Understanding the effect of urea on the phase transition of poly(N-isopropylacrylamide) in aqueous solution by temperature-dependent near-infrared spectroscopy
Understanding the effect of urea on the phase transition of poly(N-isopropylacrylamide) in aqueous solution by temperature-dependent near-infrared spectroscopy
复制标题
通过温度依赖性近红外光谱了解尿素对水溶液中聚（N-异丙基丙烯酰胺）相变的影响
DOI：
10.1016/j.saa.2021.119573
复制
发表时间：
2021-02-20
影响因子：
4.4
通讯作者：
Shao, Xueguang
中科院分区：
文献类型：
--
作者：
Ma, Biao;Wang, Li;Shao, Xueguang
通过变性剂调节折叠状态对于蛋白质的结构和功能至关重要。聚（N-异丙基丙烯酰胺）（PNIPAM）通常被视为蛋白质变性的模型。通过温度依赖性近红外（NIR）光谱研究了尿素作为变性剂对 PNIPAM 聚集的影响，特别是分析了水结构的变化。在不同温度下测量了含有不同聚合物浓度的聚合物-尿素溶液的近红外光谱。进行N路主成分分析（NPCA）来观察光谱信息。获得了包含CH基团光谱信息的三个主成分（PC），显示了系统中的三种CH。三种CH基团在溶液中的温度为27.5℃时发生明显的脱水，但在添加尿素的溶液中，两种CH的温度分别变为27℃，第三种CH的温度分别变为26.5℃。提出了尿素对促进聚合物折叠的分子内氢键形成的影响。尿素分子中NH的光谱信息表明尿素和聚合物的直接相互作用有利于聚合物球态的稳定。此外，OH的光谱信息表明，具有三个氢键（S-3）的水分子的释放可能会连接溶液中PNIPAM中的NH和CO基团，从而导致相变。当添加尿素时，尿素可以降低S-3水的含量以利于释放，使相变在低温下进行。 (C) 2021 Elsevier B.V. 保留所有权利。
Regulating the folding state by denaturants is essential for the structure and function of proteins. Poly(N-isopropyl acrylamide) (PNIPAM) is usually regarded as a model for protein denaturation. The effects of urea, as a denaturant, on the aggregations of PNIPAM was studied by temperature-dependent near-infrared (NIR) spectroscopy, and particularly the variation of water structures was analyzed. The NIR spectra of the polymer-urea solutions containing different polymer concentrations were measured at different temperatures. N-way principal component analysis (NPCA) was performed to observe the spectral information. Three principal components (PCs) containing the spectral information of CH groups were obtained, showing three kinds of CH in the system. Obvious dehydration of the three CH groups occurs at 27.5 degrees C in solution, but the temperature turns to 27 degrees C for two kinds of the CH and 26.5 degrees C for the third one, respectively, in the urea-add solution. The effect of urea on the formation of the intramolecular hydrogen bonds that promotes polymer folding is suggested. The spectral information of NH in urea molecule indicates that the direct interaction of urea and polymer facilitates the stability of the polymer globule state. Furthermore, the spectral information of OH shows that the release of the water molecules with three hydrogen bonds (S-3), which may connect the NH and CO groups in PNIPAM in solution, leads to the phase transition. When urea is added, urea may reduce the content of the S-3 water to facilitate the release, making the phase transition at a low temperature. (C) 2021 Elsevier B.V. All rights reserved.