[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.

[Spectroscopy study on the interaction of colchicine and human serum albumin].

The binding reaction of colchicine with human serum albumin (HSA) was studied by UV-Vis absorption, fluorescence and circular dichroism spectrometry. The results indicated that colchicine led to the increase in UV absorption and the quenching of intrinsic fluorescence of HSA. As the temperature increased, the quenching constant Ksv decreased. The binding constants and the numbers of the binding sites of the interaction between colchicine and HSA at different temperatures were obtained. The thermodynamic parameters, enthalpy change (DeltaH) and entropy change (DeltaS), were calculated to be -11.66 kJ x mol(-1) and 51.507 J(mol x K)(-1) respectively according to Van't Hoff equation, which suggested that the main binding force between colchicine and HSA was static interaction. The protein conformation was altered (CD date) with decreasing of alpha-helices in the presence of colchicine. The results showed that the quenching mechanism of the combination of colchicine with human serum albumin was a static quenching procedure.