Studies on the interaction between triphenyltin and bovine serum albumin by fluorescence and CD spectroscopy

The interaction between triphenyltin (TPT) and bovine serum albumin (BSA) in physiological buffer (pH=7.4) was investigated by the fluorescence quenching technique. The results of fluorescence titration revealed that TPT could strongly quench the intrinsic fluorescence of BSA through a static quenching procedure. The apparent binding constants K and number of binding sites n of TPT with BSA were (7.04±0.0057)×10(2) and (0.77±0.016) which were obtained by the fluorescence quenching method. The thermodynamic parameters enthalpy change (ΔH), entropy change (ΔS) were positive, which indicated that the interaction of TPT with BSA was driven mainly by hydrophobic forces. The process of binding was a spontaneous process in which Gibbs free energy change was negative. The distance r between donor (BSA) and acceptor (TPT) was calculated to be 3.05nm based on Forster's non-radiative energy transfer theory. The results of synchronous fluorescence, three-dimensional fluorescence and Circular Dichroism (CD) spectra showed that the triphenyltin induced conformational changes of BSA.