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https://www.readbyqxmd.com/read/28239728/chemistry-of-cs2-and-scnph-adducts-of-the-pyramidal-phosphinidene-bridged-complex-mo2cp-%C3%AE-%C3%AE%C2%BA-1-%C3%AE%C2%BA-1-%C3%AE-5-pc5h4-co-2-%C3%AE-6-hmes-pme3
#1
Isabel G Albuerne, M Angeles Alvarez, M Esther García, Daniel García-Vivó, Miguel A Ruiz
The title complex reacted readily with CS2 and SCNPh to give the phosphinidene-cumulene adducts [Mo2Cp{μ-κ(1)P:κ(1)S,η(5)-P(CS2)C5H4}(CO)2(η(6)-HMes*)(PMe3)] and [Mo2Cp{μ-κ(1)P:κ(1)S,η(5)-P(C(NPh)S)C5H4}(CO)2(η(6)-HMes*)(PMe3)] respectively (Mes* = 2,4,6-C6H2(t)Bu3), as a result of the formal insertion of the C[double bond, length as m-dash]S bond of the heterocumulene into the metallocene Mo-P bond of the phosphinidene complex. The newly formed species bear a pyramidal P atom with a lone electron pair involved in fast inversion, and displayed strong nucleophilicity which enabled easy addition at the P site of carbon-based electrophiles and chalcogen atoms, while the uncoordinated S and N atoms were also competitive nucleophilic sites in these complexes...
February 27, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28236644/theoretical-dosimetric-evaluation-of-carbon-and-oxygen-minibeam-radiation-therapy
#2
Wilfredo González, Cécile Peucelle, Yolanda Prezado
PURPOSE: Charged particles have several advantages over x-rays radiations, both in terms of physics and radiobiology. The combination of these advantages with those of minibeam radiation therapy (MBRT) could help enhancing the therapeutic index for some cancers with poor prognosis. Among the different ions explored for therapy, carbon ions are considered to provide the optimum physical and biological characteristics. Oxygen could be advantageous due to a reduced oxygen enhancement ratio along with a still moderate biological entrance dose...
February 25, 2017: Medical Physics
https://www.readbyqxmd.com/read/28230813/characterization-of-carbonic-anhydrase-9-in-the-alimentary-canal-of-aedes-aegypti-and-its-relationship-to-homologous-mosquito-carbonic-anhydrases
#3
Daniel P Dixon, Leslie Van Ekeris, Paul J Linser
In the mosquito midgut, luminal pH regulation and cellular ion transport processes are important for the digestion of food and maintenance of cellular homeostasis. pH regulation in the mosquito gut is affected by the vectorial movement of the principal ions including bicarbonate/carbonate and protons. As in all metazoans, mosquitoes employ the product of aerobic metabolism carbon dioxide in its bicarbonate/carbonate form as one of the major buffers of cellular and extracellular pH. The conversion of metabolic carbon dioxide to bicarbonate/carbonate is accomplished by a family of enzymes encoded by the carbonic anhydrase gene family...
February 21, 2017: International Journal of Environmental Research and Public Health
https://www.readbyqxmd.com/read/28230105/interface-confined-hydrogen-evolution-reaction-in-zero-valent-metal-nanoparticles-intercalated-molybdenum-disulfide
#4
Zhongxin Chen, Kai Leng, Xiaoxu Zhao, Souradip Malkhandi, Wei Tang, Bingbing Tian, Lei Dong, Lirong Zheng, Ming Lin, Boon Siang Yeo, Kian Ping Loh
Interface confined reactions, which can modulate the bonding of reactants with catalytic centres and influence the rate of the mass transport from bulk solution, have emerged as a viable strategy for achieving highly stable and selective catalysis. Here we demonstrate that 1T'-enriched lithiated molybdenum disulfide is a highly powerful reducing agent, which can be exploited for the in-situ reduction of metal ions within the inner planes of lithiated molybdenum disulfide to form a zero valent metal-intercalated molybdenum disulfide...
