Comparison of mechanisms for DNA strand break formation by the direct and indirect effect of radiation.

Abstract

Irradiation of cells may lead to mutations, reproductive cell death and the disappearance of some or all cell activities. These effects, especially reproductive cell death, are believed to be the result of damage to DNA. Two kinds of formation of DNA damage are often distinguished, the so called “direct” and the “indirect” effect of irradiation.1,2 The direct effect is due to ionization or electronic excitation of the DNA, and the indirect effect is caused by reactive species, in most cases free radicals, which are produced in the vicinity of the DNA. These radicals may be primary radicals produced by energy absorption in water (the solvated electron, the H-atom and the OH radical) or organic radicals produced from organic material other than DNA either by interaction with radiation or by reaction with the primary radicals generated from water.