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.