EFFECT OF LIPID OZONATION PRODUCTS ON LIPOSOMAL MEMBRANES DETECTED BYLAURDAN FLUORESCENCE

We report here the influence of the lipid ozonation products, toyl-2-( 9-oxononanoyl)-sn-glycero-3-phosphocholine (PC-aldehyde) and oxolan-3- yl)-octanoyl]-sn-glycero-3-phosphocloline (PC-Criegee ozonide), on the phase domains of small unilamellar vesicles. (See Scheme 1 for struct ures.) 6-Lauroyl-2-dimethylaminonaphtalene (Laurdan) fluorescence exci tation and emission spectra and generalized polarization measurements allowed us to study how lipid ozonation products affect the phase comp onents of phospholipid membranes. A shift of excitation and emission s pectra and a decrease in generalized polarization reveal the presence of a more polar environment surrounding the probe. We find that when e ither PC-aldehyde or PC-Criegee ozonide are incorporated into a 1-palm itoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) membrane, or when th e POPC membrane is directly ozonated, a change in polarity of the phos pholipid environment occurs that changes the properties of the bilayer . The introduction of more oxygenated and more polar phospholipids cre ates a more polar environment allowing the deeper penetration of water molecules into the membrane. Water penetration also is facilitated by the membrane disorder-producing effect of the ozonation products. The presence of an increased number of water molecules in the membrane ef fects the bilayer, altering packing order and cooperativity among fatt y acyl chains as well as enhancing membrane fluidity.