Spectroscopic investigations on the mechanism of interaction of crystal violet with bovine serum albumin

The interaction of crystal violet (CV) and bovine serum albumin (BSA) was investigated by fluorescence and UV–vis absorption spectroscopy at different temperatures. The results revealed that CV caused the fluorescence quenching of BSA through a static quenching procedure at low concentrations of CV ranging from 1.0–9.0 × 10−6 mol/L. A combined quenching (static and dynamic) process occurs at higher concentrations of CV at 298 and 303 K. The binding constants KA, the number of binding sites n, and corresponding thermodynamic parameters ΔGΘ, ΔHΘ, ΔSΘ between CV and BSA at different temperatures were calculated. The primary binding pattern between CV and BSA was interpreted as hydrophobic interaction. In addition, the effect of CV on the conformation of BSA was analyzed using synchronous fluorescence spectroscopy. The binding average distance, r between the donor (BSA) and acceptor (CV) was determined based on the Förster’s theory and it was found to be 5.86 nm. The association constant of CV–BSA decreased in the presence of common ions.