THE RELATION OF THE PROPERTIES OF CONGO RED-STAINED AMYLOID FIBRILS TO THE β-CONFORMATION

Amyloid fibrils and the aminoterminal variable fragment of some Bence Jones proteins are known to have Congo red affinity and, after staining, to exhibit dichroism, polarization birefringence and a green polarization color. X-ray crystallographic analysis demonstrates the presence in these preparations of a 4.72-4.76Å d-spacing indicating an antiparallel chain β-pleated sheet structure as the major conformation. Only the β-form of poly-l-lysine has all of these properties. It is suggested that the tinctorial and polarization optical properties of amyloid deposits stained with Congo red may be at least in part dependent upon the presence of the β-structure as the major protein conformation of amyloid fibrils.