesnick, Quintin Schiller, Kun Zhang, Hong Zhao, Daniel N Baker, Michael A Temerin
The Galaxy is filled with cosmic-ray particles, mostly protons with kinetic energies greater than hundreds of megaelectronvolts. Around Earth, trapped energetic protons, electrons and other particles circulate at altitudes from about 500 to 40,000 kilometres in the Van Allen radiation belts. Soon after these radiation belts were discovered six decades ago, it was recognized that the main source of inner-belt protons (with kinetic energies of tens to hundreds of megaelectronvolts) is cosmic-ray albedo neutron decay (CRAND)...
December 13, 2017: Nature
Jakub Kollar, Vladimir Frecer
During the last decades, the application of hybrid quantum mechanical/molecular mechanical (QM/MM) methods has been extended to the field of drug design. In principle, the approximate QM/MM approach offers a more complete description of drug-receptor non-covalent interactions. This is especially true when charge or proton transfer, chelation of metal ions or strong polarization of ligand and protein or surface chemical groups are involved. The aim of this work was to assess the accuracy of calculated non-covalent ligand-protein interaction energies ([Formula: see text]) obtained by the hybrid QM/MM approach employed in QSite/Jaguar of Schrödinger's Small-Molecule Drug Discovery Suite on a set of small-molecule model systems when compared to rigorous QM calculations...
December 12, 2017: Journal of Molecular Modeling
Joakim S Jestilä, Einar Uggerud
Electrospray ionization of mixtures of succinic acid (here denoted H2Su) and magnesium chloride in water/methanol give rise to ions of the type ESu- (E = H or ClMg). The unimolecular dissociation of these ions was studied by collisionally induced dissociation mass spectrometry and interpreted by quantum chemical calculations (density functional theory and the composite Gaussian-4 method) of relevant parts of the potential energy surfaces. The major dissociation pathways from HSu- were seen to be dehydration and decarboxylation, while ClMgSu- mainly undergoes decarboxylation...
January 1, 2017: European Journal of Mass Spectrometry
Juan Sanz García, Federica Maschietto, Marco Campetella, Ilaria Ciofini
To provide tools to interpret photochemical reactions, in this paper we demonstrate how a recently developed density-based index (DCT), up to now used in conjunction with Time Dependent Density Functional Theory methods, can be extended to multi-configurational methods. This index can guide chemists in the interpretation of photochemical reactions providing a measure of the spatial extent of a photo-induced charge transfer and, more generally, of charge transfer phenomena. This qualitative and quantitative description can be particularly relevant in the case of multi-configurational calculations providing a simple tool for the interpretation of their complex outputs...
December 12, 2017: Journal of Physical Chemistry. A
Bradley S Launikonis, Tanya R Cully, Laszlo Csernoch, D George Stephenson
The complex membrane structure of the tubular system (t-system) in skeletal muscle fibers is open to the extracellular environment, which prevents measurements of H+ movement across its interface with the cytoplasm by conventional methods. Consequently, little is known about the t-system's role in the regulation of cytoplasmic pH, which is different from extracellular pH. Here we describe a novel approach to measure H+-flux measurements across the t-system of fast-twitch fibers under different conditions. The approach involves loading the t-system of intact rat fast-twitch fibers with a strong pH buffer (20 mM HEPES) and pH-sensitive fluorescent probe (10 mM HPTS) before the t-system is sealed off...
December 11, 2017: Journal of General Physiology
Aditya Wibawa Sakti, Yoshifumi Nishimura, Chien-Pin Chou, Hiromi Nakai
The structural, dynamical, and energetic properties of the excess proton in ice were studied using density-functional tight-binding molecular dynamics simulations. The ice systems investigated herein consisted of low-density hexagonal and cubic crystalline variants (ice Ih and Ic) and high-density structures (ice III and melted ice VI). Analysis of the temperature dependence of radial distribution function and bond order parameters served to characterize the distribution and configuration of hundreds of water molecules in a unit cell...
