Peptide–surfactant interactions: Consequences for the amyloid-beta structure

The conformation of amyloid-beta peptide (Aβ) determines if toxic aggregates are formed. The peptide structure by its turn depends on the environment and molecule–molecule interactions. We characterized the secondary structure of Aβ-(1–40) in surfactant solutions and interacting with monolayers. The peptide adopts β-sheet structure in solutions of ionic surfactants at sub-micelle concentrations and α-helix in the presence of ionic micelles. Uncharged micelles induce β-sheets. Aβ-(1–40) alters the critical micelle concentration value of the non-ionic surfactant, underlining hydrophobic interactions. At ionic monolayers the peptide forms β-sheets when its concentration at the surface is high enough. These results suggest that only electrostatic interactions of charged micelles that surround completely the peptide are able to induce non-aggregated α-helix structure.

► The interaction of amyloid beta-peptide (1–40)(Aβ40) with surfactants is described. ► The secondary structure of Aβ40 depends on the surfactant concentration and charge. ► Only charged micelles can induce α-helix structure on Aβ40. ► If electrostatic interactions are not sufficiently strong, Aβ40 forms β-sheets.