Influence of temperature on the binding of sodium aurothiosulphate to human serum albumin.

The influence of temperature on the binding of aurothiosulphate by human serum albumin was studied in unbuffered solutions at pH 7.4 and ionic strength 0.15 M by means of equilibrium dialysis. It was found that the high affinity association constant was temperature dependent. The thermodynamic characteristics of binding delta G1 degrees less than 0, delta H1 degrees greater than 0 and delta S1 degrees greater than 0 indicated that the binding process was endothermic and entropically driven. It was concluded that electrostatic interaction was predominantly involved in the binding of aurothiosulphate to the high affinity binding site on albumin. This is consistent with the molecular mechanism that the ligand binds as Au+ to a sulfhydryl group of albumin by replacing a hydrogen ion.