Langmuir-Blodgett film characteristics and phospholipid membrane ion conduction : Part 2. Ethylenic Acyl Chain Oxidation

The influence of polar moieties located in the non-polar hydrocarbon zone in bilayer lipid membranes on ion conduction is described. Natural egg-derived phosphatidyl choline combined with cholesterol produces membranes containing several ethylenic residues in the hydrocarbon interior. Catalytic oxidation of these residues by ultraviolet radiation provides a significant density of permanently-bound polar species within the membrane. The extent of such oxidation is correlated with the Arrhenius energy barrier to ion conduction for bilayer membranes and molecular packing characteristics obtained from Langmuir-Blodgett monolayer compression experiments. The results confirm that membrane ion current is almost entirely controlled by molecular packing.