Structural Studies of Amyloid Fibrils by Paramagnetic Solid-State Nuclear Magnetic Resonance Spectroscopy.

Application of paramagnetic solid-state NMR to amyloids is demonstrated, using Y145Stop human prion protein modified with nitroxide spin-label or EDTA-Cu ²⁺ tags as a model. By using sample preparation protocols based on seeding with preformed fibrils, we show that paramagnetic protein analogs can be induced into adopting the wild-type amyloid structure. Measurements of residue-specific intramolecular and intermolecular paramagnetic relaxation enhancements enable determination of protein fold within the fibril core and protofilament assembly. These methods are expected to be widely applicable to other amyloids and protein assemblies.