Nanostructures from the self-assembly of α-helical peptide amphiphiles.

Self-assembly of PAs composed of palmitic acid and several repeated heptad peptide sequences, C₁₅H₃₁CO-(IEEYTKK)(n)-NH₂ (n = 1-4, represented by PA1-PA4), was investigated systematically. The secondary structures of the PAs were characterized by CD. PA3 and PA4 (n = 3 and 4, respectively) showed an α-helical structure, whereas PA1 and PA2 (n = 1 and 2, respectively) did not display an α-helical conformations under the tested conditions. The morphology of the self-assembled peptides in aqueous medium was studied by transmission electron microscopy. As the number of heptad repeats in the PAs increased, the nanostructure of the self-assembled peptides changed from nanofibers to nanovesicles. Changes of the secondary structures and the self-assembly morphologies of PA3 and PA4 in aqueous medium with various cations were also studied. The critical micelle concentrations were determined using a pyrene fluorescence probe. In conclusion, this method may be used to design new peptide nanomaterials.