Abstract: The reaction between ciprofloxacin and bovine serum albumin(BSA) in aqueous solution was studied by fluorescence spectra and microcalorimetry.The binding constant K was found to be 8.39×104L•mol－1 and the binding sites n to be 1.18 by fluorescence quenching method.The binding distance (r=2.46 nm) and transfer efficiency (E=0.33) between ciprofloxacin and BSA were also obtained according to the Fōrster theory of non-radiation energy transfer.Microcalorimetric measurements showed that the molar change of enthalpy ΔrHm≈0 for the reaction.The interaction between ciprofloxacin and BSA is stronger and the main binding force is hydrophobic interaction.

Key words: Ciprofloxacin, Bovine serum albumin, Fluorescence, Microcalorimetry