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https://www.readbyqxmd.com/read/28346937/in-crystal-reaction-cycle-of-a-toluene-bound-diiron-hydroxylase
#1
Justin F Acheson, Lucas J Bailey, Thomas C Brunold, Brian G Fox
Electrophilic aromatic substitution is one of the most important and recognizable classes of organic chemical transformation. Enzymes create the strong electrophiles that are needed for these highly energetic reactions by using O2, electrons, and metals or other cofactors. Although the nature of the oxidants that carry out electrophilic aromatic substitution has been deduced from many approaches, it has been difficult to determine their structures. Here we show the structure of a diiron hydroxylase intermediate formed during a reaction with toluene...
March 27, 2017: Nature
https://www.readbyqxmd.com/read/28346735/carbenes-as-electron-pair-donors-for-p%C3%A2-c-pnicogen-bonds
#2
Janet E Del Bene, Ibon Alkorta, Jose Elguero
Ab initio MP2/aug'-cc-pVTZ calculations have been performed on the P…C pnicogen-bonded complexes of the singlet carbene molecules C(NH2)2, C(OH)2, and cyclic C(OCH)2 [OHC] with the molecules H2XP for X = F, Cl, NC, OH, CH3, CN, CCH, and H. H2XP:C(NH2)2 and H2XP:C(OH)2 complexes have Cs symmetry and two different structures: one in which the symmetry plane of the complex and the local symmetry plane of the carbene are non-coplanar, and the other in which they are coplanar. The non-coplanar H2XP:C(NH2)2 and H2XP:C(OH)2 complexes arise only when X is one of the more electronegative substituents...
March 27, 2017: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
https://www.readbyqxmd.com/read/28345907/simulating-protein-mediated-hydrolysis-of-atp-and-other-nucleoside-triphosphates-by-combining-qm-mm-molecular-dynamics-with-advances-in-metadynamics
#3
Rui Sun, Olaseni Sode, James F Dama, Gregory A Voth
The protein mediated hydrolysis of nucleoside triphosphates such as ATP or GTP is one of the most important and challenging biochemical reactions in nature. The chemical environment (water structure, catalytic metal, and amino acid residues) adjacent to the hydrolysis site contains hundreds of atoms, usually greatly limiting the amount of the free energy sampling that one can achieve from computationally demanding electronic structure calculations such as QM/MM simulations. Therefore, the combination of QM/MM molecular dynamics with the recently developed Transition-tempered Metadynamics (TTMetaD), an enhanced sampling method that can provide a high-quality free energy estimate at an early stage in a simulation, is an ideal approach to address the biomolecular nucleoside triphosphate hydrolysis problem...
March 27, 2017: Journal of Chemical Theory and Computation
https://www.readbyqxmd.com/read/28345855/surface-modification-of-na3v2-po4-3-by-nitrogen-and-sulfur-dual-doped-carbon-layer-with-advanced-sodium-storage-property
#4
Xinghui Liang, Xing Ou, Fenghua Zheng, Qichang Pan, Xunhui Xiong, Renzong Hu, Chenghao Yang, Meilin Liu
Nitrogen and sulfur dual-doped carbon layer wrapped Na3V2(PO4)3 nanoparticles (NVP@NSC) have been successfully fabricated by a facile solid-state method. In this hierarchical structure, the Na3V2(PO4)3 nanoparticles are well dispersed and closely coated by nitrogen and sulfur dual-doped carbon layer, constructing an effective and interconnected conducting network to reduce the internal resistance. Furthermore, the uniform coating layers alleviate the agglomeration of Na3V2(PO4)3, as well as mitigate the side reaction between electrode and electrolyte...
March 27, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28345798/multimetallic-and-mixed-environment-iridium-iii-complexes-a-modular-approach-to-luminescence-tuning-using-a-host-platform
#5
Victoria Pritchard, Diego Rota Martir, Eli Zysman-Colman, Michaele Jane Hardie
Mononuclear and trinuclear bis-cyclometalled Ir(III) complexes of the host ligands tris(4-[4'-methyl-2,2'-bipyridyl]methyl)cyclotriguaiacylene (L1) and tris(4-(4'-methyl-2,2'-bipyridyl)carboxy)cyclotriguaiacylene (L2) have been prepared. Complexes [{Ir(ppy)2}3(L1)](PF6)3 1.1, [{Ir(ppy)2}(L1)](PF6)3 1.2, [{Ir(ppy)2}3(L2)](PF6)3 2.1 and [{Ir(ppy)2}(L2)](PF6)3 2.2 (where ppy = phenylpyridinato) showed distinct photophysical properties according to L-ligand with L1 complexes comparatively blue-shifted in solution, with longer lifetimes and higher quantum yields...
