Study of the interaction between 5-sulfosalicylic acid and bovine serum albumin by fluorescence spectroscopy

The interaction between 5-sulfosalicylic acid (SSA) and bovine serum albumin (BSA) at pH 7.40 was studied by fluorescence and UV–vis absorption spectroscopy at different temperatures. The results revealed that SSA caused the fluorescence quenching of BSA through a static quenching procedure. The binding constant K was measured by fluorescence quenching method. The thermodynamic parameters, ΔH and ΔS, were calculated to be 23.16 kJ mol−1>0 and 162.37 J mol−1 K−1>0, respectively, which suggested that the hydrophobic force played a major role in the reaction of SSA on BSA. The distance r between donor (BSA) and acceptor (SSA) was obtained according to the Förster non-radiation energy transfer theory. The results of synchronous fluorescence spectra, three-dimensional fluorescence spectra and far-UV circular dichroism spectra showed that the interaction between BSA and SSA induced conformational changes in BSA.