FIG. 1.

EPR spectra demonstrating formation of metronidazole anion radicals by the hydrogenosomes of wild-type, drug-sensitive T. vaginalis in the presence of 43 mM metronidazole. (A) Signal generated in the presence of pyruvate, CoA, and ferredoxin (PFOR activity). (B) Signal generated in the presence of malate, ferredoxin, and NAD⁺ (malic enzyme activity). (C) Signal generated in the presence of NADH and ferredoxin (NDH activity). The spectra were recorded at 25°C with 20 mW of microwave power, a frequency of 9.64 GHz, and a modulation amplitude of 0.19 mT. The hyperfine coupling constants were a_NO2^N = 1.565 mT, a₄^H = 0.542 mT, and a_CH3^H = 0.229 mT.