Structure of a self-assembled single nanotube of cyclo[(- d -Ala- l -Ala)4-]

Diameter and wall thickness of self-assembled peptide nanotube of cyclo[(-d-Ala-l-Ala)4-] were characterised by molecular simulation. In order to verify the existence of peptide nanotube of cyclo[(-d-Ala-l-Ala)4-], cyclo[(-d-Ala-l-Ala)4-] was firstly synthesised through Fmoc solid-phase synthesis method and then self-assembled in trifluoroacetic acid. Based on the results of experiment, the single nanotube structure was further characterised by molecular dynamics (MD) employing the COMPASS force field. The results indicate that cyclo[(-d-Ala-l-Ala)4-] is self-assembled into nanotube bundles of about 0.5 μm in diameter and 10 μm in length; the inner and outer diameter of the single nanotube is 8.5 and 15.9 Å, respectively, and the nanotube wall thickness is 3.3 Å.