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https://www.readbyqxmd.com/read/28726415/enhanced-diffusion-of-passive-tracers-in-active-enzyme-solutions
#1
Xi Zhao, Krishna Kanti Dey, Selva Jeganathan, Peter J Butler, Ubaldo M Córdova-Figueroa, Ayusman Sen
Colloidal suspensions containing microscopic swimmers have been the focus of recent studies aimed at understanding the principles of energy transfer in fluidic media at low Reynolds number conditions. Going down in scale, active enzymes have been shown to be force-generating, non-equilibrium systems, thus offering opportunity to examine energy transfer at the ultralow Reynolds number regime. By monitoring the change of diffusion of inert tracers dispersed in active enzyme solutions, we demonstrate that the nature of energy transfer in these systems is similar to that reported for larger microscopic active systems, despite the large differences in scale, modes of energy transduction and propulsion...
July 20, 2017: Nano Letters
https://www.readbyqxmd.com/read/28720966/biochemical-characterization-and-thermal-inactivation-of-polyphenol-oxidase-from-elephant-foot-yam-amorphophallus-paeoniifolius
#2
Anuradha Singh, Neeraj Wadhwa
Polyphenol oxidase from Amorphophallus corm was purified (5.54 fold) by acetone precipitation and ion exchange chromatography. Electrophoretic-blot analysis revealed that the molecular weight of enzyme is 40 kDa. Enzyme preferred catechol as substrate and showed optimum activity at pH 6 and 35 °C with Km of 17.56 mM and Vmax 0.023 U/ml/min. Thermal inactivation kinetics study showed that 5.68% inactivation was achieved at 75 °C within 40 min. The half-life time of PPO is between 126.00 and 32.54 min...
June 2017: Journal of Food Science and Technology
https://www.readbyqxmd.com/read/28715681/adsorption-of-nh4-n-on-chinese-loess-non-equilibrium-and-equilibrium-investigations
#3
Haijian Xie, Shaoyi Wang, Zhanhong Qiu, Jianqun Jiang
NH4(+)-N is a crucial pollutant in landfill leachate and can be in high concentrations for a long period of time due to anaerobic condition of landfills. The adsorption properties of NH4(+)-N on the Chinese loess were investigated using Batch test. The influences of ammonium concentration, temperature, reaction time, slurry concentration, and pH on the adsorption process are evaluated. Adsorption kinetics and isotherm behaviors were studied by applying different models to the test data to determine the adsorption parameters...
July 14, 2017: Journal of Environmental Management
https://www.readbyqxmd.com/read/28710960/bioremediation-potential-of-arsenic-by-non-enzymatically-biofabricated-silver-nanoparticles-adhered-to-the-mesoporous-carbonized-fungal-cell-surface-of-aspergillus-foetidus-mtcc8876
#4
Triparna Mukherjee, Shatarupa Chakraborty, Aksar Ali Biswas, Tapan Kumar Das
Our study aiming for the diminution of arsenic concentration in arsenic contaminated aqua environment by using novel adsorbents based on bio-fabricated silver nanoparticles on a fungal cell surface. Bioreduction of silver ion was done in a non-enzymatic manner in presence of the biomass of fungus Aspergillus foetidus MTCC8876. Aspergillus spp. cells were harvested following the bioreduction and made into carbon by carbonization that led to pore formation (pore width of 2.35 nm) on the cell surface. The average size of silver nanoparticles in the sample of SACF (silver nanoparticles adhered to mesoporous carbonized fungal cell) was 35 nm...
July 12, 2017: Journal of Environmental Management
https://www.readbyqxmd.com/read/28708608/magnetic-schiff-s-base-sorbent-based-on-shrimp-peels-wastes-for-consummate-sorption-of-chromate
#5
Khalid Z Elwakeel, Ahmed M Elgarahy, Samya H Mohammad
Magnetic Schiff's base chitosan composite has been prepared starting from shrimp peels as a raw material. Chitosan extraction involved three main stages as preconditioning, demineralization deproteinization and deacetylation. Chitosan modification process took place through the reaction between chitosan and polymeric Schiff's base of thiourea/glutaraldehyde in the presence of magnetite. The synthetic hybrid composite was characterized by Fourier transform infrared spectroscopy and scanning electron microscopy-energy dispersive X-ray analyses and tested as sorbent for Cr(VI) recovery from aqueous solution...
