Effects of in vitro treatment with ozone on the physical and chemical properties of membranes

Pauls,, K. P. and Thompson, J. E. 1981. Effects of in vitro treatment with ozone onthe physical and chemical properties of membranes. - Physiol. Plant. 53: 255-262,Treatment of microsomal membranes from cotyledons of Phaseolus vulgaris withozone raises the liquid-crystalline to g,el lipid phase transition temperature and resultsin the formation of distinct domains of gel phase lipid in the membranes. Liposomesprepared from the total lipid extracts of ozone-treated membranes undergo phaseseparations just a few degrees below the transition temperature for intact mem-branes, indicating that the fonnation of gel phase lipids is largely attributable toozone-induced alterations in the membrane lipids. Levels of unsaturated fatty ,acidsas well as the sterol to phospholipid ratio are markedly reduced in the ozone-treatedmembranes, and the neutral lipid fraction from treated membranes shows an in-creased propensity to induce the formation of gel phase phospholipid when incorpo-rated into liposomes of egg phosphatidylcholine. Since gel phase phospholipid alsoforms in naturally senescing plant membranes and appears to be attributable tochanges in the neutral lipid fraction, the effects of natural senescence and ozone onmembranes have been compared.Additional key-words: Microsomal membranes, geS phase lipid, lipid peroxidation,bean cotyledons, liposomes.K. P. Pauls and J. E. Thompson, Department of Biology, University of Waterloo,Waterloo, Ontario, Canada NIL 3G1.