A 2H-NMR study of Acholeplasma laidlawii membranes highly enriched in myristic acid.

Myristic acid specifically deuterated at several positions along the acyl chain was biosynthetically incorporated into the membrane lipids of Acholeplasma laidlawii B to the level of greater than or equal to 90%. 2H-NMR was used to study the molecular order and lipid phase composition of the membranes as a function of temperature. Isolated membranes and intact cells give rise to similar 2H spectra. Below 25 degrees C the spectra exhibit a broad gel phase component which at 0 degrees C reaches the rigid limit value expected for an immobilized methylene group. Spectral moments were used to determine the relative amounts of gel and liquid crystalline phase lipids throughout the gel-liquid crystal phase transition. The results indicate that at the growth temperature (37 or 30 degrees C) the A. laidlawii B membrane lipids are approximately 85-90% in the gel state, and that protein has little effect on lipid order of the liquid crystalline lipid, but leads to an increase in the linewidth by approx. 20%.