title: The Physical Properties and Self-Assembly Potential of the RFFFR Peptide.
abstract: The self-assembly of fibers from peptides has attracted a tremendous amount of attention due to its many applications, such as in drug-delivery systems, in tissue engineering, and in electronic devices. Recently, the self-assembly potential of the designer peptide RFFFR has been reported. Here it is experimentally verified that the peptide forms fibers that are entangled and form solid spheres without water inside. Upon dilution below the critical fiber concentration, the fibers untangle and become totally separated prior to dissolution. These structures readily bind thioflavin T, resulting in a characteristic change in fluorescent properties consistent with β-sheet-rich amyloid structures with aromatic/hydrophobic grooves. The circular dichroism spectroscopy data are dominated by a π→π* transition, thus indicating that the fibers are stabilized by π-stacking. Contrary to what was expected, the dissolution of the spheres/fibers results in increasing fluorescence anisotropy over time. This is explained in terms of HomoFRET between phenylalanine residues with a T-shaped π-stacking mode, which was determined in another study to be the dominant mode through atomistic simulations and semiempirical calculations. Kelvin probe force microscopy measurements indicate that the spheres and fibers have a conductivity comparable to that of gold. Hence, these self-assembled structures might be applicable in organic solid-state electronic devices. The dissolution properties of the spheres further suggest that they might be used as drug-delivery systems.
authors: Department of Physics and Nanotechnology, Aalborg University, Skjernvej 4 A, 9220, Aalborg Øst, Denmark.
authors: Morten
authors: M
authors: Slyngborg
authors: Department of Physics and Nanotechnology, Aalborg University, Skjernvej 4 A, 9220, Aalborg Øst, Denmark.
authors: Dennis Achton
authors: DA
authors: Nielsen
authors: Department of Physics and Nanotechnology, Aalborg University, Skjernvej 4 A, 9220, Aalborg Øst, Denmark. fp@nano.aau.dk.
authors: Peter
authors: P
authors: Fojan
mesh_terms: D002942:Circular Dichroism; D016503:Drug Delivery Systems; D031541:Fluorescence Resonance Energy Transfer; D057927:Hydrophobic and Hydrophilic Interactions; D009842:Oligopeptides / Q000138:chemical synthesis* / Q000737:chemistry*; D017433:Protein Structure, Secondary
chemical_list: D009842:Oligopeptides; C000622104:arginyl-phenylalanyl-phenylalanyl-phenylalanyl-arginine
keywords: RFFFR; designer peptides; drug delivery; molecular electronics; self-assembly