Gonnelli M, Strambini G B
Biophys Chem. 1986 Jul;24(2):161-7. doi: 10.1016/0301-4622(86)80009-6.
The kinetics of the irreversible urea denaturation of equine liver alcohol dehydrogenase have been studied as a function of temperature and urea concentration. The unfolding of the macromolecule, monitored by means of the phosphorescence properties of a deeply buried tryptophan residue, was found to be strictly a two-state process over the entire temperature range. It is characterized by a steep dependence on urea concentration typical of highly cooperative transitions and below room temperature it possesses large negative activation energies. The reaction is comparatively slow, does not seem to be preceded by a fast phase, and the rate-limiting step does not have the characteristics of proline isomerization. When the data are analyzed in terms of binding equilibria the temperature dependence results from an anomalously large change in heat capacity. Although this is a property of strong hydrophobic interactions in model compounds the slow rates of denaturation are best understood with a model of protein stability which emphasizes the cooperative nature of intramolecular interactions such as hydrogen bonding.
研究了马肝醇脱氢酶不可逆尿素变性的动力学，该动力学是温度和尿素浓度的函数。通过深埋的色氨酸残基的磷光特性监测大分子的去折叠，发现在整个温度范围内它严格是一个两态过程。其特点是对尿素浓度有强烈依赖性，这是高度协同转变的典型特征，并且在室温以下它具有很大的负活化能。该反应相对较慢，似乎没有快速相作为前奏，并且限速步骤不具有脯氨酸异构化的特征。当根据结合平衡分析数据时，温度依赖性源于热容量异常大的变化。尽管这是模型化合物中强疏水相互作用的一个特性，但变性的缓慢速率最好用强调分子内相互作用（如氢键）协同性质的蛋白质稳定性模型来理解。
