Self-Assembled Surfactant Cyclic Peptide Nanostructures as Stabilizing Agents

A number of cyclic Peptides including [FR]₄, [FK]₄, [WR]₄, [CR]₄, [AK]₄, and [WK]_n (n = 3-5) containing L-amino acids were produced using solid-phase peptide synthesis. We hypothesized that an optimal balance of hydrophobicity and charge could generate self-assembled nanostructures in aqueous solution by intramolecular and/or intermolecular interactions. Among all the designed Peptides, [WR]_n (n = 3-5) generated self-assembled vesicle-like nanostructures at room temperature as shown by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and/or dynamic LIGHT scattering (DLS). This class of Peptides represents the first report of surfactant-like cyclic Peptides that self-assemble into nanostructures. A plausible mechanistic insight into the self-assembly of [WR]₅ was obtained by molecular modeling studies. Modified [WR]₅ analogues, such as [W_MeR]₅, [WR_(Me)2]₅, [W_MeR_(Me)2]₅, and [WdR]₅, exhibited different morphologies to [WR]₅ as shown by TEM observations. [WR]₅ exhibited a significant stabilizing effect for generated silver nanoparticles and glyceraldehyde-3-phosphate dehydrogenase activity. These studies established a new class of surfactant-like cyclic Peptides that self-assembled into nanostructures and could have potential applications for the stabilization of silver nanoparticles and protein biomolecules.