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https://www.readbyqxmd.com/read/28212031/bond-activation-and-hydrogen-evolution-from-water-through-reactions-with-m3s4-m-mo-w-and-w3s3-anionic-clusters
#1
Corrine A Kumar, Arjun Saha, Krishnan Raghavachari
Transition metal sulfides (TMS) are being investigated with increased frequency because of their ability to efficiently catalyze the hydrogen evolution reaction. We have studied the trimetallic TMS cluster ions, Mo3S4(-), W3S4(-), and W3S3(-), and probed their efficiency for bond activation and hydrogen evolution from water. These clusters have geometries that are related to the edge sites on bulk MoS2 surfaces that are known to play a role in hydrogen evolution. Using density functional theory, the electronic structures of these clusters and their chemical reactivity with water have been investigated...
February 17, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28194014/modulating-supramolecular-binding-of-carbon-dioxide-in-a-redox-active-porous-metal-organic-framework
#2
Zhenzhong Lu, Harry G W Godfrey, Ivan da Silva, Yongqiang Cheng, Mathew Savage, Floriana Tuna, Eric J L McInnes, Simon J Teat, Kevin J Gagnon, Mark D Frogley, Pascal Manuel, Svemir Rudić, Anibal J Ramirez-Cuesta, Timothy L Easun, Sihai Yang, Martin Schröder
Hydrogen bonds dominate many chemical and biological processes, and chemical modification enables control and modulation of host-guest systems. Here we report a targeted modification of hydrogen bonding and its effect on guest binding in redox-active materials. MFM-300(V(III)) {[V(III)2(OH)2(L)], LH4=biphenyl-3,3',5,5'-tetracarboxylic acid} can be oxidized to isostructural MFM-300(V(IV)), [V(IV)2O2(L)], in which deprotonation of the bridging hydroxyl groups occurs. MFM-300(V(III)) shows the second highest CO2 uptake capacity in metal-organic framework materials at 298 K and 1 bar (6...
February 13, 2017: Nature Communications
https://www.readbyqxmd.com/read/28192997/photolysis-of-antibiotics-under-simulated-sunlight-irradiation-identification-of-photoproducts-by-high-resolution-mass-spectrometry
#3
Rosa María Baena-Nogueras, Eduardo Gonzalez-Mazo, Pablo Antonio Lara-Martín
There is a growing concern on the widespread use of antibiotics and their presence in the aqueous environment. Their removal in the water column is mediated by different types of degradation processes for which the mechanisms are still unclear. This research is focused on characterizing the photodegradation kinetics and pathways of two largely employed antibiotics families: sulfonamides (9 SDs) and fluoroquinolones (6 FQs). Degradation percentages and rates were measured in pure water exposed to simulated natural sunlight at a constant irradiance value (500 W m-2) during all the experiments, and the main photoproducts formed were characterized through accurate mass measurement using ultra-performance liquid chromatography - quadrupole-time-of-flight - mass spectrometry (UPLC-QToF-MS)...
February 14, 2017: Environmental Science & Technology
https://www.readbyqxmd.com/read/28186351/determination-of-bifonazole-and-identification-of-its-photocatalytic-degradation-products-using-uplc-ms-ms
#4
Agata Kryczyk, Paweł Żmudzki, Urszula Hubicka
The main goal of the presented work was to investigate the effect of ZnO or/and TiO2 on the stability of bifonazole in solutions under UVA irradiation. To this end, a simple and reproducible UPLC method for the determination of bifonazole in the presence of its photocatalytic degradation products was developed. Linearity was studied in the range of 0.0046-0.15 mg mL(-1) with a determination coefficient of 0.9996. Bifonazole underwent photocatalytic degradation process under the experimental conditions used...
February 10, 2017: Biomedical Chromatography: BMC
https://www.readbyqxmd.com/read/28178812/understanding-inherent-substrate-selectivity-during-atomic-layer-deposition-effect-of-surface-preparation-hydroxyl-density-and-metal-oxide-composition-on-nucleation-mechanisms-during-tungsten-ald
#5
Paul C Lemaire, Mariah King, Gregory N Parsons
Area-selective thin film deposition is expected to be important for advanced sub-10 nanometer semiconductor devices, enabling feature patterning, alignment to underlying structures, and edge definition. Several atomic layer deposition (ALD) processes show inherent propensity for substrate-dependent nucleation. This includes tungsten ALD (W-ALD) which is more energetically favorable on Si than on SiO2. However, the selectivity is often lost after several ALD cycles. We investigated the causes of tungsten nucleation on SiO2 and other "non-growth" surfaces during the WF6/SiH4 W-ALD process to determine how to expand the "selectivity window...