March 27, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28345709/a-study-of-asymmetrical-mixed-valent-mo2-mo2-complexes-in-the-class-iii-regime
#6
Suman Mallick, Tao Cheng, Lu Chen, Miao Meng, Yu Yu Zhang, Chun Y Liu
Three novel asymmetrical dimolybdenum dimers, [Mo2(DAniF)3]2(μ-OOCCOS) (DAniF = N,N'-di(p-anisyl)formamidinate) ([OO-OS]), [Mo2(DAniF)3]2(μ-S2CCO2) ([SS-OO]), and [Mo2(DAniF)3]2(μ-SSCCOS) ([SS-OS]), have been synthesized and characterized by either single-crystal X-ray crystallography or (1)H NMR spectroscopy. The structural asymmetry for these compounds gives rise to a redox asymmetry, which enlarges the potential separation (ΔE1/2) between the two [Mo2] units. The mixed-valance (MV) species [OO-OS](+), [SS-OO](+) and [SS-OS](+), prepared by one-electron chemical oxidation of the neutral precursors, exhibit an intense and symmetrical intervalence charge transfer (IVCT) absorption band in the near-IR region, along with the high energy metal (δ) to ligand (π*) (ML) and ligand (π) to metal (δ) charge transfer (LMCT) absorptions...
March 27, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28345621/two-dimensional-electronic-spectra-of-the-photosynthetic-apparatus-of-green-sulfur-bacteria
#7
Tobias Kramer, Mirta Rodriguez
Advances in time resolved spectroscopy have provided new insight into the energy transmission in natural photosynthetic complexes. Novel theoretical tools and models are being developed in order to explain the experimental results. We provide a model calculation for the two-dimensional electronic spectra of Cholorobaculum tepidum which correctly describes the main features and transfer time scales found in recent experiments. From our calculation one can infer the coupling of the antenna chlorosome with the environment and the coupling between the chlorosome and the Fenna-Matthews-Olson complex...
March 27, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28345536/tuning-the-work-function-of-stepped-metal-surfaces-by-adsorption-of-organic-molecules
#8
Yingda Jiang, Jingtai Li, Guirong Su, Nicola Ferri, Wei Liu, Alexandre Tkatchenko
Understanding the binding mechanisms for aromatic molecules on transition-metal surfaces, especially with defects such as vacancies, steps, and kinks, is a major challenge in designing functional interfaces for organic devices. One important parameter in the performance of organic/inorganic devices is the barrier of charge carrier injection. In case of a metallic electrode, tuning the electronic interface potential or the work function for electronic level alignment is crucial. Here, we use density-functional theory (DFT) calculations with van der Waals (vdW) interactions treated with both screened pairwise and many-body dispersion (MBD) methods, to systematically study the interactions of benzene with a variety of stepped surfaces...
March 27, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
https://www.readbyqxmd.com/read/28345534/electron-transfer-processes-occurring-on-platinum-neural-stimulating-electrodes-calculated-charge-storage-capacities-are-inaccessible-during-applied-stimulation
#9
Eric M Hudak, Doe Kumsa, Heidi Martin, J Mortimer
<i>Objective.</i> Neural prostheses employing platinum electrodes are often constrained by a charge/charge-density parameter known as the Shannon limit. In examining the relationship between charge injection and observed tissue damage, the electrochemistry at the electrode-tissue interface should be considered. The charge-storage capacity (CSC) is often used as a predictor of how much charge an electrode can inject during stimulation, but calculating charge from a steady-state i-E curve (cyclic voltammogram) over the water window misrepresents how electrodes operate during stimulation...
March 27, 2017: Journal of Neural Engineering
https://www.readbyqxmd.com/read/28345352/metal-free-photoinduced-electron-transfer-atom-transfer-radical-polymerization-integrated-with-bio-inspired-polydopamine-chemistry-as-a-green-strategy-for-surface-engineering-of-magnetic-nanoparticles
#10
Yang Yang, Xuegang Liu, Gang Ye, Shan Zhu, Zhe Wang, Xiaomei Huo, Krzysztof Matyjaszewski, Yuexiang Lu, Jing Chen
Developing green and efficient technologies for surface modification of magnetic nanoparticles (MNPs) is of crucial importance for their biomedical and environmental applications. This study reports, for the first time, a novel strategy by integrating metal-free photoinduced electron transfer-atom transfer radical polymerization (PET-ATRP) with the bio-inspired polydopamine (PDA) chemistry for controlled architecture of functional polymer brushes from MNPs. Conformal PDA encapsulation layers were initially generated on the surfaces of MNPs, which served as the protective shells while providing an ideal platform for tethering 2-bromo-2-phenylacetic acid (BPA), a highly efficient initiator...
