微量量热法研究肌动蛋白的聚合及顺铂的影响

肌动蛋白（actin）是细胞微丝系统的结构蛋白·单体G一肌动蛋白与聚合产物F一肌动蛋白间的相互转变与细胞的运动、形态和信息传递相关＊．实际上，微丝系统处在一个动态平衡状态．即G和F不断相互转换以适应细胞功能要求．在外源性物质影响下，这个动态平衡可能被影响而产生相应的药理、毒理作用．罗世荣等问报导在荧光显微镜下观察到，顺铂（抗癌药）及其类似物会诱导微丝的重组和解聚．但机理有待研究·目前虽然有许多方法被用来研究肌动蛋白的聚合过程问，但对聚合全过程的确切描述尚无充分的实验数据，对聚合热动力学过程的研究至今尚…

Microcalorimetry Studies on the Actin Polymerization and the Effects of Cisplatin

The polymerization of actin has been studied with applying a new method of microcalorimetric measurement in vitro. The thermodynamic parameters of actin poly merization at 310.15 K is reported. △H_m= 49.26 kJ·mol~(-1)， △G=-25.62 kJ·mol~(-1) and △S=241.54 J·K~(-1)×mol~(-1). Thermogram showed that the thermokinetic process of actin polymerization had two different thermal effects where in the first exothermic step is con sidered to be the total results of several reations: metal ion (Mg~(2+), K~+) binding to actin; the change of conformation of actin and hydrolysis of ATP in actin; and the second endothermic step is assigned to the results of association and length adjustment (annealing process). Cisplatin, at lower concentration, affects the polymerization of G-actin reflected in the decrease of ΔH_m; and at higher concentration it induces the crosslinking and depolymerization of F-actin in the equilibrium system of G/G. The experimental results manifest that when the concentration of cisplatin is increased to a certain value, the sign of ΔH_m will be changed from positive to negative i.e. the magnitude and sign of ΔH_m of actin polymerization is dependent on the concentration of cisplatin. This is possibly related to the pharmacologic or toxicological action of cisplatin.