Fig. 4

The structures of polyQ helices feature sc(i) → mc(i −4) hydrogen bonds. a Frequencies of the various types of hydrogen bonds involving Gln side chains in the aggregated reweighted trajectories. b Frequencies of sc(i) → mc(i − 4) hydrogen bonds in the reweighted ensembles obtained for peptides L₄Q₄ to L₄Q₂₀ as a function of the position of the corresponding residue in the tract. c Distributions of the χ¹, χ², and χ³ dihedral angles of Gln side chains and of the subset of those side chains involved in sc(i) → mc(i −4) hydrogen bonds with an illustration of the values of the four side chains highlighted in d. d Frame of the trajectory obtained for L₄Q₁₆ where residues Q1 and Q4 (in purple), but not Q2 and Q3 (in black), are involved in sc(i) → mc(i − 4) hydrogen bonds with the CO groups of residues L1 and L4, shown in purple, with an indication of the conventional mc(i)→mc(i − 4) hydrogen bonds, shown in yellow. The Leu side chains are not shown, for clarity