Figure 6. Mapping of the observed protection ratios onto a fibril model.

The solvent protection ratios determined for residues within Aβ(1–40) and Aβ(1–42) fibrils are mapped onto corresponding models of the fibrils. The colour code is varied between the following extremes: navy blue for complete and red for no solvent protection. Residues with no protection ratios available are depicted in grey. Main-chain hydrogen bonds are directed along the fibril axis, perpendicular to the plane of the paper. (A and C) Ball-and-stick models showing a dimer of two cross-β units taken from a cross-section of the Aβ(1–40) and Aβ(1–42) fibril models respectively. Assignments are indicated in some positions with their one-letter amino acid codes. (B and D) Models of the fibrillar assembly for Aβ(1–40) and Aβ(1–42) respectively. The model is based on the structural model by Tycko and co-workers [23], the solution structure of Aβ(1–16) [37], our previous study [31], and the recently proposed filament packing arrangement [24]. The image was prepared in MOLMOL [36].