De novo design: backbone conformational constraints in nucleating helices and beta-hairpins.

A modular approach to synthetic protein design is being developed using conformationally constrained amino acid as stereochemical directors of polypeptide chain folding. An overview of studies aimed at constructing peptide helices using alpha,alpha-dialkyated residues and beta-hairpins using D-Pro as a turn nucleator is presented. The construction of helix-helix motifs and three- and four-stranded structures has been achieved using non-protein amino acids to stabilize specific elements of secondary structures.