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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Bulk-solvent and hydration-shell fluctuations, similar to alpha- and beta-fluctuations in glasses, control protein motions and functions
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Bulk-solvent and hydration-shell fluctuations, similar to alpha- and beta-fluctuations in glasses, control protein motions and functions

机译：溶剂和水化壳的波动，类似于玻璃中的α和β波动，可控制蛋白质的运动和功能

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The concept that proteins exist in numerous different conformations or conformational substates, described by an energy landscape, is now accepted, but the dynamics is incompletely explored. We have previously shown that large-scale protein motions, such as the exit of a ligand from the protein interior, follow the dielectric fluctuations in the bulk solvent. Here, we demonstrate, by using mean-square displacements (msd) from Mossbauer and neutron-scattering experiments, that fluctuations in the hydration shell control fast fluctuations in the protein. We call the first type solvent-slaved or a-fluctuations and the second type hydration-shell-coupled or beta-fluctuations. Solvent-slaved motions are similar to the alpha-fluctuations in glasses. Their temperature dependence can be approximated by a Vogel-Tammann-Fulcher relation and they are absent in a solid environment. Hydration-shell-coupled fluctuations are similar to the beta-relaxation in glasses. They can be approximated by a Ferry or an Arrhenius relation, are much reduced or absent in dehydrated proteins, and occur in hydrated proteins even if embedded in a solid. They can be responsible for internal processes such as the migration of ligands within myoglobin. The existence of two functionally important fluctuations in proteins, one slaved to bulk motions and the other coupled to hydration-shell fluctuations, implies that the environment can control protein functions through different avenues and that no real protein transition occurs at approximate to200 K. The large number of conformational substates is essential; proteins cannot function without this reservoir of entropy, which resides mainly in the hydration shell.
机译：现在已经接受了蛋白质以能量格局描述的以多种不同构象或构象亚状态存在的概念，但动力学研究不完全。先前我们已经表明，大规模的蛋白质运动（例如配体从蛋白质内部退出）遵循主体溶剂中的介电波动。在这里，我们通过使用来自Mossbauer的均方位移（msd）和中子散射实验证明，水合壳中的波动可控制蛋白质的快速波动。我们称第一类为溶剂从动或a型涨落，第二类为水化壳耦合或β涨落。溶剂控制的运动类似于玻璃中的阿尔法波动。它们的温度依赖性可以通过Vogel-Tammann-Fulcher关系来近似，并且它们在固体环境中不存在。水合壳耦合的波动类似于眼镜中的β松弛。它们可以通过Ferry或Arrhenius关系来近似，在脱水蛋白中会大大减少或不存在，即使嵌入固体中也可能在水合蛋白中出现。它们可能负责内部过程，例如配体在肌红蛋白内的迁移。蛋白质中存在两个功能上重要的波动，一个波动是由于整体运动，另一个波动是由于水化壳波动，这意味着环境可以通过不同的途径控制蛋白质的功能，并且在大约200 K时不会发生真正的蛋白质跃迁。构象亚状态的数目是必不可少的；如果没有这种熵库，蛋白质就无法发挥功能，而熵库主要存在于水合壳中。

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