Assignment of dynamic regions in biological solids enabled by spin-state selective NMR experiments.

Structural investigations are a prerequisite to understand protein function. Intermediate time scale motional processes (ns-micros) are deleterious for NMR of biological solids and obscure the detection of amide moieties in traditional CP based solid-state NMR approaches as well as in regular scalar coupling based experiments. We show that this obstacle can be overcome by using TROSY type techniques in triple resonance experiments, which enable the assignment of resonances in loop regions of a microcrystalline protein. The presented approach provides an exemplified solution for the analysis of secondary structure elements undergoing slow dynamics that might be particularly crucial for understanding protein function.