Effects of co-solvents on peptide hydration water structure and dynamics
Effects of co-solvents on peptide hydration water structure and dynamics
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DOI：
10.1039/b915888j
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发表时间：
2010-01-01
影响因子：
3.3
通讯作者：
Head-Gordon, Teresa
中科院分区：
文献类型：
--
作者：
Johnson, Margaret E.;Malardier-Jugroot, Cecile;Head-Gordon, Teresa
我们评估的分子响应的水合水作为一个函数的温度和接近的肽N-乙酰基-亮氨酸-甲基酰胺（NALM）的表面时，在存在的kosmotrope共溶剂甘油或离液剂共溶剂二甲基亚砜（DMSO），使用分子动力学模拟与极化力场。这些详细的显微镜研究补充了已建立的热力学分析的作用，共溶剂在转移平衡的蛋白质远离或朝向天然折叠状态。我们发现，在肽界面处的水的结构反映了在甘油溶液中的水合数的增加和在DMSO溶液中的水合数的减少。虽然在两种共溶剂存在下NALM周围的水动力学比单独使用水溶剂观察到的要慢，但在DMSO混合物中，我们不再测量如在纯水溶剂中所见的在低温下水运动时间尺度的分离，而是一个单一的弛豫时间。然而，在甘油中，我们确实观察到在低温下时间尺度的分离，这支持了这样的假设，即疏水溶质附近的水合水在单独的时间尺度上比更大体积的水的广泛的氢键网络演化。我们的模拟研究突出了两种共溶剂溶液中的差异，这是由于水与疏水肽表面接触的相对频率以及水与共溶剂的直接相互作用。
We evaluate the molecular response of hydration water as a function of temperature and proximity to the surface of the peptide N-acetyl-leucine-methylamide (NALMA) when in the presence of the kosmotrope co-solvent glycerol or the chaotrope co-solvent dimethyl sulfoxide (DMSO), using molecular dynamics simulation with a polarizable force field. These detailed microscopic studies complement established thermodynamic analysis on the role of co-solvents in shifting the equilibrium for proteins away from or towards the native folded state. We find that the structure of the water at the peptide interfaces reflects an increase in hydration number in the glycerol solution and a decrease in hydration numbers in the DMSO solution. While the water dynamics around NALMA in the presence of both co-solvents is slower than that observed with the water solvent alone, in the DMSO mixture we no longer measure a separation in water motion time scales at low temperatures as is seen in the pure water solvent, but rather one single relaxation time. In the glycerol, however, we do observe a separation of time scales at low temperatures, supporting the hypothesis that hydration water near a hydrophobic solute evolves on a separate time scale than the extensive hydrogen-bonding network of more bulk-like water. Our simulation studies highlight the differences in the two co-solvent solutions due to the relative frequency of water contacts with the hydrophobic vs. hydrophilic peptide surface, and direct water interactions with the co-solvents.