OxyFile #400

Effect of lipid ozonation products on liposomal membranes detected 
by Laurdan fluorescence.

Salgo MG; Cueto R; Pryor WA

Biodynamics Institute, Louisiana State University, Baton Rouge, 
USA.

Free Radic Biol Med, 19: 5, 1995 Nov, 609-16

Abstract

We report here the influence of the lipid ozonation products, 1-
palmitoyl-2-(9-oxononanoyl)-sn-glycero-3-phosphocholine (PC-
aldehyde) and 1-palmitoyl-2[8-(5-octyl-1, 2, 4,-trioxolan-3-yl)- 
octanoyl]-sn-glycero-3-phosphocholine (PC-Criegee ozonide), on the 
phase domains of small unilamellar vesicles. (See Scheme 1 for 
structures.) 6-Lauroyl-2-dimethylaminonaphtalene (Laurdan) 
fluorescence excitation and emission spectra and generalized 
polarization measurements allowed us to study how lipid ozonation 
products affect the phase components of phospholipid membranes. A 
shift of excitation and emission spectra and a decrease in 
generalized polarization reveal the presence of a more polar 
environment surrounding the probe. We find that when either PC-
aldehyde or PC-Criegee ozonide are incorporated into a 1-
palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) membrane, or 
when the POPC membrane is directly ozonated, a change in polarity 
of the phospholipid environment occurs that changes the properties 
of the bilayer. The introduction of more oxygenated and more polar 
phospholipids creates 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 effects the bilayer, 
altering packing order and cooperatively among fatty acyl chains 
as well as enhancing membrane fluidity.