考拉维酸对人血清白蛋白结构的影响

Effect of Kolavenic Acid on the Structure of Human Serum Albumin

利用多种荧光光谱法、紫外光谱法并结合分子模拟等方法,表征了模拟生理条件下一种植物药活性组分考拉维酸(KA)影响人血清白蛋白(HSA)的结构信息.同步荧光及紫外光谱证实考拉维酸的存在影响了HSA的微环境;二维及三维荧光光谱表明考拉维酸可以猝灭HSA的内源荧光,使其构象发生变化.荧光偏振的测定提供了考拉维酸与HSA作用后生成的配合物弛豫时间与聚集特性的信息,揭示KA的存在使HSA的流动性和微粘度发生变化.定量求得不同温度下(298、308和318 K)考拉维酸与HSA作用的键合参数和热力学参数.分子模拟表明考拉维酸键合位点于HSA分子的疏水腔内,并与赖氨酸Lys195和天冬氨酸Asp451形成三个氢键,与HSA的键合模式主要是疏水作用;位点竞争实验证明考拉维酸在HSA亚结构域的位点II位发生作用.另外,获得的相关物理化学参数从分子水平上揭示了考拉维酸与HSA相互作用的机制.结果表明,HSA对考拉维酸有较强的结合能力,提示人血清白蛋白对考拉维酸可起到储存和转运的作用.

The effect of Kolavenic acid （KA）, an active component isolated from the genus Polyalthia, on the structure of human serum albumin （HSA） was investigated by fluorescence polarization, synchronous fluorescence, three-dimensional （3D） fluorescence, and absorption spectroscopy in combination with molecular modeling techniques under physiological conditions. The synchronous and absorption fluorescence spectra confirmed that KA has an effect on the microenvironment around HSA in aqueous solution. The two-dimensional （2D） and 3D fluorescence spectra showed that KA could quench the intrinsic fluorescence of HSA and make its conformation change. Fluorescence polarization measurements provided useful information on the relaxation time and aggregation behavior of the complex formed between HSA and KA, and indicated that the presence of KA caused changes in the fluidity and microviscosity of HSA. The binding constants and thermodynamic parameters for KA-HSA systems were obtained under different temperatures （298, 308, and 318 K）. Molecular docking showed that the KA moiety bound to the hydrophobic cavity of HSA, and there were three hydrogenbonding interactions between KA and the Lys195 and Asp451 residues. Fluorescent displacement measurements confirmed that KA bound to HSA at site II. In addition, the binding mechanism of KA and HSA was revealed by the physicochemical parameters at the molecular level. The results showed that the interaction between KA and HSAwas strong, indicating that KA may be stored and transferred by serum albumin.