December 11, 2017: Journal of Physical Chemistry. A
Christian Delles, Naomi J Rankin, Charles Boachie, Alex McConnachie, Ian Ford, Antti Kangas, Pasi Soininen, Stella Trompet, Simon P Mooijaart, J Wouter Jukema, Faiez Zannad, Mika Ala-Korpela, Veikko Salomaa, Aki S Havulinna, Paul Welsh, Peter Würtz, Naveed Sattar
AIMS: We investigated the association between quantified metabolite, lipid and lipoprotein measures and incident heart failure hospitalisation (HFH) in the elderly, and examined whether circulating metabolic measures improve HFH prediction. METHODS AND RESULTS: Overall, 80 metabolic measures from the PROspective Study of Pravastatin in the Elderly at Risk (PROSPER) trial were measured by proton nuclear magnetic resonance spectroscopy (n = 5341; 182 HFH events during 2...
December 11, 2017: European Journal of Heart Failure
Patrick R Lawler, Akintunde O Akinkuolie, Paulo Harada, Robert J Glynn, Daniel I Chasman, Paul M Ridker, Samia Mora
BACKGROUND: It is uncertain whether pharmacological reductions in very-low-density lipoproteins (VLDLs), and their component triglyceride and cholesterol could reduce residual risk of atherosclerotic cardiovascular disease (ASCVD) events among individuals in whom low-density lipoprotein cholesterol (LDL-C) has been adequately lowered. We examined whether individuals with greater on-statin reductions in VLDL-related measures-beyond reductions in LDL-C-were at further reduced risk of ASCVD...
December 9, 2017: Journal of the American Heart Association
Yuan-Yuan Tang, Peng-Fei Li, Ping-Ping Shi, Wan-Ying Zhang, Zhong-Xia Wang, Yu-Meng You, Heng-Yun Ye, Takayoshi Nakamura, Ren-Gen Xiong
Recently, a plastic crystal of quinuclidinium perrhenate (HQReO_{4}) was reported to have the feasibility of controlling the crystallographic orientation in the grown crystal, but the corresponding temperature window is only about 22 K (345-367 K). Such a narrow window and uncertain ferroelectricity at room temperature would extremely limit its application potential. In this report, we prepared a large area high-quality polycrystalline thin film of HQReO_{4} and for the first time observed ferroelectricity in the temperature range from 298 to 367 K...
November 17, 2017: Physical Review Letters
Michael Dommett, Miguel Rivera, Rachel Crespo Otero
Aggregation induced emission (AIE) offers a route for the development of luminescent technologies with high quantum efficiencies. Excited state intramolecular proton transfer (ESIPT) coupled with AIE can produce devices with emission across the visible spectrum. In the current work, we use a combination of theoretical models to determine the factors which mediate fluorescence in molecular crystals undergoing ESIPT. Using two materials based on 2'-hydroxychalcone as exemplar cases, we analyse how inter- and intramolecular processes determine the emissive properties in the crystal environment...
December 8, 2017: Journal of Physical Chemistry Letters
Pablo Botas, Clemens Grassberger, Gregory Sharp, Harald Paganetti
The purpose of this study was to investigate Internal Tumor Volume (ITV) density overwrite strategies to minimize Intensity Modulated Proton Therapy (IMPT) plan degradation of mobile lung tumors. Four planning paradigms were compared for nine lung cancer patients. IGTV and ICTV structures were defined encompassing their respective volumes in every 4DCT phase. The paradigms use different planning CT (pCT) created from the Average Intensity Projection (AIP) of the 4DCT, overwriting the density within the IGTV to account for movement...
December 8, 2017: Physics in Medicine and Biology
Ravi Kumar, Madanakrishna Katari, Ajay Choudhary, Gopalan Rajaraman, Prasenjit Ghosh
A density functional theory (DFT) investigation performed at the B3LYP/TZVP//B3LYP/6-31G(d)-LANL2DZ level of theory on the hydroamination of dimethylamine (Me2NH) on an activated olefin (namely, acrylonitrile (CH2═CHCN)), as catalyzed by a 1,2,4-triazol based nickel(II) N-heterocyclic carbene complex (namely, [1,4-dimethyl-1,2,4-triazole-5-ylidene]2 nickel dichloride) revealed that the olefin coordination pathway is favorable over the amine coordination pathway, although the initial olefin coordination step is higher in energy than the initial amine coordination step...
