The Effects of 1,2-Diacylglycerols on the Structural Organization of Model Membranes and Their Fusion

Abstract

The effects of synthetic and natural 1,2 diacylglycerols (DAG) on structural organization of lamellar dispersions of phosphatidylcholine (PC) or PC: phosphatidylinositol (PI) mixtures has been studied with the help of NMR spectroscopy. Asymmetric accumulation of natural DAG in two-component model membranes was achieved by their treatment with phospholipase C specific for PI. It was found that high concentrations (20 mol per cent) of synthetic DAG are needed to induce partial lipid bilayer transition from lamellar into hexagonal and/or isotropic phase. Asymmetric accumulation of natural DAG in thionphosphatidylcholine: PI bilayers treated with phospholipase C resulted in modification of bilayer packing at DAG concentrations as low as 1.5 mol per cent and at physiological temperature (37°C). With the help of fluorescence spectroscopy it was shown that formation of DAG in one of membrane layers of large mono-bilayer liposomes results in the membranes destabilization and fusion.