Metal-Ion-Mediated Supramolecular Assembly of C3-Peptides

An investigation on a supramolecular assembly of C-3-molecules benzene- 1,3,5-tricarboxamides carrying tetrapeptide Gly-Ala-Gly-Ala pendants promoted by hydrogen bonding and metal ion coordination is described. A Gly-Ala peptide sequence was selected as it is the most abundant repeating unit in silkworm silk, and known to form beta-sheets through efficient intermolecular hydrogen bonds. These C-3-peptides formed long helical fibers in solvents mainly owing to strong hydrogen bonding. However, in the presence of divalent metal ions, chirality of these helical fibers was enhanced through metal coordination and could be transformed into nanospheres with an excess amount of the ions. Different metal ions show different tendencies to mediate the supramolecular chirality, which can even be inverted according to coordination differences.