AIM To study the interaction between ciprofloxacin and BSA in physiological condition by fluorescence spectroscopy. METHODS The affection of drug to the protein conformation was investigated. The binding constant between drug and BSA from a double reciprocal Lineweaver Burk plot was determined and the main sort of binding force was found according to the thermodynamic parameters. RESULTS The binding constants between BSA and ciprofloxacin at 26℃and 45℃ are about 10 4. At 26℃, the thermodynamic parameters of reaction between BSA and ciprofloxacin are Δ H = -49 13 kJ·mol -1 , Δ G = -26 45 kJ·mol -1 , Δ S = -75 kJ·mol -1 . The maximum wavelength of the synchronous fluorescence spectra of BSA moved from 279 nm to 289nm with the incresing of the amount of ciprofloxacin. CONCLUSION There exists fluorescence energy transfer between BSA and ciprofloxacin. The main sort of binding force between BSA and ciprofloxacin is Van der Waals′ interaction. Ciprofloxacin can be deposited and be transported by serum protein in vivo . Ciprofloxacin affects the protein conformation.
