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

Abstract

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. Fe²⁺/H₂O₂ and Fe³⁺/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.

Keywords:

• oxyradicals
• Fenton reaction
• DNA-deoxythymidine damage

Acknowledgments

The author thanks Prof. Stuart Linn for advice regarding the experiments performed during 1988–1990, related discussions, and recommendations later. He thanks Mrs. Sherry Ogden of the UC Berkeley mass spectrometric facility for analyzing our samples. All kinds of help from Moushumi Chattopadhyaya (1959–2006), the author’s first wife, are acknowledged during the stay in California and the paper is dedicated to her memory. Ernst S. Henle, Yongzhang Luo, and Indrani Kar are thanked for relevant discussions, Subrata Kundu for help with Adobe Photoshop, and Abhishek Santra for help with ChemDraw. This work was supported by Grant R29GM19020 from National Institutes of Health to S.M. Linn.