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International Journal of Minerals,Metallurgy and Materials 2017年第3期24卷 264-270页

作者： Hong-liang Fan Ai-min Zhao Qing-chun Li Hui Guo Jian-guo He Engineering Research Institute University of Science and Technology Beijing Beijing Institute of Technology Press Beijing Institute of Technology School of Materials Science and Engineering Liaoning University of Technology School of Materials Science and Engineering Tsinghua University

The effects of ausforming strain on bainite transformation in high-carbon low-alloy nanobainite steel were investigated using a Gleeble 3500 thermomechanical simulator machine. The bainite transformation speed at 300°C was found to be accelerated by ausforming at 300, 600, and 700°C under applied strains ranging from 10% to 50% followed by isothermal transformation at 300°C. The ausformed bainite volume fraction varied with the ausforming strain because of the mechanical stabilization of the deformed austenite. Ausforming at low temperatures not only enhanced the bainite ferrite volume fraction but also refined the microstructure substantially. Although the amount of bainite ferrite might have been reduced with increasing strain, the microstructures were refined by ausforming. © 2017, University of Science and Technology Beijing and Springer-Verlag Berlin Heidelberg.

关键词： Alloy steel Bainite Carbon enzyme kinetics Ferrite Microstructure Nanostructured materials Phase transitions Strain Volume fraction

Evaluation of arsenic pollution in field-contaminated soil at the soil’s actual pH

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Journal of Environmental Sciences 2024年第10期144卷 137-147页

作者： Tiancong Gao Haixia Tian Huimin Niu Mallavarapu Megharaj Wenxiang He College of Natural Resources and Environment Northwest A&F UniversityKey Laboratory of Plant Nutrition and Agro-environment in Northwest ChinaMinistry of AgricultureYanglingShaanxi 712100China Global Centre for Environmental Remediation College of EngineeringScience and EnvironmentUniversity of NewcastleCallaghanNSW 2308Australia

The pollution and ecological risks posed by arsenic(As)entering the soil are the major environmental challenges faced by human *** phosphatase can serve as a useful indicator for assessing As contamination under specific soil pH ***,the study of phosphatase kinetics in long-term field As-contaminated soil remains unclear,presenting a significant obstacle to the monitoring and evaluation of As pollution and *** purpose of this study was to determine phosphatase activity and explore enzyme kinetics in soils subjected to long-term field As *** revealed that the soil phosphatase activity varied among the tested soil samples,depending on the concentrations of *** relationship between total As,As fractions and phosphatase activity was found to be significant through negative exponential function *** parameters,including maximum reaction velocity(Vmax),Michaelis constant(Km)and catalytic efficiency(V_(max)/K_(m)),ranged from 3.14×10^(−2)–53.88×10^(−2) mmol/(L·hr),0.61–7.92 mmol/L,and 0.46×10^(−2)–11.20×10^(−2) hr^(−1),*** and Vmax/Km of phosphatase decreased with increasing As pollution,while Km was less ***,Vmax/Km showed a significant negative correlationwith all As fractions and total *** ecological doses(ED10)for the complete inhibition and partial inhibition models ranged from0.22–70.33 mg/kg and 0.001–55.27 mg/kg,respectively,indicating that V_(max)/K_(m) can be used as an index for assessing As pollution in field-contaminated *** study demonstrated that the phosphatase kinetics parameters in the soil’s pH system were better indicators than the optimal pH for evaluating the field ecotoxicity of As.

关键词： Arsenic pollution Ecological risk Soil phosphatase enzyme kinetics Catalytic efficiency(V_(max)/K_(m))

The Susceptibilities of Oxya chinensis(Orthoptera:Acridoidea) to Malathion and Comparison of the Esterase Properties from Three Collected Populations in Tianjin Area,China

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Agricultural Sciences in China 2009年第1期8卷 76-82页

作者： WU Hai-hua YANG Mei-ling GUO Ya-ping MA En-bo Institute of Applied Biology Shanxi University Taiyuan 030006 P.R.China

