The role of oxygen in DNA damage by ionizing particles

The actual role of oxygen in inactivation mechanism represents still an open problem, especially when Ewing (1998, Am. J. Clin. Oncol.21, 355-361) has shown that oxygen fixation hypothesis cannot be regarded as maintainable more and, on the other side, has argued that the oxygen effect can be hardly a simple consequence of greater reactivity of oxygen radicals. However, the role of oxygen in DSB formation may be more complicated even during the chemical phase of the radiobiological mechanism, as will be shown by computer simulation of the data concerning DSB number dependence on oxygen concentration (for different gas mixtures) and established experimentally by Blok and Loman in 1973 (Radiat. Res.9, 165-245) by irradiating DNA water solutions by gamma radiation.