title: Coassembly in binary mixtures of peptide amphiphiles containing oppositely charged residues.
abstract: The self-assembly in water of designed peptide amphiphile (PA) C16-ETTES containing two anionic residues and its mixtures with C16-KTTKS containing two cationic residues has been investigated. Multiple spectroscopy, microscopy, and scattering techniques are used to examine ordering extending from the β-sheet structures up to the fibrillar aggregate structure. The peptide amphiphiles both comprise a hexadecyl alkyl chain and a charged pentapeptide headgroup containing two charged residues. For C16-ETTES, the critical aggregation concentration was determined by fluorescence experiments. FTIR and CD spectroscopy were used to examine β-sheet formation. TEM revealed highly extended tape nanostructures with some striped regions corresponding to bilayer structures viewed edge-on. Small-angle X-ray scattering showed a main 5.3 nm bilayer spacing along with a 3 nm spacing. These spacings are assigned respectively to predominant hydrated bilayers and a fraction of dehydrated bilayers. Signs of cooperative self-assembly are observed in the mixtures, including reduced bundling of peptide amphiphile aggregates (extended tape structures) and enhanced β-sheet formation.
authors.affiliation: School of Chemistry, Pharmacy and Food Biosciences, University of Reading, Reading, UK.
authors.forename: I W
authors.initials: IW
authors.lastname: Hamley
authors.forename: A
authors.initials: A
authors.lastname: Dehsorkhi
authors.forename: V
authors.initials: V
authors.lastname: Castelletto
mesh_terms: D002942:Circular Dichroism; D008567:Membranes, Artificial; D010455:Peptides / Q000737:chemistry*; D017433:Protein Structure, Secondary; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D008567:Membranes, Artificial; D010455:Peptides