Figure 1.

Oxidatively generated damage to DNA and detection of DNA Other oxidants radicals. One of the major pathways of DNA oxidation is via the hydroxyl radical, which can be produced by the reaction of ROS (e.g., H₂O₂ and the superoxide radical anion) with redox active transition metals (e.g., Cu^1+/2+ and Fe^2+/3+). Thus, the formation of DNA radicals can be prevented by the removal of any of these components. Because of their high reactivity, DNA radicals can react, depending on kinetics, with other biological components or with oxygen. The oxidation products depend on the localization of the radical. DNA radicals can be studied by ESR or electron paramagnetic resonance (EPR); however, because of their high reactivity, they can be detected for only a short time and under special conditions. Alternatively, DNA radicals can be trapped in situ and in real time with the cell-diffusible nitrone spin trap DMPO. Trapping DNA radicals with DMPO produces paramagnetic species known as DMPO-DNA radical adducts (referred to hereafter as radical adducts). Like the parent radical, radical adducts can be studied with ESR; however, most radical adducts decay in a matter of minutes to DNA-DMPO nitrone adducts (referred to hereafter as nitrone adducts). Nitrone adducts can be studied by heterogeneous immuno-spin trapping assays such as ELISAs (option I) or immuno-slot blots (option II). The red sphere indicates inhibition.