Comparative Hydrophobic Core Dynamics Between Wild-Type Amyloid-β Fibrils, Glutamate-3 Truncation, and Serine-8 Phosphorylation.

Post-translational modifications (PTMs) of amyloid-β (Aβ) species are implicated in the modulation of overall toxicities and aggregation propensities. We investigated the internal dynamics in the hydrophobic core of the truncated ΔE3 mutant fibrils of Aβ and compared them with prior and new data for wild-type fibrils as well as with phosphorylated S8 fibrils. Deuteron static solid-state NMR techniques, spanning line-shape analysis, longitudinal relaxation, and chemical exchange saturation transfer methods, were employed to assess the rotameric jumps of several methyl-bearing and aromatic groups in the core of the fibrils. Taken together, the results indicate the rather significant influence of the PTMs on the hydrophobic core dynamics, which propagates far beyond the local site of the chemical modification. The phosphorylated S8 fibrils display an overall rigidifying of the core based on the higher activation barriers of motions than the wild-type fibrils, whereas the ΔE3 fibrils induce a broader variety of changes, some of which are thermodynamic in nature rather than the kinetic ones.