Abstract: This study was designed to explore the binding mode of pefloxacin mesylate(PFLX) with human serum albumin (HSA).Fluorescence spectroscopic results showed pefloxacin-HSA complex with binding constants of 1.7×10⁵ L•mol^－1.The enthalpy change (Δ_rH_m) and entropy change (Δ_rS_m) were measured by microcalorimetry to be 1.03 kJ•mol_－1 and 101.28 J•K_－1•mol_－1,which indicated that hydrophobic interaction played a major role in the binding of PFLX with HSA. The possible binding domains of HSA for PFLX were studied by molecular modeling, which predicted that the hydrophobic interaction played a dominating role in this drug-protein interaction and PFLX could bind to Sudlow’s sites I and II of HSA. The binding energies obtained from the molecular modeling were in accordance with the experiment results.

Key words: Pefloxacin mesylate, Human serum albumin, Molecular modeling, 　Binding mode