Oxidative damage to DNA constituents by iron-mediated Fenton reactions--the thymidine family.

The degradative products formed from the exposure of derivatives of thymidine to iron-mediated Fenton reactions were identified by chromatographic resolution and analysis by UV absorption spectroscopy, radio-labeling, and positive and negative mode fast atom bombardment mass spectrometry. Fe(2+)/H2O2 and Fe(3+)/H2O2 were utilized to generate oxy-radicals and the effects of ethanol and N2-flushing were studied. Substrates included thymidine, 3'- and 5'-dTMP, TpT, oligo(dT), and oligo(dT)·poly(dA) and the results are compared to those reported for ionizing radiation. It is evident from the comparisons of the products that the damaging radical species and the product distribution are perturbed by interaction of the iron atom with the various phosphomono- and diester species that are present.