Figure 3.

Amyloid fibril structure and spatial organization. (a) A diagram of the core cross-β structure common to protofilaments of all amyloid fibrils. Fibrils are formed by the longitudinal stacking of β sheets with a 4.7 Å repeat distance. Fibrils may contain different numbers of protofilaments [22· ·]. (b) Cross section of in vitro assembled Aβ42 peptides as calculated from SAXS pattern superimposed on a corresponding electron microscope reconstruction (left); as reconstructed from SAXS data (middle); with the corresponding SAXS data (right) [23]. (c) Structure of a dense amyloid plaque as visualized by optical microscopy after staining with congo red dye (left); as visualized by the intensity of the 4.7 A reflection (middle); and a map of fibril orientation as determined from the orientation of the 4.7 A reflection (right) [24].