Analysis of cooperative hydration effect on functions of biomacromolecules

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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.