Studies on glutathione transferase from grasshopper (Zonocerus variegatus)

Glutathione transferase (GST) was purified from the hindgut of grasshopper (Zonocerus variegatus) a polyphagous insect. The purified enzyme had a native molecular weight of 40 kDa and a subunit molecular weight of 19 kDa. The purified enzyme could conjugate glutathione (GSH) with 1-chloro-2,4-dinitrobenzene (CDNB), paranitrobenzylchloride, paranitrophenylacetate, 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole (NBDCl), and 1,2-dichloro-4-nitrobenzene (DCNB) with specific activities of 3.3 ± 0.3, 0.49 ± 0.10, 0.10 ± 0.002, 1.2 ± 0.2, and 1.7 ± 0.4 μmol/min/mg protein, respectively. CDNB appears to be the best substrate with a specificity constant, k_cat/K_m, of 1.8 ± 0.1 × 10⁻⁴ M⁻¹ S⁻¹. The kinetic mechanism of Z. variegatus GST (zvGST) in the conjugation of GSH with some electrophilic substrates appears complex. Conjugation of GSH with DCNB was inhibited by high DCNB concentration, while with NBDCl, as the electrophilic substrates, different values of K_m were obtained at high and low concentrations of the substrates. Cibacron blue, hematin, S-hexylglutathione, and oxidized glutathione inhibited the enzyme with I₅₀ values of 0.057 ± 0.004, 0.80 ± 0.2, 33 ± 2 μM, and 5.2 ± 0.3 mM, respectively. The nature of inhibition by each of these inhibitors is either competitive or non-competitive at varying GSH or CDNB as substrates. NADH and NAD⁺ inhibited the enzyme with an I₅₀ value of 0.4 ± 0.01 and 11 ± 1 mM, respectively. NADH at a concentration of 0.54 mM completely abolished the activity. As part of its adaptation, the flexible kinetic pathway of detoxication by zvGST may assist the organism in coping with various xenobiotics encountered in its preferred food plants.     

桑枝粉对水中Cr(Ⅵ)离子的吸附研究

桑枝粉富含纤维素和木质素,具有吸附去除废水中重金属离子的功能。采用桑枝粉吸附去除水中Cr(Ⅵ)离子,考察pH值、吸附时间、桑枝粉用量、Cr(Ⅵ)离子溶液初始浓度等因素对吸附效果的影响,测定吸附等温线,对等温吸附规律和吸附动力学过程作数学模拟。结果表明,桑枝粉对水中Cr(Ⅵ)离子有很好的吸附效果。吸附量随着pH值的增大而减小,随着吸附时间的延长而增大,吸附平衡时间为6 h;桑枝粉用量增加,吸附去除率提高;Cr(Ⅵ)离子溶液初始浓度增大,吸附去除率下降。适宜的吸附条件为:桑枝粉用量5 g/L,pH值1.5,温度25℃,吸附时间6 h,Cr(Ⅵ)离子溶液初始浓度为10 mg/L。桑枝粉对Cr(Ⅵ)离子的等温吸附规律符合Freundlich、Langmuir和Temkin模式,吸附呈单分子层形式,吸附性能良好,吸附易于进行。吸附动力学过程可用准一级和准二级动力学模式进行模拟。     

曝气扰动下底泥氮的释放动力学及硝化反硝化过程研究(英文)

[目的]研究曝气扰动下底泥氮的释放动力学及硝化反硝化过程,以期解决底泥氮释放及二次污染问题。[方法]研究了底泥原位曝气对氮污染物释放的影响,并对其释放动力学参数进行解析,同时模拟了间歇曝气下泥水界面硝化反硝化脱氮过程。[结果]底泥曝气加速了氮污染物的释放,30min后底泥NH4+-N与达到释放平衡;最大释放量与底泥扰动强度成正比,在曝气头距离泥面距离为0、1、2和3cm时(扰泥量为3.52、3.41、3.26和3.01g/L),NH4+-N与最大释放量分别为14.3、13.8、13.2、12.2mg/L和33.2、30.9、29.8、27.3mg/L;且两者的释放动力学均符合双常数方程。持续曝气可促进泥水界面硝化反应发生,8d后NH4+-N浓度由12.4mg/L下降至0.2mg/L,硝态氮浓度达到最大值;停止曝气12d后,硝态氮与总氮浓度分别由10.8和37.4mg/L下降至0.36和23.2mg/L,说明有反硝化脱氮现象发生。可见,底泥曝气可促进氮污染物的释放及硝化过程,而通过间歇曝气,可实现底泥原位硝化反硝化脱氮。[结论]该研究结果可为城市黑臭河道底泥原位修复提供技术借鉴。     

锅炉煤渣对含磷废水的吸附特征及吸附工艺优化(英文)

