Accelerated Amyloid Aggregation Dynamics of Intrinsically Disordered Proteins in Heavy Water

We explored the influence of D2O on the fibrillation kinetics and structural dynamics of amyloid intrinsically disordered proteins (IDPs), including alpha-synuclein, amyloid-beta 1-42, and K18. Our findings revealed that fibrillation of IDPs was accelerated in D2O compared to that in H2O, 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 D2O. Umbrella sampling of protein protofibrils verified that an increased level of hydrogen bonding of D2O and enhanced hydrophobic interactions stabilized beta-sheet structured fibrils in D2O. These findings indicate that stabilizing beta-sheet fibrils and a more hydrophobic microenvironment in D2O result in enhanced and faster fibrillation of IDPs. The study highlights the importance of considering D2O's differential impact on protein interactions when conducting structural and kinetic analyses, particularly for native peptides and proteins.