Ribbon structure stabilized by C10 and C12 turns in αγ hybrid peptide.

The present study describes the synthesis and crystallographic analysis of αγ hybrid peptides, Boc-Gpn-L-Pro-NHMe (1), Boc-Aib-Gpn-L-Pro-NHMe (2), and Boc-L-Pro-Aib-Gpn-L-Pro-NHMe (3). Peptides 1 and 2 adopt expanded 12-membered (C12 ) helical turn over γα segment. Peptide 3 promotes the ribbon structure stabilized by type II ß-turn (C10 ) followed by the expanded C12 helical γα turn. Both right-handed and left-handed helical conformations for Aib residue are observed in peptides 2 and 3, respectively.