微量热法研究过氧化氢酶反应

利用微量热法和热动力学方程研究了过氢化氢酶反应.该反应遵循Michaelis-Menten动力学,298.15K和pH7.0时,其米氏常数、酶转换数以及摩尔反应焓分别为2.36×10^-2mol/L、1.20×10⁴s^-1和-83.67kJ·mol^-1.过氧化氢酶反应后期对底物是一级反应,其总反应速度常数和一级速度常数分别为k_o=6.31×10⁵L·mol^-1·s^-1和k₁=6.31×10⁵/[E_o]s^-1.该反应服从Ogura机理,其酶-底物三元复合物的分解速度常数为6.00×10³s^-1.     

微量热法研究过氧化氢酶底物抑制动力学

过氧化氢酶是需氧生物体内抗氧化酶系的重要组分。过氧化氢酶催化过氧化氢分解是一个两底物酶促反应,依照Chance提出的机理,反应速率方程具有一级反应方程的形式。此反应在高浓度底物存在的情况下,表现出明显的不可逆底物抑制。本研究用热动力学方法研究了这一反应,提出了一种不可逆底物抑制机理,并应用该机理求出了相关动力学参数。在310.15K,pH=7.0时k0=9.6×10^5L·mol^-1^·s^-1,k1/k2=2.9×10^6。实验结果证明此机理正确有效。     

咪唑衍生物金属胶束模拟过氧化物酶研究

咪唑衍生物铜配合物Cu(biap)·Cl2及其与胶束形成的金属胶束模拟过氧化物酶成功地用于催化H2O2氧化苯酚反应,反应遵循酶催化的动力学规律.过氧化氢/催化剂物质的量比和酸度对反应的影响符合生物催化剂条件影响的一般规律.讨论了不同类型表面活性剂胶束对该氧化反应的影响.     

金属胶束——一类新的金属酶模型

综述了金属胶束作为水解酶模型、氧化酶模型及维生素Ｂ６相关酶模型的研究进展，同时对它催化各类反应的机理进行了讨论。     

热动力学的滴定量热法研究2: 单底物酶促反应的热动力学

用滴定量热法分别建立了滴定期和停滴反应期单底物酶促反应热动力学的数学模型。根据这两种模型,可由一次实验的滴定量热曲线同时解析出单底物酶促反应的热力学参数(Δ~rH~m)和动力学参数(K~m和k~2)。用滴定量热法研究了一个经典的单底物酶促反应---过氧化氢酶催化分解过氧化氢反应的热动力学,由滴定期和停滴反应期热动力学模型解析出在298.15K和pH=7.0时该反应的米氏常数K~m分别为(5.41±0.24)×10^-^3和(5.43±0.21)×10^-^3mol.L^-^1,酶转换数k~2分别为(3.58±0.33)×10^3和(3.60±0.41)×10^3s^-^1,摩尔反应焓为(-86.75±0.88)kJ.mol^-^1,实验结果验证了上述热动力学模型的正确性。     

胶束催化及胶束模拟酶性能的研究

本文对胶束催化的有机反应进行综述,并对其模拟酶的催化功能作了评论。     

热动力学的滴定量热法研究2: 单底物酶促反应的热动力学

用滴定量热法分别建立了滴定期和停滴反应期单底物酶促反应热动力学的数学模型。根据这两种模型,可由一次实验的滴定量热曲线同时解析出单底物酶促反应的热力学参数(Δ~rH~m)和动力学参数(K~m和k~2)。用滴定量热法研究了一个经典的单底物酶促反应---过氧化氢酶催化分解过氧化氢反应的热动力学,由滴定期和停滴反应期热动力学模型解析出在298.15K和pH=7.0时该反应的米氏常数K~m分别为(5.41±0.24)×10^-^3和(5.43±0.21)×10^-^3mol.L^-^1,酶转换数k~2分别为(3.58±0.33)×10^3和(3.60±0.41)×10^3s^-^1,摩尔反应焓为(-86.75±0.88)kJ.mol^-^1,实验结果验证了上述热动力学模型的正确性。     

细菌生长的热动力学性质的研究

前文报导了大肠杆菌在不同培养基中生长的速率及热力学函数.本文在此基础上又测定了不同细菌在相同培养基中生长的规律.细菌生长是一系列非常复杂的过程,为便于研究,使复杂问题简单化,我们采取与过渡状态理论类似的模式进行处理,得出了一些热动力学函数,这些数据为进一步探讨这一复杂过程提供了有用的信息.     

