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Hop kinetic

Jiali Wang, Thomas Albers, Christof T Grewer
Glutamate transporters maintain a large glutamate concentration gradient across synaptic membranes and are, thus, critical for functioning of the excitatory synapse. Mammalian glutamate transporters concentrate glutamate inside cells through energetic coupling of glutamate flux to the transmembrane concentration gradient of Na+. Structural models based on an archeal homologue of mammalian glutamate transporters, GltPh, suggest an elevator-like carrier mechanism. However, the energetic determinants of this carrier-based movement are not well understood...
December 8, 2017: Journal of Physical Chemistry. B
Aleksandra Bazan-Wozniak, Piotr Nowicki, Robert Pietrzak
A technology of activated bio-carbons production from the residue left after supercritical extraction of hops is described. The effect of the variant of chemical activation and impregnation ratio on the physicochemical properties as well as sorption capacity towards toxic gas of acidic character (nitrogen dioxide), basic organic dye (aqueous solution of methylene blue - MB) and iodine was investigated. The materials obtained were activated bio-carbons of well-developed surface area ranging between 897 and 1095m2/g, showing clearly acidic character of the surface...
December 4, 2017: Environmental Research
Jean-Francois Nierengarten, Marie Steffenhagen, Alina Latus, Thi Minh Nguyet Trinh, Iwona Nierengarten, Ivan T Lucas, Suzanne Joiret, Jessem Landoulsi, Béatrice Delavaux-Nicot, Emmanuel Maisonhaute
A rotaxane scaffold incorporating two dithiolane anchoring units for the modification of gold surfaces has been functionalized with multiple copies of a redox unit, namely ferrocene. Surface modification has been first assessed at the single molecule level by atomic force microscopy (AFM) and scanning tunneling microscopy (STM) imaging, while tip enhanced Raman spectroscopy (TERS) provided the local vibrational signature of the ferrocenyl subunits of the rotaxanes grafted onto the gold surface. Finally, oxidation of the redox moieties within a rotaxane scaffold grafted onto gold microelectrodes has been investigated by ultrafast cyclic voltammetry...
December 5, 2017: Chemistry: a European Journal
Shaoyang Lin, Alireza K Ravari, Jie Zhu, Pavel Usov, Meng Cai, Spencer R Ahrenholtz, Yulia Pushkar, Amanda Morris
Investigation of chemical water oxidation was conducted on the [Ru(tpy)(dcbpy)OH2]2+ (tpy = 2,2':6',2''-terpyridine, dcbpy = 5,5'-dicarboxy-2,2'-bipyridine) -doped UiO-67 metal-organic framework (MOF). The MOF catalyst exhibited single site reaction pathway with similar kinetic behavior as the homogeneous Ru complex. The reaction was first order with respect to both the concentration of Ru catalyst and cerium ammonium nitrate (CAN), with kcat = 3 (±2) ×10-3 M-1s-1 in HNO3 (pH 0.5). The common degradation pathways of ligand dissociation and dimerization were precluded by MOF incorporation, leading to sustained catalysis and greater reusability as opposed to the molecular catalyst in homogeneous solution...
December 2, 2017: ChemSusChem
Starla D Glover, Robin Tyburski, Li Liang, Cecilia Tommos, Leif Hammarström
Protein "hole" hopping typically involves spatially arranged redox-active tryptophan and/or tyrosine residues. Thermodynamic information is scarce for this type of process. The well-structured α3W model protein was studied by protein film square wave voltammetry and transient absorption spectroscopy to obtain a comprehensive thermodynamic and kinetic description of a buried tryptophan residue. A Pourbaix diagram, correlating thermodynamic potentials (E°') with pH, is reported for W32 in α3W and compared to equivalent data recently presented for Y32 in α3Y (Ravichandran, K...
November 30, 2017: Journal of the American Chemical Society
Eugene Mamontov, Alexander I Kolesnikov, Sujatha Sampath, Jeffery L Yarger
Lithium-beryllium metal hydrides, which are structurally related to their parent compound, BeH2, offer the highest hydrogen storage capacity by weight among the metal hydrides (15.93 wt. % of hydrogen for LiBeH3). Challenging synthesis protocols have precluded conclusive determination of their crystallographic structure to date, but here we analyze directly the hydrogen hopping mechanisms in BeH2 and LiBeH3 using quasielastic neutron scattering, which is especially sensitive to single-particle dynamics of hydrogen...
