盐酸胍诱导牛血红蛋白变性的微量热研究

Denaturation Study of Bovine Hemoglobin Induced by Guanidine Chloride by Microcalorimetry

应用恒温微量热技术,对盐酸胍与牛血红蛋白在30°C水溶液中的结合作用及造成牛血红蛋白变性的过程进行研究,并根据简单结合模型,计算了它们之间的结合常数、结合自由能。用变性中点的直线外推方法求出了表观变性焓。实验结果表明,盐酸胍诱导牛血红蛋白变性的相互作用分为3个阶段。牛血红蛋白在盐酸胍溶液中的变性焓在pH5.21时为200 kJ.mol-1,在pH6.70时为540 kJ.mol-1,在pH8.03时为120 kJ.mol-1。牛血红蛋白在pH6.70时,即在等电点时,较稳定。

The interactions between guanidine chloride and bovine hemoglobin in aqueous solution as well as the denaturation process of bovine hemoglobin were studied by using isothermal microcalorimetry method at 30 ℃ and three pHs. The simple binding model was employed to obtain the binding constants and the binding free energies. Furthermore,the linear extrapolation at the midpoint of transition was employed to determine the apparent denaturation enthalpy. The results showed that the interactions between guanidine chloride and bovine hemoglobin is divided into three stages. The apparent denaturation enthalpy of bovine hemoglobin by guanidine chloride is 200 kJ · mo1-1 at pH5.21 and 540 kJ· mo1-1 at pH6. 70,while it is 120 kJ · mo1-1 at pH8.03. BHb is most stable at its isoelectric pH.