1 Research Center for Analytical Sciences, College of Chemistry, Nankai University, Tianjin, China.
2 Tianjin Key Laboratory of Biosensing and Molecular Recognition, Tianjin, China.
Appl Spectrosc. 2018 Sep;72(9):1354-1361. doi: 10.1177/0003702818769410. Epub 2018 Apr 17.
Investigating the interaction between oligopeptide and water is essential for understanding the structure, dynamics and function of proteins. Temperature-dependent near-infrared (NIR) spectroscopy and independent component analysis (ICA) were employed to study the interaction between oligopeptide and water in aqueous solution. The NIR spectra of two homo-oligopeptides, penta-aspartic acid (D) and penta-lysine (K), in aqueous solution of different concentration were measured at different temperature (30-90 ℃). Independent component analysis was performed to extract the spectral information that changes with temperature. The independent components (ICs) representing the spectral information of NH and CH groups were obtained. Compared with D, the two groups in K change significantly at higher temperature. The result may suggest that K has stronger interaction with water than D. Moreover, three ICs that contain the spectral information of the water species with no (S), one (S), and two (S) hydrogen-bonds were obtained. It was shown that the spectral intensity of S and S increases while that of S decreases with the temperature, and the changes of oligopeptide solutions are weaker than those of pure water. The results indicate that water structure is sensitive to temperature and the oligopeptide in aqueous solution improves the thermal stability of the water species. When oligopeptide is added, the spectral intensity of S and S decreases and that of S increases for D solution, but the intensity of all the three species decreases for K solution. Furthermore, the concentration effect of K was found to be stronger than D. The result may reveal that D combines with water molecule through forming one hydrogen bond but K interacts with water through a different way.
研究寡肽与水之间的相互作用对于理解蛋白质的结构、动态和功能至关重要。本研究采用温度依赖的近红外（NIR）光谱和独立成分分析（ICA）研究了水溶液中寡肽与水的相互作用。在不同温度（30-90°C）下，测量了两种同型寡肽（天冬氨酸五肽（D）和赖氨酸五肽（K））在不同浓度的水溶液中的 NIR 光谱。通过 ICA 提取随温度变化的光谱信息。得到了代表 NH 和 CH 基团光谱信息的独立成分（ICs）。与 D 相比，K 中的两个基团在较高温度下变化较大。结果表明，K 与水的相互作用强于 D。此外，得到了包含无（S）、一（S）和二（S）氢键的水物种光谱信息的三个 IC。结果表明，随着温度的升高，S 和 S 的光谱强度增加，而 S 的光谱强度降低，寡肽溶液的变化比纯水的变化弱。结果表明，水结构对温度敏感，水溶液中的寡肽提高了水物种的热稳定性。当添加寡肽时，D 溶液中 S 和 S 的光谱强度降低，S 的光谱强度增加，但 K 溶液中所有三种物质的强度都降低。此外，还发现 K 的浓度效应强于 D。结果表明，D 通过形成一个氢键与水分子结合，而 K 通过不同的方式与水相互作用。
