Two- and Three-Dimensional 13C-17O Heteronuclear Correlation NMR Spectroscopy for Studying Organic and Biological Solids.

We report two- and three-dimensional (2D and 3D) 13C-17O heteronuclear correlation solid-state NMR experiments under magic-angle spinning (MAS) conditions. These experiments utilize the D-RINEPT (Dipolar-mediated Refocused Insensitive Nuclei Enhanced by Polarization Transfer) scheme with symmetry-based SR412 recoupling blocks for coherence transfer between 13C and 17O nuclei. First, a 2D 17O → 13C correlation experiment was performed for the [1-13C,17O]-Gly/Gly·HCl cocrystal and [U-13C, 1-17O]-α/β-d-glucose samples. Second, a 2D 17O → 13C MQ-D-RINEPT correlation experiment where the indirect dimension incorporates the multiple-quantum MAS (MQMAS) scheme was tested for obtaining isotropic 17O resolution with [U-13C, 1-17O]-α/β-d-glucose. Third, a new 3D 17O → 13C → 13C correlation experiment was demonstrated where 17O → 13C and 13C → 13C correlations are achieved by D-RINEPT and DARR (Dipolar Assisted Rotational Resonance) sequences, respectively (thus termed as a 3D D-RINEPT/DARR OCC experiment). This new 3D 17O NMR experiment is implemented with the aim for site-resolved solid-state 17O NMR studies.