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本文用恢复电位法、荧光分光光度法及粘度法研究了镉(Ⅱ)与牛血清白蛋白(BSA)的配位平衡和pH的影响。结果表明BSA有两类镉结合部位(2个强结合和10个弱结合部位)。Cd—BSA配位反应受pH影响,在近中性pH范围Cd(Ⅱ)与BSA结合未接近饱和时,以CURFIT程序对结合曲线拟合发现,每摩尔BSA平均结合Cd(Ⅱ)摩尔数的对数值与游离镉浓度的对数间成线性关系,进一步用Marguardt法处理得到Cd(Ⅱ)与BSA结合平衡方程式:(?)=K[Cd~(2+)]~m,K和m均为pH函数。构象研究表明H~+和Cd(Ⅱ)的结合都能引起BSA构象改变。用凝胶色谱法测定了Zn(Ⅱ)、Ca(Ⅱ)、吐温—80和十二烷基硫酸钠(SDS)对Cd—BSA结合的影响。Z_n(Ⅱ)可以竞争Cd(Ⅱ)在BSA上结合部位使Cd(Ⅱ)活动化。SDS能够有效抑制Cd(Ⅱ)与BSA结合,这种作用可能与SDS引起BSA构象改变有关。
In this paper, the effect of cadmium (Ⅱ) and bovine serum albumin (BSA) coordination equilibrium and pH on the potentiometry, fluorescence spectrophotometry and viscometry were studied. The results show that there are two types of BSA cadmium binding sites (2 strong binding and 10 weak binding sites). The Cd-BSA coordination reaction is affected by pH. When the binding of Cd (Ⅱ) to BSA is not close to saturation in the near-neutral pH range, the binding curve is fitted by CURFIT program and the average number of moles of Cd (Ⅱ) The linear relationship between the logarithm and the logarithm of free cadmium concentration was further treated by the Marguardt method to obtain the equilibrium equation of Cd (Ⅱ) binding to BSA: (?) = K [Cd ~ (2 +)] ~ m, For the pH function. Conformational studies show that the conformational changes of BSA can be induced by the combination of H ~ + and Cd (Ⅱ). The effects of Zn (Ⅱ), Ca (Ⅱ), Tween-80 and sodium dodecyl sulfate on the binding of Cd-BSA were determined by gel chromatography. Z_n (Ⅱ) competes with Cd (Ⅱ) to activate Cd (Ⅱ) at the binding site of BSA. SDS can effectively inhibit the binding of Cd (Ⅱ) with BSA, which may be related to the conformational changes of BSA caused by SDS.