November 24, 2017: Scientific Reports
Alejandro Méndez-Ardoy, Nagula Markandeya, Xuesong Li, Yu-Tang Tsai, Gilles Pecastaings, Thierry Buffeteau, Victor Maurizot, Luca Muccioli, Frédéric Castet, Ivan Huc, Dario M Bassani
Aromatic foldamers are bioinspired architectures whose potential use in materials remains largely unexplored. Here we report our investigation of vertical and horizontal charge transport over long distances in helical oligo-quinolinecarboxamide foldamers organized as single monolayers on Au or SiO2. Conductive atomic force microscopy showed that vertical conductivity is efficient and that it displays a low attenuation with foldamer length (0.06 Å(-1)). In contrast, horizontal charge transport is found to be negligible, demonstrating the strong anisotropy of foldamer monolayers...
October 1, 2017: Chemical Science
Hiroya Tanaka, Hideo Iizuka, Yuriy V Pershin, Massimiliano Di Ventra
Ionic Coulomb blockade in nanopores is a phenomenon that shares some similarities but also differences with its electronic ounterpart. Here, we investigate extensively this phenomenon using all-atom molecular dynamics of ionic transport through nanopores of about one nanometer in diameter and up to several nanometers in length. Our goal is to better understand the role of atomic roughness and structure of the pore walls in facilitating ionic Coulomb blockade. Our numerical results reveal the following general trends...
November 13, 2017: Nanotechnology
Mogens L L Andersen, Matheo Gundermann, Bente P Danielsen, Marianne N Lund
Thiol-containing proteins have been suggested to have antioxidative properties in beer. A kinetic model has been setup for the reactivity of thiols during early stages of oxidative degradation of beer. Kinetic analysis based on the proposed reaction mechanism allowed evaluation of the relative reactivity of beer components, such as bitter acids from hops and polyphenols. The rate constants for the reaction of 1-hydroxyethyl radicals, which are generated during radical mediated oxidation of ethanol in beer, with hop bitter acids and thiols were very similar, and the concentration of the compounds in beer is therefore essential for the relative reactivity...
November 12, 2017: Journal of Agricultural and Food Chemistry
Giridhar Nandipati, Xiujuan Jiang, Rama S Vemuri, Suveen Mathaudhu, Aashish Rohatgi
Si-atom and vacancy diffusion in α-Fe-Si alloys in the ferromagnetic state, with and without magnetic order and in various temperature ranges, is studied using AKSOME, an on-lattice self-learning KMC code. Si-atom diffusion in the dilute limit and vacancy diffusion in A2- phase of the α-Fe-Si alloy up to Si concentrations of 12at.% is studied in the temperature range of 350-700 K and 350-500 K, respectively. Local Si-atom neighborhood dependent activation energies for vacancy hops were calculated on-the-fly using a broken-bond model based on pairwise interaction...
November 1, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Hayley C Powell, Karin Grävare Silbernagel, Annelie Brorsson, Roy Tranberg, Richard W Willy
Study Design Cross sectional, laboratory study. Background Asymmetrical knee loading has been reported in individuals post-Achilles tendon rupture during jogging and hopping. Yet, no studies have examined knee loads in individuals post-Achilles tendon rupture during high demand tasks, such as single limb landings. Objectives We sought to determine if individuals post-Achilles tendon rupture demonstrated asymmetrical knee loads and impact forces during drop countermovement jumps (Drop CMJ). Methods Achilles tendon length and single leg heel rise test for endurance were assessed in 34 individuals (31 male) 6...
October 26, 2017: Journal of Orthopaedic and Sports Physical Therapy
Yangzheng Lin, Kristen A Fichthorn
We use first-principles density-functional theory to characterize the binding sites and diffusion mechanisms for a Ga adatom on the GaAs(001)β2(2 × 4) surface. Diffusion in this system is a complex process involving eleven unique binding sites and sixteen different hops between neighboring binding sites. Among the binding sites, we can identify four different superbasins such that the motion between binding sites within a superbasin is much faster than hops exiting the superbasin. To describe diffusion, we use a recently developed local superbasin kinetic Monte Carlo (LSKMC) method, which accelerates a conventional kinetic Monte Carlo (KMC) simulation by describing the superbasins as absorbing Markov chains...
October 21, 2017: Journal of Chemical Physics
Grégoire David, Nathalie Guihéry, Nicolas Ferré
Analytical expressions of the interactions present in the Heisenberg-Dirac van Vleck and Hubbard Hamiltonians have been derived as functions of both the energy of several broken symmetry DFT solutions and their expectation value of the S(2) spin operator. Then, following a strategy of decomposition of the magnetic exchange coupling into its main contributions (direct exchange, kinetic exchange, and spin polarization) and using a recently proposed method of spin decontamination, values of these interactions have been extracted...