February 23, 2017: Nature Communications
https://www.readbyqxmd.com/read/28229634/biochemical-characterization-of-the-native-%C3%AE-carbonic-anhydrase-purified-from-the-mantle-of-the-mediterranean-mussel-mytilus-galloprovincialis
#5
Rosa Perfetto, Sonia Del Prete, Daniela Vullo, Giovanni Sansone, Carmela Barone, Mosè Rossi, Claudiu T Supuran, Clemente Capasso
A α-carbonic anhydrase (CA, EC 4.2.1.1) has been purified and characterized biochemically from the mollusk Mytilus galloprovincialis. As in most mollusks, this α-CA is involved in the biomineralization processes leading to the precipitation of calcium carbonate in the mussel shell. The new enzyme had a molecular weight of 50 kDa, which is roughly two times higher than that of a monomeric α-class enzyme. Thus, Mytilus galloprovincialis α-CA is either a dimer, or similar to the Tridacna gigas CA described earlier, may have two different CA domains in its polypeptide chain...
December 2017: Journal of Enzyme Inhibition and Medicinal Chemistry
https://www.readbyqxmd.com/read/28229512/a-phosphorus-bisylide-exploring-a-new-class-of-superbases-with-two-interacting-carbon-atoms-as-basicity-centers
#6
Julius F Kögel, Davor Margetić, Xiulan Xie, Lars H Finger, Jörg Sundermeyer
Herein we present the first superbase MHPN with two interacting P-ylide entities. Unlike classical proton sponges, this novel compound class has carbon atoms as basicity centers which are forced into close proximity by a naphthalene scaffold. The bisylide exhibits an experimental pKBH(+)  value of 33.3±0.2 on the MeCN scale and a calculated gas-phase proton affinity of 277.9 kcal mol(-1) (M062X/6-311+G**//M062X/6-31G*+ZPVE method) exceeding that of the corresponding monoylide by nearly 15 kcal mol(-1) ...
February 23, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28226220/water-oxidation-mechanisms-of-metal-oxide-catalysts-by-vibrational-spectroscopy-of-transient-intermediates
#7
Miao Zhang, Heinz Frei
Water oxidation is an essential reaction of an artificial photosystem for solar fuel generation because it provides electrons needed to reduce carbon dioxide or protons to a fuel. Earth-abundant metal oxides are among the most attractive catalytic materials for this reaction because of their robustness and scalability, but their efficiency poses a challenge. Knowledge of catalytic surface intermediates gained by vibrational spectroscopy under reaction conditions plays a key role in uncovering kinetic bottlenecks and provides a basis for catalyst design improvements...
February 22, 2017: Annual Review of Physical Chemistry
https://www.readbyqxmd.com/read/28225622/how-the-coordinated-structures-of-ag-i-catalysts-affect-the-outcomes-of-carbon-dioxide-incorporation-into-propargylic-amine-a-dft-study
#8
Ruming Yuan, Baohuan Wei, Gang Fu
Density functional theory calculations have been carried out to explore the detailed mechanisms for carbon dioxide incorporation of N-unsubstituted propargylic amine catalyzed by Ag(I) catalysts. We show that the reaction undergoes substrate adsorption or displacement, isomerization from amine-coordinated species to the alkyne-coordinated species, CO2 attack and proton transfer, giving the carbamate intermediate. Subsequently, the reaction would bifurcate at the intermolecular ring closing step, which produces five-membered ring (5MR) and six-membered ring (6MR) products at the same time, thus raising a regioselectivity issue...
February 22, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28224790/ph-dependent-photodeprotection-of-formaldehyde-homolytic-c-c-scission-in-acidic-aqueous-solution-versus-heterolytic-c-c-scission-in-basic-aqueous-solution
#9
Mingyue Liu, Wenjian Tang, Ming-De Li, David Lee Phillips
The photodeprotection of formaldehyde was investigated for 3-(1-hydroxypropan-2-yl)benzophenone (3-HPBP) with ultrafast time-resolved spectroscopy. The femtosecond transient absorption results indicated the singlet excited state of 3-HPBP transformed efficiently into its triplet state by a fast intersystem crossing. In acidic (pH=0) and basic (pH=12.5) aqueous solutions, the triplet intermediate was a key precursor for the deprotection of formaldehyde via two different pathways. However little photodeprotection was observed in neutral (pH=7) aqueous solution where the triplet intermediate appeared to undergo a proton coupled electron transfer process to form a ketyl radical transient...
February 22, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28221098/ion-transport-by-ameloblasts-during-amelogenesis
#10
A L J J Bronckers
Hypomineralization of developing enamel is associated with changes in ameloblast modulation during the maturation stage. Modulation (or pH cycling) involves the cyclic transformation of ruffle-ended (RE) ameloblasts facing slightly acidic enamel into smooth-ended (SE) ameloblasts near pH-neutral enamel. The mechanism of ameloblast modulation is not clear. Failure of ameloblasts of Cftr-null and anion exchanger 2 ( Ae2)-null mice to transport Cl(-) into enamel acidifies enamel, prevents modulation, and reduces mineralization...
