ToF-SIMS analysis of amyloid beta aggregation on different lipid membranes

Amyloid beta (A beta) peptides are considered to be strongly related to Alzheimer's disease. A beta peptides form a beta-sheet structure on hard lipid membranes and it would aggregate to form amyloid fibrils, which are toxic to cells. However, the aggregation mechanism of A beta is not fully understood. To evaluate the influence of the lipid membrane condition for A beta aggregation, the adsorption forms of A beta (1-40) on mixture membranes of lipid 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and cholesterol beta-D-glucoside (beta-CG) were investigated by time-of-flight secondary ion mass spectrometry. As a result, A beta adsorbed along the localized DMPC lipid on the mixture lipid membranes, whereas it was adsorbed homogeneously on the pure DMPC and beta-CG membranes. Moreover, amino acid fragments that mainly existed in the n-terminal of A beta (1-40) peptide were strongly detected on the localized DMPC region. These results suggested that the A beta was adsorbed along the localized DMPC lipid with a characteristic orientation. These findings suggest that the hardness of the membrane is very sensitive to coexisting materials and that surface hardness is important for aggregation of A beta. (C) 2016 American Vacuum Society.