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Li Zhang, Hongsheng Yuan, Yue Meng, Ho-Kwang Mao
A deep lower-mantle (DLM) water reservoir depends on availability of hydrous minerals which can store and transport water into the DLM without dehydration. Recent discoveries found hydrous phases AlOOH ( Z = 2) with a CaCl2 -type structure and FeOOH ( Z = 4) with a cubic pyrite-type structure stable under the high-pressure-temperature ( P-T ) conditions of the DLM. Our experiments at 107-136 GPa and 2,400 K have further demonstrated that (Fe,Al)OOH is stabilized in a hexagonal lattice. By combining powder X-ray-diffraction techniques with multigrain indexation, we are able to determine this hexagonal hydrous phase with a = 10...
March 5, 2018: Proceedings of the National Academy of Sciences of the United States of America
S Jeremić, A Amić, M Stanojević-Pirković, Z Marković
Disruption of homeostasis can increase the amount of free radicals formed during metabolic processes. This phenomenon known as oxidative stress can have numerous negative outcomes. The role of dietary antioxidants is to help the prevention of oxidative stress. We investigated free radical scavenging capacity of six structurally similar anthraquinones (alizarin, purpurin, chrysophanol, emodin, aloe-emodin and 1,3,8-trihydroxyanthraquinone) for inactivating a set of ten hydroxy and peroxy free radicals. The antioxidant capacity of anthraquinones was estimated by considering Gibbs free energy of three studied reaction mechanisms: hydrogen atom transfer (HAT), single-electron transfer followed by proton transfer (SET-PT) and sequential proton loss electron transfer (SPLET)...
February 26, 2018: Organic & Biomolecular Chemistry
Hifza Jabeen, Samia Saleemi, Humaira Razzaq, Azra Yaqub, Saira Shakoor, Rumana Qureshi
Reactive oxygen (hydroxyl OH, hydroperoxyl OOH) species are highly unstable to be studied experimentally under normal conditions. The present study reports the antioxidant potential of the vitamins namely ascorbic acid, riboflavin and nicotinic acid against these reactive oxygen species (ROS) using the predictive power of Density Functional Theory (DFT) (B3LYP with 6311G basis set) calculations. The order of reactivity of aforementioned vitamins was assessed by determining the bond dissociation enthalpy (BDE) of the OH bond, which is the controlling factor, if hydrogen atom transfer (HAT) mechanism is considered...
February 22, 2018: Journal of Photochemistry and Photobiology. B, Biology
Zhen Liu, Vinh Son Nguyen, Jeremy Harvey, Jean-François Müller, Jozef Peeters
In this work, we theoretically elucidated the mechanism and predicted the major products of the photolysis of α-hydroperoxycarbonyls, known to be products of the atmospheric oxidation of biogenic volatile organic compounds (BVOC) and components of secondary organic aerosol (SOA) in rural and remote areas. Using 2-hydroperoxypropanal OCHCH(OOH)CH3 as a model compound, we show that the likely major photolysis mechanism is a fast 1,5 H-shift in the initially excited singlet S1 state followed by spontaneous elimination of singlet oxygen to yield an enol HOCH[double bond, length as m-dash]CHCH3 , while intersystem crossing (ISC) to the triplet T1 state and C-C scission into HC˙O + HOOC˙HCH3 followed by expulsion of a hydroxyl radical from the unstable HOOC˙HCH3 is another product channel...
February 21, 2018: Physical Chemistry Chemical Physics: PCCP
Sheng-Hua Ye, Zi-Xiao Shi, Jin-Xian Feng, Ye-Xiang Tong, Gao-Ren Li
Iron-substituted CoOOH porous nanosheet arrays grown on carbon fiber cloth (denoted as Fex Co1-x OOH PNSAs/CFC, 0≤x≤0.33) with 3D hierarchical structures are synthesized by in situ anodic oxidation of α-Co(OH)2 NSAs/CFC in solution of 0.01 m (NH4 )2 Fe(SO4 )2 . X-ray absorption fine spectra (XAFS) demonstrate that CoO6 octahedral structure in CoOOH can be partially substituted by FeO6 octahedrons during the transformation from α-Co(OH)2 to Fex Co1-x OOH, and this is confirmed for the first time in this study...
