光谱和微量热法分析柑橘苷与BSA分子间作用及构建其理论模型

光谱和微量热法分析柑橘苷(naringin，NAR)与牛血清白蛋白（bovine serum albumin, BSA）分子间作用，构建NAR与BSA分子间作用的理论模型。采用紫外-荧光光谱法解析Fōrster方程求得NAR与BSA分子间作用及分子间作用的临界距离r，等温滴定微量热技术测定NAR与BSA分子间作用的积分量热曲线，获得Δ H并通过Gibbs-Helmholtz方程获取Δ S和Δ G。基于光谱和微量热辅助分析，构建NAR与BSA分子间作用的理论模型。结果表明，光谱法测出NAR与BSA发生分子间作用，NAR与BSA分子间作用的临界距离为2.06 nm，表明NAR与BSA分子间作用为短程分子间作用。微量热法成功测定出NAR与BSA分子间的热力学参数Δ H<0，Δ S>0，Δ G<0，说明NAR与BSA分子间作用是自发进行的放热相互作用。依据Ross理论分析NAR与BSA分子间作用力主要是疏水作用力和静电作用力。模型构建结果说明，NAR与BSA分子间作用主要发生在BSA的domain IIA区域，NAR与BSA分子间作用力主要是静电作用力，兼有范德华作用力和氢键。实验与理论模型构建结果基本一致。本研究工作可为深入了解蛋白质与大分子化合物间的作用以及研究微观药理学机制提供有益的参考。

Spectroscopic and Microcalorimetric Analysis of Intermolecular Interaction between Naringin and BSA and Its Theoretical Modeling

The intermolecular interaction between naringin (NAR) and bovine serum albumin (BSA) was studied by fluorescence spectrum and microcalorimetry. The theoretical model of the interaction between NAR and BSA was established. Δ H, Δ S and Δ G were obtained by using the isothermal titration microcalorimetric technique and Gibbs-Helmholtz equation. The Fōrster equation was used to analyze the critical distance between NAR and BSA in the UV-fluorescence spectra. Based on spectroscopy- and microcalorimetry-assisted analysis, the theoretical model of the interaction between NAR and BSA was established. The critical distance between NAR and BSA was 2.06 nm, which indicated that the interaction between NAR and BSA was short-range intermolecular interaction. The results showed that the thermodynamic parameters Δ H <0, Δ S> 0 and Δ G <0 between NAR and BSA molecules have been successfully established by microcalorimetry. These microcalorimetry results showed that the interaction between NAR and BSA was spontaneous exothermic molecule interaction. According to the Ross theory analysis of NAR and BSA, intermolecular forces are mainly hydrophobic and electrostatic forces. Based on the analysis of UV-fluorescence spectra to obtain the binding distance, the intermolecular interactions between NAR and BSA were short-range. The theoretical model results showed that the intermolecular interaction of NAR and BSA occurred mainly in the domain IIA region of BSA. The NAR and BSA intermolecular forces are mainly electrostatic forces. Both van der Waals force and the presence of hydrogen bonds and the intermolecular interaction between BSA and NAR were a spontaneous process. The experimental results are basically consistent with the theoretical modeling results. These data can provide a useful reference for a comprehensive understanding of the intermolecular interactions between biological macromolecules and flavonoids and the study of microscopic pharmacological mechanisms.