Giorgio Careri was consumed by two different ideas about how biomolecules function. He thought that energy transport in proteins was mediated by solitons. Separately, he proposed that protein function was controlled by a network of water molecules, with a density above a critical percolation threshold. He was wrong about the first idea. He was right about the second, but perhaps not quite in the way he imagined it. The statement that “water is important to biomolecules” is so obvious that it seems pointless to even make it, let alone to set aside a special issue of the Journal of Biological Physics on the topic. Of course water is important for biological systems. We learned this in elementary school, and this is why scientists searching for life on Mars look for tell-tale evidence of water. What is so great about asserting such a manifestly self-evident statement? In the field of biological physics, we have only now begun to understand the many marvelously different ways in which water can influence the function of biomolecules. The experimental genesis of these ideas is in the early work of Frauenfelder and collaborators, and in the work of Careri and coworkers. The review by Pascale Mentre [1] in this issue provides a succinct account of the role of water in the orchestration of cell machinery. The review also corrects many misunderstandings. The central ideas are that (i) interfacial water modulates protein function, and (ii) nanoconfined water is so different from bulk water that one cannot use simply use the statistical physics models developed for bulk water. We now also know that there are actually special water molecules that directly participate in protein function. An example of such a special water molecule is in the exciting report on the detection of a special hydrogen-bonded water molecule in the proton pump archaerhodospin-3, by the Rothschild group (Saint Clair et al. [2]). Modern spectroscopic methods continue to advance (see for example the paper on terahertz spectroscopy of water nanoclusters by Johnson [3] in this issue). We expect that this discovery of special water molecules will not be isolated. From an evolutionary point of view, it is logical that some proteins have evolved to take advantage of special water molecules to assist in function, in addition to the interfacial water that inspired Careri. The single most exciting addition to the toolkit that is available to biological physicists today involves computational models and methods aimed directly at understanding water. As Fabio Bruni [4] writes in his personal memoir, Careri was singularly uncomfortable with computers. It is therefore interesting that modern computational methods may eventually provide strong support for the role of interfacial nanoconfined water in the functioning of biomolecules. There is not a single accepted computational model of water. The paper by Herzfeld and collaborators [5] describes a tractable and efficient new simulation model for dissociable water in nanoclusters and chains of water. Kumar and Keyes have developed one of the best molecular models for understanding the infrared spectra of water molecules by careful consideration of water in the first hydration shell [6]. Strekalova et al. have studied the effect of a hydrophobic environment, such as one might expect in protein pockets, on a hypothesized critical point in nanoconfined water [7]. The papers suggest the strong vitality inherent in the computational approach, which also provides new insights into the nature of the dynamics of water. One of the most vigorous arguments in the physics of water today involves the nature of the dynamics of water, whether the dynamics are similar to those observed in glassy systems, or whether there is a liquid-critical point. A combination of computational and spectroscopic studies should get us closer to an answer. Perhaps the most interesting new insight may simply be this: we have known that water is essential for structure. It is required for proteins to fold properly. We are now learning that water also strongly influences dynamics. New insights based on a combination of novel forms of spectroscopy, data from coherent X-ray sources, computational insights, and new theoretical ideas borrowed from glass transitions and critical phenomena, all have provided firm support to the idea that proteins need to be dynamic in order to function properly, and that protein dynamics are strongly controlled by the dynamic properties of water. We would like to thank especially our co-editor Feng Wang. Thanks also go to Brigita Urbanc, and to students in Gene Stanley’s group at Boston University. We gratefully acknowledge the contributions of the authors of the articles in this special issue, and to the anonymous reviewers who set aside valuable time selflessly. A final thanks to Sonya Bahar, Rudi Podgornik, especially to Maria Bellantone for her inspiration, and to Ruel Pinero and Mieke van der Fluit for their patience.

中文翻译：

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水在生物系统中的动态作用

Giorgio Careri 被关于生物分子如何运作的两种不同想法所吸引。他认为蛋白质中的能量传输是由孤子介导的。另外，他提出蛋白质功能受水分子网络控制，其密度高于临界渗透阈值。第一个想法他错了。关于第二点他是对的，但也许和他想象的不太一样。“水对生物分子很重要”的说法是如此明显，甚至似乎都没有意义，更不用说在《生物物理学杂志》上就此主题留出一期特刊了。当然，水对生物系统很重要。我们在小学学到了这一点，这就是为什么在火星上寻找生命的科学家寻找水的证据。断言如此明显不言而喻的陈述有什么好处？在生物物理学领域，我们现在才开始了解水影响生物分子功能的许多奇妙的不同方式。这些想法的实验起源于 Frauenfelder 及其合作者的早期工作，以及 Careri 及其同事的工作。Pascale Mentre [1] 在本期中的评论简要说明了水在细胞机制协调中的作用。审查还纠正了许多误解。中心思想是 (i) 界面水调节蛋白质功能，以及 (ii) 纳米封闭水与散装水如此不同，以至于不能简单地使用为散装水开发的统计物理模型。我们现在也知道，实际上存在直接参与蛋白质功能的特殊水分子。这种特殊水分子的一个例子是 Rothschild 小组关于在质子泵 archaerhodospin-3 中检测到特殊氢键水分子的激动人心的报告（Saint Clair 等人 [2]）。现代光谱方法不断发展（例如，参见本期 Johnson [3] 关于水纳米团簇的太赫兹光谱的论文）。我们预计这种特殊水分子的发现不会被孤立。从进化的角度来看，除了启发 Careri 的界面水之外，一些蛋白质已经进化为利用特殊的水分子来辅助功能，这是合乎逻辑的。今天可供生物物理学家使用的工具包中最令人兴奋的一个补充涉及直接旨在理解水的计算模型和方法。正如 Fabio Bruni [4] 在他的个人回忆录中所写，Careri 对计算机非常不舒服。因此，有趣的是，现代计算方法最终可能会为界面纳米封闭水在生物分子功能中的作用提供强有力的支持。没有一个公认的水计算模型。Herzfeld 及其合作者的论文 [5] 描述了一种适用于纳米团簇和水链中可解离水的易于处理且高效的新模拟模型。通过仔细考虑第一个水合壳中的水，Kumar 和 Keyes 开发了最好的分子模型之一，用于理解水分子的红外光谱 [6]。斯特雷卡洛娃等人。已经研究了疏水环境对纳米封闭水中假设临界点的影响，例如人们可能在蛋白质袋中预期的影响 [7]。这些论文表明了计算方法固有的强大生命力，这也提供了对水动力学性质的新见解。当今水物理学中最有力的论点之一涉及水动力学的性质，该动力学是否类似于在玻璃系统中观察到的动力学，或者是否存在液体临界点。计算和光谱研究的结合应该让我们更接近答案。也许最有趣的新见解可能就是这样：我们已经知道水对于结构来说是必不可少的。蛋白质需要正确折叠。我们现在了解到，水也会强烈影响动力学。基于新形式的光谱学、相干 X 射线源数据、计算见解以及从玻璃化转变和临界现象中借用的新理论思想相结合的新见解，都为蛋白质需要在为了正常发挥作用，蛋白质动力学受到水的动力学特性的强烈控制。我们要特别感谢我们的联合编辑王峰。还要感谢 Brigita Urbanc 和波士顿大学 Gene Stanley 小组的学生。我们衷心感谢本期特刊文章作者的贡献，以及无私地抽出宝贵时间的匿名审稿人。最后感谢 Sonya Bahar、Rudi Podgornik，特别是 Maria Bellantone 的灵感，以及 Ruel Pinero 和 Mieke van der Fluit 的耐心。