多光谱法与分子对接法研究盐酸四环素与牛血清白蛋白的相互作用

盐酸四环素属于抗生素类, 目前有关盐酸四环素和牛血清白蛋白二级结构的影响及作用机理报道较少。在模拟生理条件下，采用荧光光谱法、三维荧光光谱法、紫外-可见光谱法、圆二色谱法和傅里叶红外光谱法以及分子对接模拟法，研究了盐酸四环素与牛血清白蛋白(BSA)之间的相互作用。荧光光谱表明，盐酸四环素能有效猝灭BSA的内源荧光，猝灭机制属静态猝灭，通过Stern-Volmer方程计算结合常数Ka为2.813×105 L·mol-1(298 K)。根据Vant’s Hoff方程确定结合过程中的热力学参数ΔS=-151.1 J·mol-1·K-1、ΔH=-76.09 kJ·mol-1_， 两者之间作用为氢键和范德华力。同步荧光光谱、紫外光谱、三维荧光光谱、红外光谱、圆二色谱结果证明盐酸四环素能够改变BSA的二级结构和微环境。根据Föster’s非辐射能量转移理论，盐酸四环素与BSA结合距离为0.49 nm。希尔系数(n_H)值小于1，表明盐酸四环素与BSA结合后存在药物间协同作用。圆二色谱(CD)定量测定了盐酸四环素与BSA作用前后的二级结构含量：α-螺旋含量增加了9.16%(1:1)。分子对接模拟表明盐酸四环素通过氢键、疏水作用和范德华力等多种作用力结合在BSA的site Ⅰ(亚域ⅡA)。本研究有助于了解盐酸四环素与BSA的作用机制，也有助于理解盐酸四环素对蛋白质在储运过程中功能的影响。

Study on the Interaction between Tetracycline Hydrochloride and Bovine Serum Albumin by Multispectral and Molecular Docking

Tetracycline HCl is a new member of the class of antibiotics. Therefore, its effects on the secondary structural of Bovine Serum Albumin, and the mechanism of action are poorly understood. The interaction between Tetracycline HCL and BSA were investigated with fluorescence spectroscopy, three-dimensional fluorescence spectroscopy, ultraviolet spectroscopy, circular dichroism (CD), infrared spectroscopy and molecular docking under imitated physiological conditions. The analysis of fluorescence spectra showed that Tetracycline HCl could strongly quenching the fluorescence of BSA and the quenching process is a static process. The effective binding constants (Ka) were calculated to be 2.813×105 L·mol-1(298 K) by stern-volmer equation. According to the Vant’s Hoff equation, the thermodynamic parameters were calculated to be ΔS=-151.1 J·mol-1·K-1 ，ΔH=-76.09 kJ·mol-1，indicating that the predominant forces in the complex were hydrogen bonding and Van der Waals forces. The results of synchronous fluorescence, UV spectrum , FT-IR , CD spectrum and three dimensional fluorescence spectrum, futher demonstrated that the secondary conformation and micro-environment of BSA has been changed after interaction with Tetracycline HCL. Based on the Föster’s theory of non-radiation energy transfer, and the specific binding distance between Tetracycline HCL-BSA system was 0.49 nm. Hill’s coefficients (n_H<1) proved that a negative cooperativity was found when Tetracycline HCLbound to BSA. The alteration of the protein secondary structure were quantitatively calculated from circular dichrosim (CD) spectroscopy with increase of α-helix content about 9.16%(1:1). The result of molecular docking simulation revealed that Tetracycline HCL was located in sudlow’s site I corresponding to subdomain IIA through multiple interactions-hydrogen bond, hydrophobic and vander waals, etc. This research will provide valuable information for understanding the action mechanism of Tetracycline HCl with BSA, and is helpful for understanding its effect on protein function during the storage and transport process.