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proton density

Raquel Fonseca, Rui A Carvalho, Cristina Lemos, Ana C Sequeira, Inês R Pita, Fábio Carvalho, Carlos D Silva, Rui D S Prediger, Ivana Jarak, Rodrigo A Cunha, Carlos A Fontes Ribeiro, Attila Köfalvi, Frederico C Pereira
INTRODUCTION: We recently showed that a single high dose of methamphetamine (METH) induces a persistent frontal cortical monoamine depletion that is accompanied by helpless-like behavior in mice. However, brain metabolic alterations underlying both neurochemical and mood alterations remain unknown. AIMS: Herein, we aimed at characterizing frontal cortical metabolic alterations associated with early negative mood behavior triggered by METH. Adult C57BL/6 mice were injected with METH (30 mg/kg, i...
October 19, 2016: CNS Neuroscience & Therapeutics
Gao-Feng Bian, Yun Guo, Xiao-Jing Lv, Cheng Zhang
The preparation and the photophysical behaviour of two benzoxazinone derivatives isomers 2-(1-hydroxynaphthalen-2-yl)-4H-benzo[e][1, 3]oxazin-4-one(1) and 2-(3-hydroxynaphthalen-2-yl)-4H-benzo[e][1, 3]oxazin-4-one(2) designed for displaying were reported. The effect of substituent position and solvent effect on the excited state intramolecular proton transfer (ESIPT) dynamics and the spectroscopic properties were investigated using a combined theoretical (i.e., time-dependent density function theory (DFT)) and experimental (i...
October 18, 2016: Journal of Fluorescence
Lequan Liu, Feng Zhou, Rajesh Kodiyath, Shigenori Ueda, Hideki Abe, Defa Wang, Youquan Deng, Jinhua Ye
CO poisoning of Pt catalysts is one of the major challenges to the commercialization of proton exchange membrane fuel cells. One promising solution is to develop CO-tolerant Pt-based catalysts. A facilely synthesized Pt/FeOx catalyst exhibited outstanding CO tolerance in the oxidation of H2 and electrochemical CO stripping. Light-off temperature of H2O formation over Pt/FeOx was achieved even below 30 °C in the presence of 3000 ppm CO at a space velocity of 18 000 mL g(-1)cat h(-1). For the electrochemical oxidation of CO, the onset and peak potentials decreased by 0...
October 18, 2016: Physical Chemistry Chemical Physics: PCCP
Young Jin Sa, Dong-Jun Seo, Jinwoo Woo, Jung Tae Lim, Jae Yeong Cheon, Seung Yong Yang, Jae Myeong Lee, Dongwoo Kang, Tae Joo Shin, Hyeon Suk Shin, Hu Young Jeong, Chul Sung Kim, Min Gyu Kim, Tae-Young Kim, Sang Hoon Joo
Iron-nitrogen on carbon (Fe-N/C) catalysts have emerged as promising non-precious metal catalysts (NPMCs) for oxygen reduction reaction (ORR) in energy conversion and storage devices. It has been widely suggested that an active site structure for Fe-N/C catalysts contains Fe-Nx coordination. However, the preparation of high-performance Fe-N/C catalysts mostly involves a high-temperature pyrolysis step, which generates not only catalytically active Fe-Nx sites, but also less active large iron-based particles...
October 18, 2016: Journal of the American Chemical Society
Amin Hossein Bagi, Yousef Khaledi, Hossein Ghari, Sebastian Arndt, A Stephen K Hashmi, Brian F Yates, Alireza Ariafard
The gold-catalyzed direct functionalization of aromatic C-H bonds has attracted interest for constructing organic compounds which have application in pharmaceuticals, agrochemicals, and other important fields. In the literature, two major mechanisms have been proposed for these catalytic reactions: inner-sphere syn-addition and outer-sphere anti-addition (Friedel-Crafts-type mechanism). In the current article, the AuCl3-catalyzed hydrofurylation of allenyl ketone, vinyl ketone, ketone and alcohol substrates is investigated with the aid of density functional theory calculations and it is found that the corresponding functionalizations are best rationalized in terms of a novel mechanism called "concerted electrophilic ipso-substitution" (CEIS) in which the gold(III)-furyl σ-bond produced by furan auration acts as a nucleophile and attacks the protonated substrate via an outer-sphere mechanism...
October 17, 2016: Journal of the American Chemical Society
Carlos Gueto-Tettay, Joshua Zuchniarz, Yeyson Fortich-Seca, Luis Roberto Gueto-Tettay, Juan Carlos Drosos-Ramirez
BACE1 is an aspartyl protease which is a therapeutic target for Alzheimer's disease (AD) because of its participation in the rate-limiting step in the production of Aβ-peptide, the accumulation of which produces senile plaques and, in turn, the neurodegenerative effects associated with AD. The active site of this protease is composed in part by two aspartic residues (Asp93 and Asp289). Additionally, the catalytic site has been found to be covered by an antiparallel hairpin loop called the flap. The dynamics of this flap are fundamental to the catalytic function of the enzyme...
