Probing slow timescale dynamics in proteins using methyl H CEST.

Although N- and C-based chemical exchange saturation transfer (CEST) experiments have assumed an important role in studies of biomolecular conformational exchange, H CEST experiments are only beginning to emerge. We present a methyl-TROSY H CEST experiment that eliminates deleterious H-H NOE dips so that CEST profiles can be analyzed robustly to extract methyl proton chemical shifts of rare protein conformers. The utility of the experiment, along with a version that is optimized for CHD labeled proteins, is established through studies of exchanging protein systems. A comparison between methyl H CEST and methyl H CPMG approaches is presented to highlight the complementarity of the two experiments.