The binding of [RuCl2(L)] (L = N,N-bis(7-methyl-2-pyridylmethylene)-1,3-diiminopropane) to bovine and human serum albumin was investigated by the fluorescence quenching technique. The comparison of the quenching effect of serum albumin fluorescence by ruthenium complex allowed the estimation of subdomain IB in BSA and subdomain IIA in HSA as the binding sites for this complex. The results of fluorescence titration revealed that ruthenium complex quenches the intrinsic fluorescence of BSA through a dynamic quenching mechanism, while HSA has a static quenching mechanism. The thermodynamic parameters indicated that hydrophobic forces played a major role in the binding of ruthenium complex to proteins. The process of binding was a spontaneous process in which Gibbs free energy change was negative.
