Pb^(2+)·金属离子与牛血清白蛋白的竞争结合平衡研究

Study on the Competitive Binding Equilibrium between Pb^(2+) and Metal Ions with Bovine Serum Albumin

[目的]了解Pb2+在牛血清白蛋白上的结合部位。[方法]采用平衡透析方法,研究在模拟生理(pH6.3)条件下Pb2+、金属离子与牛血清白蛋白的结合平衡,并探讨了Pb2+-BSA体系的逐级稳定常数。[结果]Pb2+在BSA上存在2类结合部位,BSA对Pb2+有1.6个强结合部位和6.5个弱结合部位。Pb2+在白蛋白分子中可能存在第1个较强的结合部位,与Zn2+相同。Pb2+在白蛋白分子中可能存在第2个较强的结合部位,与Cu2+相同。Zn2+-Pb2+-BSA三元体系中强结合部位数明显减少,说明Pb2+的优先配位基团在位点siteA。通过非线性最小二乘法拟合Bjerrum方程,确定Pb2+-BSA体系的逐级稳定常数约为104。[结论]该研究可为判断Pb2+在BSA上各结合部位之间的协调性提供参考。

[Objective] The research aimed to understand the binding sites of Pb^2＋ on bovine serum albumin（BSA）.[Method] Using equilibrium dialysis method,the binding equilibrium of Pb^2＋ and metal ions with BSA under the simulated physiological conditions（pH 6.3） was studied.And the successive stability constants of Pb^2＋-BSA system were discussed.[Result] There were two kinds of binding sites of Pb^2＋ on BSA.BSA had 1.6 strong binding sites and 6.5 weak bindings sites with BSA.Pb^2＋ probably had the first stronger binding site in the albumin molecule,which was the same as Zn2＋.Pb^2＋ probably had the second stronger binding site in the albumin molecule,which was the same as Cu2＋.The number of stronger binding sites in Zn2＋-Pb^2＋-BSA system obviously decreased,which indicated that the priority coordination group of Pb^2＋ was located at site A.Bjerrun formula was fitted by non-linear least-square method.And the successive stability constant of Pb^2＋-BSA system was confirmed as about 104.[Conclusion] The research could provide references for judging the coordination among different binding sites of Pb^2＋ on BSA.