*3.3. Cellular Repair of SBs*

We studied the effect of vitamin C on the kinetics of repair of SBs induced by H2O2 after pre-incubating HeLa cells with different concentrations of vitamin C overnight. After H2O2

treatment cells were incubated and SBs remaining were measured at intervals. As is seen in Figure 4, rejoining of SBs is rapid, with a t1/2 of about 20 min and complete repair by 60 min. Pre-incubation of cells with 50 or 100 μM vitamin C overnight did not affect the repair of the SBs induced by H2O2.

**Figure 4.** Effect of overnight pre-incubation of HeLa cells with different concentrations of vitamin C on the kinetics of repair of SBs: residual SBs were measured after different times of incubation after H2O2 treatment. C-: control cells without any kind of treatment. Bars: SD calculated from the results of 3 independent experiments. No significant effects were seen.
