Structural determinants of the packing and electrostatic behavior of unsaturated phosphoglycerides.

Docosahexaenoic acid-containing phosphoglycerides accumulate preferentially in membranes of the retina, brain, and spermatozoa, but the functional significance of this largely remains to be determined. Previously we compared the physical properties of homogeneous monolayers of these and other phosphoglyceride species to obtain insights into their physiological roles. Particularly noteworthy were the unusually low dipole moments of species having sn-2-docosahexaenoyl chains.

Role of docosahexaenoic acid in neuronal plasma membranes.

The omega-3 fatty acid docosahexaenoic acid (DHA n-3) has long been known to be a major component of phosphoglycerides in the gray matter of mammalian brains. Furthermore, early studies of synaptosomes that had been isolated from gray matter showed that the plasma membranes of the synaptosomes contained DHA n-3 that was selectively esterified to phosphatidylethanolamine, plasmenylethanolamine (alkenylacyl-glycero-phosphorylethanolamine), and phosphatidylserine. In contrast, the phosphatidylcholine in these membranes contained esterified oleic acid, and the sphingomyelin and glycolipids in the membranes contained amide-linked stearic acid instead of a mixture of this acid with other, amide-linked fatty acids.

Packing and electrostatic behavior of sn-2-docosahexaenoyl and -arachidonoyl phosphoglycerides.

Mammalian synaptic membranes appear to contain high proportions of specific, sn-1-stearoyl-2-docosahexaenoyl- and sn-1-stearoyl-2-arachidonoyl phosphoglycerides, but the structural significance of this is unclear. Here we used a standardized approach to compare the properties of homogeneous monolayers of the corresponding phosphatidylcholines, phosphatidylethanolamines, phosphatidylserines, and phosphatidic acids with those of control monolayers of sn-1-stearoyl-2-oleoyl- and sn-1-palmitoyl-2-oleoyl phosphoglycerides. Major findings were: 1), that the presence of an sn-2-docosahexaenoyl group or an sn-2-arachidonoyl group increases the molecular areas of phosphoglycerides by 3.