Effects of Dimethyl Sulfoxide and Mutations on the Folding of Abeta(25-35) Peptide: Molecular Dynamics Simulations

The 25-35 fragment of the amyloid β(Aβ) peptide is a naturally occurring proteolytic by-product of its larger parent molecule that retains the amyloid characteristics and toxicity of the full length parent molecule. Aggregation of this peptide occurs rapidly in aqueous solutions and thus characterization of its folding process is very difficult. In the present study, early stages of Aβ(25-35) folding were observed in the presence of two mutations (N27A and M35A) in pure water, before and after exposure to pure dimethyl sulfoxide (DMSO) by conducting molecular dynamics simulations. Hydrophobic mutations decreased flexibility in the peptides structures, and peptide terminal mutation resulted in more compactness and beta secondary structure formation. Meanwhile, pure DMSO dramatically reduced the peptides dynamics, and pre-treatment with pure DMSO caused reduction and delay in beta structure formation in all studied peptides. It is concluded that the introduction of dimethyl sulfoxide and hydrophobic terminal M35A mutation could notably affect the folding of Aβ(25- 35).