Microsecond Timescale Protein Dynamics: a Combined Solid-State NMR Approach.

Conformational exchange in proteins is a major determinant in protein functionality. In particular, the µs-ms timescale is associated with enzymatic activity and interactions between biological molecules. We show here that a comprehensive data set of R1ρ relaxation dispersion profiles employing multiple effective fields and tilt angles can be easily obtained in perdeuterated, partly back-exchanged proteins at fast magic-angle spinning and further complemented with chemical-exchange saturation transfer NMR experiments. The approach exploits complementary sources of information and enables the extraction of multiple exchange parameters for µs-ms timescale conformational exchange, most notably including the sign of the chemical shift differences between the ground and excited states.