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

Abstract

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-I4KGK-NH2 with different combinations of L-lysine and D-lysine residues as the model molecules. TEM, AFM and SANS results showed that Ac-I4 L KG L K-NH2, Ac-I4 L KG D K-NH2, and Ac-I4 D KG L K-NH2 formed the morphologies of nanofibers, and Ac-I4 D KG D K-NH2 formed nanoribbons. All the self-assembled nanofibers, including the intermediate nanofibers of Ac-I4 D KG D K-NH2 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 L-isoleucine with Da-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.