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https://www.readbyqxmd.com/read/29676661/atomistic-mechanisms-of-the-double-proton-transfer-in-the-h-bonded-nucleobase-pairs-qm-qtaim-computational-lessons
#1
Ol'ha O Brovarets', Dmytro M Hovorun
In this Review we have summarized and generalized the results of the investigation of the microstructural mechanisms of the tautomerisation by the counter movement of the protons along the neighboring intermolecular H-bonds in 22 biologically important pairs of nucleotide bases in the framework of the original method, which allows to trace the evolution of the physico-chemical parameters, that characterize these processes along the intrinsic reaction coordinate (IRC). It was demonstrated the performance of the introduction of the conception of the key points (KPs) (from nine to five, depending on the symmetry and nature of system), which exhaustively characterize the flow of the tautomerisation processes...
April 20, 2018: Journal of Biomolecular Structure & Dynamics
https://www.readbyqxmd.com/read/29676433/proton-pump-inhibitors-and-long-term-risk-of-community-acquired-pneumonia-in-older-adults
#2
Jan Zirk-Sadowski, Jane A Masoli, Joao Delgado, Willie Hamilton, W David Strain, William Henley, David Melzer, Alessandro Ble
OBJECTIVES: To estimate associations between long-term use of proton pump inhibitors (PPIs) and pneumonia incidence in older adults in primary care. DESIGN: Longitudinal analyses of electronic medical records. SETTING: England PARTICIPANTS: Individuals aged 60 and older in primary care receiving PPIs for 1 year or longer (N=75,050) and age- and sex-matched controls (N=75,050). MEASUREMENTS: Net hazard ratios for pneumonia incidence in Year 2 of treatment were estimated using the prior event rate ratio (PERR), which adjusts for pneumonia incidence differences before initiation of treatment...
April 20, 2018: Journal of the American Geriatrics Society
https://www.readbyqxmd.com/read/29676417/electron-paramagnetic-resonance-of-a-copper-doped-ch-3-2-nh-2-zn-hcoo-3-hybrid-perovskite-framework
#3
Mantas Šimėnas, Aneta Ciupa, Gediminas Usevičius, Kęstutis Aidas, Daniel Klose, Gunnar Jeschke, Mirosław Mączka, Georg Völkel, Andreas Pöppl, Jūras Banys
We report a continuous-wave (CW) and pulse electron paramagnetic resonance (EPR) as well as pulse electron nuclear double resonance (ENDOR) study of Cu2+ doped [(CH3)2NH2][Zn(HCOO)3] hybrid perovskite which exhibits a structural phase transition. The multifrequency (X, Q and W-band) CW EPR measurements allow the temperature evolution of the Cu2+ ion local environment to be studied. The spectrum of the ordered (low-temperature) phase reveals an axially distorted octahedral Cu2+ site confirming the successful replacement of the Zn2+ ions and formation of the CuO6 octahedra...
April 20, 2018: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/29676410/newly-proposed-proton-abstraction-roundabout-with-backside-attack-mechanism-for-the-s-n-2-reaction-at-the-nitrogen-center-in-f-nh-2-cl
#4
Yongfang Li, Dunyou Wang
Recent studies have improved our understanding of the mechanism and dynamics of the bimolecular nucleophilic substitution (SN2) reaction at the carbon center. Nonetheless, the SN2 reaction at the nitrogen center has received scarce attention and is less understood. Herein, we propose a new reaction mechanism for the SN2 reaction at the nitrogen center in the F- + NH2Cl reaction using ab initio molecular dynamics calculations. The newly proposed mechanism involves the rotation of NHCl with one proton of NH2Cl abstracted by the nucleophile, followed by the classical backside-attack process...
April 20, 2018: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/29676148/functional-studies-on-oligotropha-carboxidovorans-molybdenum-copper-co-dehydrogenase-produced-in-escherichia-coli
#5
Paul Kaufmann, Benjamin R Duffus, Christian Teutloff, Silke Leimkühler
The Mo/Cu-dependent CO dehydrogenase (CODH) from Oligotropha carboxidovorans is an enzyme that is able to catalyze both the oxidation of CO to CO2 and the oxidation of H2 to protons and electrons. Despite the close to atomic resolution structure (1.1 Å), significant uncertainties have remained with regard to the reaction mechanism of substrate oxidation at the unique Mo/Cu-center, as well as the nature of intermediates formed during the catalytic cycle. So far the investigation of the role of amino acids at the active site was hampered due to the lack of a suitable expression system that allowed for detailed site-directed mutagenesis studies at the active-site...