July 2017: Water Science and Technology: a Journal of the International Association on Water Pollution Research
https://www.readbyqxmd.com/read/28692096/a-quantum-rovibrational-state-selected-study-of-the-proton-transfer-reaction-h2-x-2-%C3%AE-v-1-3-n-0-3-ne-%C3%A2-neh-h-using-the-pulsed-field-ionization-photoion-method-observation-of-the-rotational-effect-near-the-reaction-threshold
#6
Bo Xiong, Yih-Chung Chang, Cheuk-Yiu Ng
Using the sequential electric field pulsing scheme for vacuum ultraviolet (VUV) laser pulsed field ionization-photoion (PFI-PI) detection, we have successfully prepared H2(+)(X(2)Σ: v(+) = 1-3; N(+) = 0-5) ions in the form of an ion beam in single quantum-rovibrational-states with high purity, high intensity, and narrow laboratory kinetic energy spread (ΔElab ≈ 0.05 eV). This VUV-PFI-PI ion source, when coupled with the double-quadrupole double-octupole ion-molecule reaction apparatus, has made possible a systematic examination of the vibrational- as well as rotational-state effects on the proton transfer reaction of H2(+)(X(2)Σ: v(+); N(+)) + Ne...
July 10, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28691770/influence-of-the-water-phase-state-on-the-thermodynamics-of-aqueous-phase-reforming-for-hydrogen-production
#7
Séverine Le Gac, Renée M Ripken, Jan Meuldijk, Johannes G E Gardeniers
Hydrogen is a promising renewable energy source that can be produced from biomass using Aqueous Phase Reforming (APR). Here, using data obtained from AspenPlus and the literature, we evaluated the phase state, temperature-dependent enthalpy, and Gibbs free energy for the APR of small biomass model substrates. Phase equilibrium studies reveal that, under typical APR reaction conditions, the reaction mixture is in the liquid phase. Therefore, we show for the first time that the water-gas-shift (WGS), which is the second main reaction of APR, must be modeled in the liquid phase, resulting in an endothermic instead of an exothermic enthalpy of reaction...
July 10, 2017: ChemSusChem
https://www.readbyqxmd.com/read/28686937/effective-removal-of-phosphate-from-aqueous-solution-using-humic-acid-coated-magnetite-nanoparticles
#8
Mamun Rashid, Nathaniel T Price, Miguel Ángel Gracia Pinilla, Kevin E O'Shea
Effective removal of excess phosphate from water is critical to counteract eutrophication and restore water quality. In this study, low cost, environmentally friendly humic acid coated magnetite nanoparticles (HA-MNP) were synthesized and applied for the remediation of phosphate from aqueous media. The HA-MNPs, characterized by FTIR, TEM and HAADF-STEM showed the extensive coating of humic acid on the magnetite surface. The magnetic nanoparticles with diameters of 7-12 nm could be easily separated from the reaction mixture by using a simple hand held magnet...
June 30, 2017: Water Research
https://www.readbyqxmd.com/read/28684353/removal-of-cd-ii-and-cr-vi-ions-by-highly-cross-linked-thiocarbohydrazide-chitosan-gel
#9
Ronghua Li, Wen Liang, Manlin Li, Shuncheng Jiang, Hui Huang, Zengqiang Zhang, Jim J Wang, Mukesh Kumar Awasthi
A highly cross-linked Thiocarbohydrazide-modified chitosan (TCCS) gel was synthesized by using formaldehyde as linkage, and was used in removal of Cd(II) and Cr(VI) from aqueous solution. The results showed that TCCS could be used in a wider pH range and had higher adsorption abilities than raw chitosan for Cd(II) and Cr(VI) ions. The maximum adsorption capacities of the synthetic TCCS for two ions reached 81.26 and 144.68mg/g at 298K, respectively. The endothermic adsorption exhibited pseudo-second-order kinetic behavior and the adsorption isotherm could be well described by Langmuir model...
July 3, 2017: International Journal of Biological Macromolecules
https://www.readbyqxmd.com/read/28672109/effect-of-barley-%C3%AE-glucan-on-the-gluten-polymerization-process-in-dough-during-heat-treatment
#10
Ze-Hua Huang, Yang Zhao, Ke-Xue Zhu, Xiao-Na Guo, Wei Peng, Hui-Ming Zhou
Barley (Hordeum vulgare L.) β-glucan (BBG) is of interest as a result of its health benefits, but BBG presents significant disruptions on the gluten network, with a negative impact on food texture. To clarify the interaction between BBG and gluten in dough, the dynamic rheological, thermochemical process of gluten and microstructure of dough with BBG during heating were detected. The results showed that BBG delayed the gluten thermopolymerization reaction during heating and affected polymerization of specific molecular weight protein subunits...
