Modular salt-induced nanostructures formed by a functionalized dipeptide system.

Self-assembling peptides have great potential in nanotechnology. We introduce the naphthalene-modified dipeptide isoleucine-phenylalanine (2NapIF) as a modular system for creating various nanostructures via self-assembly, including fibers, nanotubes, and bundles, resulting from the addition of salts. Mechanical stirring is crucial for developing certain supramolecular architectures. Using cryo-electron microscopy (cryo-EM), we found that the structural organization of these nanostructures is primarily driven by hydrophobic stacking of aromatic rings and hydrogen bonding among peptide atoms. The diversity in packing arises from the ability of 2NapIF to adopt multiple conformations, with our studies revealing 18 distinct conformations within a KCl-induced nanotube. This results in a large asymmetric unit containing 18 molecules, with 18 conformations, that could never have been predicted with current tools. This modular system has potential applications in creating innovative materials, including robust, salt-responsive "noodles" that exceed a meter in length.