February 7, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28171724/crown-ether-nucleophilic-catalysts-cencs-agents-for-enhanced-silicon-radiofluorination
#6
Susovan Jana, Mohammed H Al-Huniti, Bo Yeun Yang, Shuiyu Lu, Victor W Pike, Salvatore D Lepore
New bifunctional phase transfer agents were synthesized and investigated for their abilities to promote rapid fluorination at silicon. These agents, dubbed crown ether nucleophilic catalysts (CENCs), are 18-crown-6 derivatives containing a side-arm and a potentially nucleophilic hydroxyl group. These CENCs proved efficacious in the fluorination of hindered silicon substrates, with fluorination yields dependent on the length of linker connecting the metal chelating unit to the hydroxyl group. The efficacy of these CENCs was also demonstrated for rapid radiofluorination under mild conditions for eventual application in molecular imaging with positron emission tomography (PET)...
February 20, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28165251/enantioselective-synthesis-of-4-ethynyl-2-fluoro-2-deoxyadenosine-efda-via-enzymatic-desymmetrization
#7
Mark McLaughlin, Jongrock Kong, Kevin M Belyk, Billy Chen, Andrew W Gibson, Stephen P Keen, David R Lieberman, Erika M Milczek, Jeffrey C Moore, David Murray, Feng Peng, Ji Qi, Robert A Reamer, Zhiguo J Song, Lushi Tan, Lin Wang, Michael J Williams
An enantioselective synthesis of the potent anti-HIV nucleoside EFdA is presented. Key features of stereocontrol include construction of the fully substituted 4'-carbon via a biocatalytic desymmetrization of 2-hydroxy-2-((triisopropylsilyl)ethynyl)propane-1,3-diyl diacetate and a Noyori-type asymmetric transfer hydrogenation to control the stereochemistry of the 3'-hydroxyl bearing carbon. The discovery of a selective crystallization of an N-silyl nucleoside intermediate enabled isolation of the desired β-anomer from the glycosylation step...
February 6, 2017: Organic Letters
https://www.readbyqxmd.com/read/28159225/microwave-induced-production-of-boron-doped-hap-b-hap-and-b-hap-coated-composite-scaffolds
#8
Ekin Ö Tunçay, T Tolga Demirtaş, Menemşe Gümüşderelioğlu
The aim of the present study is to produce boron (B) doped hydroxyapatite (B-HAp), which has an osteoinductive property, and investigate in-vitro osteogenesis potential of B-HAp coated chitosan (B-HAp/Ch) scaffolds. At first, B-HAp was produced by the interaction of ions within the concentrated synthetic body fluid containing boron (B-SBF) with microwave energy. Boron incorporation into HAp structure was performed by the substitution of borate ions with phosphate and hydroxyl ions. Experiments were carried out with different microwave powers and exposure times, and optimum conditions for the production of B-HAp were determined...
March 2017: Journal of Trace Elements in Medicine and Biology
https://www.readbyqxmd.com/read/28153925/the-formation-and-sequestration-of-non-endogenous-ketocarotenoids-in-transgenic-nicotiana-glauca
#9
Cara Louise Mortimer, Norihiko Misawa, Laura Perez-Fons, Francesca Pamela Robertson, Hisashi Harada, Peter M Bramley, Paul David Fraser
Ketolated and hydroxylated carotenoids are high-value compounds with industrial, food and feed applications. Chemical synthesis is presently the production method of choice for these compounds, with no amenable plant sources readily available. In the present study, the 4, 4' β-oxygenase (crtW) and 3, 3' β-hydroxylase (crtZ) genes from Brevundimonas sp SD-212. have been expressed under constitutive transcriptional control in Nicotiana glauca, which has an emerging potential as biofuel and biorefining feedstock...
January 30, 2017: Plant Physiology
https://www.readbyqxmd.com/read/28147280/ebi2-is-highly-expressed-in-multiple-sclerosis-lesions-and-promotes-early-cns-migration-of-encephalitogenic-cd4%C3%A2-t-cells
#10
Florian Wanke, Sonja Moos, Andrew L Croxford, André P Heinen, Stephanie Gräf, Bettina Kalt, Denise Tischner, Juan Zhang, Isabelle Christen, Julia Bruttger, Nir Yogev, Yilang Tang, Morad Zayoud, Nicole Israel, Khalad Karram, Sonja Reißig, Sonja M Lacher, Christian Reichhold, Ilgiz A Mufazalov, Avraham Ben-Nun, Tanja Kuhlmann, Nina Wettschureck, Andreas W Sailer, Klaus Rajewsky, Stefano Casola, Ari Waisman, Florian C Kurschus
Arrival of encephalitogenic T cells at inflammatory foci represents a critical step in development of experimental autoimmune encephalomyelitis (EAE), the animal model for multiple sclerosis. EBI2 and its ligand, 7α,25-OHC, direct immune cell localization in secondary lymphoid organs. CH25H and CYP7B1 hydroxylate cholesterol to 7α,25-OHC. During EAE, we found increased expression of CH25H by microglia and CYP7B1 by CNS-infiltrating immune cells elevating the ligand concentration in the CNS. Two critical pro-inflammatory cytokines, interleukin-23 (IL-23) and interleukin-1 beta (IL-1β), maintained expression of EBI2 in differentiating Th17 cells...
