Reactions of ozone with fatty acid monolayers: a model system for disruption of lipid molecular assemblies by ozone

Ozone concentrations of 0.03 ppm are shown to initiate physical disruption of both oleic and linoleic acid spread monolayers in a few seconds. Approximately equal yields of water soluble products in nitrogen- and oxygen-containing environments as well as in the two acid systems suggest that the dominant reaction pathway involves direct attack on fatty acid double bonds and not oxidative chain reactions. A possible explanation for the observed loss of monolayer material is provided by the Criegee mechanism for ozonide rearrangement following ozone attachment to double bonds. In this scheme polar intermediates are generated which could pass into the aqueous subphase before recombination can occur. alpha-Tocopherol exhibits a protective effect only when present at a high fraction in the fatty acid monolayer (6 mole%). These systems provide an efficient elementary model for studying the physical effects of ozone on lipid membrane structure.