February 8, 2018: Angewandte Chemie
Shize Liu, Lin Cheng, Kai Li, Ying Wang, Yuewen Yang, Zhijian Wu
The transition metal and nitrogen co-doped graphene as efficient electrocatalysts of oxygen reduction reaction (ORR) is promising to achieve large-scale applications of the full cells. In this work, we investigated the active sites and ORR mechanism on IrN4 doped divacancy graphene (IrN4-Gra) by using the density functional method. The active sites are identified as the IrN4 moiety and its adjacent ten C atoms. ORR on IrN4-Gra is a four-electron process. OOH hydrogenated into OH + OH is the kinetically most favorable pathway...
January 31, 2018: Journal of Molecular Graphics & Modelling
Maria Luisa Corrado, Tanja Knaus, Francesco Mutti
The styrene monooxygenase (SMO) system from Pseudomonas sp. is constituted by two enzymes (StyA and StyB). StyB catalyses the reduction of FAD at the expense of NADH. After the transfer of FADH2 from StyB to StyA, reaction with O2 generates FAD-OOH that is the epoxidising agent. The waste of redox equivalents due to a partial diffusive transfer of FADH2, the insolubility of recombinant StyB and the impossibility to express StyA and StyB in a 1:1 molar ratio reduce the catalytic efficiency of the natural system...
January 29, 2018: Chembiochem: a European Journal of Chemical Biology
Lucienne Buannic, Luke Sperrin, Riza Dervişoğlu, Frédéric Blanc, Clare P Grey
Perovskite-based material Sc-doped BaZrO3 is a promising protonic conductor but with substantially lower conductivities than its Y-doped counterpart. 1H solid-state NMR spectroscopy in combination with DFT modelling was used to analyze the protonic distribution in BaZr1-xScxO3-x/2-y(OH)2y and its effect on charge carrier mobility. 1H single pulse and 1H-45Sc TRAPDOR MAS NMR experiments highlighted the mobile character of the proton charge carriers at room temperature, giving rise to a single broad resonance, protons hopping between multiple sites on the NMR timescale...
January 25, 2018: Physical Chemistry Chemical Physics: PCCP
Joseph H Montoya, Andrew D Doyle, Jens K Nørskov, Aleksandra Vojvodic
The reactivity of solid oxide surfaces towards adsorption of oxygen and hydrogen is a key metric for the design of new catalysts for electrochemical water splitting. In this paper, we report on trends in the adsorption energy of different adsorbed intermediates derived from the oxidation and reduction of water for ternary ABO3 oxides in the cubic perovskite structure. Our findings support a previously reported trend that rationalizes the observed lower bound in oxygen evolution (OER) overpotentials from correlations in OH* and OOH* adsorption energies...
January 19, 2018: Physical Chemistry Chemical Physics: PCCP
Mette Tranberg, Peter Vedsted, Bodil Hammer Bech, Morten Bondo Christensen, Søren Birkeland, Grete Moth
BACKGROUND: Low patient satisfaction with the quality of out-of-hours primary care (OOH-PC) has been linked with several individual and organizational factors. However, findings have been ambiguous and may not apply to the Danish out-of-hours (OOH) setting in which general practitioners (GPs) perform the initial telephone triage. This study aimed to identify patient-related, GP-related and organizational factors associated with low patient satisfaction. METHODS: The study was based on data from a 1-year population-based survey of OOH-PC (LV-KOS) in the Central Denmark Region in 2010-2011...