April 20, 2018: Biochemistry
https://www.readbyqxmd.com/read/29675988/dose-dependent-impact-of-proton-pump-inhibitors-on-the-clinical-course-of-spontaneous-bacterial-peritonitis
#6
Tammo L Tergast, Anika Wranke, Hans Laser, Svetlana Gerbel, Michael P Manns, Markus Cornberg, Benjamin Maasoumy
BACKGROUND & AIMS: Spontaneous bacterial peritonitis (SBP) is a severe complication in patients with liver cirrhosis leading to acute kidney injury (AKI), hepatic encephalopathy (HE) and a high mortality. In this study we aimed to investigate the impact of proton pump inhibitors (PPI) and the potential relevance of the taken dosage on the incidence and clinical course of SBP. METHODS: Overall, 613 consecutive patients with decompensated liver cirrhosis were included...
April 19, 2018: Liver International: Official Journal of the International Association for the Study of the Liver
https://www.readbyqxmd.com/read/29675453/nafld-phenotype-in-patients-with-v-atpase-proton-pump-assembly-defects
#7
EDITORIAL
Jos C Jansen, David Wolthuis, Monique Van Scherpenzeel, Vlad Ratziu, Joost P H Drenth, Dirk J Lefeber
No abstract text is available yet for this article.
March 2018: Cellular and Molecular Gastroenterology and Hepatology
https://www.readbyqxmd.com/read/29675247/a-luminescent-organic-radical-with-two-pyridyl-groups-high-photostability-and-dual-stimuli-responsive-properties-with-theoretical-analyses-of-photophysical-processes
#8
Shun Kimura, Akira Tanushi, Tetsuro Kusamoto, Shuntaro Kochi, Tohru Sato, Hiroshi Nishihara
Luminescent monoradicals are expected to show unique properties based on their doublet state, where establishing a method to improve their photostability is an important issue for expanding their photofunctionality. We synthesized a highly photostable luminescent organic radical, the bis(3,5-dichloro-4-pyridyl)(2,4,6-trichlorophenyl)methyl radical (bisPyTM), containing two pyridyl groups on a tris(2,4,6-trichlorophenyl)methyl radical (TTM) skeleton. bisPyTM in dichloromethane exhibited fluorescence with an emission peak wavelength, λ em , of 650 nm...
February 21, 2018: Chemical Science
https://www.readbyqxmd.com/read/29675207/a-practical-organic-mediated-hybrid-electrolyser-that-decouples-hydrogen-production-at-high-current-densities
#9
Niall Kirkaldy, Greig Chisholm, Jia-Jia Chen, Leroy Cronin
Hydrogen is seen as a sustainable fuel of the future, yet the vast majority of global hydrogen production comes from the reformation of fossil fuels. Electrolytic water splitting using proton exchange membrane electrolysers (PEMEs) provides a pathway to sustainable hydrogen production through coupling to renewable energy sources, but can suffer from gas crossover at low current densities and high operating pressures, causing explosive gas mixtures and decreasing cell lifetimes. Here we demonstrate the application of a highly stable, organic electron-coupled proton buffer (ECPB) which allows the decoupling of hydrogen and oxygen production during water splitting...
February 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/29675201/tagging-effects-on-the-mid-infrared-spectrum-of-microsolvated-protonated-methane
#10
Alexander Esser, Harald Forbert, Dominik Marx
Although bare protonated methane is by now essentially understood at the level of intramolecular large-amplitude motion, scrambling dynamics and broadband vibrational spectra, the microsolvated species still offer plenty of challenges. One aspect is the effect of the attached solvent molecules on the infrared absorption spectra of microsolvated CH5 + complexes compared to the bare parent molecule. In this study we analyze, based on ab initio molecular dynamics simulations, protonated methane molecules that have been microsolvated with up to three hydrogen molecules, i...
