In the present study the phase behavior of multilamellar dispersions of 1-O-(l'-alkenyl)-2oleoyl-glycerophosphoethanolamine (ethanolamine plasmalogen), 1-O-alkyl-2-oleoyl-glycerophosphoethanolamine and 1-acyl-2-oleoyl-glycerophosphoethanolamine was compared using differential scanning calorimetry (DSC) and 31p-NMR. The three compounds differed only in the type of bonding (vinyl ether, alkyl ether or acyl ester) linking the aliphatic moiety to position 1 of sn-glycerol.
The gel to liquid-crystalline phase transition temperature as determined by DSC was lowest for ethanolamine plasmalogen (26ยฐC) and was similar for the alkylacyl and diacyl analogs (29.5ยฐC and 30ยฐC, respectively). Enthalpies of the G-~ L phase transition were not significantly different for the three phospholipids tested.
Ethanolamine plasmalogen undergoes the lamellar to hexagonal phase transition at 30ยฐC, the analogous alkylacyl-glycerophosphoethanolamine(alkylacyl-GPE) and diacyl-GPE at 53ยฐC and 69ยฐC, respectively. Thus, an alkenyl ether bond in position 1 of sn-glycerol, the structural characteristic of plasmalogens, effectively stabilizes the hexagonal Hn arrangement of ethanolamine glycerophospholipids, while it has relatively little effect on destabilization of the lamellar gel state.