Quantitative measurement of exchange dynamics in proteins via (13)C relaxation dispersion of (13)CHD2-labeled samples.

Methyl groups have emerged as powerful probes of protein dynamics with timescales from picoseconds to seconds. Typically, studies involving high molecular weight complexes exploit (13)CH3- or (13)CHD2-labeling in otherwise highly deuterated proteins. The (13)CHD2 label offers the unique advantage of providing (13)C, (1)H and (2)H spin probes, however a disadvantage has been the lack of an experiment to record (13)C Carr-Purcell-Meiboom-Gill relaxation dispersion that monitors millisecond time-scale dynamics, implicated in a wide range of biological processes. Herein we develop an experiment that eliminates artifacts that would normally result from the scalar coupling between (13)C and (2)H spins that has limited applications in the past. The utility of the approach is established with a number of applications, including measurement of ms dynamics of a disease mutant of a 320 kDa p97 complex.