January 31, 2017: Cell Reports
https://www.readbyqxmd.com/read/28126283/fenton-process-on-single-and-mixture-components-of-phenothiazine-pharmaceuticals-assessment-of-intermediaries-fate-and-preliminary-ecotoxicity
#11
Marcelo L Wilde, Mandy Schneider, Klaus Kümmerer
Pharmaceuticals do not occur isolated in the environment but in multi-component mixtures and may exhibit antagonist, synergistic or additive behavior. Knowledge on this is still scarce. The situation is even more complicated if effluents or potable water is treated by oxidative processes or such transformations occur in the environment. Thus, determining the fate and effects of parent compounds, metabolites and transformation products (TPs) formed by transformation and degradation processes in the environment is needed...
January 23, 2017: Science of the Total Environment
https://www.readbyqxmd.com/read/28099024/surface-interactions-and-confinement-of-methane-a-high-pressure-magic-angle-spinning-nmr-and-computational-chemistry-study
#12
Salim Ok, David W Hoyt, Amity Andersen, Julie Sheets, Susan A Welch, David R Cole, Karl T Mueller, Nancy M Washton
Characterization and modeling of the molecular-level behavior of simple hydrocarbon gases, such as methane, in the presence of both nonporous and nanoporous mineral matrices allows for predictive understanding of important processes in engineered and natural systems. In this study, changes in local electromagnetic environments of the carbon atoms in methane under conditions of high pressure (up to 130 bar) and moderate temperature (up to 346 K) were observed with (13)C magic-angle spinning (MAS) NMR spectroscopy while the methane gas was mixed with two model solid substrates: a fumed nonporous, 12 nm particle size silica and a mesoporous silica with 200 nm particle size and 4 nm average pore diameter...
February 6, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28080043/plasma-based-water-treatment-efficient-transformation-of-perfluoroalkyl-substances-in-prepared-solutions-and-contaminated-groundwater
#13
Gunnar R Stratton, Fei Dai, Christopher L Bellona, Thomas M Holsen, Eric R V Dickenson, Selma Mededovic Thagard
A process based on electrical discharge plasma was tested for the transformation of perfluorooctanoic acid (PFOA). The plasma-based process was adapted for two cases, high removal rate and high removal efficiency. During a 30 min treatment, the PFOA concentration in 1.4 L of aqueous solutions was reduced by 90% with the high rate process (76.5 W input power) and 25% with the high efficiency process (4.1 W input power). Both achieved remarkably high PFOA removal and defluorination efficiencies compared to leading alternative technologies...
January 26, 2017: Environmental Science & Technology
https://www.readbyqxmd.com/read/28054692/in-situ-liquid-cell-electron-microscopy-of-ag-au-galvanic-replacement-reactions
#14
Eli A Sutter, Peter W Sutter
Galvanic replacement reactions are important as they transform nanoparticle templates into complex porous and hollow metal or alloy nanostructures with interesting properties for a variety of applications. Real-time liquid cell electron microscopy (LCEM) observations of the transformation of solid nanoparticles into hollow shell and cage bimetallic nanostructures are challenging because the high-energy electron beam strongly affects the galvanic process via species such as aqueous electrons and hydroxyl radicals generated through the radiolysis of water in the liquid cell...
January 19, 2017: Nanoscale
https://www.readbyqxmd.com/read/28054688/oh-production-from-the-photolysis-of-isoprene-derived-peroxy-radicals-cross-sections-quantum-yields-and-atmospheric-implications
#15
Robert F Hansen, Tom R Lewis, Lee Graham, Lisa K Whalley, Paul W Seakins, Dwayne E Heard, Mark A Blitz
In environments with high concentrations of biogenic volatile organic compounds and low concentrations of nitrogen oxides (NOx = NO + NO2), significant discrepancies have been found between measured and modeled concentrations of hydroxyl radical (OH). The photolysis of peroxy radicals from isoprene (HO-Iso-O2) in the near ultraviolet represents a potential source of OH in these environments, yet has not been considered in atmospheric models. This paper presents measurements of the absorption cross-sections for OH formation (σRO2,OH) from the photolysis of HO-Iso-O2 at wavelengths from 310-362...
