Quantifying fast protein dynamics by magic-angle spinning NMR: Progress in experimental and analytical approaches

Far from being static structures, it is now well accepted that proteins are highly dynamic entities even in the solid state. Here, we review recent progress in application of magic-angle spinning (MAS) NMR for studying the site-specific dynamics of proteins, as assessed using spin-relaxation and measurement of anisotropic spin interactions. We focus on the types of experimental data that are available, and how best to access the information which is provided by these experimental measurements; in particular, we provide a retrospective on the field in light of recent advances in analytical methodologies, which have led to a slow paradigm shift in how we interpret relaxation rate constant measurements made in the solid state.