Zhang S, Rich A
Department of Biology, Center for Biomedical Engineering, Massachusetts Institute of Technology, Cambridge 02139-4307, USA.
Proc Natl Acad Sci U S A. 1997 Jan 7;94(1):23-8. doi: 10.1073/pnas.94.1.23.
A 16-amino acid oligopeptide forms a stable beta-sheet structure in water. In physiological solutions it is able to self-assemble to form a macroscopic matrix that stains with Congo red. On raising the temperature of the aqueous solution above 70 degrees C, an abrupt structural transition occurs in the CD spectra from a beta-sheet to a stable alpha-helix without a detectable random-coil intermediate. With cooling, it retained the alpha-helical form and took several weeks at room temperature to partially return to the beta-sheet form. Slow formation of the stable beta-sheet structure thus shows kinetic irreversibility. Such a formation of very stable beta-sheet structures is found in the amyloid of a number of neurological diseases. This oligopeptide could be a model system for studying the protein conformational changes that occurs in scrapie or Alzheimer disease. The abrupt and direct conversion from a beta-sheet to an alpha-helix may also be found in other processes, such as protein folding and protein-protein interaction. Furthermore, such drastic structure changes may also be exploited in biomaterials designed as sensors to detect environmental changes.
一种16个氨基酸的寡肽在水中形成稳定的β-折叠结构。在生理溶液中，它能够自组装形成用刚果红染色的宏观基质。当水溶液温度升至70℃以上时，圆二色光谱中会发生从β-折叠到稳定α-螺旋的突然结构转变，且未检测到随机卷曲中间体。冷却后，它保持α-螺旋形式，在室温下需要几周时间才能部分恢复到β-折叠形式。因此，稳定β-折叠结构的缓慢形成表现出动力学不可逆性。在许多神经疾病的淀粉样蛋白中都发现了这种非常稳定的β-折叠结构的形成。这种寡肽可能是研究羊瘙痒病或阿尔茨海默病中发生的蛋白质构象变化的模型系统。从β-折叠到α-螺旋的突然直接转变也可能出现在其他过程中，如蛋白质折叠和蛋白质-蛋白质相互作用。此外，这种剧烈的结构变化也可用于设计作为传感器来检测环境变化的生物材料。
