Fig. 1.

Schematic illustration of the catalytic power of an α-helix. a Illustration of possible binding sites at the termini of a free α-helical polypeptide. Intrahelical H-bonds are represented with orange lines. Side chains are omitted for simplicity. b Analysis of H-bond acceptors (red) and donors (blue) in an NCA molecule and its polymerization to synthesize polypeptides. c Proposed binding of NCA with the N terminus of an α-helix and subsequent ring-opening reaction for the growth of polypeptide. The newly formed residue from NCA is highlighted in green.