Helical Sense Control of Metal-Peptide Torus Frameworks Leading to the Folding and Assembly of a AgL Braided Peptide Nanotube.

The chirality of helical polypeptides is correlated to that of their constituent amino acid residues. For polypeptides with non-natural backbones, however, such correlations are less clear. Here, circular double helices with torus knot/link topologies were assembled from non-natural metal-peptide chains composed of Ag(I) ions and ditopic tripeptides with Gly-Gly-Ala and Gly-Ala-Gly sequences. We found that the chirality of the assembled helical structures is determined by the l-Ala's dihedral angles. A tubular dimeric structure with an ML composition was further achieved via additional metal cross-linking, showing rational design potential for artificial peptide helices.