Unprecedented Chain-Length-Dependent Conformational Conversion Between 11/9 and 18/16 Helix in α/β-Hybrid Peptides

Angewandte Chemie, 2014, Volume: 53, Issue: 48, Pages: 13131-13135, DOI: 10.1002/anie.201407329

B. Legrand, C. Andre, L. Moulat, E. Wenger, C. Didierjean, E. Aubert, M. Averlant-Petit, J. Martinez, M. Calmes, M. Amblard


α,β-Hybrid oligomers of varying lengths with alternating proteogenic α-amino acid and the rigid β2,3,3-trisubstituted bicyclic amino acid ABOC residues were studied using both x-ray crystal and NMR soln. structures.  While only an 11/9 helix was obtained in the solid state regardless of the length of the oligomers, conformational polymorphism as a chain-length-dependent phenomenon was obsd. in soln.  Consistent with DFT calcns., short oligomers adopted an 11/9 helix, whereas an 18/16 helix was favored for longer oligomers in soln.  A rapid interconversion between the 11/9 helix and the 18/16 helix occurred for oligomers of intermediate length.