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https://www.readbyqxmd.com/read/28727189/inversion-of-cpadh5-enantiopreference-and-altered-chain-length-specificity-for-methyl-3-hydroxyalkanoates
#1
Yunus Ensari, Gaurao V Dhoke, Mehdi D Davari, Marco Bocola, Anna Joelle Ruff, Ulrich Schwaneberg
Expanding the substrate scope of enzymes opens up new routes for synthesis of valuable chemicals. Ketone-functionalized fatty acid derivatives and corresponding chiral alcohols are valuable building blocks for the synthesis of a variety of chemicals including pharmaceuticals. The alcohol dehydrogenase from Candida parapsilosis (cpADH5) catalyzes the reversible oxidations of chiral alcohols and has a broad substrate range; a challenge for cpADH5 is to convert alcohols with small substituents (methyl or ethyl) next to the oxidized alcohol moiety...
July 20, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28726950/one-dna-strand-homo-polymerizes-into-defined-nanostructures
#2
Mo Li, Hua Zuo, Jinwen Yu, Xinfeng Zhao, Chengde Mao
We report a strategy for programmed DNA self-assembly that is favorable in terms of both thermodynamics and kinetics. In a previous study, it has been demonstrated that DNA self-assembly is primarily driven by thermodynamics and the assembly kinetics is not considered. To reach such stable states at equilibria, prolonged annealing duration is needed. In addition, there are cases where the desired structures could not compete with alternative structures. For example, a single-stranded DNA with a palindromic sequence quickly folds into a one-stranded hairpin instead of forming a two-stranded DNA duplex...
July 20, 2017: Nanoscale
https://www.readbyqxmd.com/read/28725263/modeling-and-simulation-of-the-redox-regulation-of-the-metabolism-in-escherichia-coli-at-different-oxygen-concentrations
#3
Yu Matsuoka, Hiroyuki Kurata
BACKGROUND: Microbial production of biofuels and biochemicals from renewable feedstocks has received considerable recent attention from environmental protection and energy production perspectives. Many biofuels and biochemicals are produced by fermentation under oxygen-limited conditions following initiation of aerobic cultivation to enhance the cell growth rate. Thus, it is of significant interest to investigate the effect of dissolved oxygen concentration on redox regulation in Escherichia coli, a particularly popular cellular factory due to its high growth rate and well-characterized physiology...
2017: Biotechnology for Biofuels
https://www.readbyqxmd.com/read/28724897/x-ray-crystallographic-structure-of-a-bacterial-polysialyltransferase-provides-insight-into-the-biosynthesis-of-capsular-polysialic-acid
#4
Christian Lizak, Liam J Worrall, Lars Baumann, Moritz M Pfleiderer, Gesa Volkers, Tianjun Sun, Lyann Sim, Warren Wakarchuk, Stephen G Withers, Natalie C J Strynadka
Polysialic acid (polySia) is a homopolymeric saccharide that is associated with some neuroinvasive pathogens and is found on selective cell types in their eukaryotic host. The presence of a polySia capsule on these bacterial pathogens helps with resistance to phagocytosis, cationic microbial peptides and bactericidal antibody production. The biosynthesis of bacterial polySia is catalysed by a single polysialyltransferase (PST) transferring sialic acid from a nucleotide-activated donor to a lipid-linked acceptor oligosaccharide...
July 19, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28723220/constructing-slow-release-formulations-of-ammonium-nitrate-fertilizer-based-on-degradable-poly-3-hydroxybutyrate
#5
Anatoly Nikolayevich Boyandin, Eugenia Andreevna Kazantseva, Daria Eugenievna Varygina, Tatiana Volova
The present study describes construction and investigation of experimental formulations of ammonium nitrate embedded in a matrix of degradable natural polymer poly-3-hydroxybutyrate (P3HB) and P3HB blended with wood flour shaped as tablets, some of them coated with P3HB. Kinetics of ammonium release into soil as dependent on the composition of the polymer matrix was investigated in laboratory experiments. The rates of fertilizer release from formulations coated with a biopolymer layer were considerably (two months or longer) slower than the rates of fertilizer release from uncoated formulations, while release from polymer and composite (polymer/wood flour) formulations occurred with comparable rates...
