Off-resonance 13C–2H REDOR NMR for site-resolved studies of molecular motion

We introduce a 13 C- 2 H Rotational Echo DOuble Resonance (REDOR) technique that uses the difference between on-resonance and off-resonance 2 H irradiation to detect dynamic segments in deuterated molecules. By selectively inverting specific regions of the 2 H magic-angle spinning (MAS) sideband manifold to recouple some of the deuterons to nearby carbons, we distinguish dynamic and rigid residues in 1D and 2D 13 C spectra. We demonstrate this approach on deuterated GB1, H/D exchanged GB1, and perdeuterated bacterial cellulose. Numerical simulations reproduce the measured mixing-time and 2 H carrier-frequency dependence of the REDOR dephasing of bacterial cellulose. Combining numerical simulations with experiments thus allow the extraction of motionally averaged quadrupolar couplings from REDOR dephasing values.