NMR Spectroscopic Assignment of Backbone and Side-Chain Protons in Fully Protonated Proteins: Microcrystals, Sedimented Assemblies, and Amyloid Fibrils

We demonstrate sensitive detection of alpha protons of fully protonated proteins by solid-state NMR spectroscopy with 100-111 kHz magic-angle spinning (MAS). The excellent resolution in the C alpha-H alpha plane is demonstrated for 5 proteins, including microcrystals, a sedimented complex, a capsid and amyloid fibrils. A set of 3D spectra based on a C alpha-H alpha detection block was developed and applied for the sequence-specific backbone and aliphatic side-chain resonance assignment using only 500 mu g of sample. These developments accelerate structural studies of biomolecular assemblies available in submilligram quantities without the need of protein deuteration.