Sensitivity enhancement in solid state 15N NMR by indirect detection with high-speed magic angle spinning

Enhancement of sensitivity in solid state N-15 NMR by indirect detection through H-1 NMR signals under high-speed magic angle spinning and high-field conditions is demonstrated experimentally on two N-15-labeled peptides, polycrystalline AlaGlyGly and the helix-forming, 17-residue peptide MB(i + 4)EK in lyophilized form. Sensitivity enhancement factors ranging from 2.0 to 3.2 are observed experimentally, depending on the (1)5N and H-1 linewidths and polarization transfer efficiencies. The H-1-detected two-dimensional H-1/N-15 correlation spectrum of AlaGlyGly illustrates the possibility of increased spectral resolution and resonance assignments in indirectly detected experiments, in addition to the sensitivity enhancement.