July 13, 2017: Journal of Agricultural and Food Chemistry
https://www.readbyqxmd.com/read/28638992/a-qm-mm-study-on-the-enzymatic-inactivation-of-cefotaxime
#11
Ignacio Lizana, Eduardo J Delgado
The reaction between the antibiotic cefotaxime and the CTX-M-14 class A serine hydrolase is addressed from a theoretical point of view, by means of hybrid quantum mechanics/molecular mechanical (QM/MM) calculations, adopting a new approach that postulates that the residue Ser70 itself should play the role of the acid-base species required for the cefotaxime acylation. The proposed mechanism differs from earlier proposals existing in literature for other class A β-lactamases. The results confirm the hypothesis, and show that the reaction should occur via a concerted mechanism in which the acylation of the lactam carbonyl carbon, protonation of the N7 lactam atom, and opening of the β-lactam ring occurs simultaneously...
July 2017: Journal of Molecular Modeling
https://www.readbyqxmd.com/read/28628903/functional-kaolin-supported-nanoscale-zero-valent-iron-as-a-fenton-like-catalyst-for-the-degradation-of-direct-black-g
#12
Jiajiang Lin, Mengqiang Sun, Xinwen Liu, Zuliang Chen
Kaolin supported nanoscale zero-valent iron (K-nZVI) is synthesized and applied as the Fenton-like oxidation catalyst to degrade a model azo dye, Direct Black G (DBG). The characterization of K-nZVI by the high resolution transmission electronmicroscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), Energy Diffraction Spectrum (EDS) and X-ray diffraction (XRD) show that kaolin as a support material not only reduces the aggregation of zero-valent iron (nZVI) but also facilitates the Fenton-like oxidation by increasing the local concentration of DBG in the vicinity of nZVI...
June 12, 2017: Chemosphere
https://www.readbyqxmd.com/read/28614751/molecular-spectroscopic-and-thermodynamic-studies-on-the-interaction-of-anti-platelet-drug-ticlopidine-with-calf-thymus-dna
#13
Shumaila Afrin, Yusra Rahman, Tarique Sarwar, Mohammed Amir Husain, Abad Ali, Shamsuzzaman, Mohammad Tabish
Ticlopidine is an anti-platelet drug which belongs to the thienopyridine structural family and exerts its effect by functioning as an ADP receptor inhibitor. Ticlopidine inhibits the expression of TarO gene in S. aureus and may provide protection against MRSA. Groove binding agents are known to disrupt the transcription factor DNA complex and consequently inhibit gene expression. Understanding the mechanism of interaction of ticlopidine with DNA can prove useful in the development of a rational drug designing system...
June 11, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
https://www.readbyqxmd.com/read/28608897/the-dynamics-of-the-hg-br2-reaction-elucidation-of-the-reaction-mechanism-for-the-br-exchange-reaction
#14
P G Jambrina, M Menéndez, F J Aoiz
In spite of its importance in the Hg atmospheric chemistry, the dynamics of the Hg + Br2 → HgBr + Br reaction is poorly understood. In this article, we have carried out a comprehensive study of the reaction mechanism of this reaction by means of quasiclassical trajectories (QCTs) on an existing ab initio potential energy surface (PES). The reaction has a non trivial dynamics, as a consequence of its large endothermicity, the presence of a deep potential well, and the competition between the Br exchange and the collision induced dissociation processes...
June 28, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28596568/influence-of-rovibrational-excitation-on-the-non-diabatic-state-to-state-dynamics-for-the-li-2p-%C3%A2-%C3%A2-h2%C3%A2-%C3%A2-%C3%A2-lih%C3%A2-%C3%A2-h-reaction
#15
Di He, Jiuchuang Yuan, Maodu Chen
The non-adiabatic state-to-state dynamics of the Li(2p) + H2 → LiH + H reaction has been studied using the time-dependent wave packet method, based on a set of diabatic potential energy surfaces recently developed by our group. Integral cross sections (ICSs) can be increase more than an order of magnitude by the vibrational excitation of H2, whereas the ICSs are barely affected by the rotational excitation of H2. Moreover, ICSs of the title reaction with vibrationally excited H2 decrease rapidly with increasing collision energy, which is a typical feature of non-threshold reaction...
