Amyloid palques are insoluble fibrous protein aggregates sharing specific structural traits. Abnormal accumulation of amyloid in organs may lead to amyloidosis, and may play a role in various other neurodegenerative diseases.

Amyloid beta (Aß or Abeta) appears to be the main constituent of amyloid plaques in the brains of Alzheimer's disease patients.

References

Shankar GM, Li S, Mehta TH, Garcia-Munoz A, Shepardson NE, Smith I, Brett FM, Farrell MA, Rowan MJ, Lemere CA, Regan CM, Walsh DM, Sabatini BL, Selkoe DJ (2008). "Amyloid-protein dimers isolated directly from Alzheimer's brains impair synaptic plasticity and memory". Nature Medicine (June 22, 2008 online). doi:10.1038/nm1782. PMID 18568035. Scmid, Randolf (June 2008). "New clue to Alzheimer's found". Yahoo News.