Protein dynamics revealed by CPMG dispersion

Since internal motion is essential to enable biomolecular function, it is important to understand the internal motion of proteins by applying biophysical methods. Nuclear magnetic resonance (NMR) methods can be used to probe protein dynamics in a nucleus-specific manner covering motions that occur over a wide range of time scales from the picosecond-nanosecond range to greater than seconds. Among these NMR methods, constant-time (CT) Carr-Purcell-Meiboom-Gill (CPMG) dispersion experiments are often applied to characterize protein equilibrium conformations that interconvert on the microsecond to millisecond time scale through the chemical exchange contribution to the detected transverse relaxation rates. This review covers developments and practical aspects of 15N-backbone CT-CPMG dispersion experiments that are frequently used for biomolecular studies, followed by 13C-methyl CT-CPMG dispersion experiments that are suitable for studies of proteins or assemblies in excess of about 50 kDa. Finally, for the efficient application of CPMG dispersion experiments, other NMR experiments that may be useful to cover a wider range of protein dynamics and so permit a more informed implementation and interpretation of CPMG dispersion experiments.