NMR Spectroscopy
With its ability to study macromolecules in the aqueous state, NMR is a powerful adjunct to X-ray crystallography and the two techniques are highly complementary. Protein structure determination is routine on proteins less than 40 kDa and, using higher field magnets, doable up to almost 100 kDa. Additionally, the analysis of NMR relaxation rates can be used to quantitatively describe molecular motions in solution, allowing the identification and characterization of minor structural states that make large contributions to function. Lastly, NMR is commonly used to monitor protein conformational changes and ligand-binding reactions.
NMR Spectroscopy Image Gallery
Superposed backbone traces for the NMR-derived structural ensemble of the N-terminal "pleckstrin homology domain" from the phosphoinositide-metabolizing protein, INPP5B (aka OCRL2). Image from the Hodsdon lab.
1H-15N HSQC NMR spectrum of 6-thiopurine methyltransferase. Individual resonances represent J-coupling between singly-bonded backbone amides providing residue-specific markers of protein structure and behavior in solution. Image from the Hodsdon lab.
Structure of Calcium-bound EF hand domain of polycystin-2. Backbone atoms for the top model (heavy blue ribbon) and side chain atoms for the top 20 conformers (blue lines). Petri et al., PNAS 2010;107(20):9176-81.