DNA–Oxygen complex (DNA–O2)

The DNA–O2 complex, also known as the DNA peroxyl radical, is a critical chemical intermediate formed during the interaction of ionizing radiation with cellular DNA in the presence of molecular oxygen. According to the oxygen fixation hypothesis, radiation-induced DNA radicals react rapidly with oxygen to form these stable, non-restorable complexes, which "fix" the damage and prevent chemical repair by endogenous thiols like glutathione. This process significantly enhances the lethality of radiation, a phenomenon known as the oxygen effect, making oxygenated cells much more sensitive to radiotherapy than hypoxic ones. In clinical oncology, the DNA–O2 complex is a central target for radiosensitizers, which are drugs designed to mimic the action of oxygen in hypoxic tumor regions to promote the formation of these lethal lesions. Understanding the dynamics of this complex is essential for improving the efficacy of cancer treatments and overcoming the radioresistance associated with tumor hypoxia.

Other names

DNA peroxyl radicalDNA–O2 radicalFixed DNA lesionOxidized DNA radical

Oxygen fixation (reacting with radiation-induced DNA radicals to prevent chemical restoration and ensure permanent strand breaks)