Accessible NMR experiments studying the hydrodynamics of (15) N-enriched ubiquitin at low fields

We have recently developed and implemented two experiments in biomolecular NMR for an undergraduate-level biophysical chemistry laboratory with commercially available (15) N-enriched human ubiquitin. These experiments take advantage of (15) N direct detection of the NMR signal. The first experiment develops skills in acquiring and interpreting one-dimensional and two-dimensional NMR data of an aqueous protein sample (D. Rovnyak, L. E. Thompson (2005) An accessible two-dimensional solution nuclear magnetic resonance experiment on human ubiquitin, Biochem. Mol. Biol. Educ. 33, 117-122). In the second experiment, discussed here, students examine the overall dynamics of a protein in solution. Students measure spin relaxation times T(1) and T(2) and use these data to estimate a rotational correlation time, τ(c) , and the diameter of ubiquitin using the Stokes-Einstein relation. This is a fast and simple experiment, requiring about 1 h of instrument time, and a valuable opportunity to provide a hands-on experience in studying macromolecular size and dynamics. This experiment is conducted in synchrony with lecture material on hydrodynamics and sedimentation.