fig1

Figure 1. Redox centers in the mitochondrial respiratory chain (left) and EPR signals observed in frozen tissue with geff -values on the top scale and resonant fields at 9.5 GHz on the bottom scale (right). The labels “C I”, “C II”, “C III”, and “C IV” refer to mitochondrial respiratory chain complexes I, II, III, and IV, respectively. The spectra are computer simulations of the signals as expressed in whole, unprocessed, frozen tissue; details of the signals (precise geff values; splittings; line widths) can differ noticeably in isolated proteins or mitochondrial fragments, particularly due to differences in redox potential and spin-spin interactions between redox centers. The signal due to the whole mitochondrion in the lower right panel is shown at two different amplitudes superimposed with one at 20 × the amplitude of the other, in order to have appreciable amplitude of each of the contributory signals in one or other of the traces (this is clearest at g_eff = 6), while the signals shown individually have normalized peak amplitudes