July 19, 2017: Journal of Agricultural and Food Chemistry
https://www.readbyqxmd.com/read/28723153/understanding-the-reactivity-of-co3-%C3%A2-and-no2-%C3%A2-radicals-towards-s-containing-and-aromatic-amino-acids
#6
Sharmistha Karmakar, Ayan Datta
The reactivity of CO3-(.) and NO2(.) radicals towards six amino acid side chains namely, cysteine (Cys), methionine (Met), phenylalanine (Phe), tyrosine (Tyr), histidine (His) and tryptophan (Trp), has been explored using state-of-art density functional theory (DFT) and transition state theory (TST). Three reaction mechanisms, namely hydrogen atom abstraction (HAT), radical adduct formation (RAF) and single electron transfer (SET) have been considered for detailed study. While CO3-(.) radical is highly reactive towards majority of amino acids, the reactivity of NO2(...
July 19, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28722407/quantum-chemical-study-of-ch3-o2-combustion-reaction-system-catalytic-effects-of-additional-co2-molecule
#7
Artëm E Masunov, Elizabeth Wait, Subith S Vasu
The supercritical carbon dioxide diluent is used to control the temperature and to increase the efficiency in oxycombustion fossil fuel energy technology. It may affect the rates of combustion by altering mechanisms of chemical reactions, compared to the ones at low CO2 concentrations. Here, we investigate potential energy surfaces of the four elementary reactions in the CH3 + O2 reactive system in the presence of one CO2 molecule. In the case of reaction CH3 + O2 → CH2O + OH (R1 channel), van der Waals (vdW) complex formation stabilizes the transition state and reduces the activation barrier by ∼2...
July 19, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28718792/recombinant-lipase-from-gibberella-zeae-exhibits-broad-substrate-specificity-a-comparative-study-on-emulsified-and-monomolecular-substrate
#8
Fanghua Wang, Hui Zhang, Zexin Zhao, Ruixia Wei, Bo Yang, Yonghua Wang
Using the classical emulsified system and the monomolecular film technique, the substrate specificity of recombinant Gibberella zeae lipase (rGZEL) that originates from Gibberella zeae was characterized in detail. Under the emulsified reaction system, both phospholipase and glycolipid hydrolytic activities were observed, except for the predominant lipase activity. The optimum conditions for different activity exhibition were also determined. Compared with its lipase activity, a little higher ratio of glycolipid hydrolytic activity (0...
July 18, 2017: International Journal of Molecular Sciences
https://www.readbyqxmd.com/read/28716944/potent-competitive-inhibition-of-human-ribonucleotide-reductase-by-a-nonnucleoside-small-molecule
#9
Md Faiz Ahmad, Intekhab Alam, Sarah E Huff, John Pink, Sheryl A Flanagan, Donna Shewach, Tessianna A Misko, Nancy L Oleinick, William E Harte, Rajesh Viswanathan, Michael E Harris, Chris Godfrey Dealwis
Human ribonucleotide reductase (hRR) is crucial for DNA replication and maintenance of a balanced dNTP pool, and is an established cancer target. Nucleoside analogs such as gemcitabine diphosphate and clofarabine nucleotides target the large subunit (hRRM1) of hRR. These drugs have a poor therapeutic index due to toxicity caused by additional effects, including DNA chain termination. The discovery of nonnucleoside, reversible, small-molecule inhibitors with greater specificity against hRRM1 is a key step in the development of more effective treatments for cancer...
July 17, 2017: Proceedings of the National Academy of Sciences of the United States of America
https://www.readbyqxmd.com/read/28715857/difference-in-growth-and-coalescing-patterns-of-droplets-on-bi-philic-surfaces-with-varying-spatial-distribution
#10
Martand Mayukh Garimella, Sudheer Koppu, Shantanu Shrikant Kadlaskar, Venkata Pillutla, Abhijeet, Wonjae Choi
This paper reports the condensation and subsequent motion of water droplets on bi-philic surfaces, surfaces that are patterned with regions of different wettability. Bi-philic surfaces can enhance the water collection efficiency: droplets condensing on hydrophobic regions wick into hydrophilic drain channels when droplets grow to a certain size, renewing the condensation on the dry hydrophobic region. The onset of drain phenomenon can be triggered by multiple events with distinct nature ranging from gravity, direct contact between a droplet and a drain channel, to a mutual coalescence between droplets...
