Senile Plaque• Alzheimer's disease has beenidentified as a protein misfoldingdisease, caused by accumulation ofabnormally folded protein in thebrain.• Both amyloid plaques andneurofibrillary tangles (NFTs) areclearly visible by microscopy inbrains of those afflicted by AD.• Plaques are dense, mostlyinsoluble deposits of protein andcellular material outside and aroundthe neurons.• Plaques are made up of smallpeptides, 39–43 amino acids inlength, called beta-amyloid (alsowritten as amyloid β or Aβ),