Formation of closed-cage nanostructures by self-assembly of aromatic dipeptides

We recently demonstrated that the diphenylalanine recognition motif of the Alzheimer's beta-amyloid polypeptide self-assembles into ordered and discrete nanotubes. Here, we reveal that diphenylglycine, a highly similar analogue and the simplest aromatic peptide, forms spherical nanometric assemblies. As the nanotubes, the nanospheres assemble efficiently and have remarkable stability. The introduction of a thiol group into the diphenylalanine peptide alters its assembly from tubular to spherical particles similar to those formed by diphenylglycine. The formation of either nanotubes or closed-cages by fundamentally similar peptides is consistent with a two-dimensional layer closure, as described both for carbon and inorganic nanotubes and their corresponding buckminsterfullerene and fullerene-like structures.