High-resolution 39K NMR spectroscopy of bio-organic solids.

We report the first implementation of the multiple-quantum magic-angle-spinning method to obtain high-resolution 39K NMR spectra for bio-organic solids. The observed spectral resolution in the isotropic dimension is nearly at the sub-ppm level, which approaches the intrinsic resolution limit determined primarily by quadrupole relaxation. We show that high-resolution solid-state 39K NMR spectroscopy can be used as a new means of probing K+ ions in biomolecular systems.