The effect of retro-inverse D-amino acid Aβ-peptides on Aβ-fibril formation.

Peptides build from D-amino acids resist enzymatic degradation. The resulting extended time of biological activity makes them prime candidates for the development of pharmaceuticals. Of special interest are D-retro-inverso (DRI) peptides where a reversed sequence of D-amino acids leads to molecules with almost the same structure, stability, and bioactivity as the parent L-peptides but increased resistance to proteolytic degradation. Here, we study the effect of DRI-Aβ40 and DRI-Aβ42 peptides on fibril formation. Using molecular dynamics simulations, we compare the stability of typical amyloid fibril models with such where the L-peptides are replaced by DRI-Aβ40 and DRI-Aβ42 peptides. We then explore the likelihood for cross fibrilization of Aβ L- and DRI-peptides by investigating how the presence of DRI peptides alters the elongation and stability of L-Aβ-fibrils. Our data suggest that full-length DRI-peptides may enhance the fibril formation and decrease the ratio of soluble toxic Aβ oligomers, pointing out potential for D-amino-acid-based drug design targeting Alzheimer's disease.