Designer Helical Fibers and Tubes: Self-assembling Hybrid Peptides via Leu/Ile-Phe Zipper

Here, we present a family of simple peptides that show diverse self-assembling behaviors. We used aliphatic (Leu/Ile) and aromatic (Phe) amino acids to delineate our design. The design consists of phenylene urea at the N-terminus of the peptide. The urea peptides with sequence Phe-LeuOMe (1) or Phe-IleOMe (2) associate to form polygonal peptide tubes via zipper arrangements, supported by microscopic and single crystal X-ray diffraction studies. The peptide with Phe placed away from the phenylene urea (3 and 4), showed fibrous assembly. All the peptides showed autofluorescence and red edge excitation behavior upon self-assembly.