Sodium Diethyldithiocarbamate (DDC) inhibition of SOD activity. To further support the copper-zinc nature of the recombinant C. burnetii SOD, SOD activity assays were performed in the presence or absence of 1 mM DDC. Results represent the mean and standard deviation of three independent experiments. Approximately one unit of each SOD was used in the assay. (*) indicates a statistically significant difference between the 0 mM DDC and 1 mM DDC. Significant differences were determined using an unpaired two-tailed t-test.