Tuning One-Dimensional Nanostructures of Bola-Like Peptide Amphiphiles by Varying the Hydrophilic Amino Acids

By combining experimental measurements and computer simulations, we here show that for the bola-like peptide amphiphiles XI4X, where X=K, R, and H, the hydrophilic amino acid substitutions have little effect on the beta-sheet hydrogen-bonding between peptide backbones. Whereas all of the peptides self-assemble into one dimensional (1D) nanostructures with completely different morphologies, that is, nanotubes and helical nanoribbons for KI4K, flat and multilayered nanoribbons for HI4H, and twisted and bilayered nanoribbons for RI4R. These different 1D morphologies can be explained by the distinct stacking degrees and modes of the three peptide beta-sheets along the x-direction (width) and the z-direction ( height), which microscopically originate from the hydrogen-bonding ability of the sheets to solvent molecules and the pairing of hydrophilic amino acid side chains between beta-sheet monolayers through stacking interactions and hydrogen bonding. These different 1D nanostructures have distinct surface chemistry and functions, with great potential in various applications exploiting the respective properties of these hydrophilic amino acids.