Investigation on the interaction between 3, 5-dihydroxytoluene and bovine serum albumin by fluorescence spectroscopy

The interaction between 3, 5-dihydroxytoluene and bovine serum albumin (BSA) had been investigated by fluorescence spectroscopy. By the analysis of fluorescence spectrum and fluorescence intensity, it was observed that the 3, 5-dihydroxytoluene had a strong ability to quench the intrinsic fluorescence of BSA through a static quenching procedure. The binding constant and the number of binding sites were determined at 298 K based on fluorescence quenching results. The thermodynamic parameters such as enthalpy change (ΔH), entropy change (ΔS) and Gibbs free-energy change (ΔG) for the reactions were also calculated according to the thermodynamic equations. The negative ΔH and ΔS values in case of 3, 5-dihydroxytoluene-BSA complexes showed that van der Waals interactions and hydrogen bonds might play a major role in the binding of 3, 5-dihydroxytoluene to BSA. The distance, r, between donor (BSA) and acceptor (3, 5-dihydroxytoluene) was obtained according to the Förster's theory of non-radiation energy transfer. The experimental results of synchronous fluorescence spectroscopy showed that the binding of 3, 5-dihydroxytoluene to BSA induced conformational changes in BSA.