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首页> 外文期刊>Biophysical Journal >Solvation free energy of the peptide group: Its model dependence and implications for the additive-transfer free-energy model of protein stability
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Solvation free energy of the peptide group: Its model dependence and implications for the additive-transfer free-energy model of protein stability

机译：肽基团的溶剂化自由能：其模型依赖性和对蛋白质稳定性的累加转移自由能模型的启示

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The group-additive decomposition of the unfolding free energy of a protein in an osmolyte solution relative to that in water poses a fundamental paradox: whereas the decomposition describes the experimental results rather well, theory suggests that a group-additive decomposition of free energies is, in general, not valid. In a step toward resolving this paradox, here we study the peptide-group transfer free energy. We calculate the vacuum-to-solvent (solvation) free energies of (Gly)n and cyclic diglycine (cGG) and analyze the data according to experimental protocol. The solvation free energies of (Gly)n are linear in n, suggesting group additivity. However, the slope interpreted as the free energy of a peptide unit differs from that for cGG scaled by a factor of half, emphasizing the context dependence of solvation. However, the water-to-osmolyte transfer free energies of the peptide unit are relatively independent of the peptide model, as observed experimentally. To understand these observations, a way to assess the contribution to the solvation free energy of solvent-mediated correlation between distinct groups is developed. We show that linearity of solvation free energy with n is a consequence of uniformity of the correlation contributions, with apparent group-additive behavior in the water-to-osmolyte transfer arising due to their cancellation. Implications for inferring molecular mechanisms of solvent effects on protein stability on the basis of the group-additive transfer model are suggested.
机译：渗透液中蛋白质相对于水中的展开自由能的基团加和分解构成了一个基本的悖论：尽管该分解很好地描述了实验结果，但理论表明，自由能的基团加合分解是，一般而言，无效。在解决这一矛盾的步骤中，我们在这里研究了肽基转移自由能。我们计算（Gly）n和环状双甘氨酸（cGG）的真空-溶剂（溶剂化）自由能，并根据实验方案分析数据。 （Gly）n的溶剂化自由能在n中呈线性，表明基团可加性。但是，被解释为肽单元自由能的斜率与cGG的斜率相差一半，从而强调了溶剂化的背景依赖性。然而，如实验观察到的，肽单元的水-渗透物转移自由能相对独立于肽模型。为了理解这些观察，开发了一种方法来评估不同组之间溶剂介导的相关性对溶剂化自由能的贡献。我们表明，溶剂化自由能与n的线性关系是相关贡献的均匀性的结果，由于水和渗透物的消除，它们在水到渗透质的转移中具有明显的基团加性行为。建议在基团加成转移模型的基础上推断溶剂作用对蛋白质稳定性的分子机制。

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