Formation of toroids by self-assembly of an α-α corner mimetic: supramolecular cyclization

An alpha-alpha corner mimetic self-assembles to form a rod-like supramolecular structure which bends and closes end-to-end like a cyclization reaction to form uniform toroids. Each peptide fragment containing L-leucine, alpha-aminoisobutyric acid (Aib) and L-tyrosine forms rigid 3(10) helical structures stabilized by multiple intramolecular N-H. . .O hydrogen bonds. Two 3(10) helices are connected by the spacer 3-aminomethyl-benzylamine and maintain an angular distance of 120 degrees and therefore mimic the alpha-alpha corner motif of a protein super secondary structure. The individual alpha-alpha corner subunits are themselves regularly interlinked through multiple water mediated intermolecular hydrogen-bonding interactions to form the rod-like supramolecular structure and toroids. The formation of the supramolecular structure has been proven with X-ray crystallography and other spectroscopic techniques. The cyclization of the supramolecular structure and toroid formation were studied by optical microscope, AFM and FE-SEM experiments. Despite other assignments such as exfoliation of graphene from graphite, the compound exhibits significant memory to finally produce the toroids.