Exploring the Effects of Small Molecules on the Formation of Amyloid Fibrils

• Main Authors: Ying-Tz Hung, 洪櫻姿
• Other Authors: Sheng-Shih Wang
• Format: Others
• Language: en_US
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/15698358087132597598

博士 === 國立臺灣大學 === 化學工程學研究所 === 98 === Recent evidence has suggested that numerous proteins can fold abnormally resulting in the formation of amyloid fibrils/aggregation. Some proteins that form amyloid fibrils are associated with human degenerative diseases. These proteins have little sequence homology, however, they can self-assemble into stable fibrils with a characteristic cross β-sheet structure. Although many research groups extensively explored the mechanism of amyloid fibrillogenesis, the detailed molecular mechanism has remained largely unknown. Here, we investigated the effects of small molecules, including denaturant, surfactant, and short-chain phospholipids, on the aggregative behavior of hen egg-white lysozymes using in vitro methods. Our results were divided into three sections by systems explored: lysozyme-urea, lysozyme-sodium dodecyl sulfate (SDS), and lysozyme-phospholipid. Firstly, in the pH 7.4 solutions containing 8M urea at 37, 45, or 55 oC and 4M urea at 45 or 55 oC, the formation and later disappearance of amyloid fibril-like species were observed while such species were not present at all under other conditions. In addition, SDS-PAGE results further indicated that larger aggregated species with less ordered structures were formed at the later stage of the urea-induced unfolding process owing to an unidentified conformational switch. In the second section, through various spectroscopic techniques, dynamic light scattering, and electron microscopy, we first demonstrated that SDS exhibited a biphasic effect on lysozyme fibrillation. The 129-residue enzyme, hen egg-white lysozyme, has been shown to form fibrils in vitro at pH 2.0 and 55