Directional Assembly of α‑Helical Peptides Induced by Cyclization

Effective stabilization of short peptide chains into a helical structure has been a challenge in the fields of chemistry and biology. Here we report a novel method for α-helix stabilization of short peptides through their confinement in a cyclic architecture. We synthesized block peptides based on a short peptide and a flexible linker as linear precursors. Subsequent cyclization of the peptide precursors resulted in a conformational change of the peptide unit from a random coil to an α-helix. The incorporation of hydrophobic residues into the peptide unit led to a facially amphiphilic conformation of the molecular cycle. The resulting amphiphilic peptide self-assembled into undulated nanofibers through the directional assembly of small oblate micelles

Supramolecular Switching between Flat Sheets and Helical Tubules Triggered by Coordination Interaction

Here we report the spontaneous formation of switchable sheets in aqueous solution, which is based on bent-shaped aromatic amphiphiles containing <i>m</i>-pyridine units at the terminals and a hydrophilic dendron at the apex. The aromatic segments self-assemble into flat sheets consisting of a zigzag conformation through π–π stacking interactions. Notably, the sheets reversibly transform into helical tubules at higher concentration and into discrete dimeric macrocycles at a lower concentration in response to Ag­(I) ions through reversible coordination interactions between the pyridine units of the aromatic segments and the Ag­(I) ions. While maintaining the coordination bonding interactions, the helical tubules reversibly transform into the dimeric macrocycles in response to the variation in concentration