Isolation and biochemical characterization of amyloid plaques and paired helical filaments.

Extracellular deposits of amyloid fibrils in the form of parenchymal plaques and cerebrovascular lesions, as well as intracellular accumulation of paired-helical filaments in the form of neurofibrillary tangles (NFT) in selected neuronal populations are the main neuropathologic hallmarks of Alzheimer's disease. Amyloid fibrils composed of polymeric structures of the amyloid-beta (Abeta) concentrate at the center of senile plaques and accumulate in the walls of cerebral blood vessels, exhibiting extensive Congo red/thioflavin S staining. Intraneuronal NFT are composed of building blocks of aberrantly hyperphosphorylated species of the microtubule-associated protein tau, which accumulate in the perinuclear cytoplasm of vulnerable neurons in the form of paired helical filaments (PHF). This unit presents a variety of protocols for the isolation, biochemical analysis, and characterization of amyloid fibrils and neurofibrillary tangles.