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 K(b) 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.