October 7, 2016: Journal of Molecular Graphics & Modelling
Jialei Du, Jianying Wang, Lvlv Ji, Xiaoxiang Xu, Zuofeng Chen
Although significant progress has been made recently, copper-based materials had long been considered to be ineffective catalysts toward hydrogen evolution reaction (HER), in most cases, requiring high overpotentials more than 300 mV. We report here that a Cu(0)-based nanoparticle film electrodeposited in situ from a Cu(II) oxime complex can act as a highly active and robust HER electrocatalyst in neutral phosphate buffer solution. The as-prepared nanoparticle film is of poor crystallization, which incorporates significant amounts of oxime ligand residues and buffer anions PO43-...
October 17, 2016: ACS Applied Materials & Interfaces
Zhigang Wang, Zhenguo Fu, Bin He, Zehua Hu, Ping Zhang
The nuclear plus interference scattering (NIS) effect on the stopping power of hot dense beryllium (Be) plasma for multi-MeV protons is theoretically investigated by using the generalized Brown-Preston-Singleton (BPS) model, in which a NIS term is taken into account. The analytical formula of the NIS term is detailedly derived. By using this formula, the density and temperature dependence of the NIS effect is numerically studied, and the results show that the NIS effect becomes more and more important with increasing the plasma temperature or density...
September 2016: Physical Review. E
Ohgi Takahashi, Ryota Kirikoshi, Noriyoshi Manabe
In proteins and peptides, d-aspartic acid (d-Asp) and d-β-Asp residues can be spontaneously formed via racemization of the succinimide intermediate formed from l-Asp and l-asparagine (l-Asn) residues. These biologically uncommon amino acid residues are known to have relevance to aging and pathologies. Although nonenzymatic, the succinimide racemization will not occur without a catalyst at room or biological temperature. In the present study, we computationally investigated the mechanism of succinimide racemization catalyzed by dihydrogen phosphate ion, H₂PO₄(-), by B3LYP/6-31+G(d,p) density functional theory calculations, using a model compound in which an aminosuccinyl (Asu) residue is capped with acetyl (Ace) and NCH₃ (Nme) groups on the N- and C-termini, respectively (Ace-Asu-Nme)...
October 10, 2016: International Journal of Molecular Sciences
Junjie Li, Alexander B Pacheco, Krishnan Raghavachari, Srinivasan S Iyengar
We probe the structure, stability and vibrational properties of the fundamental C2H3(+) carbocation that exists with preference in a bridged hydrogen conformation. Our computational study includes electronic structure treatment, incorporation of nuclear motion through classical and quantum paradigms, the effect of temperature, and the associated sampling of the potential surface, and the effect of single H/D isotopic substitution (i.e., C2H2D(+)). We find that while the non-classical, "Bridged" isomer is most stable, the "Classical" form does have a small presence under ambient conditions since the zero point level straddles the barrier between the Classical and Bridged isomers in a reduced dimensional analysis of the Bridged ↔ Classical transfer coordinate...
October 13, 2016: Physical Chemistry Chemical Physics: PCCP
Khadija Sheikh, Fumin Guo, Dante P I Capaldi, Alexei Ouriadov, Rachel L Eddy, Sarah Svenningsen, Grace Parraga
PURPOSE: To develop and assess ultrashort echo-time (UTE) magnetic resonance imaging (MRI) biomarkers of lung function in asthma patients. MATERIALS AND METHODS: Thirty participants including 13 healthy volunteers and 17 asthmatics provided written informed consent to UTE and pulmonary function tests in addition to hyperpolarized-noble-gas 3T MRI and computed tomography (CT) for asthmatics only. The difference in MRI signal-intensity (SI) across four lung volumes (full-expiration, functional-residual-capacity [FRC], FRC+1L, and full-inspiration) was determined on a voxel-by-voxel basis to generate dynamic proton-density (DPD) maps...
October 12, 2016: Journal of Magnetic Resonance Imaging: JMRI
M C Bacchus-Montabonel, F Calvo
Solvation effects are of major interest in the context of radiation damage, due to their potential applications in cancer therapy. Reliable modeling of the solvent is, however, quite challenging, and numerous studies have been devoted to isolated biomolecules and stepwise-hydrated molecules in which the amount of solvent is controlled one molecule at a time. The influence of stepwise hydration on radiation damage is investigated here using the example of proton-induced charge transfer in two biomolecular targets...
November 2016: Journal of Molecular Modeling
Haleh Hashemi Haeri, Philipp Spindler, Jörn Plackmeyer, Thomas Prisner
Carbon-centered radicals are interesting alternatives to otherwise commonly used nitroxide spin labels for dipolar spectroscopy techniques because of their narrow ESR linewidth. Herein, we present a novel BDPA biradical, where two BDPA (α,α,γ,γ-bisdiphenylene-β-phenylallyl) radicals are covalently tethered by a saturated biphenyl acetylene linker. The inter-spin distance between the two spin carrier fragments was measured using double quantum coherence (DQC) ESR methodology. The DQC experiment revealed a mean distance of only 1...