June 30, 2017: Journal of Colloid and Interface Science
https://www.readbyqxmd.com/read/28715193/polymerization-of-nanoplates-into-controlled-architectures-with-adaptive-dynamics
#11
Binbin Luo, John W Smith, Zixuan Wu, Juyeong Kim, Zihao Ou, Qian Chen
Highly anisometric nanoparticles have distinctive mechanical, electrical, and thermal properties and are therefore appealing candidates for use as self-assembly building blocks. Here we demonstrate that ultra-anisometric nanoplates, which have a nanoscale thickness but a micrometer-scale edge length, offer many materials design capabilities. In particular, we show that these nanoplates "copolymerize" in a predictable way with patchy spheres into one- and two-dimensional structures with tunable architectural properties...
July 17, 2017: ACS Nano
https://www.readbyqxmd.com/read/28714684/the-surface-of-protein-%C3%AE-6-85-can-act-as-a-template-for-recurring-peg-structure
#12
Shu-Han Chao, Jan Schaefer, Martin Gruebele
PEGylated proteins play an increasingly important role in pharmaceutical drug delivery. We recently showed that short PEG chains can affect protein structure, even when they are not making extensive contact with the protein surface. In contrast, PEG is generally assumed to form a relatively unstructured coil, whose compactness depends on solvent conditions. Here we test whether a host protein could allow PEG to form recurrent structural motifs while the PEG chain is in contact with the protein surface. We link a PEG oligomer (n=45) to one of two nearly opposite locations on the small alpha-helical protein 6-85 to investigate this question...
July 17, 2017: Biochemistry
https://www.readbyqxmd.com/read/28714672/chemical-denaturants-smoothen-ruggedness-on-the-free-energy-landscape-of-protein-folding
#13
Pooja Malhotra, Prashant Navalbhai Jethva, Jayant B Udgaonkar
To characterize experimentally the ruggedness of the free energy landscape of protein folding is challenging, because the distributed small free energy barriers are usually dominated by one or a few, large activation free energy barriers. The present study delineates changes in the roughness of the free energy landscape by making use of the observation that a decrease in ruggedness is accompanied invariably by an increase in folding cooperativity. Hydrogen exchange coupled to mass spectrometry (HX-MS) was used to detect transient sampling of local energy minima and the global unfolded state on the free energy landscape of the small protein, single chain monellin...
July 17, 2017: Biochemistry
https://www.readbyqxmd.com/read/28713254/short-term-effects-of-thoracic-spine-manipulation-on-the-biomechanical-organisation-of-gait-initiation-a-randomized-pilot-study
#14
Sébastien Ditcharles, Eric Yiou, Arnaud Delafontaine, Alain Hamaoui
Speed performance during gait initiation is known to be dependent on the capacity of the central nervous system to generate efficient anticipatory postural adjustments (APA). According to the posturo-kinetic capacity (PKC) concept, any factor enhancing postural chain mobility and especially spine mobility, may facilitate the development of APA and thus speed performance. "Spinal Manipulative Therapy High-Velocity, Low-Amplitude" (SMT-HVLA) is a healing technique applied to the spine which is routinely used by healthcare practitioners to improve spine mobility...
2017: Frontiers in Human Neuroscience
https://www.readbyqxmd.com/read/28708484/promiscuous-binding-by-hsp70-results-in-conformational-heterogeneity-and-fuzzy-chaperone-substrate-ensembles
#15
Rina Rosenzweig, Ashok Sekhar, Jayashree Nagesh, Lewis E Kay
The Hsp70 chaperone system is integrated into a myriad of biochemical processes that are critical for cellular proteostasis. Although detailed pictures of Hsp70 bound with peptides have emerged, correspondingly detailed structural information on complexes with folding-competent substrates remains lacking. Here we report a methyl-TROSY based solution NMR study showing that the Escherichia coli version of Hsp70, DnaK, binds to as many as four distinct sites on a small 53-residue client protein, hTRF1. A fraction of hTRF1 chains are also bound to two DnaK molecules simultaneously, resulting in a mixture of DnaK-substrate sub-ensembles that are structurally heterogeneous...
