The amyloid-[beta] fibrils have a common parallel, in-register stacking organization based on the beta-pleated sheet
stacking of the amyloid-[beta] peptide [16, 23-26].
 Amyloidosis, either primary or secondary, is defined as a group of chronic infiltrative disorders that have in common a beta-pleated sheet
configuration visualized on X-ray diffraction, a fine fibrillar nonbranching appearance on electron microscopy, and an apple-green birefringence when examined under polarized light after staining with Congo red.
These appeared throughout the samples and often appeared directly adjacent to large [beta]-pleated sheets, however it is unclear whether these structures merged to form the beta-pleated sheet
or whether the fibrils were products of the large sheet of peptide.
The pathologic features of amyloid deposits include beta-pleated sheet
structures that are composed of amyloid fibrils with diameters between 8 to 10 nm.
There are 12 of these regions in one Notch protein, each containing three beta-pleated sheets
. Each EGF repeat contains one two-stranded beta-pleated sheet
Amyloidosis is not a single disease entity but a spectrum of diseases that have in common the extracellular deposition of insoluble protein fibrils in tissue or organs in a beta-pleated sheet
(16-18) Identification of amyloid is based on three criteria: (1) Congo red binding and green birefringence under polarized light, (19) (2) a fibril structure on electro microscopy, (20) and (3) confirmation of the characteristic cross beta-pleated sheet
on x-ray crystallography and infrared spectroscopy.
The most common secondary structures are the alpha helix and the ribbon-like beta-pleated sheet
(see top diagram, p.346).
Sections stained with Congo red dye demonstrated the characteristic yellow and apple-green birefringence, and the lesion had the beta-pleated sheet
structure and antiparallel conformation by low-angle x-ray diffraction, typical of amyloidosis.
In brief, amyloid protein deposits are composed of abnormally folded serum amyloid P, glycosaminoglycans, and fibril proteins which fold into characteristic beta-pleated sheets
. These abnormal protein deposits are insoluble, resistant to macrophage mediated degradation, and result in organ failure due to anatomic disruption of normal tissue function and organ blood supply.