January 18, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28053093/catalytic-determinants-of-alkene-production-by-the-cytochrome-p450-peroxygenase-oletje
#16
Sarah Matthews, James D Belcher, Kang Lan Tee, Hazel M Girvan, Kirsty J McLean, Stephen Ej Rigby, Colin W Levy, David Leys, David A Parker, Richard T Blankley, Andrew W Munro
The Jeotgalicoccus sp. peroxygenase cytochrome P450 OleTJE (CYP152L1) is a hydrogen peroxide-driven oxidase that catalyzes oxidative decarboxylation of fatty acids, producing terminal alkenes with applications as fine chemicals and biofuels. Understanding mechanisms that favor decarboxylation over fatty acid hydroxylation in OleTJE could enable protein engineering to improve catalysis or to introduce decarboxylation activity into P450s with different substrate preferences. In this manuscript, we have focused on OleTJE active site residues Phe79, His85 and Arg245 to interrogate their roles in substrate binding and catalytic activity...
January 4, 2017: Journal of Biological Chemistry
https://www.readbyqxmd.com/read/28047507/su-f-i-27-measurement-of-sar-and-temperature-elevation-during-mri-scans
#17
Y Seo
PURPOSE: The poor reliability and repeatability of the manufacturer-reported SAR values on clinical MRI systems have been acknowledged. The purpose of this study is to not only measure SAR values, but also RF-induced temperature elevation at 1.5 and 3T MRI systems. METHODS: SAR measurement experiment was performed at 1.5 and 3T. Three MRI RF sequences (T1w TSE, T1w inversion recovery, and T2w TSE) with imaging parameters were selected. A hydroxyl-ethylcelluose (HEC) gelled saline phantom mimicking human body tissue was made...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28046871/su-f-t-676-measurement-of-hydroxyl-radicals-in-radiolized-water-systems
#18
Z Ouyang, G Strack, E Sajo, W Ngwa
PURPOSE: Hydroxyl radicals can be produced within tissue by radiation therapy, and they are largely responsible for DNA damage and cell killing. Coumarin-3-carboxylic acid (3-CCA) and crystal violet are reported to react with hydroxyl radicals and can be used for fluorescence and absorbance measurements, respectively. This study assesses the ability of hydroxyl measurement for both 3-CCA and crystal violet in radiolized water systems in order to provide dosimetric information in radiation chemistry and radiation biology experiments...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28043840/characterization-of-cytochrome-p450-cyp109e1-from-bacillus-megaterium-as-a-novel-vitamin-d3-hydroxylase
#19
Ammar Abdulmughni, Ilona K Jóźwik, Natalia Putkaradze, Elisa Brill, Josef Zapp, Andy-Mark W H Thunnissen, Frank Hannemann, Rita Bernhardt
In this study the ability of CYP109E1 from Bacillus megaterium to metabolize vitamin D3 (VD3) was investigated. In an in vitro system using bovine adrenodoxin reductase (AdR) and adrenodoxin (Adx4-108), VD3 was converted by CYP109E1 into several products. Furthermore, a whole-cell system in B. megaterium MS941 was established. The new system showed a conversion of 95% after 24h. By NMR analysis it was found that CYP109E1 catalyzes hydroxylation of VD3 at carbons C-24 and C-25, resulting in the formation of 24(S)-hydroxyvitamin D3 (24S(OH)VD3), 25-hydroxyvitamin D3 (25(OH)VD3) and 24S,25-dihydroxyvitamin D3 (24S,25(OH)2VD3)...
February 10, 2017: Journal of Biotechnology
https://www.readbyqxmd.com/read/28043266/-relationship-between-urinary-polycyclic-aromatic-hydrocarbon-metabolite-and-cell-cycle-of-lymphocyte-in-coke-oven-workers
#20
B L Pan, H T Zhang, H J Zhang, W T Chen, J Yang
Objective: To investigate the relationship between urinary polycyclic aromatic hydrocarbon metabolite and cell cycle of lymphocyte in coke oven workers. Methods: 437 coke oven workers and 163 work-ers in water treatment department were recruited in this study. Flow cytometry was used to detect the cell cycle of lymphocyte. For the measurement of urinary metabolites, urine samples were treated with β-glucuronidase and analyzed using HPLC with a fluorescence detector. Results: The concentrations of urinary 2-naphthol, 2-hydroxyfluorene, 9-phenanthrol and 1-hydroxypyrene l in coke oven workers were significantly higher than those in control group (P<0...
November 20, 2016: Chinese Journal of Industrial Hygiene and Occupational Diseases
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