Spectroscopic studies on the interaction between 3,4,5-trimethoxybenzoic acid and bovine serum albumin

The interaction between 3,4,5-trimethoxybenzoic acid (TMBA) and bovine serum albumin (BSA) was studied by fluorescence and UV–vis absorption spectroscopy. In the mechanism discussion, it was proved that the fluorescence quenching of BSA by TMBA is a result of the formation of TMBA–BSA complex. Quenching constants were determined using the Stern–Volmer equation to provide a measure of the binding affinity between TMBA and BSA. The thermodynamic parameters ΔH, ΔG, ΔS at different temperatures were calculated, and electrostatic interactions play an important role to stabilize the complex. The distance r between donor (BSA) and acceptor (TMBA) was obtained according to fluorescence resonance energy transfer (FRET).