January 11, 2018: BMC Family Practice
Tobias Hens, Joël Brugger, Susan Cumberland, Barbara Etschmann, Andrew J Frierdich
The recrystallization of Mn(III,IV) oxides is catalyzed by aqueous Mn(II) (Mn(II)aq) during (bio)geochemical Mn redox cycling. It is poorly understood how trace metals associated with Mn oxides (e.g., Ni) are cycled during such recrystallization. Here, we use X-ray absorption spectroscopy (XAS) to examine the speciation of Ni associated with manganite (γ-Mn(III)OOH) suspensions in the presence or absence of Mn(II)aq under variable pH conditions (pH 5.5 and 7.5). In a second set of experiments, we used a 62Ni isotope tracer to quantify the amount of dissolved Ni that exchanges with Ni incorporated in the manganite crystal structure during reactions in 1 mM Mn(II)aq and in Mn(II)-free solutions...
January 11, 2018: Environmental Science & Technology
Yingxiang Yu, Yiran Lv, Bin Yao, Liguang Duan, Xiaoyuan Zhang, Lan Xie, Cuiqing Chang
BACKGROUND AND AIM: Information technology has been previously used for the research and practice of health promotion. Appropriate and effective health promotion methods used by professional groups remain to be investigated. This study aimed to assess the feasibility and effectiveness of a weight management program among the Chinese occupational population using and a novel information technology exercise prescription. STUDY DESIGN AND PARTICIPANTS: A 3-month open, self-monitored intervention trial, involving individualized pedometer-assisted exercise prescription and a one-time targeted dietary guidance prior to exercise was conducted on the Chinese occupational population aged 18-65 years in China from 2015 to 2016...
2018: PloS One
Xiao-Chen Liu, Hui-Hui Du, Li-Min Fu, Rui-Min Han, Peng Wang, Xi-Cheng Ai, Jian-Ping Zhang, Leif H Skibsted
We have attempted to evaluate, on the basis of optical microscopy for single giant unilamellar vesicle (GUV), the potency of antioxidants in protecting GUV membranes from oxidative destruction. Photosensitized membrane budding of GUVs prepared from soybean phosphatidylcholine with chlorophyll a (Chl a) and β-carotene (β-Car) as photosensitizer and protector, respectively, were followed by microscopic imaging. A dimensionless entropy parameter, ΔE, as derived from the time resolved microscopic images, was employed to describe the evolution of morphological variation of GUVs...
January 3, 2018: Analytical Chemistry
Grete Moth, Linda Huibers, Astrid Ovesen, Morten Bondo Christensen, Peter Vedsted
BACKGROUND: Out-of-hours primary care (OOH-PC) is intended to provide medical care services for health problems that cannot wait until normal office hours. Children under five years of age represent about 19% of all OOH-PC contacts in Denmark, and the frequency of calls assessed as severe by health professionals is markedly lower for children than for other age groups. Several studies have questioned the appropriateness of the parents' use of OOH-PC. We aimed to identify factors associated with calls from parents of pre-school children concerning perceived non-severe health problems that were ranked by the triaging GPs as more appropriate for GP office hours (defined as 'medically irrelevant')...
December 28, 2017: BMC Family Practice
Ji Liu, Xiaofeng Fan, Chang Q Sun, Weiguang Zhu
Detailed density functional theory (DFT) calculations of the adsorption energies (Ead) for oxygen on monolayer Pd on top of the Pd-Cu face-centered cubic (FCC) alloy and intermetallic B2 structure revealed a linear correspondence between the adsorption energies and the d-band center position. The calculated barrier (Ebarrier) for oxygen dissociation depends linearly on the reaction energy difference (ΔE). The O₂ has a stronger adsorption strength and smaller barrier on the intermetallic Pd-Cu surface than on its FCC alloy surface...
