Supramolecular Assembly of Collagen-Mimetic Peptide D-Periodic Fibrils and Nanoassemblies.

The collagen triple helix assembles hierarchically into bundled oligomers, solvated networks, and fibers. Synthetic peptide assemblies, driven by supramolecular interactions, can form single triple helices through intrahelical amino acid pairs; however, the principles guiding interhelical associations into higher-order structures remain unclear. Here, we incorporate cation-π and electrostatic charge pairs to probe interhelical interactions and elucidate the mechanisms driving triple helix assembly into fibrils, nanotubes, and nanosheets. Introducing cation-π pairs into a fibrillating collagen mimetic resulted in D-periodic fibrils with pH-sensitive gelation. By alternating the presentation of electrostatic and cation-π pairs, the assembly of another D-periodic fibril featuring inner and outer triple-helical layers was resolved by cryo electron microscopy to a resolution of 8 Å. At physiological pH, antiparallel association of these triple helices leads to the formation of nanotubes. The packing behavior of triple helices correlates with the interhelical interactions, where parallel associations favor fibril formation and antiparallel interactions drive nanotube and nanosheet assembly. These self-assembling triple-helical peptides demonstrate how packing of higher-order structures can be tailored with supramolecular interactions and establish the relationship of different hierarchical collagen-mimetic assemblies as pH-dependent.