The interaction between norfloxacin and bovine serum albumin, and the influence of Zinc(U) on the system of norfloxacin and bovine serum albumin was studied under physiological condition by fluorescence method. It was shown that norfloxacin has a powerful ability to quench the BSA fluorescence via a nonradiative energy transfer mechanism. The fluorescence quenching data were analyzed according to Stern-Volmer equation and double-reciprocal equation, and the binding constant(K) and the binding sites(n) were obtained. In the system of binary complex of NFLX and BSA, K=6.80 x 10(5) and n=1.21. There is a strong combination between NFLX and BSA, which offers the condition for the serum protein to be deposited and transported in vivo. Besides, the combination between NFLX and BSA becomes stronger in the presence of Zinc(II). According to Stern-Volmer equation and double-reciprocal equation, the concentration of Zinc(II) is denser, and the binding constant(K) and the binding sites(n) are bigger. By studying the binding interaction between Zinc(II), norfloxacin and BSA, the mechanism of the interaction among norfloxacin, Zinc(II) and protein in organism, is furtherly discussed.
