运用离子选择性电极研究氟离子与蛋白质的相互作用

Study on the Interactions of Fluoride Ion with Proteins Using Ion-selective Electrode

在醋酸-醋酸钠缓冲溶液中(pH=5.68),运用氟离子选择性电极研究了288～308K时F-与牛血清蛋白(BSA)、牛血红蛋白(BHb)和卵清蛋白(OVA)的相互作用.F-和3种蛋白质相互作用体系的实验数据通过Klotz方程进行处理,得到了很好的线性关系,根据拟合的直线得到了F-在3种蛋白分子上的束缚位点数以及相应的束缚常数.结果表明,F-在BSA和BHb分子上的束缚位点数随着温度的升高而增大,而在OVA分子上的束缚位点数随着温度的升高而减小.另外,F-与BSA和BHb作用的束缚常数随着温度的升高,先减小后增大;而与OVA的束缚常数则表现出相反的规律,即先增大后减小.根据蛋白质分子二级结构的差别,对上述现象进行了合理的解释.运用热力学方程计算出了不同温度下每个束缚过程的热力学函数(△G,△H,△S),说明F-和蛋白质分子之间主要依靠静电作用力相结合.

The interactions of fluoride with bovine serum albumin （BSA）, bovine hemoglobin （BHb） and ovalbumin （OVA） were studied in acetate buffer （pH=5.68）, at 288, 298 and 308 K, using a fluoride ion-selective electrode. The data for the fluoride-protein systems were treated according to the Klotz equation, and the number of binding sites and the binding constants were found. It was shown that the number of fluoride-binding sites （n） in BSA and BHb increases with increasing temperature, while for OVA, the value of n decreases under the same condition. At the same time, our studies indicate that the binding constants of BSA and BHb systems first decrease and then increase with increasing temperature. While for OVA, the results are reverse. These were reasonably interpreted with the structural and thermodynamic factors. The thermodynamic function changes of the binding process （ΔGe, ΔHe, ΔSe） at different temperatures were calculated with thermodynamic equations, which show that the binding power between F- and proteins is mainly an electrostatic interaction.