AFM and STM study of β-amyloid aggregation on graphite

Atomic force microscopy (AFM) and scanning tunneling microscopy (STM) have been employed in situ and ex situ to directly study the aggregation of β-amyloid(1-42) (Aβ42) peptide on hydrophobic graphite. n situ AFM images, Aβ42 peptides were seen to aggregate into the sheets that preferred to three orientations with characteristic 3-fold symmetry (Proc. Natl. Acad. Sci. USA 96 (1999) 3688). The sheets were formed by parallel narrow lines with a height of 0.8–1.0 nm and a width of 12–14 nm. The narrow lines looked like beaded chains and have a right-handed axial periodicity. gh-resolution ex situ AFM and STM images showed that some fibrils of β-amyloid had a characteristic domain texture, indicating they were formed through the association of protofibrils and monomers. The fibril containing lateral associated filaments that exhibited right-handed twist was clearly observed in the STM image. results provide important clues to study the detailed structure of β-amyloid aggregates and the mechanism of the Aβ fibrils formation on hydrophobic surface.