O2(SIGMA-3) AND O2(DELTA-1) PROCESSES IN MICROHETEROGENOUS SYSTEMS

The deactivation of excited pyrene derivatives by and 02(3∑) the bleaching of 9-substituted anthracene derivatives by O2(1Δ2) have been studied in micelles, reverse micelles, vesicles and membranes. Quenching rates by oxygen are mostly determined by the diffusion of the oxygen in the dispersion media in small aggregates such as micelles and reverse micelles. Due to differences in the entrance rates, deactivation in sodium dodecyl sulfate micelles and cetyl trimethyl ammonium micelles is faster than in the aqueous phase, while the opposite is observed in AOT/ hydrocarbon/water reverse micelles. In larger microphases such as vesicles and membranes, deactivation rates are determined by intrabilayer mobility and concentration. The results obtained in erythrocyte plasma membranes and hepatic microsomes indicate an increased oxygen solubility towards the center of the membrane interior, and imply that lateral diffusion contributes more than transverse diffusion to the oxygen mobility. Photobleaching rates of anthracene derivatives in microphases are extremely sensitive to the location of the probe. This sensibility is due to gradients in the oxygen concentration and micropolarities inside the microphases. The interplay of these two opposite factors determines the relative reactivity of the substrates considered. © 1990 IUPAC