A notable hysteretic effect has been observed in the interaction of Ni2 + ion with human or bovine serum albumin using UV-Visible spectrometry, which shows that the binding of Ni2+ ion can induce a slow transition of HSA and BSA from the conformation of weaker affinity for Ni2+ ion to the one of stronger affinity (T - R transition). This conformational transition is supported by the time dependence of the optical rotation of the samples. The rate constants and activation parameters of these transitions have been measured and discussed. It is inferred that such a conformational transition may mainly occur in the IA subdomain of the proteins,and is likely to be a "hinged movement", which makes the IA subdom ain become more open.%用紫外光谱观察到Ni2+离子与人或牛血清白蛋白相互作用有显著的滞后效应,表明Ni2+离子的结合可以诱导人或牛血清白蛋白发生从对Ni2+离子有较弱亲和力至较强亲和力构象态的缓慢变化(T-R转化);这一构象变化为试样的旋光能力随时间变化进一步证实;测得并讨论了这一构象变化的速度常数和活化参数;推测这一构象变化可能主要发生在蛋白质的IA亚区,并且很可能是一种促使IA亚区变得更加开放的"绞链式运动".
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