The Chemical Reactions of DNA Damage and Degradation

The main oxidation reactions of the 2-deoxyribose of DNA are mediated by "OH that are able to abstract hydrogen atoms from most of the positions with the exception of the methylene group at C2, which is a poorly reactive site [12, 14, 112], An abundant literature is available on the degradation pathways that are derived from the reactions of osidic carbon-centered radicals and that lead in most cases to the formation of strand breaks [12, 14, 112], However, there is one major exception that concerns the chemical reactions of the CT radical that is the precursor of 2-deoxyribonolactone [113]. Here, emphasis is placed on reactions of C4 and C5 radicals that may lead to the formation of base modifications either as tandem lesions or clustered damage. 

Chemical reactivity can be a two-edged sword for toxicity. It can be beneficial if the parent chemical quickly reacts and degrades to either more benign or more easily cleared products. However, reactivity can be harmful if the reactions lead to damage to proteins or DNA. This is the case discussed here. One type of reactivity-mediated toxicity is skin sensitization caused when a low molecular weight compound penetrates into the epidermis and covalently reacts with an underlying protein. 

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