Detection of oxygen-centered radicals using EPR spin-trap DEPMPO: the effect of oxygen.

Studies of the ability of the EPR spin trap DEPMPO to detect both superoxide and hydroxyl radicals produced by systems in vitro and in vivo are presented. Experiments using free radical-generating systems confirmed the suitability of the EPR spin trapping technique but also revealed the existence of an undesirable conversion of DEPMPO/OOH into DEPMPO/OH adducts. The rate of conversion decreases with oxygenation, and the production of oxygen-centered radicals increases. However, this property of DEPMPO does not have a significant influence on its ability to independently detect radicals produced by plant plasma membranes. Since the adduct conversion appears to be rather slow compared to radical generation, we conclude that the DEPMPO spin-trap can be efficiently used for detection of oxygen-centered radicals produced by systems in vivo, as demonstrated for isolated plasma membranes.