Fig. 6

DNA damage assays based on the appearance of the relaxed circular form of plasmid DNA. a Agarose gel from one experiment showing paired non-irradiated (−) and 10 Gy irradiated (+) samples. Bands corresponding to undamaged (supercoiled, SC), single-strand break (relaxed circular, RC) and double-strand break (linear, L) plasmid DNA are marked. Ld is 1 kb DNA ladder. Note that this gel is not loaded in atomic number order. b Percentage relaxed circular DNA from each experiment. c Average values from b ± SEM. d Data from c replotted as ‘real’ values (10 Gy irradiated value minus 0 Gy control) ± SEM. Dotted line shows the irradiation-induced increase due to water only. ****, *** and ** denote, respectively, P < 0.0001, P < 0.001 and P < 0.01 significant differences, compared to the respective no NP (zero) control