FIGURE 4.

Light-induced superoxide formation in wt and PTOX⁺ thylakoids. Typical EPR spectra of the DEPMPO-OOH adduct are shown. Thylakoid samples were illuminated as described in Fig. 4 in the presence of 50 mm DEPMPO. Typical EPR spectra are mixtures of superoxide (∼70%), hydroxyl and carbon-centered DEPMPO adducts (red lines, simulated spectra). DEPMPO-OOH is generated as a relatively stable radical after DEPMPO reacts with O₂^˙̄. Samples were illuminated for 5 min at high light (1500 μmol quanta m⁻² s⁻¹). Where indicated, 50 μg SOD/ml, 10 μm DNP-INT, or 10 μm DCMU was added prior to the illumination.