November 7, 2017: Journal of Chemical Theory and Computation
Tania Luthra, Rahul Agarwal, Mamidala Estari, Uma Adepally, Subhabrata Sen
α-glucosidase is an essential enzyme located at the brush border of intestines. It is an important therapeutic target for type II diabetes. Herein we have designed a library of novel α-arylketones as inhibitors of α-glucosidase (yeast origin) via scaffold hopping and bioisosteric modification of known inhibitors of α-glucosidase. The design was validated through molecular docking that revealed strong binding interactions of the newly designed compounds against α-glucosidase. A library comprising of 15 compounds was synthesized in a combinatorial fashion, where the advanced amide intermediates were accessed through "shot gun" synthesis...
October 16, 2017: Scientific Reports
M Apostolopoulou, R Day, R Hull, M Stamatakis, A Striolo
The mechanism of fluid migration in porous networks continues to attract great interest. Darcy's law (phenomenological continuum theory), which is often used to describe macroscopically fluid flow through a porous material, is thought to fail in nano-channels. Transport through heterogeneous and anisotropic systems, characterized by a broad distribution of pores, occurs via a contribution of different transport mechanisms, all of which need to be accounted for. The situation is likely more complicated when immiscible fluid mixtures are present...
October 7, 2017: Journal of Chemical Physics
Liqiang Dai, Holger Flechsig, Jin Yu
Rotary sequential hydrolysis of the metabolic machine F1-ATPase is a prominent manifestation of high coordination among multiple chemical sites in ring-shaped molecular machines, and it is also functionally essential for F1 to tightly couple chemical reactions and central γ-shaft rotation. High-speed AFM experiments have identified that sequential hydrolysis is maintained in the F1 stator ring even in the absence of the γ-rotor. To explore the origins of intrinsic sequential performance, we computationally investigated essential inter-subunit couplings on the hexameric ring of mitochondrial and bacterial F1...
October 3, 2017: Biophysical Journal
Veronika Sunko, H Rosner, P Kushwaha, S Khim, F Mazzola, L Bawden, O J Clark, J M Riley, D Kasinathan, M W Haverkort, T K Kim, M Hoesch, J Fujii, I Vobornik, A P Mackenzie, P D C King
Engineering and enhancing the breaking of inversion symmetry in solids-that is, allowing electrons to differentiate between 'up' and 'down'-is a key goal in condensed-matter physics and materials science because it can be used to stabilize states that are of fundamental interest and also have potential practical applications. Examples include improved ferroelectrics for memory devices and materials that host Majorana zero modes for quantum computing. Although inversion symmetry is naturally broken in several crystalline environments, such as at surfaces and interfaces, maximizing the influence of this effect on the electronic states of interest remains a challenge...
September 27, 2017: Nature
Justin P Waxman, Kevin R Ford, Anh-Dung Nguyen, Jeffrey B Taylor
Vertical stiffness may contribute to lower-extremity injury risk; however, it is unknown whether athletes with different stiffness levels display differences in biomechanics. This study compared differences in biomechanics between female athletes (n=99) with varying stiffness levels during a repetitive, single-leg, vertical hopping task. Vertical stiffness was calculated as the ratio of peak vertical ground-reaction force to maximum center-of-mass displacement. Tertiles were established using stiffness values, and separate one-way ANOVAs were used to evaluate between-group differences...
September 27, 2017: Journal of Applied Biomechanics
Soumya Ghosh, Alexander V Soudackov, Sharon Hammes-Schiffer
Experiments have suggested that photoreduced ZnO nanocrystals transfer an electron and a proton to organic radicals through a concerted proton-coupled electron transfer (PCET) mechanism. The kinetics of this process was studied by monitoring the decay of the absorbance that reflects the concentration of electrons in the conduction bands of the nanocrystals. Interestingly, this absorbance exhibited nonexponential decay kinetics that could not be explained by heterogeneities of the nanoparticles or electron content...
October 24, 2017: ACS Nano
Matthew L Schwartz, Daniel P Nickerson, Braden T Lobingier, Rachael L Plemel, Mengtong Duan, Cortney G Angers, Michael Zick, Alexey J Merz
Zippering of SNARE complexes spanning docked membranes is essential for most intracellular fusion events. Here, we explore how SNARE regulators operate on discrete zippering states. The formation of a metastable trans-complex, catalyzed by HOPS and its SM subunit Vps33, is followed by subsequent zippering transitions that increase the probability of fusion. Operating independently of Sec18 (NSF) catalysis, Sec17 (α-SNAP) either inhibits or stimulates SNARE-mediated fusion. If HOPS or Vps33 are absent, Sec17 inhibits fusion at an early stage...
September 19, 2017: ELife
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