Analysis of cooperative hydration effect on functions of biomacromolecules

对于蛋白质、多糖等生物大分子，其功能与其水化状态密切相关。尽管大分子的水合作用很重要，但生物大分子的功能大多从大分子方面的观点进行了广泛的分析，而从溶剂方面，特别是从水方面分析生物大分子功能的研究尝试似乎不足。在生物大分子的水合作用中，大量的水分子参与其中，因此这些水分子有望协同作用于大分子的功能。本文从溶液热力学角度分析了生物大分子协同水合作用与蛋白质热稳定性、亚基相互作用、酶功能和溶胶-凝胶转变的关系。结果表明，在蛋白质解折叠、亚基解离和溶胶-凝胶转变过程中，水化状态发生了显著的变化，因此考虑水活度对分析这些现象的影响是非常重要的。考虑到这一点，提出了一个新的热力学模型，首次分析的功能，生物大分子的水化状态的影响，这是由水活度的影响。利用该模型成功地分析了溶菌酶和乙醇脱氢酶的热稳定性以及明胶的溶胶-凝胶转变，证明了蛋白质的熔融温度和明胶的溶胶-凝胶转变温度与体系的水活度呈线性关系。此外，不仅水活度的影响，而且还观察到的生物大分子的各种功能的溶剂结构的影响，这可以与文献中报道的水结构参数。

As for biomacromolecules such as proteins and polysaccharides, their functions are strongly related to their hydration state. In spite of the importance of the hydration of macromolecules, functions of biomacromolecules have been extensively analyzed mostly from the standpoint of macromolecular side and there seem to be insufficient research attempts to analyze functions of biomacromolecules from the viewpoint of solvent side, especially from water Generally, lots of water molecules are involved in the hydration of biomacromolecules so that these water molecules are expected to react cooperatively on the functions of macromolecules.In the present research, the relationship between the cooperative hydration effect of biomacromolecules, and thermal stability of proteins, subunit interactions, enzyme functions, and sol-gel transitions have been analyzed by using the solution thermodynamic approach. As a result, considerable changes in the hydration states were estimated to occur in the protein unfolding, subunit dissociation, and sol-gel transition so that it was very important to take the water activity into account to analyze these phenomena. In consideration of this, a new thermodynamic model was proposed for the first time to analyze functions of biomacromolecules reflecting the effect of hydration state, which was influenced by the water activity. By using this model, thermal stability of lysozyme and alcohol dehydrogenase, and sol-gel transition of gelatin were successfully analyzed and melting temperature of proteins and sol-gel transition temperature of gelatin were proved to be linear dependent on the water activity of the system. In addition, not only the effect of water activity but also the effect of the solvent structure observed on various functions of biomacromolecules, which could be correlated to the water structure parameters reported in the literature.