Figure 4. Water-facing surface of polyQ amyloid.

(A) Atomistic MD snapshot of the D₂Q₁₅K₂ peptide fibril’s polyQ surface in contact with water. Exposed and buried Gln residues are colored green and gray, respectively. Note how the Gln side-chains internal to the (model M1) amyloid core are well-ordered, while the water-facing side-chains display more mobility. (B) Side-chain dihedral angle distributions for the buried Gln residues, and (C) for the Gln residues on the fibril surface. The surface-facing residues show more disorder, but are nonetheless constrained to eight varyingly prominent specific rotamer states.