Figure 1.

Formation of structurally different amyloid species. Starting from monomeric proteins (green), monomers can follow the on-pathway and aggregate into fibrillar oligomers (brown). Fibrillar oligomers will over time grow into mature fibrils (blue) that might, together with other species and molecules, deposit as plaques. Mature fibrils can undergo secondary nucleation during which monomers attach to a mature fibril and form a new fibril. In addition, fibrillar oligomers could seed formation of fibrils with monomers of a different protein (yellow), referred to as cross-seeding. Monomers might also follow the off-pathway and fold into oligomers (beige) and further into curvilinear fibrils (dark blue).