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[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] To understand the binding sites of Pb2 + on bovine serum albumin. [Method] The balance of Pb2 +, metal ions and bovine serum albumin in simulated physiological (pH6.3) conditions was studied by equilibrium dialysis method, and the stepwise stability constants of Pb2 + -BSA system were discussed. [Result] There were two kinds of binding sites on BSA for Pb2 +, and 1.6 strong binding sites and 6.5 weak binding sites on Pb2 +. Pb2 + may have the first strong binding site in albumin molecules, which is the same as Zn2 +. Pb2 + may have the second strongest binding site in albumin, which is the same as Cu2 +. Zn2 + -Pb2 + -BSA ternary system significantly reduced the number of strong binding sites, indicating that priority Pb2 + coordination site in siteA. By fitting the Bjerrum equation by nonlinear least square method, the step-by-step stability constant of Pb2 + -BSA system was determined to be about 104. [Conclusion] This study may provide reference for judging the coordination of Pb2 + binding sites in BSA.