Application of One-Dimensional Dipolar Shift Solid-State NMR Spectroscopy To Study the Backbone Conformation of Membrane-Associated Peptides in Phospholipid Bilayers

Abstract

A simple one-dimensional dipolar shift solid-state NMR experiment is demonstrated to study the backbone conformation of membrane-associated peptides embedded in phospholipid bilayers. The nitrogen-15 chemical shift and 1H−15N dipolar coupling parameters are measured on a magainin peptide selectively labeled with a 15N isotope at the Gly-18 site. Fully hydrated multilamellar vesicles and uniaxially oriented bilayer samples are used to determine the orientation of the peptide plane relative to the direction of the external magnetic field. It is inferred that the 1H−15N dipolar coupling 15N chemical shift doublet of the [15N-Gly-18]magainin peptide oriented in lipid bilayers is asymmetrical. Calculation of the experimental dipolar shift spectrum suggests that the shape of the asymmetrical doublet is highly sensitive to the orientation of the principal axes of the 15N chemical shift tensors in the molecular frame as well as the backbone conformation of the peptide embedded in lipid bilayers.