为探究山药多糖能否抑制低密度脂蛋白(low density lipoprotein,LDL)氧化,本实验提取了山药(Dioscorea opposita)多糖并除杂,分析了多糖的成分及体外抗氧化活性,对多糖能否抑制LDL氧化进行了初步探讨。结果表明,山药多糖的总糖质量分数...为探究山药多糖能否抑制低密度脂蛋白(low density lipoprotein,LDL)氧化,本实验提取了山药(Dioscorea opposita)多糖并除杂,分析了多糖的成分及体外抗氧化活性,对多糖能否抑制LDL氧化进行了初步探讨。结果表明,山药多糖的总糖质量分数为(65.79±1.03)%,蛋白质量分数为(5.89±0.43)%,灰分质量分数为(5.51±0.14)%,糖醛酸质量分数为(10.81±1.14)%;4个主要多糖组分的分子质量分别为933742、148878、39233、17318 Da;对1,1-二苯基-2-三硝基苯肼自由基、超氧化物自由基和羟自由基清除率的半抑制质量浓度分别为1.06、1.06 mg/mL和0.98 mg/mL;可有效减缓共轭二烯的形成,1.0μg/mL山药多糖对硫代巴比妥酸反应物的抑制率为CuSO_(4)组的16.28%(P>0.05);但对LDL糖化的抑制作用不大。本研究可为了解山药多糖对LDL氧化的抑制作用提供参考。展开更多
Investigations on the pyrolysis and kinetic behaviors during pyrolysis of fossil fuel samples, such as coal, are fundamental for developing the related technology and practical application. In this work, pyrolysis beh...Investigations on the pyrolysis and kinetic behaviors during pyrolysis of fossil fuel samples, such as coal, are fundamental for developing the related technology and practical application. In this work, pyrolysis behavior and kinetics in the pyrolysis process of a coal sample were investigated by the thermogravimetric analyzer at a heating rate of 10, 40, 70,100, 200, and 500 °C/min, respectively. The pyrolysis process could be divided into four stages according to the TG/DTG curves. The first stage was mainly attributed to the removal of volatiles, and the second peak was the polycondensation reaction between the volatile components. It was found that more volatiles could be released from coal during pyrolysis at higher heating rate and the higher pyrolysis temperature was necessary for a rapid pyrolysis process. Kinetic analysis revealed that both the model-free(KAS and FWO) and the Coats-Redfern methods were suitable to describing the pyrolysis process, and the variation of activation energy(E) with the two types of kinetic models was consistent during the whole pyrolysis process. Furthermore, the heating rate did not alter the reaction sequence of the whole pyrolysis process, but higher heating rate could make the E value of the initial pyrolysis stage smaller.展开更多
文摘【背景】硫氧还蛋白系统是细菌重要的氧化还原状态维持系统。假结核耶尔森氏菌(Yersinia pseudotuberculosis)YPⅢ是肠道常见的机会致病菌,在YPⅢ中进行过氧化氢胁迫下的转录组测序,结果发现硫氧还蛋白系统的相关基因有所上调,可能参与细菌氧化胁迫的应答。【目的】研究假结核耶尔森氏菌中硫氧还蛋白系统应答氧化胁迫的方式。【方法】利用同源重组方法构建硫氧还蛋白系统缺失突变株(ΔtrxA、ΔtrxC和ΔtrxR),研究假结核耶尔森氏菌在过氧化氢胁迫下的生长,测定过氧化氢对细菌的最低抑菌浓度、过氧化氢清除能力,以及过氧化氢处理下的存活率等。同时,通过lacZ报告基因系统对硫氧还蛋白系统的表达调控进行探究。【结果】构建硫氧还蛋白系统缺失突变株,发现缺失trxA后显著影响了假结核耶尔森氏菌的抗氧化胁迫能力,因此TrxA是硫氧还蛋白系统中应答氧化胁迫的主要蛋白;在ΔtrxA中过氧化氢酶的表达上调,但不足以保护细菌及时修复受损的生物大分子;启动子活性测定及实时荧光定量PCR(real time quantitative PCR,RT-qPCR)实验结果表明trxC和trxR的表达可能受到细菌氧化胁迫转录调控因子OxyR的影响。【结论】硫氧还蛋白系统作为细菌内部还原环境的维持系统,在OxyR的调控下参与氧化胁迫应答,并发挥了重要的作用。
基金the financial support from the National Natural Science Foundation of China(Grant Nos.21576293 and 21576294)
文摘Investigations on the pyrolysis and kinetic behaviors during pyrolysis of fossil fuel samples, such as coal, are fundamental for developing the related technology and practical application. In this work, pyrolysis behavior and kinetics in the pyrolysis process of a coal sample were investigated by the thermogravimetric analyzer at a heating rate of 10, 40, 70,100, 200, and 500 °C/min, respectively. The pyrolysis process could be divided into four stages according to the TG/DTG curves. The first stage was mainly attributed to the removal of volatiles, and the second peak was the polycondensation reaction between the volatile components. It was found that more volatiles could be released from coal during pyrolysis at higher heating rate and the higher pyrolysis temperature was necessary for a rapid pyrolysis process. Kinetic analysis revealed that both the model-free(KAS and FWO) and the Coats-Redfern methods were suitable to describing the pyrolysis process, and the variation of activation energy(E) with the two types of kinetic models was consistent during the whole pyrolysis process. Furthermore, the heating rate did not alter the reaction sequence of the whole pyrolysis process, but higher heating rate could make the E value of the initial pyrolysis stage smaller.
