Intramolecular Interactions Overcome Hydration to Drive the Collapse Transition of Gly15
Intramolecular Interactions Overcome Hydration to Drive the Collapse Transition of Gly15
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DOI：
10.1021/acs.jpcb.7b05469
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发表时间：
2017-08-31
影响因子：
3.3
通讯作者：
Pettitt, B. Montgomery
中科院分区：
文献类型：
--
作者：
Asthagiri, D.;Karandur, Deepti;Pettitt, B. Montgomery
模拟和实验表明，寡甘氨酸、缺少的多肽、任何侧链都可以在水中崩解。我们通过计算反应坐标每个端点处的水合自由能来评估这次坍塌的水化热力学，这里取为链中端到端的距离(R)。为了考察不同构象对给定的r的作用，我们研究了给定r值的旋转半径的条件分布P(R(G)LR)。与过量水化自由能的相应变化相比，P(R(G)LR)中的自由能随R-g的变化-k(B)T变化较小。在势分布定理的多态推广下，利用这一观察结果，我们计算了给定r的多肽的水合自由能的一个严格的上界。在此基础上，我们发现，尽管原始疏水效应有利于链的崩溃，但多肽的水化极大地有利于链的展开状态。坍塌的净自由能被认为是相反的肽内作用和水合作用之间的微妙平衡，而肽内的贡献有利于坍塌。
Simulations and experiments show oligo-glycines, polypeptides lacking, any side chains, can collapse in water. We assess the hydration thermodynamics Of this collapse by calculating the hydration free energy at each of the end points of the reaction coordinate, here taken as the end-to-end distance (r) in the chain. To examine the role of the various conformations for a given r, we study the conditional distribution, P(R(g)lr), of the radius of gyration for a given value of r. The free energy change versus R-g, -k(B)T In P(R(g)lr), is found to vary more gently compared to the corresponding variation in the excess hydration free energy. Using this observation within a multistate generalization of the potential distribution theorem, we calculate a tight upper bound for the hydration free energy of the peptide for a given r. On this basis, we find that peptide hydration greatly favors the expanded state of the chain, despite primitive hydrophobic effects favoring chain collapse. The net free energy of collapse is seen to be a delicate balance between opposing intrapeptide and hydration effects, with intrapeptide contributions favoring collapse.