Interaction of Bovine Serum Albumin with Propyl Gallate and Methyl Gallate Investigated by Fluorescence Spectroscopy

The interaction of antioxidant ligands, propyl gallate (PG) and methyl gallate (MG) with bovine serum albumin (BSA) was studied by means of fluorescence spectroscopy. Intrinsic fluorescence of BSA was monitored as a function of ligand concentrations, and fluorescence quenching assays were used to characterize the interaction between BSA and the ligands and to determine various quenching and binding constants. The quenching constants obtained for both PG and MG suggest a static quenching mechanism, and complex formation between BSA and PG or MG was confirmed by UV/Vis absorption spectroscopy. The site marker displacement experiments were performed to identify the binding site of BSA using warfarin and ibuprofen as site markers. The temperature dependence of the BSA-ligand binding interaction was investigated, and Delta H and Delta S for the binding process were determined using the van't Hoff equation. The results indicate that the binding interaction between BSA and PG are distinctively different in nature from that between BSA and MG.