Phosphorus-31 nuclear magnetic resonance spectra characteristic of hexagonal and isotropic phospholipid phases generated from phosphatidylethanolamine in the bilayer phase.

31P nuclear magnetic resonance (NMR) spectroscopy is recognized as a technique which yields information concerning both the dynamics and organization of phospholipid molecules in biological membranes and phospholipid dispersions. In this theoretical paper, we examine the relationship between the conformation of the phospholipid molecule and the shape of the predicted 31P NMR spectrum. Using a simple model of rotation of the phospholipid molecule about its long axis, we show that it is possible to generate spectra previously considered typical of the bilayer (sigma parallel to less than sigma perpendicular), isotropic (sigma parallel to congruent to sigma perpendicular), and hexagonal II (sigma parallel to greater than sigma perpendicular) packing arrangements by simply changing the phospholipid head-group conformation while retaining the molecules in the bilayer phase.