Figure 4: Spectra of oxidized (black line) and reduced (red line) forms of (a) decPQ, (b) decUQ, and (c) HPMC (see text). The spectra were normalized to 1 μM of the substance to assess the impact of oxidation of these compounds into total absorbance changes during the experiment. All the three redox pairs have isosbestic points at 230–240 nm suggesting a minimal interference with the robust signal of conjugated dienes. The ubiquinone/ubiquinol pair also has an “oxidized minus reduced” difference absorption maximum at ~275 nm, which does not strongly overlap with the spectrum of conjugated dienes.