基于蛋白构象变化研究pH值对茜素红与牛血清白蛋白相互作用的影响

Study on Effect of pH Value on Interaction between Alizarin Red S and Bovine Serum Albumin Based on Conformational Changes in Protein

利用光谱法和分子对接技术研究了不同pH值对牛血清白蛋白(BSA)与茜素红(ARS)键合作用的影响。pH值为4.0的酸性环境引起BSA天然紧缩构象逐渐发生去折叠,BSA的ⅡA区疏水空腔的展开降低了其与ARS的相互作用,键合常数Kb仅为3.39×104L·mol-1。而pH值大于等电点(pI 4.8)或呈现中性时,两者的键合作用增强,Kb增至3.16×106L·mol-1(pH 7.0)。而且,由于氢键和范德华力的键合作用力较强,BSA和ARS的相互作用受表面电荷影响较小,与理论模拟对接结果相吻合。

The interactions between alizarin red S （ARS） and bovine serum albumin （BSA） at various pH values were investigated by spectrometry and molecular docking technique. At pH 4. 0, the natu- ral compact conformation of BSA was unfolded gradually, which led to the exposure of hydrophobic cavity of domain 1I A in BSA and decreased the interaction between BSA and ARS. Consequently, the binding constant Kb is only 3.39 x 104 L · mol-1. However, when the pH value was higher than the isoelectric point（pI 4. 8 ）of BSA, the interaction between BSA and ARS was enhanced and Kb in- creased to 3.16 x 106 L · mol-1 at pH 7.0. Moreover, the effect of surface charges on the interaction of BSA with ARS was not obvious due to the strong hydrogen bonds and van der Waals, forces, which was in accord with the results of molecular docking.