Mapping chemical exchange in proteins with MW > 50 kD.

Chemical exchange reveals motions in proteins that are critical for ligand binding, catalysis, and allosteric regulation at the microsecond to millisecond time scale. The detection of chemical exchange is inherently difficult in large proteins because of the fast transverse relaxation rate (R2) and spectral overlap. Here we report novel pulse sequences for the rapid identification of chemical exchange applicable to large deuterated proteins with MW greater than 30 kD. The success of our method is demonstrated in triosephosphate isomerase (TIM, MW = 54 kD).