NMR Spectroscopy vs. X-Ray Crystallography
Although they utilize different approaches, nuclear magnetic resonance (NMR) spectroscopy and x-ray crystallography comprise the two best means of analyzing protein structure and function at or near atomic resolution. The degree to which these techniques differ and complement each has been a source of long-standing debate. Do proteins amenable to structural analysis by NMR also crystallize well? Does crystallography provide better structural resolution? Is NMR protein analysis closer to the native state? Despite some similarities and differences, each technique excels where the other falls short, making protein NMR and x-ray crystallography two very complementary spectroscopic methods for high resolution analysis of protein structure and function.
Below is a brief summary of the basic technical aspects of protein NMR spectroscopy as compared to x-ray crystallography. A more thorough analysis for each technique can be found in existing UC Davis Wiki pages for Nuclear Magnetic Resonance (NMR) Spectroscopy and X-ray Crystallography.
In the end, protein x-ray crystallography and NMR spectroscopy are not mutually exclusive techniques; one can easily pick up where the other falls short. In analyzing NMR dynamics experiments, for example, one can greatly benefit from existing crystal structure data onto which the NMR structural data can be superimposed. Similarly, NMR structure data can be used to supplement a crystal structure with more information on the protein's dynamics, binding information, and conformational changes in solution. Because a protein that can be analyzed by NMR is not necessarily amenable to crystallization (and vice-versa), the two techniques, either alone or in conjunction with one another, serve as two of the top complementary methods for protein structure determination.