Effects of lengthscales and attractions on the collapse of hydrophobic polymers in water
Effects of lengthscales and attractions on the collapse of hydrophobic polymers in water
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DOI：
10.1073/pnas.0605139104
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发表时间：
2007-01-16
影响因子：
11.1
通讯作者：
Garde, Shekhar
中科院分区：
文献类型：
--
作者：
Athawale, Manoj V.;Goel, Gaurav;Garde, Shekhar
我们提出了疏水性聚合物在明确水中的塌陷转变的广泛分子动力学模拟的结果，重点是了解疏水性表面的长度尺度和吸引力相互作用对折叠的影响。疏水性聚合物表现出抛物线、类似蛋白质、温度依赖性的展开自由能。有吸引力的小聚合物的折叠状态在 300 K 下稍微稳定，并且可以通过加热或冷却来展开。增加长度尺度或减少聚合物-水吸引力可以显着稳定折叠状态，前者主要由水合贡献决定。这种水合作用可以通过表面张力模型 Delta G = gamma(T)Delta A 来描述，其中表面张力 gamma 与长度相关，并且随温度单调减小。由此产生的水合熵随聚合物长度尺度的变化与Huang和Chandler的理论预测一致[Huang DM, Chandler D (2000) Proc Natl Acad Sci USA 97:8324-8327]，这解释了在蛋白质折叠热力学中观察到的熵收敛的模糊性。水结构分析表明，聚合物-水疏水界面柔软且弱去湿，并具有界面密度波动增强的特点。该界面的形成会引起聚合物折叠，与蒸气-液体界面类似，受到焓的强烈反对而受到熵的有利。
We present results from extensive molecular dynamics simulations of collapse transitions of hydrophobic polymers in explicit water focused on understanding effects of lengthscale of the hydrophobic surface and of attractive interactions on folding. Hydrophobic polymers display parabolic, protein-like, temperature-dependent free energy of unfolding. Folded states of small attractive polymers are marginally stable at 300 K and can be unfolded by heating or cooling. Increasing the lengthscale or decreasing the polymer-water attractions stabilizes folded states significantly, the former dominated by the hydration contribution. That hydration contribution can be described by the surface tension model, Delta G = gamma(T)Delta A, where the surface tension, gamma, is lengthscale-dependent and decreases monotonically with temperature. The resulting variation of the hydration entropy with polymer lengthscale is consistent with theoretical predictions of Huang and Chandler [Huang DM, Chandler D (2000) Proc Natl Acad Sci USA 97:8324-8327] that explain the blurring of entropy convergence observed in protein folding thermodynamics. Analysis of water structure shows that the polymer-water hydrophobic interface is soft and weakly dewetted, and is characterized by enhanced interfacial density fluctuations. Formation of this interface, which induces polymer folding, is strongly opposed by enthalpy and favored by entropy, similar to the vapor-liquid interface.