What sort of advantages do NMR and X-ray crystallography offer?
MAJUMDAR: NMR can report on both the structure and dynamics of a protein, so it is useful for following chemical kinetics and “real-time” molecular interactions. Crystallography, though, can tackle much larger molecules; even state-of-the-art NMR techniques can only reliably determine proteins up to 50 kD, far less than the megadaltons that crystallography can handle. Also, since NMR structures are both dynamic and interpretative, pieced together from a variety of experiments, they tend to be more fuzzy than crystal structures. NMR machines often are defined by their MHz frequency; what exactly does this mean? MAJUMDAR: The frequency is directly proportional to the magnetic field generated. An 800 MHz spectrometer corresponds to an 18.7 Tesla magnet. The earth’s magnetic field is about 5 microTesla, so this is a really powerful magnet. For most studies, a higher magnetic field, or “MHz rating,” is desirable as it offers greater resolution—ability to distinguish two resonances—and sensi
