Effect of Achiral Glycine Residue on the Handedness of Surfactant-Like Short Peptide Self-Assembly Nanofibers.

Surfactant-like short peptides are a kind of ideal model for the study of chiral self-assembly. At present, there are few studies on the chiral self-assembly of multicharged surfactant-like peptides. In this study, we adopted a series of short peptides of Ac-IKGK-NH with different combinations of -lysine and -lysine residues as the model molecules. TEM, AFM and SANS results showed that Ac-IKGK-NH, Ac-IKGK-NH, and Ac-IKGK-NH formed the morphologies of nanofibers, and Ac-IKGK-NH formed nanoribbons. All the self-assembled nanofibers, including the intermediate nanofibers of Ac-IKGK-NH nanoribbons, showed the chirality of left handedness. Based on the molecular simulation results, it has been demonstrated that the supramolecular chirality was directly dictated by the orientation of single β strand. The insertion of glycine residue demolished the effect of lysine residues on the single strand conformation due to its high conformational flexibility. The replacement of -isoleucine with -isoleucine also confirmed that the isoleucine residues involved in the β-sheet determined the supramolecular handedness. This study provides a profound mechanism of the chiral self-assembly of short peptides. We hope that it will improve the regulation of chiral molecular self-assembly with achiral glycine, as well.