Conformational characteristics of peptides containing alpha, beta-dehydroamino acid residues.

The structural preferences of synthetic peptides containing alpha, beta-dehydroamino acid residues, as determined by theoretical studies, x-ray diffraction analyses, and spectroscopic studies, are reviewed. The role of delta ZPhe residues in stabilizing type II beta-turn structures in small peptides and in nucleating helical structure in longer peptides is exemplified by several crystal as well as solution structural studies. From the few studies reported so far it appears that delta ZLeu influences the peptide backbone, much like the delta ZPhe residue, whereas delta Ala prefers the extended conformation, suggesting that the nature of beta substituents might influence the conformation restriction behavior of the dehydroresidues. Conformational studies on synthetic peptides containing delta E, delta ZAbu, and delta Val have also been described.