Spectroscopic investigations on the mechanism of interaction of bioactive dye with bovine serum albumin

The mechanism of binding of rose bengal (RB) with bovine serum albumin (BSA) was investigated by spectroscopic methods. The analysis of fluorescence data indicated the presence of both dynamic and static quenching mechanisms in the binding. Various binding parameters have been evaluated. The thermodynamic parameters, ΔH0 and ΔS0 were observed to be −79.61 kJ mol−1 and −143.37 J mol−1 K−1, respectively. The quantitative analysis of CD results revealed that the α-helicity of BSA decreased from 66.4% (in free BSA) to 48.64% (in bound BSA). The binding average distance, r between the BSA (donor) and RB (acceptor) was determined based on Förster's theory and it was found to be 2.75 nm. The effects of common ions on the binding constant of RB–BSA were also examined.