Observation of metastable Abeta amyloid protofibrils by atomic force microscopy

Chem Biol. 1997 Feb;4(2):119-25. doi: 10.1016/s1074-5521(97)90255-6.


Background: Brain amyloid plaque, a diagnostic feature of Alzheimer's disease (AD), contains an insoluble fibrillar core that is composed primarily of variants of the beta-amyloid protein (Abeta). As Abeta amyloid fibrils may initiate neurodegeneration, the inhibition of fibril formation is a possible therapeutic strategy. Very little is known about the early steps of the process, however.

Results: Atomic force microscopy was used to follow amyloid fibril formation in vitro by the Abeta variants Abeta1-40 and Abeta1-42. Both variants first form small ordered aggregates that grow slowly and then rapidly disappear, while prototypical amyloid fibrils of two discrete morphologies appear. Abeta1-42 aggregates much more rapidly than Abeta1-40, which is consistent with its connection to early-onset AD. We propose that the metastable intermediate species be called Abeta amyloid protofibrils.

Conclusions: Abeta protofibrils are likely to be intermediates in the in vitro assembly of Abeta amyloid fibrils, but their in vivo role has yet to be determined. Numerous reports of a nonfibrillar form of Abeta aggregate in the brains of individuals who are predisposed to AD suggest the existence of a precursor form, possibly the protofibril. Thus, stabilization of Abeta protofibrils may be a useful therapeutic strategy.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Alzheimer Disease / pathology
  • Amyloid beta-Peptides / chemistry*
  • Brain Chemistry
  • Humans
  • Microscopy, Atomic Force / methods*


  • Amyloid beta-Peptides