[目的]研究锅炉煤渣对含磷废水的吸附特征,并对其吸附工艺进行优化。[方法]采用锅炉渣单级吸附工艺处理农村生活污水,研究锅炉渣对废水中磷的吸附动力学及热力学过程,并对单级吸附工艺中锅炉渣最小用量进行优化计算。[结果]不同温度下,锅炉渣对磷的吸附等温式可用Langmuir等温式进行描述,吸附动力学均符合准二级动力学方程,且最大吸附量及初始吸附速率随温度升高而增加,40℃时分别达0.1591g/g和0.1698mg/(g·min);热力学参数ΔG0<0,ΔH0>0,表明该吸附过程属于自发吸热吸附,提高温度有利于吸附反应的进行;单级吸附时,最小吸附剂投加量随温度上升而减少,40℃时1m3污水处理投加量为3.31kg。[结论]采用锅炉渣吸附工艺处理农村含磷废水是一种经济可行的方法。     

土壤中磷解吸动力学特征及过渡态理论的应用

在２℃、１２℃、２２℃、３２℃和４２℃５个温度条件下,应用动力学和过渡态理论研究了陕西省具代表性的４种土壤对所吸附磷的解吸反应特征。结果表明,土壤磷解吸的一级反应速度常数值随温度升高而明显增大,     

Vertical ground reaction force-time histories of sound Warmblood horses trotting on a treadmill

The objective of this study was to establish representative treadmill ground reaction force (GRF) and interlimb co-ordination time data of clinically sound horses at the trot. It was anticipated that these normative standards would provide a reference data base against which lame horses could be compared. GRF-time histories were collected from 30 Warmblood riding horses with easy, wide natural gaits. Data were recorded of all four limbs simultaneously by the use of an instrumented treadmill. A total of 912 stride cycles per limb were analysed for force, time and spatial parameters and were averaged. The shape and amplitude of the treadmill force curves were very similar to force traces recorded with a stationary force plate. The horses showed a high degree of symmetry in all investigated parameters (95% reference interval of left-right asymmetry +/-1.8-6.8%). No significant differences were found between left and right mean values. Intra-individual coefficients of variance of the various parameters did not exceed 2.7%. Inter-individual coefficients of variance were 2.5-3.5 times larger than the respective intra-individual coefficients. An instrumented treadmill provides a number of decisive advantages, such as time-efficient data acquisition of all four feet simultaneously over successive strides, or the high regularity of the horse's gait pattern at controlled velocities, which allow the clinical assessment of locomotor performance of horses.     

细胞质雄性不育水稻线粒体能量释放的热力学和动力学特征

高等植物细胞质雄性不育(Cytoplasmic male sterile, CMS)现象, 已在271种植物中发 现 。 根据少数几种较为深入的植物CMS研究, 人们认为这是一种可能由许多不同原因导致的 复 杂现象。 目前已有许多证据证明CMS与植物线粒体密切相关, 人们确信细胞质的不育 因子主要位于线粒体上, 不育系线粒体结构和功能均存在明显差异     

硅酸盐木材胶黏剂的固化动力学特征

为探讨硅酸盐木材胶黏剂的固化过程和固化特性,通过胶黏剂中水分蒸发速率测定试验,对不同温度下胶黏剂固化过程中的失水规律和动力学特征进行了研究。结果表明:硅酸盐胶黏剂的固化是物理作用和化学作用联合的结果,物理作用中的失水过程是控制固化速度的关键步骤,而且失水率随时间的变化规律可用非线性方程X=X_∞/1+be~(-kt)来描述。硅酸盐胶黏剂的固化可大致分为3个阶段,均具有非整数级动力学特征,活化能分别为16.78、23.02kJ/mol和52.29kJ/mol。     

天然沸石对NH4＋吸附、解吸动力学的影响

通过室内分析的方法研究了天然沸石对NH4＋离子的吸附及解吸动力学影响。结果表明,天然沸石对 NH4＋的吸附和解吸动力学符合一级动力学方程、修正的 Freundlich方程、抛物线扩散模型和异分子扩散模型。沸石对NH4＋的解吸速度很快,在60 min内解吸完全。     

固体碱法制备生物柴油组分生成动力学

[目的]探讨固体碱法制备生物柴油中组分油酸甲酯的生成动力学。[方法]以精制菜籽油和甲醇为原料,固体碱CaO/MgO作催化剂,菜籽油与甲醇在固体碱催化下进行酯交换反应制备生物柴油,用气相色谱法跟踪分析生物柴油(脂肪酸甲酯)的含量,考察生物柴油中组分油酸甲酯的生成动力学。[结果]动力学研究表明,固体碱CaO/MgO催化菜籽油和甲醇的酯交换反应速率方程为rA=dCp/dt=k1CA2。反应速率动力学方程分3个阶段,反应开始为引发阶段,逐步转变为增长阶段的2级反应,最终反应达到平衡阶段。油酸甲酯增长阶段反应活化能为58.48 kJ/mol,频率因子为9.18×105 L/(mol.min)。[结论]该研究为固体碱催化菜籽油与甲醇酯交换反应的动力学提供了理论基础。