Investigation On The Interaction Of Vincristine With Serum Albumin

Exploring the interaction mechanisms on protein with drug small molecules at the molecular level are of current interest in many research areas such as life science, chemistry and so on.In this paper, the interaction of VCR with HSA was investigated by fluorescence spectra and circular dichroism spectra under physiological conditions at 288,298 and 308 K, respectively. With fluorescence quenching method, the quenching constants and the binding constants were determined at different temperatures. The capability of binding decreased with the increasing of temperatures, and belongs to the quenching mechanism which forms a static component. The ?H, ?S were calculated to be -17.38 kJ/moland 22.62 J/mol?K, and Gibbs free energy were -23.89, -24.12, -24.35 kJ/molaccording to the Van't Hoff equation, which indicated that the interaction was a spontaneous molecular process in which Gibbs free energy decreases and the hydrophobic interaction and the electrostatic interaction played major roles in the binding process of VCR and HSA. The dichroism spectra and synchronous fluorescence spectra proved that the protein secondary structure and conformation changed in the interaction, with the tendency of decreasing ofα-helix and increasing ofβ-pleated sheet. Furthermore, the computational modeling method was used to study the interaction, VCR could bind to the Trp-214 of HSA, and the main interaction forces were in consistent with the experimental results.The interactions of VCR with BSA and of ACET with HSA were also investigated using the same methods at different temperatures. At first, we confirmed that the interaction occurred by UV-Vis absorption spectra. And then with fluorescence quenching method, the binding properties including the fluorescence quenching mechanisms, binding constants and the number of binding sites were investigated in detail, the quenching mechanism were static quenching. The dichroism spectra and synchronous fluorescence spectra proved that the protein secondary structure and conformation changed in the interaction. For VCR and BSA, the ?H, ?S were calculated to be -62.07 kJ/moland -129.38 J/mol?K according to the Van't Hoff equation, which indicated that the hydrogen bond and the Van der Waals force played major roles in the binding process. But the ?H, ?S were calculated to be -18.32 kJ/mol and 24.61 J/mol?K, which indicated that the hydrophobic interaction and the electrostatic interaction played major roles in the binding process of ACET and HSA.