The interaction between vincristine (VCR) and human serum albumin (HSA) was investigated by fluorescence and circular dichroism (CD) spectra at 288, 298 and 308 K. With fluorescence quenching method, the binding constants K were determined to be 2.14×10⁴, 1.73×10⁴ and 1.35×10⁴ L•mol^－1 respectively, indicating that the binding of VCR to HSA was strong, and the quenching mechanism was a static quenching. Enthalpy change (ΔH) was calculated to be －17.38 kJ•mol^－1 and entropy change (ΔS) was 22.62 J•mol^－1•K^－1. Taking into account the result of molecule modeling study, all these results indicated that the hydrophobic interaction played major roles between the tryptophan (214) residue of HSA and the indole moiety of VCR, but the electrostatic interaction mostly existed between the molecules of HSA and VCR in the binding process. The secondary structure of HSA was altered (CD data) with reductions of α-helices from 51.7% to 32.9%, but increases of β-sheet by about 9.2% after VCR bound to HSA.

Key words: vincristine, human serum albumin, fluorescence spectra, circular dichroism spectra