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应用恒温微量热技术和平衡渗析技术,对尿素与牛血红蛋白在30℃水溶液中的结合作用及造成牛血红蛋白变性的过程进行了研究,得到了尿素在牛血红蛋白上的平均结合数、二者之间的结合焓及每摩尔尿素与牛血红蛋白结合的焓效应,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.对实验结果的热力学分析表明,尿素是通过直接和间接的两种作用造成牛血红蛋白变性的,它们之间的相互作用分为三个阶段:尿素浓度达到4molL-1之前为第一阶段,主要产生的是尿素与牛血红蛋白的直接结合作用,在弱酸性条件下这种作用较强;尿素浓度为4molL-1到6molL-1之间为第二阶段,主要通过尿素与溶剂水的作用造成牛血红蛋白周围水结构的变化,在尿素浓度达到6molL-1时两种作用的叠加造成牛血红蛋白结构的破坏,暴露出原来处于结构内部的基团;尿素浓度超过6molL-1之后为第三阶段,尿素分子继续与暴露出来的基团进行结合.牛血红蛋白次级结构的维系具有协作性,其结构的破坏不是渐进的,而是一次性全部打开,结构破坏产生的热效应并不太大.
The combination of urea and bovine hemoglobin in aqueous solution at 30 ℃ and the process of denaturation of bovine hemoglobin were studied by means of constant temperature microcalorimetry and equilibrium dialysis. The average binding number of urea on bovine hemoglobin was obtained. , And the enthalpy of binding between urea and bovine hemoglobin per unit urea, and according to the simple binding model, the binding constants and free energy were calculated.The thermodynamic analysis of the experimental results showed that urea was directly and indirectly The role of the role of bovine hemoglobin denatured, the interaction between them is divided into three stages: urea concentration reached 4molL-1 before the first phase, the main is the direct binding of urea and bovine hemoglobin, in weakly acidic conditions This effect is strong; urea concentration of 4molL-1 to 6molL-1 for the second phase, mainly through the role of urea and solvent water caused by changes in the structure of water around the bovine hemoglobin in the urea concentration of 6molL-1 when the two The superimposition of the action causes the destruction of the structure of bovine hemoglobin, exposing the group originally in the structure; after the concentration of urea exceeds 6 molL-1 For the third phase, the urea molecules continue to combine with the exposed groups.The maintenance of the secondary structure of bovine hemoglobin is collaborative, the destruction of its structure is not gradual, but all at once, and the thermal effect caused by structural destruction is not Too big.