Institute of Agricultural and Life Sciences, Academic Assembly, Shimane University, 1060 Nishikawatsu, Matsue, Shimane 690-8504, Japan.
Department of Chemistry, Graduate School of Science, Kobe University, Nada, Kobe 657-8501, Japan.
J Phys Chem B. 2023 Aug 17;127(32):7111-7122. doi: 10.1021/acs.jpcb.3c01803. Epub 2023 Jul 21.
This study investigated how the secondary structural changes of proteins in aqueous solutions affect their hydration and the hydrogen-bond network of water molecules using near-infrared (NIR) spectroscopy. The aqueous solutions of three types of proteins, i.e., ovalbumin, β-lactoglobulin, and bovine serum albumin, were denatured by heating, and changes in the NIR bands of water reflecting the states of hydrogen bonds induced via protein secondary structural changes were investigated. On heating, the intermolecular hydrogen bonds between water molecules as well as between water and protein molecules were broken, and protein molecules were no longer strongly bound by the surrounding water molecules. Consequently, the denaturation was observed to proceed depending on the thermodynamic properties of the proteins. When the aqueous solutions of proteins were cooled after denaturation, the hydrogen-bond network was reformed. However, the state of protein hydration was changed owing to the secondary structural changes of proteins, and the variation patterns were different depending on the protein species. These changes in protein hydration may be derived from the differences in the surface charges of proteins. The elucidation of the mechanism of protein hydration and the formation of the hydrogen-bond network of water molecules will afford a comprehensive understanding of the protein functioning and dysfunctioning derived from the structural changes in proteins.
本研究利用近红外（NIR）光谱法研究了蛋白质在水溶液中的二级结构变化如何影响其水合作用和水分子的氢键网络。通过加热使三种类型的蛋白质（卵清蛋白、β-乳球蛋白和牛血清白蛋白）的水溶液变性，并研究了反映蛋白质二级结构变化引起的氢键状态变化的水的近红外带的变化。加热时，水分子之间以及水和蛋白质分子之间的分子间氢键被打破，蛋白质分子不再被周围水分子强烈束缚。因此，变性取决于蛋白质的热力学性质。蛋白质水溶液变性后冷却时，氢键网络重新形成。然而，由于蛋白质的二级结构发生了变化，蛋白质的水合状态发生了变化，其变化模式因蛋白质种类而异。这种蛋白质水合作用的变化可能源于蛋白质表面电荷的差异。阐明蛋白质水合作用和水分子氢键网络的形成机制，将有助于全面了解蛋白质结构变化所导致的蛋白质功能障碍。
