Yan Yong-Bin, Wang Qi, He Hua-Wei, Hu Xin-Yao, Zhang Ri-Qing, Zhou Hai-Meng
NMR Laboratory, Department of Biological Sciences and Biotechnology, and State Key Laboratory of Biomembrane and Membrane Biotechnology, Tsinghua University, Beijing 100084, China.
Biophys J. 2003 Sep;85(3):1959-67. doi: 10.1016/S0006-3495(03)74623-2.
Unfolding and aggregation are basic problems in protein science with serious biotechnological and medical implications. Probing the sequential events occurring during the unfolding and aggregation process and the relationship between unfolding and aggregation is of particular interest. In this study, two-dimensional infrared (2D IR) correlation spectroscopy was used to study the sequential events and starting temperature dependence of Myoglobin (Mb) thermal transitions. Though a two-state model could be obtained from traditional 1D IR spectra, subtle noncooperative conformational changes were observed at low temperatures. Formation of aggregation was observed at a temperature (50-58 degrees C) that protein was dominated by native structures and accompanied with unfolding of native helical structures when a traditional thermal denaturation condition was used. The time course NMR study of Mb incubated at 55 degrees C for 45 h confirmed that an irreversible aggregation process existed. Aggregation was also observed before fully unfolding of the Mb native structure when a relative high starting temperature was used. These findings demonstrated that 2D IR correlation spectroscopy is a powerful tool to study protein aggregation and the protein aggregation process observed depends on the different environmental conditions used.
蛋白质的去折叠和聚集是蛋白质科学中的基本问题，具有严重的生物技术和医学意义。探究蛋白质去折叠和聚集过程中发生的一系列事件以及去折叠和聚集之间的关系尤为重要。在本研究中，二维红外（2D IR）光谱用于研究肌红蛋白（Mb）热转变的一系列事件和起始温度依赖性。尽管传统的一维红外光谱可以得到两态模型，但在低温下观察到了细微的非协同构象变化。在使用传统热变性条件时，在蛋白质以天然结构为主导的温度（50-58摄氏度）下观察到聚集的形成，同时伴随着天然螺旋结构的去折叠。对在55摄氏度下孵育45小时的肌红蛋白进行的时间进程核磁共振研究证实存在不可逆的聚集过程。当使用相对较高的起始温度时，在肌红蛋白天然结构完全去折叠之前也观察到了聚集。这些发现表明二维红外光谱是研究蛋白质聚集的有力工具，并且观察到的蛋白质聚集过程取决于所使用的不同环境条件。
