Solid-state nuclear magnetic resonance structural studies of proteins using paramagnetic probes

Determination of three-dimensional structures of biological macromolecules by magic-angle spinning (MAS) solid-state NMR spectroscopy is hindered by the paucity of nuclear dipolar coupling-based restraints corresponding to distances exceeding 5Å. Recent MAS NMR studies of uniformly 13C,15N-enriched proteins containing paramagnetic centers have demonstrated the measurements of site-specific nuclear pseudocontact shifts and spin relaxation enhancements, which report on electron–nucleus distances up to ∼20Å. These studies pave the way for the application of such long-distance paramagnetic restraints to protein structure elucidation and analysis of protein–protein and protein–ligand interactions in the solid phase. Paramagnetic species also facilitate the rapid acquisition of high resolution and sensitivity multidimensional solid-state NMR spectra of biomacromolecules using condensed data collection schemes, and characterization of solvent-accessible surfaces of peptides and proteins. In this review we discuss some of the latest applications of magic-angle spinning NMR spectroscopy in conjunction with paramagnetic probes to the structural studies of proteins in the solid state. [Display omitted] ► Review of MAS solid-state NMR studies of proteins containing paramagnetic centers. ► Paramagnetic probes enable measurements of electron-nucleus distances up to ∼20Å. ► Paramagnetic restraints are applicable to protein structure determination. ► Paramagnetic species facilitate condensed solid-state NMR data collection. ► Paramagnetic species allow analysis of solvent-accessible surfaces in biomolecules.