平衡透析和差示吸收光谱法研究铅(Ⅱ)与BSA的相互作用

The interaction between Pb (Ⅱ) ions and BSA studied by equilibrium dialysis and differiential absorption spectrum

使用平衡透析和差示紫外吸收光谱法研究了铅(Ⅱ)与牛血清白蛋白(BSA)的相互作用.平衡透析的实验结果表明铅(Ⅱ)与BSA的相互作用受缓冲溶液pH的影响,在pH为6.3和pH为5.4条件下,铅(Ⅱ)在BSA上的强结合位点数分别是1.5个和0.8个,弱结合位点数分别为6个和4个,用非线性最小二乘法拟合Bjerrum方程,报道了铅(Ⅱ)-BSA体系的逐级稳定常数,Hill系数表明铅(Ⅱ)与BSA的结合部位之间有负协同效应.使用差示紫外吸收光谱法研究铅(Ⅱ)-BSA体系的电荷转移谱带,发现组氨酸咪唑基是铅(Ⅱ)在BSA中的优先配位基团.进一步根据Zn2+与Pb2+竞争结合BSA上的强结合位点,推断Pb2+在BSA中优先结合位点是位点A.

The binding of Pb2＋ to bovine serum albumin（BSA） has been studied by equilibrium dialysis.The results showed that the interaction between Pb2＋ ions and BSA was significantly influenced by pH of buffer solution.There existed 1.6 and 0.8 strong bindings site within BSA at pH6.3 and pH5.4 respectively.The successive stability constants which are reported for the first time are obtained by non linear least square method fitting Bjerrum formula.For Pb2＋-BSA sys-tems,The analyses of Hill plot indicate that there exists weak negative cooperative effect in Pb2＋-BSA systems.The charge transition absorption bands of Pb2＋-BSA system had been further studied with differential absorption spectrum.The results indicated that histidine imidazole nitrogen was the preferential binding groups of Pb2＋ ions in BSA.The results of Pb2＋ ions competing with Zn2＋ ions to bind to the strong binding site in BSA suggested that the primary binding site for Pb2＋ ions was site A in albumin.