RESUMEN
Adsorption of sequential amphiphilic peptides on solid substrates triggered the spontaneous construction of nanoscaled architecture. An amphiphilic peptide designed with a cationic amino acid as a hydrophilic residue turned an anionic mica substrate into a water-repellent surface, simply by adsorbing it on the substrate surface. In contrast, an amphiphilic peptide designed with an anionic amino-acid residue formed a precisely controlled fiber array comprising a ß-sheet fiber monolayer at the anionic substrate/water interface. This phenomenon was based on the secondary structural transition from random-coil to ß-sheet, which occurred specifically when amphiphilic peptide adsorbed on the substrate surface. Such surface-specific nonorder/order transition was implemented by exploiting the strength of adsorption between the peptide and the substrate. A strategic design exploiting weak bonding such as hydrophobic interactions is essential for constructing precisely controlled nano-architectures in two dimensions.
RESUMEN
An amphiphilic peptide derivative, conjugated to polyethylene glycol (PEG) via the C-terminus, spontaneously assembled into nanodot and nanofiber arrays aligned with nanometer periodicity at the solid/water interface. The obtained planar structure was precisely controlled by the ß-sheet conformation of the peptide on the surface, while the peptide segment adopted a random-coil in aqueous solution. The peptide and PEG segments were hierarchically segregated after the peptide-PEG conjugate was adsorbed on the substrate, and the peptide segment transitioned from a random-coil to a ß-sheet conformation specifically at the solid/water interface. In this 2D self-assembly, the high dispersity of the peptide-PEG molecule in solution such that it exists as single molecules is essential for improving the uniformity of the 2D patterned nanostructures. The secondary structure based on the peptide segment was controlled by pH of the solution. Configuration of the peptide-PEG conjugate was also controlled by the temperature of the solution, which depended on the lower critical solution temperature (LCST) of the PEG segments. The variation in concentration of the peptide-PEG conjugate drastically influenced the morphologies of the 2D nanostructures because of the difference in the adsorbed amounts at equilibrium.