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Updated: Aug 10, 2026
11:56
A Rapid and Specific Microplate Assay for the Determination of Intra- and Extracellular Ascorbate in Cultured Cells
Published on: April 11, 2014
Ascorbic acid oxidation and DNA scission catalyzed by iron and copper chelates
J Aronovitch1, D Godinger, A Samuni
1Department of Molecular Biology, School of Medicine, Hebrew University Jerusalem, Israel.
Free Radical Research Communications
|January 1, 1987
Summary
Ascorbic acid oxidation accelerates DNA degradation when catalyzed by copper or iron chelates. Ternary complexes form, initially slowing oxidation but then efficiently inducing DNA double-strand breaks.
Area of Science:
- Biochemistry
- Molecular Biology
- Chemical Biology
Background:
- Ascorbic acid (AH-) auto-oxidation is influenced by metal ions and chelates.
- Copper and iron chelates, like 1,10-phenanthroline (OP) and bleomycin (BLM), catalyze AH- oxidation.
- DNA degradation can occur concurrently with AH- oxidation.
Purpose of the Study:
- To investigate the kinetics of ascorbic acid auto-oxidation catalyzed by metal chelates in the presence of DNA.
- To elucidate the mechanism of DNA scission induced by these metal-chelate complexes.
- To compare the DNA-damaging efficiency of different metal-chelate systems.
Main Methods:
- Kinetic studies of ascorbic acid auto-oxidation.
- DNA scission assays using techniques like pulse radiolysis.
- Characterization of ternary complex formation between DNA, metal chelates, and ascorbic acid.
Main Results:
- Metal chelates, particularly in ternary complexes with DNA, significantly enhance DNA degradation compared to free metal ions.
- DNA formation of ternary complexes with chelates initially slows AH- oxidation but leads to efficient DNA double-strand breaks.
- The reaction of the ternary complex DNA-(OP)2Cu(I) with H2O2 is a key pathway for DNA degradation with OP.
- A sigmoidal pattern in oxidation curves suggests an acceleration of oxidative activity as DNA is cleaved.
- Ascorbic acid oxidation with (OP)2Cu(II) induced more DNA double-strand breaks per single-strand break than bipyridine-copper.
Conclusions:
- The formation of ternary complexes is crucial for the site-specific DNA damaging activity of these metal chelates.
- The observed DNA damaging mechanisms are relevant to the cytotoxic effects of bleomycin and similar agents.
- Understanding these reactions provides insights into the molecular mechanisms of drug action and DNA damage.
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