EFFECT OF LIPID PROPERTIES AND COMPOSITION ON MEMBRANE PERMEABILITY TO DIOXYGEN
Oxygen is the most important respiratory gas playing a central role in aerobic life. However, the mechanisms of its transmembrane flow are not fully understood. Oxygen is poorly dissolved in water and membrane lipids, with partition coefficient γ~1. Consequently, oxygen transmembrane gradient determines the barrier properties of biological membranes are localized on both sides of the membrane a hydrocarbon zone. Analysis of erythrocyte oxygenation using stop-flow method with dual wavelength detection of oxy-deoxy transition at millisecond resolution showed that membrane permeability to O2 is more than two orders of magnitude lower than that of water layer of the same thickness. This method of measurement is complicated by the presence of unstirred layers in diluted cell suspensions. Therefore, we developed another method in our laboratory based on scanning electrochemical microscopy (SECM), which allowed us to determine that the resistance of membrane lipid layer to O2 diffusion depends on lipid composition, their packing density, the presence of branched chains, charge and volume of phospholipid heads and the presence of monovalent cations forming dimer and trimer complexes with lipids in membranes. These results contribute to a better understanding of membrane lipids under normoxic conditions, their response to changing oxygen environment and toxic damage.