黄芩素及黄芩苷与牛血清白蛋白结合作用比较研究及葡萄糖的影响

目的比较研究黄芩素和黄芩苷与牛血清白蛋白(BSA)分子间的结合作用及机制。方法通过光谱法比较研究黄芩素和黄芩苷与BSA结合作用,并观察葡萄糖对二者与BSA结合的影响。以能量传递原理和Lineweaver-Burk双倒数方程计算二者与BSA反应的结合常数和结合距离;以热力学参数判断二者与BSA间的作用力类型;以同步荧光技术考察黄芩素和黄芩苷对BSA构象的影响。结果黄芩素和黄芩苷与BSA反应的结合常数和结合距离均随着温度的升高而降低;与黄芩素相比,黄芩苷与BSA的结合距离增大,作用强度减弱。葡萄糖能明显增加二者与BSA的结合常数及结合位点。黄芩素与BSA的结合力为氢键和范德华力、黄芩苷为静电引力,从而导致BSA内在荧光静态猝灭。黄芩素和黄芩苷均能使BSA构象发生变化,黄芩素还能使BSA的色氨酸所处环境的疏水性降低。结论黄芩素分子上糖取代可降低其与BSA之间的结合作用并改变其作用力类型。生理浓度的葡萄糖可明显增加黄芩素和黄芩苷与BSA的结合常数及结合位点。

The comparative studies on the interaction of baicalein and baicalin with bovine serum albumin and the influence of glucose

Aim To compare the interactions of baicalein and baicalin with bovine serum albumin (BSA) and their mechanism. Methods The binding reactions of baicalein and baicalin with BSA and the effects of glucose on them were studied by spectroscopy to compare the binding constants and binding distances of baicalein-BSA and baicalin-BSA,which were calculated according to Lineweaver-Burk equation and F?ster' energy transfer theory. Thermodynamic parameters were used to calculate the types of interaction force between BSA with baicalein or baicalin and the technique of synchronous fluorescence spectra was used to observe the effects of baicalein or baicalin on the conformation of BSA. Results Both the binding constants and binding distances of baicalein-BSA and baicalin-BSA decreased with temperature increasing and were increased by glucose. Relative to baicalein,the binding affinity of baicalin to BSA decreased obviously with an increase in binding distance. Both baicalein and baicalin could form non-covalent compounds with BSA mainly to quench the intrinsic fluorescence of BSA through a static quenching procedure. Baicalein could interact with BSA through hydrogen bonds and Van der Waals force,and baicalin did it mainly through electrostatic force. Though baicalein or baicalin could induce the conformational changes of BSA by binding reaction,only the former reduced the hydrophobicity in microenvironment around the tryptophan moieties of BSA. Conclusions The glycosylation substitution of baicalein molecule can decrease the binding to BSA (baicalin-BSA) and change the types of interaction force. The physiological concentration of glucose increases the binding constants and the number of binding sites of baicalein and baicalin with BSA.