LAUSR

Abstract The interaction of bovine serum albumin (BSA) with a naturally occurring surfactant (trans-crocetin di-(β-D-gentiobiosyl) ester, crocin) was studied under biophysical conditions by using various techniques such as surface tensiometry, UV–visible spectrophotometery and fluorescence. Upon the addition of a small amount of BSA, the λmax of a crocin dispersion in water shifted to lower wavelengths, indicating either a ground state complex formation between BSA and crocin or solubilization of BSA into the micelles of crocin. The critical micelle concentration (cmc) of crocin decreases in the presence of increasing BSA concentrations. The complex formation constant (KC), surface pressure πcmc, maximum surface excess (Γmax), the minimum surface area per molecule (Amin), enthalpy (ΔH0), entropy (ΔS0), and Gibbs free energy change (ΔG0) were calculated for the BSA-crocin interactions. BSA fluorescence was quenched in the presence of crocin. The fluorescence data were used for determining the apparent association constant (Kapp), the Stern-Volmer constant (KSV), the bimolecular rate constant of the quenching process (kq) and the thermodynamic parameters.