December 26, 2017: Materials
Mikel Leturiondo, Sofía Ruiz de Gauna, Jesus M Ruiz, J Julio Gutiérrez, Luis A Leturiondo, Digna M González-Otero, James K Russell, Dana Zive, Mohamud Daya
BACKGROUND: Capnography has been proposed as a method for monitoring the ventilation rate during cardiopulmonary resuscitation (CPR). A high incidence (above 70%) of capnograms distorted by chest compression induced oscillations has been previously reported in out-of-hospital (OOH) CPR. The aim of the study was to better characterize the chest compression artefact and to evaluate its influence on the performance of a capnogram-based ventilation detector during OOH CPR. METHODS: Data from the MRx monitor-defibrillator were extracted from OOH cardiac arrest episodes...
December 12, 2017: Resuscitation
Eric Gonzalez, Kevin M Johnson, Pradeep S Pallan, Thanh T N Phan, Wei Zhang, Li Lei, Zdzislaw Wawrzak, Francis K Yoshimoto, Martin Egli, F Peter Guengerich
Cytochrome P450 (P450) 17A1 catalyzes the oxidations of progesterone and pregnenolone and is the major source of androgens. The enzyme catalyzes both 17α-hydroxylation and a subsequent 17α,20-lyase reaction, and several mechanisms have been proposed for the latter step. Zebrafish P450 17A2 catalyzes only the 17α-hydroxylations. We previously reported high similarity of the crystal structures of zebrafish P450 17A1 and 17A2 and human P450 17A1. Five residues near the heme, which differed, were changed. We also crystallized this five-residue zebrafish P450 17A1 mutant, and the active site still resembled the structure in the other proteins, with some important differences...
January 12, 2018: Journal of Biological Chemistry
Feng Shao, Lifei Gu, Huijuan Chen, Ronghua Liu, Huilian Huang, Lanying Chen, Ming Yang
Background: Hawthorn ( Crataegus pinnatifida ) fruit has enjoyed a great popularity as a pleasant-tasting food associated with hypolipidemic and antioxidant effects. Objective: Our aim was to screen the effective fraction of hawthorn fruit in the treatment of hyperlipidemia rats. Materials and Methods: In this study, ethanol extract of hawthorn fruit (Fr.1) and four fractionated extracts (Fr.2, Fr.3, Fr.4, and Fr.5) were compared to total phenol content evaluated using Folin-Ciocalteu method, and hypolipidemic and antioxidant effects were assessed in hyperlipidemic rats...
October 2017: Pharmacognosy Magazine
Weiyu Chen, Ghassan J Maghzal, Anita Ayer, Cacang Suarna, Louise L Dunn, Roland Stocker
Bilirubin, a byproduct of heme catabolism, has been shown to be an effective lipid-soluble antioxidant in vitro. Bilirubin is able to inhibit free radical chain reactions and protects against oxidant-induced damage in vitro and ex vivo. However, direct evidence for bilirubin's antioxidant effects in vivo remains limited. As bilirubin is formed from biliverdin by biliverdin reductase, we generated global biliverdin reductase-a gene knockout (Bvra-/- ) mice to assess the contribution of bilirubin as an endogenous antioxidant...
February 1, 2018: Free Radical Biology & Medicine
Joan Serrano-Plana, Ferran Acuña-Parés, Valeria Dantignana, Williamson N Oloo, Esther Castillo, Apparao Draksharapu, Christopher J Whiteoak, Vlad Martin-Diaconescu, Manuel G Basallote, Josep M Luis, Lawrence Que, Miquel Costas, Anna Company
A novel hydroperoxoiron(III) species [FeIII (OOH)(MeCN)(PyNMe3 )]2+ (3) has been generated by reaction of its ferrous precursor [FeII (CF3 SO3 )2 (PyNMe3 )] (1) with hydrogen peroxide at low temperatures. This species has been characterized by several spectroscopic techniques and cryospray mass spectrometry. Similar to most of the previously described low-spin hydroperoxoiron(III) compounds, 3 behaves as a sluggish oxidant and it is not kinetically competent for breaking weak C-H bonds. However, triflic acid addition to 3 causes its transformation into a much more reactive compound towards organic substrates that is capable of oxidizing unactivated C-H bonds with high stereospecificity...
November 28, 2017: Chemistry: a European Journal
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