Figure 4.

Length dependence of t/c for the series Ac-Hel₁–A_n-NH₂ (n = 1–6; open circles) and Ac-Hel₁–A₅KA_m-NH₂ (m = 0–6; filled circles). Data are taken from ref. 5. Error bars represent a 3% uncertainty in the experimentally determined t/c ratios. The solid line corresponds to the t/c ratios predicted from the Lifson–Roig-based model by using the parameters determined from fitting the Ac-Hel₁–A_n-OH series in water. The dotted line indicates the best fit to the Ac-Hel–A₅KA_m-NH₂ series when the intrinsic template propensities are allowed to vary. The Inset shows the relative increase in the t/c ratio for Ac-Hel₁–A₅KA_m-NH₂ series members on addition of a single alanine residue (see Discussion).