Core Structure of Amyloid Fibril Proposed from IR-Microscope Linear Dichroism

摘要

In recent years, the amyloid fibril has been recognized as another stable phase of peptide chains and also an origin of some kinds of diseases. Generally, it shows needlelike morphology (typically ～μm in length and ～10 nm in thickness). Cryoelectron microscopy proved the twisted nature of the needle for the SH3 domain of the phosphatidylinositol-3'-kinase and insulin fibrils. X-ray diffraction measurements on several fibrils showed the presence of the integrative β-sheet structure at the core of the fibril as a common feature, where the peptide chain runs perpendicular to the long axis of the fibril. The presence of a similar β-sheet core in β_2-microglobulin amyloid fibril was deduced from the H/D exchange efficiency. Solid-state NMR experiments provided the information on dihedral angles of the peptide chain, which elucidated the conformation of Aβ peptide within the fibril. We report here a new approach based on IR linear dichroism analysis of amyloid fibrils using a microscope.