Chemical repair of base lesions, AP sites, and strand breaks on plasmid DNA in dilute aqueous solution by ascorbic acid

Hata, Kuniki ; Urushibara, Ayumi; Yamashita, Shinichi; Shikazono, Naoya; Yokoya, Akinari; Katsumura, Yosuke*

In order to clarify whether ascorbic acid, which is a major antioxidant in living systems, chemically repairs radiation damage to DNA. We quantified the yields of base lesions, AP sites and single strand breaks (SSBs) produced in plasmid DNA by -irradiation in the presence of ascorbic acid with concentrations of 10-100 MM. By comparing the suppression efficiencies to the induction of each DNA lesion, it was found that ascorbic acid promotes the chemical repair of precursors of AP-sites and base lesions more effectively than those of single strand breaks. We estimated the efficiency of the chemical repair of each lesion using a kinetic model. Approximately 50-60% of base lesions and AP-sites were repaired by 10 M ascorbic acid, although strand breaks were largely unrepaired by ascorbic acid at low concentrations. The methods in this study will provide a route to understanding the mechanistic aspects of antioxidant activity in living systems.