Stabilization of β-hairpin structures via inter-strand π-π and hydrogen bond interactions in α-, β-, γ-hybrid peptides

Helix formation in preorganized beta/gamma-peptide foldamers: hydrogen-bond analogy to the alpha-helix without alpha-amino acid residues

We report the first high-resolution structural data for the beta/gamma-peptide 13-helix (i,i+3 C=O...H-N H-bonds), a secondary structure that is formed by oligomers with a 1:1 alternation of beta- and gamma-amino acid residues. Our characterization includes both crystallographic and 2D NMR data. Previous studies suggested that beta/gamma-peptides constructed from conformationally flexible residues adopt a different helical secondary structure in solution. Our design features preorganized beta- and gamma-residues, which strongly promote 13-helical folding by the 1:1 beta/gamma backbone.