Secondary structure analysis of the polyQ peptides.

Here, we give the (a) population (as a percentage) of the residues in the different Ramachandran regions (, , PPII, and ), as well as the population of residues involved in repeats; (b) the population (as a percentage) of residues in different secondary structures (helix, turn, and other secondary structures); (c) the percentage of conformations having at least one PPII, , or extended secondary structures including isolated strands and hairpins. The isolated , , or (, , or ) strands – identified in the table as PPII-s, -s, -s – are defined based on at least three (four) adjacent residues with the backbone dihedral angles falling into the region associated with these structures; and not involved in any inter-residual hydrogen bonding. Similarly a hairpin – identified in the table as PPII-h, -h, -h – is defined based on two adjacent strands of at least three residues with one or more hydrogen bonds between the two strands and a turn in between. For more details of this analysis, that is based on both DSSP [58], [59] and dihedral-based clustering, see Methods.