Effects of unsaturation on 2H-NMR quadrupole splittings and 13C-NMR relaxation in phospholipid bilayers.

Motional order and motional rates in unsonicated phospholipid bilayers were assessed as a function of unsaturation of the phospholipid. A measurement sensitive to motional order was obtained using 2H-NMR of 18:1, 18:1-phosphatidylcholine labelled at positions 9 and 10 with deuterium and included as a probe in phospholipid bilayers of interest at 10 mole percent. Spin lattice relaxation times from magic angle spinning 13C-NMR spectra of phospholipid dispersions of interest were used as a measure of motional rates. Measurements were made of phospholipid bilayers containing from 0 to 8 double bonds per molecule. No large effect of an increase in unsaturation was noted for the 2H-NMR quadrupole splittings or for the 13C-NMR spin lattice relaxation rate.