酸度对氧氟沙星与牛血清白蛋白结合的影响

牛血清白蛋白在不同pH的溶液中存在N（pH ～7.0），B（pH ～9.0）和E（pH 3.5以下）等几种同分异构形态。 采用紫外-可见光谱和荧光光谱研究了酸度对牛血清白蛋白（BSA）的结构以及对不同结构的BSA和氧氟沙星的相互作用的影响，应用荧光猝灭现象和Frster理论，求出了4个不同pH下两者结合的猝灭常数、 能量转移效率和结合距离等参数。结果显示，氧氟沙星与牛血清白蛋白在pH 4.9时结合常数最大（1.928 1×105 L·mol-1），结合距离小（r=2.55 nm），猝灭效应最好（8.63×104 L·mol-1）；氧氟沙星与牛血清白蛋白的结合过程中，静态猝灭和非辐射能量转移是导致牛血清白蛋白荧光猝灭的原因；中性、 弱酸和弱碱性环境对两者的结合没有太大的影响，静电作用不是两者相互作用的主要作用力。使用同步荧光技术考察了氧氟沙星对BSA构象的影响。

Effect of Acidity on the Interaction of Oflxacin and Bovine Serum Albumin

Bovine serum albumin (BSA) exists as N(pH -7.0), B(pH -9.0), and E (pH＜3.5)＝ isomeric forms in the solution of different pH. Acid effect on the structure of bovine serum albumin and the interaction of different structure of BSA with Oflxacin were studied by UV-Vis and fluorescence spectroscopy. Based on the fluorescence quenching of bovine serum albumin and Frster energy transfer mechanism, the quenching constants, energy transfer efficiencies and the binding distances were determined at four different pHs. The results showed that Oflxacin has the ability to quench bovine serum albumin fluorescence with the optimal condition of fluorescence quenching constants of 1.928 1×105 L·mo·l-1, binding distance of r=2.55 nm and quenching efficiency of 8.63×104 L·mo·l-1 at pH 4.9. Non-radiative energy transfer and static quenching were the cause of fluorescence quenching. The influence on the binding of Oflxacin and bovine serum albumin under neutral, subacidity and alkalescent conditions was not obviously observed, and the electrostatic interaction was not the main force. The effect of Oflx on the conformation of BSA was also investigated using synchronous fluorescence spectrometry.