The susceptibilities of Oxya chinensis to malathion were studied in three populations collected from outskirt of Tianjin, China, using bioassays and biochemical analysis. Populations were chosen to represent different exposure to insecticides： BDG （Beidagang; low exposure）, BD （Baodi; high exposure previously but low exposure now）, and JN （Jinnan; high exposure）. The results showed that the LD50 values of BD and JN populations were 3.95- and 12.02-fold and 3.64- and 10.07- fold higher than that of BDG population in females and males, respectively. The LD50 values in females were higher than those in males. The results of biochemical analysis indicated that the esterase （EST） activities in JN population were higher than those in BD and BDG populations. They showed that when α-NA, α-NB, and α-NA were used as substrates, females＇ EST activities of JN population were 1.11-, 1.30-, and 1.14-fold and 1.39-, 1.59-, and 1.54-fold higher than those of BD and BDG populations, respectively. When α-NA, α-NB, and β-NA were used as substrates, males＇ EST activities of JN population were 1.13-, 1.12-, and 1,00-fold and 1.20-, 1.14-, and 1.07-fold higher than those of BD and BDG populations, respectively. The results also showed that the specific activities of the females were higher than those of the males in the BD and JN populations, whereas the specific activities of the males were higher than those of the females in the BDG population. The results of bioassay were consistent with those of biochemical analysis. Thus, it was inferred that the elevated ESTs activities might play an important role in conferring the differences of susceptibility of O. chinensis to malathion in the three collected populations. enzyme kinetic studies indicated that the Km and Vmax values were different among the three collected populations and between the females and the males. The observed changes in the kinetic parameters might be explained by differential expression patterns of isozymes so that th

关键词： Oxya chinensis esterase enzyme kinetics malathion susceptibility

Heterologous expression and characterization of two chitinase 5 enzymes from the migratory locust Locusta migratoria

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Insect Science 2016年第3期23卷 406-416页

作者： Ying-Long Li Hui-Fang Song Xue-Yao Zhang Da-Qi Li Ting-Ting Zhang En-Bo Ma Jian-Zhen Zhang Research Institute of Applied Biology College of Life Science Shanxi University Taiyuan China

Insect chitinases are involved in degradation of chitin from the exoskeleton or peritrophic metrix ofmidgut. In Locusta migratoria, two duplicated Cht5s （LmCht5-1 and LmCht5-2） have been shown to have distinct molecular characteristics and biological roles. To explore the protein properties of the two LmCht5s, we heterologously expressed both enzymes using baculovirus expression system in SF9 cells, and characterized kinetic and carbohydrate-binding properties of purified enzymes. LmCht5-1 and LmCht5-2 exhibited similar pH and temperature optimums. LmCht5-1 has lower Km value for the oligomeric substrate （4MU-（GlcNAe）3）, and higher Km value for the longer substrate （CM-Chitin- RBV） compared with LmCht5-2. A comparison of amino acids and homology modeling of catalytic domain presented similar TIM barrel structures and differentiated amino acids between two proteins. LmCht5-1 has a chitin-binding domain （CBD） tightly bound to colloidal chitin, but LmCht5-2 does not have a CBD for binding to colloidal chitin. Our results suggested both LmCht5- I and LmCht5-2, which have the critical glutamate residue in region II of catalytic domain, exhibited chitinolytic activity cleaving both polymeric and oligomeric substrates. LmCht5-1 had relatively higher activity against the oligomeric substrate, 4MU-（GlcNAc）3, whereas LmCht5-2 exhibited higher activity toward the longer substrate, CM-Chitin-RBE These findings are helpful for further research to clarit}g their different roles in insect growth and development.

关键词： chitinase 5 enzyme kinetics heterologous expression Locusta migratoria

Insights into the catalytic mechanism of a type I sulfide quinone oxidoreductase(SQR)from Acidithiobacillus caldus

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Systems Microbiology and Biomanufacturing 2023年第3期3卷 414-426页

作者： Xiaoyang Lu Linghui Zhao Yanjun Tong Hailin Yang Shoushuai Feng Key Laboratory of Industrial Biotechnology Ministry of EducationSchool of BiotechnologyJiangnan UniversityWuxiChina State Key Laboratory of Food Science and Technology Jiangnan UniversityWuxiChina School of Food Science and Technology Jiangnan University1800 Lihu RoadWuxiChina

