Molecular dynamics simulations of amyloid-β(16-22) peptide aggregation at air-water interfaces

Oligomers of amyloid-beta (A beta) peptides are known to be related to Alzheimer's disease, and their formation is accelerated at hydrophilic-hydrophobic interfaces, such as the cell membrane surface and air-water interface. Here, we report molecular dynamics simulations of aggregation of A beta(16-22) peptides at air-water interfaces. First, 100 randomly distributed A beta(16-22) peptides moved to the interface. The high concentration of peptides then accelerated their aggregation and formation of antiparallel beta-sheets. Two layers of oligomers were observed near the interface. In the first layer from the interface, the oligomer with less beta-bridges exposed the hydrophobic residues to the air. The second layer consisted of oligomers with more beta-bridges that protruded into water. They are more soluble in water because the hydrophobic residues are covered by N- and C-terminal hydrophilic residues that are aligned well along the oligomer edge. These results indicate that amyloid protofibril formation mainly occurs in the second layer.