Effect of water potential on sol-gel transition and intermolecular interaction of gelatin near the transition temperature
Effect of water potential on sol-gel transition and intermolecular interaction of gelatin near the transition temperature
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DOI：
10.1002/bip.10473
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发表时间：
2003-12-01
期刊：
影响因子：
2.9
通讯作者：
Sakurai, H
中科院分区：
文献类型：
--
作者：
Miyawaki, O;Norimatsu, Y;Sakurai, H
通过热分析和粘度测量，从聚合物分子水化状态的变化来分析明胶的溶胶-凝胶转变。提出了一个新的热力学模型，其中明确考虑了水势的影响，用于评估溶胶-凝胶转变过程中的自由能变化。由于大量的水分子参与和小的自由能变化的过渡过程中，水活度，a（W）的贡献，被证明是不可忽略的溶胶-凝胶转变过程中的溶液中含有这样的低分子共溶质，如糖，甘油，尿素，和甲酰胺。糖和甘油的凝胶稳定效果与a（W）呈线性关系，这似乎与所提出的模型中的水势的贡献一致。糖和甘油之间的不同的稳定效果解释了溶剂排序的差异，这影响了蛋白质分子之间的疏水相互作用。尿素和甲酰胺的凝胶不稳定效应只能通过它们通过氢键与蛋白质分子直接结合来解释。相反，在聚乙二醇和葡聚糖溶液中，通过粘度分析测量的聚合物-聚合物相互作用对a（W）的变化不敏感，这表明在这些聚合物溶液中没有发生水合状态与a（W）的实质性变化。(C)2003 Wiley Periodicals，Inc.
The sol-gel transition of gelatin, measured by thermal analysis and viscosity measurement, was analyzed in terms of the change in hydration state of polymer molecules. A new thermodynamic model was proposed in which the effect of water potential is explicitly taken into account for the evaluation of the free energy change in the sol-gel transition process. Because of the large number of water molecules involved and the small free energy change in the transition process, the contribution of water activity, a(W), was proved to be not negligible in the sol-gel transition process in solutions containing such low-molecular cosolutes as sugars, glycerol, urea, and formamide. The gel-stabilization effect of sugars and glycerol was linear with a(W), which seemed consistent with the contribution of water potential in the proposed model. The different stabilization effect among sugars and glycerol was explained by the difference in solvent ordering, which affects hydrophobic interaction among protein molecules. The gel-destabilization effect of urea and formamide could be explained only by the direct binding of them to protein molecules through hydrogen bonding. On the contrary, the polymer-polymer interaction, measured by the viscosity analysis, in polyethyleneglycol and dextran solutions was not sensitive to the change in a(W), suggesting that no substantial change in hydration state with a(W) occurred in these polymer solutions. (C) 2003 Wiley Periodicals, Inc.