Fabrication of nanofibers with uniform morphology by self-assembly of designed peptides

Fabrication of controlled peptide nanofibers with homogeneous morphology has been demonstrated. Amphiphilic P-sheet peptides were designed as sequences of Pro-Lys-X-1-Lys-X-2-X-2-Glu-X-1-Glu-Pro. X-1 and X-2 were hydrophobic residues selected from Phe, Ile, Val, or Tyr. The peptide FI (X-1 = Phe; X-2 = Ile) self-assemble into straight fibers with 80-120 nm widths and clear edges, as examined by transmission electron microscopy (TEM) and atomic force microscopy (AFM). The fiber formation is performed in a hierarchical manner: beta-sheet peptides form a protofibril; the protofibrils assemble side-by-side to form a ribbon, and the ribbons then coil in a left-handed fashion to make up a straight fiber. These type of fibers are formed from peptides possessing hydrophobic aromatic Phe residue(s). Furthermore, a peptide with Ala residues at both N and C termini does not form fibers (100 nm scale) with clear edges; this causes random aggregation of small pieces of fibers instead. Thus, the combination of unique amphiphilic sequences and terminal Pro residues determine the fiber morphology.