Coassembly in binary mixtures of peptide amphiphiles containing oppositely charged residues

Hamley, I.W. ORCID: https://orcid.org/0000-0002-4549-0926, Dehsorkhi, A. and Castelletto, V. (2013) Coassembly in binary mixtures of peptide amphiphiles containing oppositely charged residues. Langmuir, 29 (16). pp. 5050-5059. ISSN 0743-7463 doi: 10.1021/la400163q

Abstract/Summary

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.