July 14, 2017: ELife
https://www.readbyqxmd.com/read/28704677/hydrated-electron-based-decomposition-of-perfluorooctane-sulfonate-pfos-in-the-vuv-sulfite-system
#16
Yurong Gu, Tongzhou Liu, Hongjie Wang, Huili Han, Wenyi Dong
As one of the most reactive species, hydrated electron (eaq(-)) is promising for reductive decomposition of recalcitrant organic pollutants, such as perfluorooctane sulfonate (PFOS). In this study, PFOS decomposition using a vacuum ultraviolet (VUV)/sulfite system was systematically investigated in comparison with sole VUV and ultraviolet (UV)/sulfite systems. A fast and nearly complete (97.3%) PFOS decomposition was observed within 4h from its initial concentration of 37.2μM in the VUV/sulfite system. The observed rate constant (kobs) for PFOS decomposition in the studied system was 0...
July 10, 2017: Science of the Total Environment
https://www.readbyqxmd.com/read/28702655/controlling-the-morphology-and-crystallization-of-a-thiophene-based-all-conjugated-diblock-copolymer-by-solvent-blending
#17
Huina Cui, Xiubao Yang, Juan Peng, Feng Qiu
We report the crystallization and microphase separation behavior of an all-conjugated poly(3-hexylthiophene)-b-poly[3-(6-hydroxy)hexylthiophene] (P3HT-b-P3HHT) block copolymer in mixed solvents and demonstrate how the conformations of P3HT and P3HHT chains influence the photophysical properties of the copolymer. It is shown that the balance among π-π stacking of P3HT, P3HHT and microphase separation of the copolymer can be dynamically shifted by controlling the rod-rod interactions of the copolymer via changing the block ratio and solvent blending...
July 12, 2017: Soft Matter
https://www.readbyqxmd.com/read/28702545/direct-examination-of-the-relevance-for-folding-binding-and-electron-transfer-of-a-conserved-protein-folding-intermediate
#18
Emilio Lamazares, Sonia Vega, Patricia Ferreira, Milagros Medina, Juan J Galano-Frutos, Marta Martínez-Júlvez, Adrián Velázquez-Campoy, Javier Sancho
Near the minimum free energy basin of proteins where the native ensemble resides, partly unfolded conformations of slightly higher energy can be significantly populated under native conditions. It has been speculated that they play roles in molecular recognition and catalysis, but they might represent contemporary features of the evolutionary process without functional relevance. Obtaining conclusive evidence on these alternatives is difficult because it requires comparing the performance of a given protein when populating and when not populating one such intermediate, in otherwise identical conditions...
July 12, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28699731/in-situ-grown-s-nanosheets-on-cu-foam-an-ultrahigh-electroactive-cathode-for-room-temperature-na-s-batteries
#19
Binwei Zhang, Yundan Liu, Yunxiao Wang, Lei Zhang, Mingzhe Chen, Weihong Lai, Shu-Lei Chou, Hua Kun Liu, Shixue Dou
oom-temperature sodium-sulfur (RT-Na/S) batteries are emerging as a competitive candidate for large-scale stationary energy storage due to their low price and high theoretical capacity. Achieving high reversible capacity is the most important challenge, however, which is ascribed to the insulating nature of S, the sluggish electrochemical kinetics between Na and S, and the high dissolution of polysulfide intermediates in electrolyte. We show that pure S nanosheet cathodes can be grown in-situ on three-dimensional Cu foam substrate with the condensation between binary polymeric binders, serving as a model system to investigate the formation of unique S nanosheets and the electrochemical catalysis by the Cu current collector in S cathode...
July 12, 2017: ACS Applied Materials & Interfaces
https://www.readbyqxmd.com/read/28699670/aminopyridine-borane-complexes-as-hydrogen-atom-donor-reagents-reaction-mechanism-and-substrate-selectivity
#20
Florian Barth, Florian Achrainer, Alexander Pütz, Hendrik Zipse
Lewis base-borane complexes are shown to be potent hydrogen atom donors in radical chain reduction reactions. Results obtained in 1H, 11B, and 13C NMR measurements and kinetic experiments support a complex reaction mechanism involving the parent borane as well as its initial reaction products as active hydrogen atom donors. Efficient reduction reactions of iodides, bromides, and xanthates in apolar solvents rely on initiator systems generating oxygen-centered radicals under thermal conditions and pyridine-borane complexes carrying solubilizing substituents...
July 12, 2017: Chemistry: a European Journal
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