March 2017: Journal of Dental Research
https://www.readbyqxmd.com/read/28221047/excited-state-proton-transfer-in-indigo
#11
Joao Pina, Daniela Santos Sarmento, Marco Accoto, Pier Luigi Gentili, Luigi Vaccaro, Adelino M Galvão, J Sérgio Seixas de Melo
Excited state proton transfer (ESPT) in Indigo (Ind) and its mono hexyl-substituted derivative (NHxInd) in solution was investigated experimentally as a function of solvent viscosity, polarity and temperature, and theoretically by time-dependent DFT (TDDFT) calculations. Although a single emission band is observed, the fluorescence decays (collected at different wavelengths along the emission band using time-correlated single photon counting (TCSPC)) are bi-exponential, with two identical decay times but different pre-exponential factors, consistent with the existence of excited state keto and enol species...
February 21, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28220994/positional-enrichment-by-proton-analysis-pepa-a-one-dimensional-1-h-nmr-approach-for-13-c-stable-isotope-tracer-studies-in-metabolomics
#12
Maria Vinaixa, Miguel A Rodríguez, Suvi Aivio, Jordi Capellades, Josep Gómez, Nicolau Canyellas, Travis H Stracker, Oscar Yanes
A novel metabolomics approach for NMR-based stable isotope tracer studies called PEPA is presented, and its performance validated using human cancer cells. PEPA detects the position of carbon label in isotopically enriched metabolites and quantifies fractional enrichment by indirect determination of (13) C-satellite peaks using 1D-(1) H-NMR spectra. In comparison with (13) C-NMR, TOCSY and HSQC, PEPA improves sensitivity, accelerates the elucidation of (13) C positions in labeled metabolites and the quantification of the percentage of stable isotope enrichment...
February 21, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28220847/atomic-layer-confined-vacancies-for-atomic-level-insights-into-carbon-dioxide-electroreduction
#13
Shan Gao, Zhongti Sun, Wei Liu, Xingchen Jiao, Xiaolong Zu, Qitao Hu, Yongfu Sun, Tao Yao, Wenhua Zhang, Shiqiang Wei, Yi Xie
The role of oxygen vacancies in carbon dioxide electroreduction remains somewhat unclear. Here we construct a model of oxygen vacancies confined in atomic layer, taking the synthetic oxygen-deficient cobalt oxide single-unit-cell layers as an example. Density functional theory calculations demonstrate the main defect is the oxygen(II) vacancy, while X-ray absorption fine structure spectroscopy reveals their distinct oxygen vacancy concentrations. Proton transfer is theoretically/experimentally demonstrated to be a rate-limiting step, while energy calculations unveil that the presence of oxygen(II) vacancies lower the rate-limiting activation barrier from 0...
February 21, 2017: Nature Communications
https://www.readbyqxmd.com/read/28220172/mechanistic-insights-into-biomimetic-carbonic-anhydrase-action-catalyzed-by-doped-carbon-nanotubes-and-graphene
#14
Manju Verma, Parag A Deshpande
Electronic structural analyses of hydrogen terminated metal doped carbon nanotube/graphene (M-CNT/Gr, MN3-CNT/Gr, M = Ru/Rh) and ruthenium cluster decorated carbon nanotube/graphene (Ru4-CNT/Gr) were carried out for examining the biomimetic catalytic activity towards CO2 hydration reaction. The carbonic anhydrase action was followed for the reaction of CO2 with H2O resulting in a bicarbonate ion and a proton. All the catalysts were found to be active for CO2 hydration and the mechanism proved them to be biomimetic...
February 21, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28218247/laser-driven-ion-acceleration-from-plasma-micro-channel-targets
#15
D B Zou, A Pukhov, L Q Yi, H B Zhou, T P Yu, Y Yin, F Q Shao
Efficient energy boost of the laser-accelerated ions is critical for their applications in biomedical and hadron research. Achiev-able energies continue to rise, with currently highest energies, allowing access to medical therapy energy windows. Here, a new regime of simultaneous acceleration of ~100 MeV protons and multi-100 MeV carbon-ions from plasma micro-channel targets is proposed by using a ~10(20) W/cm(2) modest intensity laser pulse. It is found that two trains of overdense electron bunches are dragged out from the micro-channel and effectively accelerated by the longitudinal electric-field excited in the plasma channel...
