Degradation of deoxyribonucleic acid by a 1,10-phenanthroline-copper complex: the role of hydroxyl radicals

• Published in: Biochemistry (Easton) Vol. 19; no. 26; pp. 5987 - 5991
• Main Authors: Que, Benito G, Downey, Kathleen M, So, Antero G
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 01.12.1980
• Subjects: Catalase; Chelating Agents; Copper; DNA; Free Radicals; Hydroxylation; Oxidation-Reduction; Phenanthrolines; Superoxide Dismutase
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi00567a007

Degradation of deoxyribonucleic acid (DNA) by 1,10-phenanthroline has been shown to require Cu(II), a reducing agent, and O2. Other metal ions do not substitute for Cu(II), and degradation of DNA is inhibited by metal ions that can form stable complexes with 1,10-phenanthroline, such as Co(II), Cd(II), Ni(II), or Zn(II), as well as by chelators that can bind copper, such as triethyltetraamine, neocuproine, or ethylenediaminetetraacetic acid (EDTA). Neocuproine, a specific copper chelator, is more effective than EDTA in inhibiting the breakdown of DNA. The degradation of DNA shows a requirement for a reducing agent which can be satisfied by either ascorbate or a thiol. A free radical generating system, e.g., xanthine oxidase-hypoxanthine, can substitute for the reducing agent. DNA degradation, in the presence of either an organic reducing agent or xanthine oxidase-hypoxanthine, is inhibited by hydroxyl radical scavengers and by catalase, suggesting that hydroxyl radical is the reactive species in DNA degradation and that hydrogen peroxide is an intermediate in hydroxyl radical generation.