[Study on the interaction between vincristine and bovine serum albumin]

The interaction between vincristine (VCR) and bovine serum albumin (BSA) was investigated by UV-Vis absorption, fluorescence and circular dichroism (CD) spectra at 296, 303 and 310 K, respectively. With fluorescence quenching method, the binding constants Ka were determined to be 1.5 x 10(4) L x mol(-1), 9.5 x 10(3) L x mol(-1), 4.9 x 10(3) L x mol(-1) and the number of binding site was 1 at three temperatures, respectively. The conformation of BSA was altered (CD data) with the reductions of alpha-helices from 33.5% for free BSA to 29.7%, and with increases of beta-sheet from 13.6% for free BSA to 18.4% in the presence of VCR. The thermodynamic parameters, enthalpy change (deltaH) and entropy change (deltaS), were calculated to be -62.07 kJ x mol(-1) and -129.38 J x (mol x K)(-1) respectively, according to van't Hoff equation, which indicated that hydrogen bonds and van der walls interactions played major roles in the binding process.