February 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/29675195/photoinduced-oxidative-activation-of-electron-rich-arenes-alkenylation-with-h-2-evolution-under-external-oxidant-free-conditions
#11
Xia Hu, Guoting Zhang, Faxiang Bu, Xu Luo, Kebing Yi, Heng Zhang, Aiwen Lei
The dehydrogenative cross-coupling of arenes and alkenes is a particularly ideal approach for the synthesis of aryl alkenes. Herein, we report a photo-induced C-H/C-H cross-coupling between electron-rich arenes and styrene derivatives using a dual catalytic system containing an acridinium photosensitizer and a cobaloxime proton-reducing catalyst. This catalytic system enables the Csp2 -Csp2 bond formation accompanying H2 evolution. Various substituted aryl alkenes can be afforded with good to excellent yields and high β-regioselectivity...
February 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/29675191/synthesis-and-ph-responsive-dissociation-of-framboidal-abc-triblock-copolymer-vesicles-in-aqueous-solution
#12
C J Mable, L A Fielding, M J Derry, O O Mykhaylyk, P Chambon, S P Armes
A series of pH-responsive all-methacrylic ABC triblock copolymer vesicles were prepared from precursor diblock copolymer vesicles via RAFT seeded emulsion polymerisation. Microphase separation between the two hydrophobic membrane-forming B and C blocks produced a distinctive framboidal morphology, for which the mean globule size can be tuned by adjusting the triblock copolymer composition. These vesicles remain intact at neutral pH, but undergo irreversible dissociation on addition of acid as a result of protonation of the tertiary amine groups located within the third block...
February 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/29675190/addition-of-dihydrogen-to-a-borylborenium-center
#13
Junhao Zheng, Zhen Hua Li, Huadong Wang
The activation of a H-H bond, the simplest covalent bond, is a fundamentally important process. Addition of H2 to an elemental center typically occurs on low valent transition metal or main group complexes through oxidative addition to afford metal dihydride complexes. In contrast, activation of H2 on a high valent center generally results in heterolytic cleavage of the H-H bond to a proton and hydride. Here, we report experimental and computational evidence for the addition of H2 to a borenium center in an N-heterocyclic carbene (NHC) coordinated borylborenium cation, which leads to the formation of a dihydroborenium complex accompanied by the elimination of two σ-bonded substituents, namely mesityl (Mes) and pinacolboryl (Bpin) groups, as mesitylboronic ester...
February 14, 2018: Chemical Science
https://www.readbyqxmd.com/read/29675166/dual-emissive-2-2-hydroxyphenyl-oxazoles-for-high-performance-organic-electroluminescent-devices-discovery-of-a-new-equilibrium-of-excited-state-intramolecular-proton-transfer-with-a-reverse-intersystem-crossing-process
#14
Bijin Li, Linsen Zhou, Hu Cheng, Quan Huang, Jingbo Lan, Liang Zhou, Jingsong You
The photoluminescence (PL) and electroluminescence (EL) properties of two highly efficient excited state intramolecular proton transfer (ESIPT) molecules, 2-(2'-hydroxyphenyl)oxazoles containing one triphenylamine (TPA) ( 1 ) and two TPAs ( 2 ) respectively, are studied systematically. The enol-forms of both 1 and 2 possess highly hybridized local and charge transfer (HLCT) excited state character, while their excited-state keto-forms are not of obvious HLCT character. A 1 -based device exhibits green-white electroluminescence with Commission Internationale d'Eclairage (CIE) coordinates of (0...
February 7, 2018: Chemical Science
https://www.readbyqxmd.com/read/29675165/sub-nanosecond-tryptophan-radical-deprotonation-mediated-by-a-protein-bound-water-cluster-in-class-ii-dna-photolyases
#15
Pavel Müller, Elisabeth Ignatz, Stephan Kiontke, Klaus Brettel, Lars-Oliver Essen
Class II DNA photolyases are flavoenzymes occurring in both prokaryotes and eukaryotes including higher plants and animals. Despite considerable structural deviations from the well-studied class I DNA photolyases, they share the main biological function, namely light-driven repair of the most common UV-induced lesions in DNA, the cyclobutane pyrimidine dimers (CPDs). For DNA repair activity, photolyases require the fully reduced flavin adenine dinucleotide cofactor, FADH- , which can be obtained from oxidized or semi-reduced FAD by a process called photoactivation...
