黄体酮(Progesterone, PROG)是临床用于治疗先兆流产的常用药物之一, 但其在生物体内的运输机制尚不明确。本文整合荧光光谱、红外光谱及分子对接等实验技术研究了PROG和牛血清白蛋白(BSA)之间的相互作用机制。光谱学实验结果表明, PROG在BSA的结合位点Ⅰ处与其结合, 从而引起BSA的内源荧光猝灭, 猝灭机制为静态猝灭和非辐射能量转移, 两者之间的结合距离为1.63 nm。在人体正常体温条件下, 两者的结合常数为1.423×104 L·mol-1。根据热力学公式计算得到两者结合过程中ΔH=－65.31 kJ·mol-1和ΔS=－131.63 J·mol-1·K-1, 说明PROG和BSA之间的主要作用力为氢键和范德华力。红外光谱研究结果表明,PROG能使BSA构象发生改变, 其中α-螺旋结构和β-片层结构含量下降, β-折叠结构含量上升。分子对接结果表明,PROG与Trp214之间的相互作用是引起BSA荧光猝灭的主要原因, 且PROG与Lys195残基之间存在的氢键有利于PROG-BSA复合物的稳定。分子对接结果与光谱实验结果相互印证, 为揭示PROG在人体运输储藏过程提供了数据支撑。

Progesterone(PROG) is a common drug for treatment of threatened abortion in clinical practice, but its transport mechanism in human body is still unclear. Here, fluorescence spectrum, infrared spectrum, and molecular docking were employed to comprehensively analyze the mechanism underlying the interaction between PROG and bovine serum albumin (BSA). The results indicated that a stable PROG-BSA complex was formed and van der Waals forces played a major role in this binding process. The order of magnitude of the binding constants (Ka) was 1.423×104 L·mol-1 at normal body temperature of human. Solution experiments showed that the binding site for PROG was located at Sudlow site I of BSA, and the distance between PROG and BSA was obtained(r=1.63 nm) according to the Frster theory of non-radiative energy transfer. Infrared spectrum results revealed the changes in secondary structure of the protein upon interaction with PROG. The results of Ligplus+ highlighted the role of hydrogen bonds in the bind process whereas in well agreement with solution experiments. The data of spectrum and molecular docking experiments confirmed each other, which provided data support for revealing the transport and storage process of PROG in human body. This work will be helping us to understand the binding mode of PROG-BSA system and provide a new insight about the effect of PROG on human health.