Three-dimensional solid-state NMR spectroscopy of a peptide oriented in membrane bilayers.

A three-dimensional 1H chemical shift/1H-15N dipolar coupling/15N chemical shift correlation spectrum was obtained on a sample of specifically 15N-labeled magainin peptides oriented in lipid bilayers between glass plates in a flat-coil probe. The spectrum showed complete resolution of the resonances from two labeled amide sites in all three dimensions. The three orientationally dependent frequencies associated with each resonance enabled the orientation of the peptide planes to be determined relative to the direction of the applied magnetic field. These results demonstrate the feasibility of multiple-pulse spectroscopy in a flat-coil probe, the ability to measure three spectral parameters from each site in a single experiment, and the potential for resolving among many labeled sites in oriented membrane proteins.