March 27, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28345349/a-self-assembled-ratiometric-polymeric-nanoprobe-for-highly-selective-fluorescence-detection-of-hydrogen-peroxide
#11
Chongchong Feng, Fengyang Wang, Yijing Dang, Zhiai Xu, Haijun Yu, Wen Zhang
In this study, a dual-emission fluorescence resonance energy transfer (FRET) polymeric nanoprobe by single-wavelength excitation was developed for sensitive and selective hydrogen peroxide (H2O2) detection. Polymeric nanoprobe was prepared by simple self-assembly of functional lipopolymers, which were 4-carboxy-3-fluorophenylboronic acid (FPBA)-modified DSPE-PEG (DSPE-PEG-FPBA) and 7-hydroxycoumarin (HC)-conjugated DSPE-PEG (DSPE-PEG-HC). Subsequent binding of alizarin red S (ARS) to FPBA endowed the nanoprobe with a new fluorescence emission peak at around 600 nm...
March 27, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28345308/expeditious-and-solvent-free-nickel-catalyzed-c-h-arylation-of-arenes-and-indoles
#12
Rahul A Jagtap, Vineeta Soni, Benudhar Punji
An efficient solvent-free nickel-catalyzed method for the C-H bond arylation of arenes and indoles is described that proceeds expeditiously via chelation-assistance. The reaction is highly selective for mono-arylation, and tolerates sensitive and structurally diverse functionalities, such as halides, ethers, amines, indole, pyrrole and carbazole. This reaction represents the first example of nickel-catalyzed C-H arylation by mono-chelate assistance, and symbolizes a rare precedent of solvent-free C-H arylation...
March 27, 2017: ChemSusChem
https://www.readbyqxmd.com/read/28345273/tuning-hole-and-electron-transfer-from-photo-excited-cdse-quantum-dot-to-phenol-derivatives-effect-of-electron-donating-and-withdrawing-moiety
#13
Hirendra Nath Ghosh, Tushar Debnath, Deepa Sebastian, Sourav Maiti
Charge transfer processes from photo-excited CdSe QDs to phenol derivatives with electron donating (4-methoxy) and electron withdrawing (4-nitro) moiety have been demonstrated by using steady state and time-resolved emission and femto-second transient absorption spectroscopy. Steady state and time-resolved emission studies suggest that in presence of both 4-nitro phenol (4NP) and 4-methoxy phenol (4MP) CdSe QDs luminescence gets quenched. Stern-Volmer analysis suggests both static and dynamic mechanisms are active for both the QD/phenol composites...
March 27, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28345242/multi-electron-oxidation-of-anthracene-derivatives-by-nonheme-manganese-iv-oxo-complexes
#14
Namita Sharma, Jieun Jung, Yong-Min Lee, Mi Sook Seo, Wonwoo Nam, Shunichi Fukuzumi
Six-electron oxidation of anthracene to anthraquinone by a nonheme Mn(IV)-oxo complex, [(Bn-TPEN)MnIV(O)]2+, proceeds via the rate-determining electron transfer from anthracene to [(Bn-TPEN)MnIV(O)]2+, followed by subsequent fast oxidation reactions to give anthraquinone. The reduced Mn(II) complex ([(Bn-TPEN)MnII]2+) is oxidized by [(Bn-TPEN)MnIV(O)]2+ rapidly to produce the μ-oxo dimer ([(Bn-TPEN)MnIII-O-MnIII(Bn-TPEN)]4+). The oxygen atoms of the anthraquinone product were found to derive from the manganese-oxo species by the 18O labelling experiments...
March 27, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28345095/a-simple-functional-carbon-nanotube-fiber-for-in-vivo-monitoring-of-no-in-a-rat-brain-following-cerebral-ischemia
#15
Li Liu, Limin Zhang, Zhihui Dai, Yang Tian
Nitric oxide (NO) is key free-radical messenger and neuronal signal which is closely related to many brain diseases. It is a challenge to develop a sensitive and reliable biosensor for in vivo monitoring of NO in the brain. In this research, a simple ratiometric electrochemical biosensor for NO monitoring in rat brain following cerebral ischemia was developed using a carbon nanotube fiber (CNF) modified with hemin, in which the CNF not only served as a platform to assemble the hemin molecule, but greatly facilitated the electron transfer of hemin on to the electrode surface...
