[Microcalorimetric study of the effect of temperature on methicillin binding with human serum albumin].

The curves of the calorimetric titration of human serum albumin (HSA) with methicillin at different temperatures were plotted. Unlike the widely used serial continuous flow calorimeters, the presented modification of a differential continuous flow microcalorimeter provided its application at wider temperature ranges and higher sensitivity. The possibility of obtaining equilibrium characteristics of the complexing at diverse temperatures, including the temperature of 37 degrees C allowed a more profound investigation of the molecular mechanism of the drug binding to the carrier protein. Methicillin interacted with 4 active sites of the HSA, the entropy factor part in changing of the process free energy being the main. With increase of the temperature the association constant and entropy of the system lowered in an insignificant increase of the exothermal heat effect. The analysis of the thermodynamic association parameters suggested that the hydrophobic interactions were predominating in the system.