百草枯与牛血清白蛋白结合作用的荧光光谱

Fluorescence Spectra of the Binding Reaction between Paraquat and Bovine Serum Albumin

在模拟动物体生理条件下,用荧光光谱和紫外-可见吸收光谱法研究了在不同温度下,百草枯(PQ)与牛血清白蛋白(BSA)结合反应的光谱行为.试验发现,PQ对BSA有较强的荧光猝灭作用.用Stern-Volmer和Lineweaver-Burk方程分别处理试验数据,发现BSA与PQ发生反应生成了新的复合物,属于静态荧光猝灭,发生分子内的非辐射能量转移.根据F?rster的偶极-偶极非辐射能量转移理论计算出结合位置距离212位色氨酸残基2.07nm.由Lineweaver-Burk方程求出了不同温度下反应时复合物的形成常数KLB(297K:2.035×104L?mol-1;304K:3.256×104L?mo-1;311K:2.889×104L?mol-1)及对应温度下结合反应的热力学参数(?H=18.50kJ?mol-1;?S=144.7J?K-1/145.2J?K-1/141.0J?K-1;?G=-24.50kJ?mol-1/-25.66kJ?mol-1/-25.36kJ?mol-1),证明二者主要靠疏水作用力结合.同时用三维荧光光谱及同步荧光光谱法探讨了PQ对BSA构象的影响,为预防和医治PQ中毒提供了重要依据.

Under the imitated physiological condition of animal body, the binding of paraquat to bovine serum albumin （BSA） was studied by fluorescence spectrum and ultra-violet spectrum. It was shown that this compound has a quite strong ability to quench the fluorescence launching from BSA. After analyzing the fluorescence quenching data according to Stern-Volmer equation and Lineweaver-Burk double-reciprocal equation, we found that BSA had reacted with paraquat and formed a certain new compound. The quenching belonged to static fluorescence quenching, with non-radiation energy transfer happening within single molecule. The binding locality was an area 2.07 nm away from tryptophan residue-212 in BSA based on F（oe）rster＇s non-radiation energy transfer mechanism. According to Lineweaver-Burk equation, KLB （297 K： 2.035×10^4 L·mol^-1; 304 K： 3.256×10^4 L·mo^-1; 311 K： 2.889×10^4 L·mol^-1）, the forming constants of the compound at different temperatures and the thermodynamic parameters （△H^⊙ = 18.50 kJ·mol^-l; △S^⊙ = 144.7 J·K^-1/145.2 J·K^-1/141.0 J·K^-1; △G^⊙ =-24.50 kJ·mol^-l/-25.66 kJ·mol^-l/-25.36 kJ·mol^-1） at correspondence temperatures were obtained. The latter shows that binding power between them is mainly the hydrophobic interaction. The effect of paraquat on the conformation of BSA was analyzed by three-dimensional fluorescence spectra, contour spectra and synchronous spectra, and some useful information was offered for preventing animals from infecting paraquat and curing those who had caught it.