Structural biology relies on several powerful techniques, but these tend to be limited in their ability to characterize protein fluctuations and mobility. Overreliance on structural approaches can lead to omission of critical information regarding biological function. Currently there is a need for complementary biophysical methods to visualize these mobile aspects of protein function. Here, we review hydrostatic and osmotic pressure-based techniques to address this shortcoming for the paradigm of rhodopsin. Hydrostatic and osmotic pressure data contribute important examples, which are interpreted in terms of an energy landscape for hydration-mediated protein dynamics. We find that perturbations of rhodopsin conformational equilibria by force-based methods are not unrelated phenomena; rather they probe various hydration states involving functional proton reactions. Hydrostatic pressure acts on small numbers of strongly interacting structural or solvent-shell water molecules with relatively high energies, while osmotic pressure acts on large numbers of weakly interacting bulk-like water molecules with low energies. Local solvent fluctuations due to the hydration shell and collective water interactions affect hydrogen-bonded networks and domain motions that are explained by a hierarchical energy landscape model for protein dynamics.

中文翻译：

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隐藏的水对视紫红质活化的影响


结构生物学依赖于几种强大的技术，但这些技术在表征蛋白质波动和迁移率的能力方面往往受到限制。过度依赖结构方法会导致遗漏有关生物功能的关键信息。目前需要互补的生物物理方法来可视化蛋白质功能的这些移动方面。在这里，我们回顾了基于静水和渗透压的技术，以解决视紫红质范式的这一缺点。静水压和渗透压数据提供了重要示例，这些示例从水合介导的蛋白质动力学的能量景观的角度进行解释。我们发现，通过基于力的方法对视紫红质构象平衡的扰动并非无关的现象;相反，它们探测涉及功能性质子反应的各种水合状态。静水压作用在少量能量相对较高的强相互作用结构或溶剂壳水分子上，而渗透压作用在大量能量较低的弱相互作用的体状水分子上。由于水合壳和集体水相互作用引起的局部溶剂波动会影响氢键网络和域运动，这可以通过蛋白质动力学的分层能源景观模型来解释。