Targeting the early steps of Abeta16-22 protofibril disassembly by N-methylated inhibitors: a numerical study.

Aggregation of the Abeta1-40/Abeta1-42 peptides is a key factor in Alzheimer's disease. Though the inhibitory effect of N-methylated Abeta16-22 (mAbeta16-22) peptides is well characterized in vitro, there is little information on how they disassemble full-length Abeta fibrils or block fibril formation. Here, we report coarse-grained implicit solvent molecular dynamics (MD) and replica exchange molecular dynamics (REMD) simulations on Abeta16-22 and mAbeta16-22 monomers, and then a preformed six-chain Abeta16-22 bilayer with either four copies of Abeta16-22 or four copies of mAbeta16-22. Our simulations show that the effect of N-methylation on mAbeta16-22 monomer is to reduce the density of compact forms. While 100 ns MD trajectories do not reveal any significant differences between the two ten-chain systems, the REMD simulations totaling 1 micros help understand the first steps of Abeta16-22 protofibril disassembly by N-methylated inhibitors. Notably, we find that mAbeta16-22 preferentially interacts with Abeta16-22 by blocking both beta-sheet extension and lateral association of layers, but also by intercalation of the inhibitors allowing sequestration of Abeta16-22 peptides. This third binding mode is particularly appealing for blocking Abeta fibrillogenesis.