Entropy-enthalpy compensation: Fact or artifact?
Entropy-enthalpy compensation: Fact or artifact?
复制标题
DOI：
10.1110/ps.37801
复制
发表时间：
2001-03-01
期刊：
影响因子：
8
通讯作者：
Sharp, K
中科院分区：
文献类型：
--
作者：
Sharp, K
熵-焓 (S-H) 补偿现象被广泛用作蛋白质、配体和核酸热力学分析中的解释原理。有人认为，这种补偿是复杂的、波动的或水性系统的固有特性。这里检查的问题是观察到的补偿是否是超热力学的（即，反映的不仅仅是众所周知的统计热力学定律），如果是，它揭示了系统的什么？文献中对补偿的定义相当不同，并且讨论了不同的用法。这里考虑的最精确和最有趣的一个是对于实验变量的一系列扰动或变化，DeltaH 和 DeltaS 之间的线性关系。最近对一些声称具有补偿作用的蛋白质热力学数据进行了分析，结果表明可以通过其他原因更好地解释。分析复杂系统的一般统计力学模型，以探讨是否以及在什么条件下可以发生热动力补偿，以及它揭示了系统的什么内容。该模型表明，最有可能看到的行为是在相当有限的扰动范围内进行线性 S-H 补偿，补偿温度 Tc = d DeltaH/d DeltaS 在实验温度的 20% 范围内。这种行为对模型的细节不敏感，因此很少揭示有关系统的额外热力学或因果信息。此外，可能很难将其与实际实验系统中更琐碎的补偿形式区分开来。
The phenomenon of entropy-enthalpy (S-H) compensation is widely invoked as an explanatory principle in thermodynamic analyses of proteins, ligands, and nucleic acids. It has been suggested that this compensation is an intrinsic property of either complex, fluctuating, or aqueous systems. The questions examined here are whether the observed compensation is extra-thermodynamic (i.e., reflects anything more than the well-known laws of statistical thermodynamics) and if so, what does it reveal about the system? Compensation is rather variably defined in the literature and different usages are discussed. The most precise and interesting one, which is considered here, is a linear relationship between DeltaH and DeltaS for some series of perturbations or changes in experimental variable. Some recent thermodynamic data on proteins purporting to show compensation is analyzed and shown to be better explained by other causes. A general statistical mechanical model of a complex system is analyzed to explore whether and under what conditions extrathermodynamic compensation can occur and what it reveals about the system. This model shows that the most likely behavior to be seen is linear S-H compensation over a rather limited range of perturbations with a compensation temperature Tc = d DeltaH/d DeltaS within 20% of the experimental temperature. This behavior is insensitive to the details of the model, thus revealing little extra-thermodynamic or causal information about the system. In addition, it will likely be difficult to distinguish this from more trivial forms of compensation in real experimental systems.