维生素B_6与牛血清白蛋白相互作用的液滴荧光法研究

Investigation on the interaction between VB_6 and bovine serum albumin by fluorescence analysis based on liquid drop

利用荧光及紫外光谱法研究了生理pH条件下水溶液体系中维生素B6与牛血清白蛋白(BSA)的相互作用机制。维生素B6对牛血清白蛋白的荧光有较强的猝灭作用,其猝灭类型为静态猝灭。根据F rster的偶极-偶极非辐射能量转移理论算出供体-受体的结合距离为2.72 nm。由Linewear-Burk方程求出不同温度下反应时复合物的形成常数KLB和结合位点数n及对应温度下结合反应的热力学参数,证明二者主要靠氢键和范德华力结合。同时采用同步荧光分析技术,对蛋白质与药物结合时构象的变化进行了探讨。

Under the physiological conditions of the body,the interaction between VB6 and bovine serum albumin（BSA） was investigated by fluorescence spectrometry and ultraviolet absorption（UV） spectrometry based on liquid drop.The experimental results showed that VB6 quenched the fluorescence of BSA by forming a VB6-BSA complex.According to the relation between thermodynamic parameters and the interaction force,VB6 depended principally on the dispersive interaction to bind with BSA.The results showed that the quenching belonged to static fluorescence quenching with non-radiation energy transfer happening within single molecule. The binding locality was an area 2.72 nm away from tryptonphan residue-212 in BSA according to Forster＇s non-radiation energy transfer mechanism. The conformational changes of BSA were evaluated by measuring the synchronous fluorescence intensity of protein amino acid residues, both before and after the addition of VB6. A slightly stronger blue-shift of tryptophan fluorescence upon the addition of drug was observed, and the emission maximum of tyrosine kept its position. It suggested that the environments of tryptophan residues in pure albumin solution are relatively polar. Binding of VB6 changes the environments into apolar ones. The shift in polarity is brought about by confirmation changes due to the interaction between albumin and ligand molecule.