March 27, 2017: Analyst
https://www.readbyqxmd.com/read/28344174/core-shell-eudragit-poly-ethylene-oxide-fibers-for-site-specific-release
#16
Dong Jia, Yanshan Gao, Gareth R Williams
Electrospinning was used to prepare core/shell fibers containing the active pharmaceutical ingredients indomethacin (IMC) or mebeverine hydrochloride (MB-HCl). The shell of the fibers was fabricated from the pH sensitive Eudragit S100 polymer, while the drug-loaded core was based on the mucoadhesive polyethylene oxide (PEO). Three different drug loadings (from 9-23% w/w of the core mass) were prepared, and for MB-HCl two different molecular weights of PEO were explored. The resultant fibers generally comprise smooth cylinders, although in some cases defects such as surface particles or flattened or merged fibers were visible...
March 23, 2017: International Journal of Pharmaceutics
https://www.readbyqxmd.com/read/28343119/synergistically-enhanced-stability-of-laccase-immobilized-on-synthesized-silver-nanoparticles-with-water-soluble-polymers
#17
M N M Cunha, H P Felgueiras, I Gouveia, A Zille
Silver nanoparticles (AgNPs) were synthesized by citrate reduction method in the presence of polymers, poly(ethylene glycol) (PEG), poly(vinyl alcohol) (PVA) and chitosan, used as stabilizing agents, and an oxidoreductase enzyme, laccase (Lac), with the goal of expanding the NPs antimicrobial action. AgNPs were characterized by UV-vis spectrometry, dynamic light scattering and transmission electron microscopy. As protecting agents, PEG and PVA promoted the formation of spherical uniformly-shaped, small-sized, monodispersed AgNPs (≈20nm)...
March 12, 2017: Colloids and Surfaces. B, Biointerfaces
https://www.readbyqxmd.com/read/28343085/guava-fruit-extract-and-its-triterpene-constituents-have-osteoanabolic-effect-stimulation-of-osteoblast-differentiation-by-activation-of-mitochondrial-respiration-via-the-wnt-%C3%AE-catenin-signaling
#18
Konica Porwal, Subhashis Pal, Kapil Dev, Shyamsundar Pal China, Yogesh Kumar, Chandan Singh, Tarun Barbhuyan, Neeraj Sinha, Sabyasachi Sanyal, Arun Kumar Trivedi, Rakesh Maurya, Naibedya Chattopadhyay
The aim of this study was to evaluate the skeletal effect of guava triterpene-enriched extract (GE) in rats and identify osteogenic compounds thereof, and determine their modes of action. In growing female rats, GE at 250 mg/kg dose increased parameters of peak bone mass including femur length, bone mineral density (BMD) and biomechanical strength, suggesting that GE promoted modeling-directed bone growth. GE also stimulated bone regeneration at the site of bone injury. In adult osteopenic rats (osteopenia induced by ovariectomy, OVX) GE completely restored the lost bones at both axial and appendicular sites, suggesting a strong osteoanabolic effect...
March 8, 2017: Journal of Nutritional Biochemistry
https://www.readbyqxmd.com/read/28342369/sensing-properties-of-monolayer-borophane-nanosheet-towards-alcohol-vapors-a-first-principles-study
#19
V Nagarajan, R Chandiramouli
The electronic properties of borophane nanosheet and adsorption behavior of three distinct alcohol vapors namely methanol, ethanol and 1-propanol on borophane nanosheet is studied using density functional theory method for the first time. The state-of-the-art provides insights on to the development of new two dimensional materials with the surface passivation on boron nanostructures. The density of states spectrum provides a clear perception on charge transfer upon adsorption of alcohol vapors on borophane nanosheets...
February 8, 2017: Journal of Molecular Graphics & Modelling
https://www.readbyqxmd.com/read/28342313/the-glyoxylate-pathway-contributes-to-enhanced-extracellular-electron-transfer-in-yeast-based-biofuel-cell
#20
Yolina Hubenova, Eleonora Hubenova, Evelina Slavcheva, Mario Mitov
This study provides a new insight into our understanding of yeast response to starvation conditions (sole acetate as carbon source) and applied polarization and offers important information about the role of the glyoxylate cycle in the carbohydrate synthesis and extracellular charge transfer processes in biofuel cells. The biosynthetic capabilities of yeast C. melibiosica 2491 and the up/down-regulation of the glyoxylate cycle are evaluated by modifying the cellular metabolism by feedback inhibition or carbohydrate presence and establishing the malate dehydrogenase activity and carbohydrate content together with the electric charge passed through bioelectrochemical system...
March 14, 2017: Bioelectrochemistry
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