Structural Characterization of α/β-Peptides having Alternating Residues: X-ray Structures of the 11/9-Helix from Crystals of Racemic Mixtures

摘要

The development of proteinlike structures of oligomers which contain unnatural amino acids (peptidic foldamers) is an active area of research. A variety of distinct conformations of peptidic foldamers that are analogous to protein secondary structures have been discovered to date. Helical structures of peptidic foldamers are particularly interesting because diverse helical conformations with unconventional hydrogen-bonding interactions are available. Two prominent helices, the α-helix and the 3_(10)-helix, in natural proteins arise from (i,i +4) and (i,i + 3) C=O—H—N hydrogen bonding, respectively. A number of helical structures in peptidic foldamers arise from a single type of C=O—H—N hydrogen bond, thus resulting in a macrodipole along the helical axis.