Figure 1.

Schematic representation of proposed structural models for aggregated mutant polyGln. β-Sheet is shown as a zig-zag. Expanded polyGln as an extended antiparallel β-sheet, first described by Max Perutz as a “polar zipper” (a), or as a parallel β-sheet (b). (c) An antiparallel β-hairpin comprised of two β-strands and a single β-turn. A highly compact structure, consisting of four antiparallel random coil (d) or β-strand (e) elements. (f) A parallel β-helix with 20 residues per turn. For simplicity, two polyGln molecules are shown each for a and b, whereas a single polyGln molecule is depicted in c–f.