Accelerated Amyloid Aggregation Dynamics of Intrinsically Disordered Proteins in Heavy Water.

We explored the influence of DO on the fibrillation kinetics and structural dynamics of amyloid intrinsically disordered proteins (IDPs), including α-synuclein, amyloid-β 1-42, and K18. Our findings revealed that fibrillation of IDPs was accelerated in DO compared to that in HO, exhibiting faster kinetics in contrast to the structured protein, insulin. Structural investigations using electrospray ionization ion mobility mass spectrometry and small-angle X-ray scattering combined with molecular dynamics simulations demonstrated that IDPs did not show significant structural changes that could influence accelerated fibrillation in DO. Umbrella sampling of protein protofibrils verified that an increased level of hydrogen bonding of DO and enhanced hydrophobic interactions stabilized β-sheet structured fibrils in DO. These findings indicate that stabilizing β-sheet fibrils and a more hydrophobic microenvironment in DO result in enhanced and faster fibrillation of IDPs. The study highlights the importance of considering DO's differential impact on protein interactions when conducting structural and kinetic analyses, particularly for native peptides and proteins.