October 12, 2016: Physical Chemistry Chemical Physics: PCCP
Smita A Bhadane, Dipali N Lande, Shridhar P Gejji
The ωB97X based density functional theory has been employed to characterize molecular interactions between adamantane carbonitrile (ACN) or adamantane methyl carbonitrile (AMCN) and the ethylated pillar[6]arene (EtP[6]) molecular cage. The inclusion complexes in 1:1 stoichiometry are stabilized through non-covalent interactions such as hydrogen bonding, C-H•••π and dipole-dipole interactions. Gibbs free energies accompanying the encapsulation of ACN or AMCN within EtP[6] revealed that the formation of complex is spontaneous and thermodynamically favorable...
October 11, 2016: Journal of Physical Chemistry. A
Nerea Alonso, Miquel Torrent-Sucarrat, Iosune Arrastia, Ana Arrieta, Fernando P Cossío
The N-demethylation reactions of N,N,N-trimethylpropan-1-ammonium and N,N-dimethyl-, and N-methylpropan-1-aminium cations in the presence of (AcO)2(imidazole)2(H2O)Fe=O complex have been studied by density functional theory. These transformations are suitable models for the N-demethylation of tri-, di-, and monomethylated lysine residues of histones in the presence of Jumonji-C containing histone demethylases. It has been found that the N-demethylation reaction is stepwise and occurs on triplet and quintet potential energy hypersurfaces...
October 11, 2016: Chemistry: a European Journal
Harald Kramer, Perry J Pickhardt, Mark A Kliewer, Diego Hernando, Guang-Hong Chen, James A Zagzebski, Scott B Reeder
OBJECTIVE: The purpose of this study was to prospectively evaluate the accuracy of proton-density fat-fraction, single- and dual-energy CT (SECT and DECT), gray-scale ultrasound (US), and US shear-wave elastography (US-SWE) in the quantification of hepatic steatosis with MR spectroscopy (MRS) as the reference standard. SUBJECTS AND METHODS: Fifty adults who did not have symptoms (23 men, 27 women; mean age, 57 ± 5 years; body mass index, 27 ± 5) underwent liver imaging with un-enhanced SECT, DECT, gray-scale US, US-SWE, proton-density fat-fraction MRI, and MRS for this prospective trial...
October 11, 2016: AJR. American Journal of Roentgenology
Beatrice N Markiewicz, Thomas Lemmin, Wenkai Zhang, Ismail A Ahmed, Hyunil Jo, Giacomo Fiorin, Thomas Troxler, William F DeGrado, Feng Gai
The M2 proton channel of the influenza A virus has been the subject of extensive studies because of its critical role in viral replication. As such, we now know a great deal about its mechanism of action, especially how it selects and conducts protons in an asymmetric fashion. The conductance of this channel is tuned to conduct protons at a relatively low biologically useful rate, which allows acidification of the viral interior of a virus entrapped within an endosome, but not so great as to cause toxicity to the infected host cell prior to packaging of the virus...
October 11, 2016: Physical Chemistry Chemical Physics: PCCP
Lili Du, Xiting Zhang, Jiadan Xue, Wen-Jian Tang, Mingde Li, Xin Lan, Jiangrui Zhu, Ruixue Zhu, Yuxiang Weng, Yunliang Li, David Lee Phillips
Quinone methides (QM) are crucial reactive species in molecular biology and organic chemistry, with little known regarding the mechanism(s) for the generation of short-lived reactive QM intermediates from relevant precursors in aqueous solutions. In this study, several time-resolved spectroscopy methods were used to directly examine the photophysics and photochemical pathways of 1,1'-(2,2'-dihydroxy-1,1'-binaphthyl-6,6'-diyl)bis(N,N,N-trimethylmethanaminium) bromide (BQMP-b) from initial photoexcitation to the generation of the key reactive binol QM intermediate (BQM) in aqueous solution...
October 10, 2016: Journal of Physical Chemistry. B
Didem C Dogan, Seonghun Cho, Sun-Mi Hwang, Young-Min Kim, Hwanuk Guim, Tae-Hyun Yang, Seok-Hee Park, Gu-Gon Park, Sung-Dae Yim
Supportless Pt catalysts have several advantages over conventional carbon-supported Pt catalysts in that they are not susceptible to carbon corrosion. However, the need for high Pt loadings in membrane electrode assemblies (MEAs) to achieve state-of-the-art fuel cell performance has limited their application in proton exchange membrane fuel cells. Herein, we report a new approach to the design of a supportless Pt catalyst in terms of catalyst layer architecture, which is crucial for fuel cell performance as it affects water management and oxygen transport in the catalyst layers...
October 10, 2016: ACS Applied Materials & Interfaces
Martina Lessio, Christoph Riplinger, Emily A Carter
Adsorbed protons that develop hydride character have been proposed to play a role in the mechanism of CO2 reduction catalyzed by pyridine on GaP photoelectrodes. Investigating their stability represents an important step towards vetting this mechanism. In this contribution, the relative stability of the adsorbed protons is determined using cluster models with dispersion-corrected density functional theory and continuum solvation. Proton acidity constants computed under typical experimental conditions are compared to the acidity constants of other relevant species...
September 29, 2016: Physical Chemistry Chemical Physics: PCCP
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