Isotropic solutions of phospholipid bicelles: A new membrane mimetic for high-resolution NMR studies of polypeptides

In order to illustrate the utility of phospholipid bicelles [Sanders, C.R. and Schwonek, J.P.(1992) Biochemistry, 31, 8898–8905] as a membrane mimetic for high-resolution NMRstudies, we have recorded two-dimensional 1H NMR spectra of the tetradecameric peptidemastoparan Vespula lewisii in an isotropic aqueous solution of dimyristoyl and dihexanoylphosphatidylcholine. Mastoparan is largely unstructured in water, but assumes a well-definedhelical conformation in association with the bilayers. A pronounced periodicity of thesequential NH chemical shifts provides strong evidence that the helix axis of this shortpeptide is parallel, rather than perpendicular, to the bilayer plane. The bicellar solutions stillrequire in-depth morphological characterization, but they appear to be ideal media for NMRdetermination of the mode of binding and the structure of membrane-associated peptides andproteins.