反胶束中的酶催化研究进展

评述酶在反胶束中的定位和结构、动力学特性、催化活性和稳定性，反胶束作为酶催化反应介质的优点，反胶束中酶催化反应的类型及其应用。     

一种双核铁配合物金属胶束作为模似过氧化物酶催化苯酚氧化的动力学研究

本文合成和表征了配合物Fe2EDTB。配合物Fe2EDTB与非离子表面活性剂B rij35组成的金属胶束作为模拟过氧化物酶催化H2O2氧化苯酚反应表现出了良好的催化活性。根据本文所提出的Fe2EDTB配合物催化H2O2氧化苯酚反应的机理可以较好地解释过氧化氢/催化剂物质的量比、反应体系的温度、反应体系的酸度对反应的影响。     

慢对峙反应的热动力学对比参量法

根据热动力学基本理论,推导了对峙反应的热动力学对比参量方程,建立了对峙反应对比参量法的数学模型。该法利用特征时间t~m和2t~m时对应的热谱数据计算反应的对比参量,进而解析出较慢对峙反应的速率常数和平衡常数。利用该法分别研究了硝基乙烷与氨和三(羟甲基)氨基甲烷质子转移反应的热动力学,实验结果表明了较慢对峙反应对比参量法的正确性。     

Thermokinetic Research Method for Simple-order Reactions. Double-thermoanalytical curve method

A novel thermokinetic research method for determination of the rate constant of a reaction taking place in a batch conduction calorimeter under isothermal conditions is proposed: the double-thermoanalytical curve method. The method needs only the characteristic time parameter t _m, the peak height Δ_m at time t _m and the peak area a*_m after time t _m for two thermoanalytical curves measured with different initial concentrations of the reactants: it conveniently calculates the rate constants. The thermokinetics of four reaction systems were studied with this method, and its validity was verified by the experimental results. This revised version was published online in July 2006 with corrections to the Cover Date.     

热动力学研究L-抗坏血酸和Cu~(2+)对过氧化氢酶的协同抑制

在 310 15K ,pH =7 0的 0 1mol·L-1Na2 HPO4 NaH2 PO4 缓冲溶液中 ,利用热动力学方法研究了L 抗坏血酸 ,Cu2 +及二者同时存在时 ,过氧化氢酶催化H2 O2 分解反应的动力学规律 .发现L 抗坏血酸和Cu2 +单独存在时对酶反应没有明显的抑制作用 ,二者共存时 ,对反应有非线性抑制作用 .在一定的酶和底物浓度下 ,L 抗坏血酸和Cu2 +不影响总反应的一级速率方程的形式 ,只减小了一级反应速率常数 .酶活性随抑制剂浓度变化关系呈S形曲线 .结合实验结果和文献 ,提出了一种L 抗坏血酸和Cu2 +协同抑制过氧化氢酶的可能机理     

Activity and stability studies of ultrafine nanoencapsulated catalase and penicillinase

The enzymes catalase (bovine liver, EC 1.11.1.6) and -penicillinase (bacillus cereus strain 569, type I, EC 3.5.2.6) were successfully encapsulated in the polyacrylamide matrix. The encapsulation was carried out in the water pool of water/aerosol OT/n-hexane reverse micelles. The polymeric particles of encapsulated enzymes were reasonably monodisperse and had diameters in the range of several tens of nanometers as measured from quasi-elastic laser light scattering. The activity- pH profile of the encapsulated enzymes in buffer followed the same pattern as that of free enzymes. However, the encapsulated enzymes were found to be less active than their free forms. The enzymes in the encapsulated form were more stable (both thermal stability and shelf-life) as compared to free enzymes. The activity of the encapsulated enzymes was found to be dependent on the degree of cross-linking of the polymer matrix. The greater the cross-linking in the matrix, the lesser were the activity of the encapsulated enzyme.     

