The structure of cross-β tapes and tubes formed by an octapeptide, αSβ1

A number of short peptides and larger proteins are able to self-assemble to form cross-b amyloid-like fibrils.[1] These bsheet peptides have been increasingly explored as potentially useful bionanomaterials due to their propensity to spontaneously assemble to form large complex structures from simple monomers.[2] An eight-residue fragment of the amyloidogenic Parkinsons disease related peptide a-synuclein,[3] named aSb1, assembles to form a helical nanostructure. Here we report the supramolecular and molecular architecture of these helical nanotubes. The supramolecular structure consists of two peptide molecules forming an amphiphilic bilayer that extends into a tape, which subsequently adopts a helical arrangement that closes to form the nanotube morphology. The structural model is proposed based on interpretation of fiber diffraction data from nanotube samples with two different textures. Analysis reveals a cross-b structure within the tapes, which go on to form an elaborate cross-b nanotubular architecture