New Helical Folds in a-Peptides with Alternating Chirality

摘要

In α-peptides, the 8/10 helix is theoretically predicted to be energetically unstable and has not been experimentally observed so far. Based on our earlier studies on 'helical induction' and 'hybrid helices', we have adopted the 'end-capping' strategy to induce the 8/10 helix in α-peptides by using short α/β-peptides. Thus, α-peptides containing a regular string of α-amino acids with alternating chirality were end capped by α/β-peptides with 11/9-helical motifs at the termini. Extensive NMR spectroscopy studies of these peptides revealed the presence of a hitherto unknown 8/10- helical pattern; the H-bonds in the shorter pseudorings were rather weak. The approach of using short helical motifs to induce new mixed helices in α-peptides could provide avenues for more versatile design strategies.