February 7, 2018: Chemical Science
https://www.readbyqxmd.com/read/29675157/the-mechanism-of-a-green-fluorescent-protein-proton-shuttle-unveiled-in-the-time-resolved-frequency-domain-by-excited-state-ab-initio-dynamics
#16
Greta Donati, Alessio Petrone, Pasquale Caruso, Nadia Rega
We simulated an excited state proton transfer in green fluorescent protein by excited state ab initio dynamics, and examined the reaction mechanism in both the time and the frequency domain through a multi resolution wavelet analysis. This original approach allowed us, for the first time, to directly compare the trends of photoactivated vibrations to femtosecond stimulated Raman spectroscopy results, and to give an unequivocal interpretation of the role played by low frequency modes in promoting the reaction...
February 7, 2018: Chemical Science
https://www.readbyqxmd.com/read/29674846/costs-of-medication-in-older-patients-before-and-after-comprehensive-geriatric-assessment
#17
Gulcin Done Unutmaz, Pinar Soysal, Busra Tuven, Ahmet Turan Isik
Background: Polypharmacy and inappropriate drug use cause numerous complications, such as cognitive impairment, frailty, falls, and functional dependence. The present study aimed to determine the effect of the comprehensive geriatric assessment (CGA) on polypharmacy, potentially inappropriate medications (PIMs) and potential prescribing omissions (PPOs), and to evaluate the economic reflections of medication changes. Methods: One thousand five hundred and seventy-nine older patients, who had undergone CGA, were retrospectively evaluated...
2018: Clinical Interventions in Aging
https://www.readbyqxmd.com/read/29674667/a-mixed-periodic-paralysis-myotonia-mutant-p1158s-imparts-ph-sensitivity-in-skeletal-muscle-voltage-gated-sodium-channels
#18
Mohammad-Reza Ghovanloo, Mena Abdelsayed, Colin H Peters, Peter C Ruben
Skeletal muscle channelopathies, many of which are inherited as autosomal dominant mutations, include myotonia and periodic paralysis. Myotonia is defined by a delayed relaxation after muscular contraction, whereas periodic paralysis is defined by episodic attacks of weakness. One sub-type of periodic paralysis, known as hypokalemic periodic paralysis (hypoPP), is associated with low potassium levels. Interestingly, the P1158S missense mutant, located in the third domain S4-S5 linker of the "skeletal muscle", Nav1...
April 19, 2018: Scientific Reports
https://www.readbyqxmd.com/read/29674639/design-and-optimization-of-a-compact-laser-driven-proton-beamline
#19
M Scisciò, M Migliorati, L Palumbo, P Antici
Laser-accelerated protons, generated by irradiating a solid target with a short, energetic laser pulse at high intensity (I > 1018  W·cm-2 ), represent a complementary if not outperforming source compared to conventional accelerators, due  to their intrinsic features, such as high beam charge and short bunch duration. However, the broadband energy spectrum of these proton sources is a bottleneck that precludes their use in applications requiring a more reduced energy spread. Consequently, in recent times strong effort has been put to overcome these limits and to develop laser-driven proton beamlines with low energy spread...
April 19, 2018: Scientific Reports
https://www.readbyqxmd.com/read/29674316/activation-of-renal-clc-k-chloride-channels-depends-on-an-intact-n-terminus-of-their-accessory-subunit-barttin
#20
Daniel Wojciechowski, Stefan Thiemann, Christina Schaal, Alina Rahtz, Jeanne de la Roche, Birgit Begemann, Toni Becher, Martin Fischer
ClC-K channels belong to the CLC family of chloride channels and chloride/proton antiporters. They contribute to sodium chloride reabsorption in Henle's loop of the kidney and to potassium secretion into the endolymph by the stria vascularis of the inner ear. Their accessory subunit barttin stabilizes the ClC-K/barttin complex, promotes its insertion into the surface membrane, and turns the pore-forming subunits into a conductive state. Barttin mutations cause Bartter syndrome type IV, a salt wasting nephropathy with sensorineural deafness...
April 19, 2018: Journal of Biological Chemistry
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