Aromatic Motifs Dictate Nanohelix Handedness of Tripeptides.

Self-assembly of peptides and amyloid fibrils offers an appealing approach for creating chiral nanostructures, which has promising applications in the fields of biology and materials science. Although numerous self-assembled chiral materials have been designed, the precise control of their twisting tendency and their handedness is still a challenge. Herein, we report the self-assembly of chiral nanostructures with precisely tailored architectures by changing the amino acid sequences of the peptides. We designed a series of self-assembling tripeptides bearing different l-amino acid sequences. The peptide with l-Phe-l-Phe sequence preferred to self-assemble into left-handed nanohelices, while with l-Phe-l-Trp right-handed nanohelices would be formed. Moreover, the diameter of the self-assembled nanohelices could be tailored by changing the terminal amino acids (His, Arg, Ser, Glu, and Asp). Circular dichroism (CD) and molecular dynamics simulations (MDSs) revealed that both of the right- and left-handed nanohelices formed by the tripeptides showed negative Cotton effects in the peptide adsorption region but exhibited nearly opposite CD Cotton effects in the aromatic regions. These results indicated that the handedness of the self-assembled helical nanofibers was not only determined by the chirality of the peptide backbone but also closely related to the aromatic stacking, hydrogen bonding and steric interactions induced by the side chains. The findings deepen our understanding on the chiral self-assembly of peptide and offer opportunities for the creation of highly functional chiral nanomaterials.