The diffusion-solubility of oxygen in lipid bilayers.

The product, Do alpha, of the oxygen diffusion coefficient, Do, and the oxygen solubility, alpha, is determined in phosphatidylcholine bilayers at temperatures above the lipid phase transitions from ESR spin-exchange measurements. The resulting values of Do alpha are in good agreement with those obtained from fluorescence-quenching experiments. The use of fatty acid spin labels makes it possible to measure Do alpha as a function of the coordinate perpendicular to the bilayer surface. The results indicate that do alpha is a strong function of this coordinate; it is greatest in the bilayer center and least near the bilayer head groups.