光谱法研究哈巴俄苷与人血清白蛋白的结合反应

在不同温度及模拟血液pH值条件下,采用荧光光谱法和紫外-可见吸收光谱法研究了哈巴俄苷(Harpagoside, HAR)与人血清白蛋白(Human serum albumin, HSA)的结合反应.结果表明,HAR有规律地使HSA内源荧光猝灭,猝灭常数随温度升高而降低,其猝灭机制为两者形成复合物而引起的的静态猝灭;不同条件下两者结合常数KA均大于105 L/mol,结合位点数n≈1.由Van′t Hoff方程计算获得了不同条件下HAR与HSA相互作用的热力学参数,由ΔG、ΔH和ΔS均小于0可知,两者结合的主要作用力是氢键和范德华力,且两者结合是吉布斯自由能降低的自发过程.根据F(o)rster非辐射转移理论计,计算了不同条件下HAR与HSA的结合距离r在4.01~4.28 nm范围内,表明两者结合过程发生了非辐射能量转移.同步荧光光谱表征结果表明,HAR使HSA的色氨酸和酪氨酸残基所处的微环境极性增强,疏水性减弱,导致HSA构象发生了一定程度的改变.

Spectroscopic Study of Interaction of Harpagoside and Human Serum Albumin

Harpagoside (HAR) is believed to be a main compound in Scrophularia ningpoensis which possess a broad of biological activities.Human serum albumin (HSA) has important physiological roles in transportation, distribution and metabolism of many endogenous and exogenous substances in body.It is great significance in pharmacology to investigate the interaction mechanism of HAR and HSA.In this work, the interaction between HAR and HSA was investigated by fluorescence and ultraviolet absorption spectroscopy at different pH (pH=4.0, 7.4, and 9.0) and temperatures (297, 310 and 323 K).The experimental results showed that the HAR could cause the fluorescence quenching of HSA through a static quenching procedure, showing that the HAR regularly quenched the intrinsic fluorescence of HSA, and a decrease in the quenching constant was observed with an increase in temperature.Under different conditions, all the magnitude of binding constants (KA) was larger than 105 L/mol and the number of binding sites (n) in the binary system were approximate to 1.Base on the magnitude of enthalpy and entropy changes, the negative values of ΔG, ΔH and ΔS revealed that the binding of HAR with HSA was spontaneous and exothermic process, and the main interaction forces of the HAR with HAR were van der Waals forces and/or hydrogen bonding interaction.The binding distance (r) between the HAR and HSA was calculated to be about 4.2 nm based on the theory of F(o)rster′s nonradiation energy transfer, which indicated that the energy transfer from HSA to HAR occurred with high possibility.What was more, the synchronous florescence spectroscopy confirmed the conformational changes of HSA during the binding reaction.