Oxygen diffusion in biological and artificial membranes determined by the fluorochrome pyrene

Abstract

Quenching of pyrene fluorescence by oxygen was used to determine oxygen diffusion coefficients in phospholipid dispersions and erythrocyte plasma membranes. The fluorescence intensity and lifetime of pyrene in both artificial and natural membranes decreases about 80 % in the presence of 1 atm O2, while the fluorescence excitation and emission spectra and the absorption spectrum are unaltered. Assuming the oxygen partition coefficient between membrane and aqueous phase to be 4.4, the diffusion coefficients for oxygen at 37°C are 1.51 × 10-5 cm2/s in dimyristoyl lecithin vesicles, 9.32 × 10-6 cm2/s in dipalmitoyl lecithin vesicles, and 7.27 × 10-6 cm2/s in erythroeyte plasma membranes. The heats of activation for oxygen diffusion are low (< 3 kcal/degree-mol). A dramatic increase in the diffusion constant occurs at the phase transition of dimyristoyl and dipalmitoyl lecithin, which may result from an increase in either the oxygen diffusion coefficient, partition coefficient, or both. The significance of the change in oxygen diffusion below and above the phase transition for biological membranes is discussed. © 1975, Rockefeller University Press., All rights reserved.