title: AFM and STM study of beta-amyloid aggregation on graphite.
abstract: Atomic force microscopy (AFM) and scanning tunneling microscopy (STM) have been employed in situ and ex situ to directly study the aggregation of beta-amyloid(1-42) (Abeta42) peptide on hydrophobic graphite. From in situ AFM images, Abeta42 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 0.8-1.0nm and a width of 12-14nm. The narrow lines looked like beaded chains and have a right-handed axial periodicity. The high-resolution ex situ AFM and STM images showed that some fibrils of beta-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. These results provide important clues to study the detailed structure of beta-amyloid aggregates and the mechanism of the Abeta fibrils formation on hydrophobic surface.
authors.affiliation: The Center for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, PR China.
authors.forename: Zhigang
authors.initials: Z
authors.lastname: Wang
authors.forename: Chunqing
authors.initials: C
authors.lastname: Zhou
authors.forename: Chen
authors.initials: C
authors.lastname: Wang
authors.forename: Lijun
authors.initials: L
authors.lastname: Wan
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Fang
authors.forename: Chunli
authors.initials: C
authors.lastname: Bai
mesh_terms: D000544:Alzheimer Disease / Q000473:pathology; D000595:Amino Acid Sequence; D016229:Amyloid beta-Peptides / Q000737:chemistry* / Q000648:ultrastructure*; D006108:Graphite / Q000737:chemistry*; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D018625:Microscopy, Atomic Force / Q000379:methods*; D016252:Microscopy, Scanning Tunneling / Q000379:methods*; D008969:Molecular Sequence Data
chemical_list: D016229:Amyloid beta-Peptides; D006108:Graphite