Studies on the thermokinetic characterisation of actin polymerization and the effect of cisplatin

The microcalorimetic measurement for studying the thermokinetic of actin polymerization in vitro was employed for the first time. The thermodynamic parameters of actin polymerization at 310.15 K are reported as delta Hm = 49.26 kJ/mol, delta Gm = 25.62 kJ/mol and delta Sm = 241.54 J/K.mol. The thermogram shows that polymerization of actin is a complicate process in which multistep reactions occur corresponding to exothermic and endothermic effects. Cisplatin, at lower concentration, affects the polymerization of G-actin resulting in a decrease of delta Hm; and, at higher concentration, induce the crosslinking and depolymerization of F-actin in the equilibrium system of G/F. The experimental results show that as the concentration of cisplatin increases, the sign of delta Hm changes from positive to negative, i.e. the magnitude and sign of delta Hm of actin polymerization depends on the concentration of cisplatin.