Fig. 6. IRP1-transformed cfd1-1 yeast lack [3Fe–4S] c-aconitase. Strains 0615d and AR27 were transformed with IRP1 and transformants were grown to mid-log phase in selective SD medium, harvested, and prepared for whole-cell EPR as described in Materials and methods. Non-transformed yeast were grown in SD-complete medium. Where indicated, cells were exposed to 0.6 mM H₂O₂ for 15 min prior to harvest. Spectra shown are the difference spectra resulting after subtracting non-transformed cell spectra from IRP1-transformed cell spectra.