Figure 3.

Effect of oxygen on decomposition of the blue complex. For data in A–C, reaction mixtures contained 80 mM histidine, 150 μM Fz, 50 μM Fe(II), and 50 mM Hepes buffer (pH 7.6). The gas phase was as follows: air, A; 100% O₂, B; 100% N₂, C. For data in D–F, reaction mixtures (in air) contained 50 mM histidine, 150 μM Fz, and 150 μM Fe(II). In addition, in D and F mixtures contained 1 μM catalase and 50 μg of SOD, and in E and F mixtures contained 75 μM H₂O₂. All reactions were initiated by addition of iron and spectra were recorded at 2-min intervals. Immediately after the 10-min spectra had been recorded, 30 mM H₂O₂ was added and the spectra were recorded again (dotted lines) to disclose the amount of purple compound formed. Symbols as in Fig 2.