白杨素与不同构型人血清白蛋白的作用机制

采用多种光谱学手段研究了白杨素(CHR)和不同构型人血清白蛋白(HSA)相互作用的分子机制.研究表明,白杨素能使蛋白质荧光发射峰发生静态淬灭,同时,白杨素的紫外吸收谱带也发生了明显的位移,说明与蛋白质的结合可使白杨素分子中的酚羟基发生解离.蛋白质还可以引起白杨素荧光发射峰强度的明显增强.利用荧光淬灭和荧光增强两种模式计算得到的白杨素和人血清白蛋白在生理条件下(pH 7.4)的结合常数(KA)分别为(9.97±0.24)×104和(9.75±0.11)×104L mol-1,其结合比例为1:1.随着pH值的降低,蛋白质与白杨素的结合常数逐渐减小,这与蛋白质的构型变化有关.根据不同异构体血清蛋白质的结构特征,判定白杨素在蛋白质分子上的结合位置位于IIA亚域的Site I活性位点.结合分子模拟,讨论了白杨素与蛋白质分子的结合机制.

Mechanism of Interaction between Chrysin and Different Configurations of Human Serum Albumin

The mechanism of the interaction between Chrysin (CHR) and human serum albumin (HSA) was investigated using various spectroscopic techniques. It was found that CHR can induce HSA fluorescence emission quenching by static process. Additionally, HSA caused a significant red shift in the ultraviolet absorption of CHR. This indicated that binding with a protein can result in dissociation of the phenolic hydroxyl in CHR. HSA can also cause CHR fluorescence emission. The binding constants of CHR and HAS were calculated based on the fluorescence quenching and emission modes. The results obtained using these two methods were consistent. The binding constant (K_A) values at pH 7.4 were (9.97±0.24)×10⁴ and (9.75±0.11)×10⁴ L·mol^-1, respectively; and the ratio of combination was 1:1. The binding constants decreased gradually with decreasing the pH value. This is related to conformational changes in the protein. The protein is partly denatured at pH 3.5, with the site Ⅱ in the HSA opening chain. It was found that CHR was located at site I, which is in subdomain ⅡA of HAS. Based on molecular modeling, the mechanism of the interaction between CHR and HAS was investigated.