N-溴代丁二酰亚胺氧化异丙醇反应的热动力学研究

利用Batch型热导式热量计测定了N-溴代丁二酰亚胺(NBS)氧化异丙醇反应的热谱曲线,并分别利用简单级数反应和连续一级反应热动力学特征对比参量法的数学模型计算了反应的动力学参数,计算结果表明:利用连续一级反应热动力学研究法处理得到的动力学参数与文献通过碘量法的测定值是吻合的,因此,在质子性溶剂中的NBS氧化异丙醇反应遵从连续一级反应的动力学规律。     

NaF抑制精氨酸酶催化反应的热动力学研究

在37 ℃, pH＝7.4～9.4, 40 mmol?L^－1的巴比妥钠-HCl缓冲体系中, 利用热动力学方法研究了NaF对精氨酸酶催化L-精氨酸水解反应的抑制作用. 实验结果表明, NaF对精氨酸酶反应的抑制作用, 属于非竞争性可逆抑制, 其抑制率依赖于反应体系的pH值, 底物L-精氨酸和外源Mn^2＋离子对相对抑制率和抑制常数的影响不显著. 在pH值为7.4, 外源锰离子浓度分别为0和0.167 mmol?L^－1时的抑制常数分别为1.48和1.84 mmol?L^－1. F^－离子对精氨酸酶的抑制不是与底物L-精氨酸竞争酶的活性位, 而是影响了水分子与双核锰簇的桥式配位作用, 使反应过程中, 作为亲核试剂进攻L-精氨酸胍基碳的羟基离子难于生成或使其浓度减小, 从而降低了酶反应活性.     

Thermokinetic Studies on the Activation of Arginase by Glycine

The activation of bovine liver arginase, which catalyzes the hydrolysis of L‐arginine to L‐ornithine and urea, by glycine was studied by thermokinetic methods at 37°C in 40 mmol·L^?1 sodium barbiturate‐HCl buffer solution (pH 9.4). Results of this experiment indicate that an appropriate concentration of glycine can enhance the activity of arginase, and the relative activation rate reached its maximum value, 74%, when the concentration of glycine in reaction system was 1 mmol·L^?1 and the initial concentration of arginine was 5 mmol·L^?1. With the increase of substrate concentration, the relative activation rate decreased in a definite glycine concentration. Michealis constant K_m of reaction decreased from 5.53 to 3.31 mmol·L^?1 and inhibition constant of product L‐ornithine K_p increased from 1.18 to 3.73 mmol·L^?1 when glycine concentration was 1 mmol·L^?1. For these reasons one possible activation mechanism of arginase by glycine was suggested that the activation effect results from the competition of glycine and arginine to enzyme activity position. When one or two of the activity positions of arginase are occupied by glycine, it is propitious for the enzyme to complex with substrate and obstruct L‐ornithine from combining with enzyme, and when all of the activity positions are occupied by glycine, the activation effect vanishs and the inhibition effect appears.     

Studies on thermokinetics of consecutive first-order reactions

The transformation equation for the thermokinetics of consecutive first-order reactions has been deduced, and a thermokinetic research method of irreversible consecutive first-order reactions, which can be used to determine the rate constants of two steps simultaneously, is proposed. The method was validated and its theoretical basis was verified by the experimental results.     

Thermokinetic Study on the Reversible Competitive Inhibition of Bovine Liver Arginase

Introduction Arginase (EC 3.5.3.1) is a widespread and very im-portant enzyme in mammals, which specifically cata-lyzes the hydrolysis of L-arginine to urea and the non-protein amino acid L-ornithine, a key step in the urea cycle.1 Urea is the principal metabolite for disposal of nitrogen as a neutral and nontoxic waste product formed during amino acid metabolism in mammals. L-ornithine serves as a biosynthetic precursor to L-proline and the polyamines such as putrescine, sper-mine (in eucar…