3-DIMENSIONAL SOLID-STATE NMR-SPECTROSCOPY OF A PEPTIDE ORIENTED IN MEMBRANE BILAYERS

A three-dimensional H-1 chemical shift/H-1-N-15 dipolar coupling/N-15 chemical shift correlation spectrum was obtained on a sample of specif ically N-15-labeled magainin peptides oriented in lipid bilayers betwe en glass plates in a flat-coil probe. The spectrum showed complete res olution of the resonances from two labeled amide sites in all three di mensions. The three orientationally dependent frequencies associated w ith each resonance enabled the orientation of the peptide planes to be determined relative to the direction of the applied magnetic field. T hese results demonstrate the feasibility of multiple-pulse spectroscop y in a flat-coil probe, the ability to measure three spectral paramete rs from each site in a single experiment, and the potential for resolv ing among many labeled sites in oriented membrane proteins.