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Interaction of the Alzheimer Aβ(25–35) peptide segment with model membranes

Publication . Cuco, Andreia; Serro, Ana Paula; Farinha, José Paulo; Saramago, Benilde; Silva, Amélia Gonçalves da

Alzheimer’s disease is characterized by the presence of amyloid plaques in the brain. The main components of these plaques are the Aβ(1–40) and Aβ(1–42) peptides but the Aβ(25–35) sequence is the most frequently studied fragment because it represents a biologically active region of the longer Aβ peptides. In the present work, the interactions of Aβ(25–35) peptide with model membranes were investigated, taking into consideration the aggregation state of the peptide. Monolayers and liposomes were taken as model membranes with two lipid compositions: the equimolar ternary mixture of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), sphingomyelin (SM), and cholesterol (Chol) and the equimolar POPC/SM binary mixture. The interaction of Aβ(25–35) with the monolayers, investigated at low concentrations (0.25–4 μM), suggested a three step mechanism: adsorption—monomers or dimers adsorb at the polar region of the lipid monolayer; nucleation—adsorbed peptides act as nucleation sites for higher aggregates; and penetration—these aggregates insert in the hydrophobic region of the monolayer. Chol slightly enhances the peptide–lipid monolayer interaction. The large aggregates nucleated in the bulk solution evidenced a weak interaction with monolayers. The interaction of Aβ(25–35) with liposomes, followed by a Quartz Crystal Microbalance with Dissipation (QCM-D) in a large range of peptide concentrations (10–80 μM), was very small, independently of the peptide concentration.

2016-05Journal article

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