Transverse-dephasing optimized homonuclear j-decoupling in solid-state NMR spectroscopy of uniformly 13C-labeled proteins.

A transverse-dephasing optimized S(3)E (spin-state selective excitation) method is implemented in solid-state NMR experiments of uniformly labeled protein samples, and it is shown to provide a simultaneous significant gain in both resolution (up to a factor of 2.2) and sensitivity (up to a factor of 1.4). This is illustrated with high-resolution NCO and NCA correlations of a microcrystalline sample of the oxidized form of the 153 residue human Cu(II)Zn(II) superoxide dismutase (SOD), a dimeric paramagnetic enzyme of 32 kDa. This method allows the resolution of 145 signals in the highly crowded carbonyl region in the NCO correlation spectrum.