Anchoring of Amyloid-β onto Polyunsaturated Phospholipid Membranes

The interaction between the toxic amyloid-beta and phospholipid membranes in the early stage of Alzheimer's disease is complicated and depends on many factors. It was found that polyunsaturated fatty acids affect the incidence of Alzheimer's disease. The number of double bonds in the phospholipid layer may play an important role in the molecular dynamic behavior of amyloid-beta on cell membranes. In the present paper, the interactions between A beta(25-35) and each of four phospholipids, 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), 1-stearoyl-2-arachidonoyl-sn-glycero-3-phosphocholine (SAPC), 1-stearoyl-2-docosahexaenooyl-sn-glycero-3-phosphocholine (SDPC), and 1,2-diarachidonoyl-sn-glycero-3-phosphocholine (DAPC), are investigated by using all-atom molecular dynamics simulation. It is interesting that, as the number of double bonds in the membrane increases, the peptide fragment prefers to stay in the surface region of the membrane rather than penetrates deeply into the membrane. With the increasing number of double bonds, the interaction between A beta(25-35) and the membrane surface becomes stronger, especially for the interaction between the residue 28 (LYS28) in A beta(25-35) and the phospholipids, anchoring A beta(25-35) onto the membrane. The double bonds in phospholipid determine not only the adsorption of the peptide fragment A beta(25-35) but also its conformation, which will influence further aggregation of A beta in later stages.