Acidithiobacillus caldus,a typical sulfur oxidizer,derives the majority of its energy from sulfur *** the essential enzyme for sulfide oxidation catalysis is sulfide quinone oxidoreductase(SQR),an ancient ***,the catalytic mechanism of SQR generated from *** was investigated(SQR^(Ac)).According to phylogenetic study,SQR^(Ac)(ACAty RS11315)is closely related to SQR(BAD99305)of Acidithiobacillus ferrooxidans NASF-1 and is classified as a type I Sqr ***^(Ac)heterologously produced in Escherichia coli exhibits the distinctive absorption peaks(375,450 nm)of the flavoproteins family of proteins in its absorption *** site-directed mutagenesis,the function of conserved cysteines in the catalytic pathway was *** on the sulfide quinone redox reactions in vitro of SQR^(Ac)and variations,Cys160 and Cys356 have been identified as enzyme-active *** of another cysteine present in all type I SQRs(Cys128)decreased enzyme activity by 56%,indicating that this residue plays an important but non-essential role in enzyme *** addition,the binding affinities of SQR^(Ac),the visualization of its 3D structure,and the interaction between receptors and ligands were ***,a suitable sulfide quinone redox catalytic mechanism for *** was proposed.

关键词： Sulfide quinone oxidoreductase Sulfur metabolism Quinone redox Acidithiobacillus caldus enzyme kinetics

Characterization of Carboxylesterase Associated with Malathion Insensitivity in the Field Population of the Oriental Migratory Locust

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Agricultural Sciences in China 2008年第5期7卷 591-598页

作者： YANG Mei-ling ZHANG Jian-zhen ZHANG Jian-qin GUO Ya-ping MA En-bo Institute of Applied Biology Shanxi University Taiyuan 030006 P.R. China

Carboxylesterases （CarEs） from two field populations of the oriental migratory locust, Locusta migratoria manilensis （Meyen）, were examined to try to understand their contribution to malathion insensitivity. The CarEs activities in Wudi population （WD） were 1.75- and 1.50-fold significantly higher than those in Huangliu population （HL） when a-naphthyl acetate （a-NA） and [3-naphthyl acetate were used as substrates, respectively. Such elevated CarEs activities presented in the WD could be because of an increased staining intensity of the a-NA-hydrolyzing CarEs as shown on the nondenaturing polyacrylamide gel electrophoresis. Inhibition studies of CarEs using paraoxon and malaoxon indicated that CarE activities in the HL were more strongly inhibited than those in the WD. Furthermore, a 449-bp DNA fragment of CarE was obtained from L. migratoria manilensis. Hemiquantity reverse transcription-polymerase chain reaction analysis showed that CarE gene expression level in the WD was higher than that in the HL. The higher CarE activities and the increased CarE mRNA level in the WD appeared to be associated with decreased susceptibility to malathion in the WD due to the application of organophosphorus insecticides.

关键词： carboxylesterases enzyme kinetics enzyme inhibition RT-PCR Locusta migratoria manilensis

Comparisons of Properties of Acetylcholinesterase from Two Field-Collected Populations of Oxya chinensis Thunberg(Orthoptera:Acrididae)and the Role of Acetylcholinesterase in the Susceptibility to Malathion

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Agricultural Sciences in China 2005年第1期4卷 47-53页

作者： MA En-bo College of Life Science and Technology Shanxi University Taiyuan 030006 P.R.China

In this study, acetylcholinesterase (AChE) was extracted from two field-collected populations of Oxya chinensis (XinxiangCity, Henan Province and Changzhi City, Shanxi Province). AChE activities were decreased when concentrations of ATCincreased, showing a characteristic phenomenon of substrate inhibition at high concentration in both populations. Suchinhibition occurred at relatively low concentration for AChE from Xinxiang population but relatively high for AChE fromChangzhi population. The kinetic study showed that there were no significant differences between the two populations inthe Km values. The Km value in Changzhi population was only 1.09-fold higher than that in Xinxiang population. However,significant differences were observed between the two populations in Vmax values. The Vmax value in Changzhi populationwas 1.32-fold higher than that in Xinxiang population. The inhibition study in vitro showed that the AChE from bothpopulations exhibited similar rank order in sensitivity to inhibition by three OPs, as determined by comparison of theirbimolecular rate constants (ki), from the most potent inhibition to the least was chlopyrifos-oxon > paraoxon >demeton-s-methyl for AChE from the two populations and that the ki values in Xinxiang population were lower than those in Changzhipopulation. The I50 values of AChE from Xinxiang population were 4.84-, 2.66-, and 1.92-fold less sensitive to inhibition byparaoxon, chlopyrifos-oxon, and demeton-s-methyl. These results were consistent with the results in bioassay. It isinferred that AChE insensitivity to OP insecticides plays an important role in the differences of insusceptibility of Oxyachinensis to malathion between the two populations.

