Synergistic effect and hierarchical nanostructure formation in mixing two designer lipid-like peptide surfactants Ac-A6D-OH and Ac-A6K-NH2.

We here report the nanostructures from combinational self-assembly of two designer lipid-like peptides Ac-A6D-OH and Ac-A6K-NH2 using dynamic light scattering (DLS) and atomic force microscopy (AFM). The synergistic phenomenon is observed by measuring the critical aggregation concentrations (CACs) of these two mixed peptides, in different molar ratios by DLS. The nanoropes were observed in AFM images at a molar ratio of Ac-A6D-OH/Ac-A6K-NH2 = 1:1, and the thin film formation with aligned nanoropes is shown at a molar ratio of 2:1. The well aligned nanoropes at the molar ratio of Ac-A6D-OH/Ac-A6K-NH2 = 2:1 indicated the competition factor between the electrostatic repulsion according to DLVO theory and the hydrophobic interaction arising from the long side chains on lysine residues. This study will further our understanding for designing new nanomaterials based on designer lipid-like peptide surfactants.