Robert A. Floyd** and C. Ann Lewis abstract: Oxygen free radicals are implicated in many biological processes and as etiological agents of certain pathological conditions. Hydroxyl free radicals react readily and indiscriminately, causing damage. Ferrous iron catalyzes hydroxyl free radical formation from hydrogen peroxide. The ability of Fe (II) to carry out this reaction depends upon the particular ligands of the metal ion. The present study examines the ability of the adenosine nucleotides to aid in the apparent ligation of added Fe (II) to catalyze H202-dependent formation of hydroxylfree radicals detected by the spin-trap 5, 5-dimethyl-1-pyrroline 1-oxide (DMPO). The results demonstrate that Fe (II)-catalyzed OH formation from H202 inthe presence of ADP, and more so in the presence of ATP, was on the order of 20-50-fold higher than in the absence of the nucleotides. AMP was without effect in this system. Ferric ion was con-siderably less effective, on the order of one-fifth to one-tenth

Oxygen free radicals have been demonstrated in many biological processes and implicated as etiological agents in several pathological conditions (Fridovich, 1978). Superoxide and hydroxyl free radical are two oxygen free radical species of consequence in biological systems. Normally, the enzymes catalase, superoxide dismutase, and glutathione peroxidase maintain superoxide and hydrogen peroxide at low levels in biological systems, but under certain circumstances, higher levels of these compounds may be attained, thus leading to oxidative damage.