关键词： Acetylcholinesterase enzyme inhibition enzyme kinetics Oxya chinensis

Screening and Statistical Optimization of Physiochemical Parameters for the Production of Xylanases from Agro-Industrial Wastes

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Advances in enzyme Research 2016年第1期4卷 20-33页

作者： Mirza Baasit Ali Muhammad Irshad Zahid Anwar Mudassar Zafar Muhammad Imran Department of Biochemistry & Molecular Biology Faculty of Sciences University of Gujrat Gujrat Pakistan Institute of Biochemistry & Biotechnology University of Veterinary and Animal Sciences Lahore Pakistan

Xylanases are mostly produced through submerged fermentation;nonetheless solid-state fermentation has increased profound attention and consideration of scholars having high conversion level biomass to energy conservation. This study depicted the purification of xylanases and their possible utilization in industry. The present study was carried out to examine the culture influence of fungal strain Fomes fomentarius (F. fomentarius) using different agro-industrial residues (wheat straw, rice husk, sugarcane bagasse and siris pods). F. fomentarius showed maximum enzyme production after 72 h of fermentation, when grown on wheat straw in solid state fermentation process while maximum activity showed on pH 6.0 at 30°C. The other parameters optimized by statistical design (RSM) showed maximum xylanase activity (146 ± 8 IU/mL) at 65% moisture content, 4 mL inoculums size, 175 mg Ammonium sulphate, 200 mg Calcium carbonate and 1.4 grams of glucose. Xylanase was salted out at 60% ammonium sulphate concentration and enzyme was further purified by Sephadex G-100 gel filtration chromatography with 2.2 fold increase in activity. The purified xylanase from F. fomentarius had optimum pH 6.0 and 40°C. Xylanase showed higher specificity for oat spelt xylan with kinetic constants Km 1.25 mg/mL and Vmax 54 mM/min. Xylanases have an industrial important enzyme used extensively in food, feed and paper industry.

关键词： Xylanases Wheat Straw enzyme kinetics F. fomentarius Siris Pods

Enzymatic Activity of Escherichia Coil Lactate Dehydrogenase and Cytochrome c Oxidase

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Journal of Physical Science and Application 2012年第6期2卷 143-151页

作者： Yury Shamis Alex Taube Rodney Croft Russell J. Crawford Elena P. Ivanova Faculty of Life and Social Sciences Swinburne University of Technology Melbourne 3122 Australia Faculty of Engineering and Industrial Sciences Swinburne University of Technology Melbourne 3122 Australia Australian Centre for Radiofrequency Bioeffects Research Melbourne 3122 Australia School of Psychology University of Wollongong Wollongong 2522 Australia

The catalytic activity of two common bacterial enzymes, lactate dehydrogenase （LDH） and cytochrome c oxidase （COX） from Escherichia coli was examined following bacterial exposure to microwave （MW） radiation under well-defined experimental conditions. The experiments were conducted in a specialized microwave processing apparatus, with an exposure frequency of 18 GHz, and a temperature profile that was restricted to below 40℃ to avoid thermal degradation of the bacteria. The absorbed power was calculated to be 1,500 kW/m3 and the electric field was determined to be 300 Wm. Both values were theoretically confirmed using Computer Simulation Technology （CST） Microwave Studio 3D Electromagnetic Stimulation Software. Results showed that the activity of both enzymes was increased following MW radiation compared to negative controls and thermally treated samples subjected to similar temperature profiles. It is suggested that the increase in COX and LDH enzyme activity could not be explained by conventional heating alone, but was rather a result of micro-thermal effects that incorporated ＇undetectable＇ thermal mechanisms.

关键词： Non-thermal microwave radiation specific microwave effects enzyme kinetics cytochrome c oxidase lactatedehydrogenase instantaneous temperature.