光谱法与分子模拟研究胡椒碱对牛血清白蛋白的键合作用

Investigation on the Binding of Piperine to Bovine Serum Albumin by Optical Spectroscopy and Molecular Modeling

利用荧光光谱法及紫外吸收光谱法结合计算机模拟技术研究了在模拟生理条件下胡椒碱(piperine)与牛血清白蛋白(Bovine Serum Albumin,BSA)的相互作用.根据荧光猝灭的有关方程分别求得不同温度下(298,308和318K)药物与蛋白相互作用的结合常数、结合位点数及键合距离.实验所得到的热力学参数(ΔHθ=-9.55kJ/mol,ΔSθ=46.75J·mol-1·K-1)表明维持药物与蛋白质的相互作用力主要是疏水作用和静电作用.分子模拟的结果显示了胡椒碱与BSA的键合机理和键合模式,表明维持药物与蛋白质的相互作用力主要是疏水作用和氢键(位于氨基酸残基His242,Arg222和Arg218位).此外,基于胡椒碱的荧光猝灭效应,首次探讨了药物-蛋白质体系的几种物理化学参数,包括电荷密度(δ)、离解常数(Kd)及量子产率(Φ)的变化效应.

The interaction of piperine with bovine serum albumin （BSA） was investigated by fluorescence and absorption spectra in combination with molecular modeling under the simulated physiological conditions. The binding constants and the number of binding sites between piperine and BSA at different temperatures （298, 308 and 318 K） were calculated according to the data obtained from fluorescence titration. The results of spectroscopic measurements and the thermodynamic parameters obtained （the enthalpy change △H and the entropy change △S were calculated to be --9.55 kJ·mol^-1 and 46.75 J·mol^-l·K^-1 according to the Van＇t Hoff equation） suggested that hydrophobic and electrostatic interaction be the predominant intermolecular forces stabilizing the complex. Molecular docking was performed to reveal the possible binding mode or mechanism, suggesting that piperine can strongly bind to BSA. Under the conditions studied, the values of the negative charge density （δ）, the dissociation constants （Kd） and quantum yield （φ） of piperine-BSA system were calculated.