Promotion of Folding in Hybrid Peptides through Unconstrained γ Residues: Structural Characterization of Helices in (αγγ)_<i>n</i> and (αγα)_<i>n</i> Sequences

Abstract

The γ-amino acid residue γ4(R)Val promotes helical folding even in short (αγα)n sequences. A mixed C12/C14 helix (in which hydrogen bonds close a ring of 12 or 14 atoms) is established in a 12-residue (αγγ)4 sequence (see picture, right). The 6-residue (αγα)2 sequence (left), devoid of backbone conformational constraints, folds into a C12/C10 helix.