February 20, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28215081/photocatalytic-co2-reduction-by-carbon-coated-indium-oxide-nanobelts
#16
Yun-Xiang Pan, Ya You, Sen Xin, Yutao Li, Gengtao Fu, Zhiming Cui, Yu-Long Men, Fei-Fei Cao, Shu-Hong Yu, John B Goodenough
Indium-oxide (In2O3) nanobelts coated by a 5-nm-thick car-bon layer provide an enhanced photocatalytic reduction of CO2 to CO and CH4, yielding CO and CH4 evolution rates of 126.6 and 27.9 mol h-1, respectively, with water as reductant and Pt as co-catalyst. Experiments and theoretical calcula-tions indicate that the carbon coat promotes the absorption of visible light, improves the separation of photoinduced electron-hole pairs, increases the chemisorption of CO2, makes more protons from water splitting participate in CO2 reduction, and thereby faciliates the photocatalytic reduction of CO2 to CO and CH4...
February 19, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28212755/stimulating-central-carbon-metabolism-to-re-sensitize-pseudomonas-aeruginosa-to-aminoglycosides
#17
Dorival Martins, Dao Nguyen
In this issue of Cell Chemical Biology, Meylan et al. (2017) examine how stimulation of central carbon metabolism of Pseudomonas aeruginosa modulates aminoglycoside lethality in tolerant bacteria. They identify fumarate as a tobramycin potentiator that stimulates proton motive force-dependent drug uptake and increases respiration-dependent killing.
February 16, 2017: Cell Chemical Biology
https://www.readbyqxmd.com/read/28211935/the-vertical-location-of-%C3%AE-tocopherol-in-phosphatidylcholine-membranes-is-not-altered-as-a-function-of-the-degree-of-unsaturation-of-the-fatty-acyl-chains
#18
Alessio Ausili, Ana M de Godos, Alejandro Torrecillas, Francisco J Aranda, Senena Corbalán-García, Juan C Gómez-Fernández
α-Tocopherol is a natural preservative that prevents free radical chain oxidations in biomembranes. We have studied the location of α-tocopherol in model membranes formed by different unsaturated phosphatidylcholines, namely 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), 1-palmitoyl-2-linoleoyl-sn-glycero-3-phosphocholine (PLPC), 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine (PAPC) and 1-palmitoyl-2-docosahexaenoyl-sn-glycero-3-phosphocholine (PDPC). Small angle X-ray diffraction revealed that α-tocopherol was well mixed with all the phospholipids...
February 17, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28211796/fluence-correction-factor-for-graphite-calorimetry-in-a-clinical-high-energy-carbon-ion-beam
#19
Ana Lourenco, Russell Thomas, Michael Homer, Hugo Bouchard, Severine Rossomme, James Renaud, Tatsuaki Kanai, Gary Royle, Hugo Palmans
The aim of this work is to develop and adapt a formalism to determine absorbed dose to water from graphite calorimetry measurements in carbon-ion beams. Fluence correction factors, <i>k</i><sub>fl</sub>, needed when using a graphite calorimeter to derive dose to water, were determined in a clinical high-energy carbon-ion beam. Measurements were performed in a 290 MeV/n carbon-ion beam with a field size of 11 x 11 cm<sup>2</sup>, without modulation. In order to sample the beam, a plane-parallel Roos ionization chamber was chosen for its small collecting volume in comparison with the field size...
February 17, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28209066/determination-of-the-relative-configuration-of-terminal-and-spiroepoxides-by-computational-methods-advantages-of-the-inclusion-of-unscaled-data
#20
María M Zanardi, Alejandra G Suárez, Ariel M Sarotti
The assignment of the relative configuration of spiroepoxides or related quaternary carbon-containing oxiranes can be troublesome and difficult to achieve. The use of GIAO NMR shift calculations can provide helpful assistance in challenging cases of structural elucidation. In this regard, the DP4 probability is one of the most popular methods to be employed when only one set of experimental data is available, though modest results were obtained when dealing with spiroepoxides. Recently, we introduced an improved probability (DP4+) that includes the use of both scaled and unscaled NMR data computed at higher levels of theory...
February 17, 2017: Journal of Organic Chemistry
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