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| NMR SPECTROSCOPY | home > about hwi > what does hwi do? > structural biology > nmr spectroscopy | ||||
NMR Spectroscopy as a Tool for the Study of Macromolecules Nuclear Magnetic Resonance (NMR) was first detected in 1945 by Edward M Purcell at Massachusetts Institute of Technology’s Radiation Laboratory. However, it was not until the 1980s that the technique was used for determining the three-dimensional structures of macromolecules. Today, NMR is an important and unique tool for the study of small and medium-sized proteins (10-50 kDa) that are stable at room temperature and are soluble at high (millimolar) concentrations. For macromolecules that satisfy these criteria and give spectra in which the individual resonances can be resolved, NMR can be extremely valuable for solution structure determination, dynamic studies, and in drug discovery. NMR is useful for the study of unfolded or partly folded proteins that are difficult to crystallize. |
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An important
distinction between NMR
and X-ray crystallography is that NMR studies
reveal the solution structure of a molecule, and no crystals are required. The
solution structure is relevant since macromolecules perform their functions
in solution, and NMR conditions can be optimized to mimic physiological
fluids closely. Also, unlike crystallography, NMR generates a family
of structures rather than a single averaged structure with a
low energy conformation.
One of the features of NMR spectroscopy that makes it so powerful in the study of macromolecules is its ability to obtain site-specific information about each proton, nitrogen and carbon nucleus in the molecule. In the study of protein dynamics, different time scales of motion can be studied, from fast (nanosecond) motions to slower motions that take on the order of seconds. NMR has also been exploited extensively for the study of protein-ligand, protein-protein, and protein-nucleic acid interactions. Some of the limitations of NMR techniques are that only small to medium-sized proteins that are soluble, homogeneous, do not aggregate, and are stable during the length of the NMR experiments can be studied in detail. Structure calculation by NMR is also a slower process compared to X-ray crystallography since many experiments are required before the information can be put together to compute a structural ensemble. NMR is also inherently insensitive and milligram amounts of protein are required. In spite of these difficulties, recent advances in NMR methodology have allowed detailed structural characterization of hundreds of proteins and protein-ligand complexes. NMR and X-ray crystallography are complementary tools and provide different approaches towards understanding how macromolecules function at the atomic level. The NMR Facility on the Buffalo Niagara Medical Campus is housed and maintained by Roswell Park Cancer Institute. |
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