Hydrogen peroxide-induced base damage in deoxyribonucleic acid.

Area of Science:

• Biochemistry
• Molecular Biology
• Chemical Biology

Background:

• Deoxyribonucleic acid (DNA) is susceptible to oxidative damage.
• Hydrogen peroxide can generate damaging radical species.
• Trace metal ions bound to DNA are implicated in site-specific radical formation.

Purpose of the Study:

• To investigate the role of transition metal ions in hydrogen peroxide-induced DNA base damage.
• To identify and quantify DNA base products formed by hydrogen peroxide exposure.
• To elucidate the mechanism of radical generation and DNA modification.

Main Methods:

• Exposure of calf thymus DNA to hydrogen peroxide in aqueous solution.
• Identification and quantification of DNA base products using gas chromatography-mass spectrometry after acid hydrolysis and trimethylsilylation.
• Assessment of damage in the presence of hydroxyl radical scavengers (dimethyl sulfoxide) and after metal ion chelation.

Main Results:

• Specific DNA bases were altered, with yields dependent on hydrogen peroxide concentration.
• The order of base product formation was identified: 8-hydroxyadenine, cytosine glycol, 2,6-diamino-4-hydroxy-5-formamidopyrimidine, 8-hydroxyguanine, thymine glycol, and 4,6-diamino-5-formamidopyrimidine.
• Dimethyl sulfoxide reduced base product yields by 40-60%.
• DNA pretreated to remove metal ions showed minimal hydrogen peroxide-induced base damage.

Conclusions:

• Trace transition metal ions bound to DNA readily react with hydrogen peroxide to produce hydroxyl radicals.
• These radicals cause site-specific damage to DNA bases.
• Metal ion catalysis is crucial for hydrogen peroxide-induced DNA oxidative damage.