Conejero-Lara F, Mateo P L, Aviles F X, Sanchez-Ruiz J M
Departamento de Quimica Fisica (Facultad de Ciencias) e Instituto de Biotecnologia, Universidad de Granada, Spain.
Biochemistry. 1991 Feb 26;30(8):2067-72. doi: 10.1021/bi00222a010.
A differential scanning calorimetry study on the thermal denaturation of porcine pancreas carboxypeptidase B (in 20 mM pyrophosphate buffer, pH 9.0) has been carried out. The calorimetric transitions have been found to be calorimetrically irreversible and to depend on the Zn2+ concentration in the buffer. The effect of the Zn2+ concentration on the temperatures corresponding to maximum heat capacity appears to conform the dictates of the van't Hoff equation. In spite of this, analysis of the scanning rate effect on the transitions, together with studies on the thermal inactivation kinetics, show that the heat absorption is entirely determined by the rate of formation of the final (irreversibly denatured) state of the protein; therefore, analysis of the calorimetric transitions according to equilibrium thermodynamics models is not permissible. The effect of Zn2+ on the calorimetric transitions can be explained on the basis of a simple kinetic model that does not assume chemical equilibrium to be established between the significantly populated states of the protein.
已对猪胰羧肽酶B（在20 mM焦磷酸盐缓冲液，pH 9.0中）的热变性进行了差示扫描量热法研究。已发现量热转变在量热上是不可逆的，并且取决于缓冲液中的Zn2+浓度。Zn2+浓度对对应于最大热容量的温度的影响似乎符合范特霍夫方程的要求。尽管如此，对扫描速率对转变的影响的分析，以及对热失活动力学的研究表明，热吸收完全由蛋白质最终（不可逆变性）状态的形成速率决定；因此，根据平衡热力学模型对量热转变进行分析是不允许的。Zn2+对量热转变的影响可以基于一个简单的动力学模型来解释，该模型不假定在蛋白质的大量存在状态之间建立化学平衡。