December 8, 2017: Inorganic Chemistry
Ran B Luo, Toshiaki Suzuki, Jonathan C Hooker, Yesenia Covarrubias, Alexandra Schlein, Shanglei Liu, Jeffrey B Schwimmer, Scott B Reeder, Luke M Funk, Jacob A Greenberg, Guilherme M Campos, Bryan J Sandler, Santiago Horgan, Claude B Sirlin, Garth R Jacobsen
INTRODUCTION: Nonalcoholic fatty liver disease (NAFLD) is an epidemic in the obese population. Bariatric surgery is known to reverse multiple metabolic complications of obesity such as diabetes, dyslipidemia, and NAFLD, but the timing of liver changes has not been well described. MATERIALS AND METHODS: This was an IRB-approved, two-institutional prospective study. Bariatric patients received MRIs at baseline and after a pre-operative liquid diet. Liver biopsies were performed during surgery and if NAFLD positive, the patients received MRIs at 1, 3, and 6 months...
December 7, 2017: Surgical Endoscopy
Dominik A Megger, Patrick M Lax, Jeroen Paauwe, Célia Fonseca Guerra, Bernhard Lippert
Structural variations of the well-known guanine quartet (G4) motif in nucleic acid structures, namely substitution of two guanine bases (G) by two adenine (A) nucleobases in mutual trans positions, are discussed and studied by density functional theory (DFT) methods. This work was initiated by three findings, namely (1) that GA mismatches are compatible with complementary pairing patterns in duplex-DNA structures and can, in principle, be extended to quartet structures, (2) that GA pairs can come in several variations, including with a N1 protonated adeninium moiety (AH), and (3) that cross-linking of the major donor sites of purine nucleobases (N1 and N7) by transition metal ions of linear coordination geometries produces planar purine quartets, as demonstrated by some of us in the past...
December 7, 2017: Journal of Biological Inorganic Chemistry: JBIC
Ramesh Kheirabadi, Mohammad Izadyar, Mohammad Reza Housaindokht
The catalytic cycle of a new derivative of ebselen, 1, was elucidated via three steps by the density functional theory and solvent-assisted proton exchange procedure involving indirect proton exchange through a hydrogen-bonded transfer network. Different behaviors of the aromatic and aliphatic thiols were investigated in the reduction of selenoxide (step 2→3) and selenurane (step 3→1) based on their nucleophilicity. The reduction of selenoxide in the presence of thiophenol (ΔG≠=15.9 kcal.mol-1) is faster than methanethiol (ΔG≠=29...
December 7, 2017: Journal of Physical Chemistry. A
Sigrun Rumpel, Enrico Ravera, Constanze Sommer, Edward J Reijerse, Christophe Farès, Claudio Luchinat, Wolfgang Lubitz
The [FeFe] hydrogenase HydA1 from Chlamydomonas reinhardtii has been studied using 1H NMR spectroscopy identifying the paramagnetically shifted 1H resonances associated with both the [4Fe-4S]H and the [2Fe]H subclusters of the active site "H-cluster". The signal pattern of the unmaturated HydA1 containing only [4Fe-4S]H is reminiscent of standard bacterial-type ferredoxins. The spectra of maturated HydA1, with a complete H-cluster in the active Hox and Hox-CO inhibited state, reveal additional upfield and downfield shifted 1H resonances originating from the four methylene protons of the azadithiolate ligand in the [2Fe]H subsite...
December 6, 2017: Journal of the American Chemical Society
Han Gao, Filippo Maglia, Peter Lamp, Khalil Amine, Zonghai Chen
Current developments of electrolyte additives to stabilize electrode-electrolyte interface in Lithium-ion batteries highly rely on a trial-and-error search, which involves repetitive testing and intensive amount of resources. The lack of understandings on the fundamental protection mechanisms of the additives significantly increases the difficulty for the transformational development of new additives. In this study, we investigated two types of individual protection routes to build a robust cathode-electrolyte interphase at high potentials: (i) a direct reduction in the catalytic decomposition of the electrolyte solvent; and (ii) formation of a "corrosion inhibitor film" that prevents severely attack and passivation from protons that generated from the solvent oxidation, even the decomposition of solvent cannot not mitigated...
December 6, 2017: ACS Applied Materials & Interfaces
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