June 8, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28595394/surprising-behaviors-in-the-temperature-dependent-kinetics-of-diatomic-interhalogens-with-anions-and-cations
#16
Nicholas S Shuman, Oscar Martinez, Shaun G Ard, Justin P Wiens, Nicholas R Keyes, Hua Guo, Albert A Viggiano
Rate constants and product branching fractions of reactions between diatomic interhalogens (ICl, ClF) and a series of anions (Br(-), I(-)) and cations (Ar(+), N2(+)) are measured using a selected ion flow tube apparatus and reported over the temperature range 200-500 K. The efficiency of both anion reactions with ICl is 2%-3% at 300 K to yield Cl(-), increasing with temperature in a manner consistent with the small endothermicities of the reactions. The anion reactions with ClF are 10%-20% efficient at 300 K to yield Cl(-) and also show a positive temperature dependence despite being highly exothermic...
June 7, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28594362/green-synthesis-of-zinc-oxide-nanoparticles-for-enhanced-adsorption-of-lead-ions-from-aqueous-solutions-equilibrium-kinetic-and-thermodynamic-studies
#17
Susan Azizi, Mahnaz Mahdavi Shahri, Rosfarizan Mohamad
In the present study, ZnO nanoparticles (NPs) were synthesized in zerumbone solution by a green approach and appraised for their ability to absorb Pb(II) ions from aqueous solution. The formation of as-synthesized NPs was established by X-ray diffraction (XRD), Transmission Electron Microscopy (TEM), and UV-visible studies. The XRD and TEM analyses revealed high purity and wurtzite hexagonal structure of ZnO NPs with a mean size of 10.01 ± 2.6 nm. Batch experiments were performed to investigate the impact of process parameters viz...
June 8, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/28593755/exothermicity-is-not-a-necessary-condition-for-enhanced-diffusion-of-enzymes
#18
Pierre Illien, Xi Zhao, Krishna K Dey, Peter J Butler, Ayusman Sen, Ramin Golestanian
Recent experiments have revealed that the diffusivity of exothermic and fast enzymes is enhanced when they are catalytically active, and different physical mechanisms have been explored and quantified to account for this observation. We perform measurements on the endothermic and relatively slow enzyme aldolase, which also shows substrate-induced enhanced diffusion. We propose a new physical paradigm, which reveals that the diffusion coefficient of a model enzyme hydrodynamically coupled to its environment increases significantly when undergoing changes in conformational fluctuations in a substrate concentration dependent manner, and is independent of the overall turnover rate of the underlying enzymatic reaction...
June 14, 2017: Nano Letters
https://www.readbyqxmd.com/read/28550737/activated-carbon-from-sugarcane-bagasse-ash-for-melanoidins-recovery
#19
A Kaushik, S Basu, K Singh, V S Batra, M Balakrishnan
This work investigates the value added utilization of two sugar-distillery wastes: (i) melanoidins, which are complex Maillard reaction products in molasses distillery wastewater, and (ii) unburnt carbon in sugarcane bagasse ash. Activated unburnt carbon (AUC), prepared by deashing and steam activation, had properties comparable to commercial activated carbon (CAC). Both carbons are suitable for melanoidins adsorption followed by desorption using 25% pyridine solution. For AUC, the equilibrium adsorption data is well described by Langmuir isotherm up to 35 °C while Freundlich model fits better at higher temperature...
May 24, 2017: Journal of Environmental Management
https://www.readbyqxmd.com/read/28527388/abiotic-transformation-of-hexabromocyclododecane-by-sulfidated-nanoscale-zerovalent-iron-kinetics-mechanism-and-influencing-factors
#20
Dan Li, Xifen Zhu, Yin Zhong, Weilin Huang, Ping'an Peng
Recent studies showed that sulfidated nanoscale zerovalent iron (S-nZVI) is a better reducing agent than nanoscale zerovalen iron (nZVI) alone for reductive dechlorination of several organic solvents such as trichloroethylene (TCE) due to the catalytic role of iron sulfide (FeS). We measured the rates of transformation of hexabromocyclododecane (HBCD) by S-nZVI and compared them to those by FeS, nZVI, and reduced sulfur species. The results showed that: i) HBCD (20 mg L(-1)) was almost completely transformed by S-nZVI (0...
May 9, 2017: Water Research
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