Study of the interaction between a new Schiff-base complex and bovine serum albumin by fluorescence spectroscopy

A new Schiff-base compound, N′-(2-hydroxynaphthalenemethylene)-4-(2-hydroxyl naphthalenemethylenamine)benzoylhydrazine (1), was synthesized and the interaction between zinc complex (1-Zn) and bovine serum albumin (BSA) was investigated by fluorescence and absorption spectroscopies. A marked increase in the fluorescence intensity of 1-Zn was observed at 475 nm upon addition of BSA when excitation wavelength was set at 370 nm in pH 7.4 Tris–HCl buffer solution. Reversely, the intrinsic fluorescence of BSA could be quenched by 1-Zn complex. The quenching mechanism was suggested as static quenching according to the Stern–Volmer equation and the UV–vis absorption spectral change of 1-Zn upon addition of BSA. The binding constants Kb and the number of binding sites n were calculated. The effect of 1-Zn on the conformation of BSA was studied using synchronous fluorescence spectroscopy and three-dimensional fluorescence spectroscopy. In addition, the binding average distance r between the donor (BSA) and acceptor (1-Zn) was estimated based on the Förster's non-radiation energy transfer theory.