Cytochrome infrared spectrum

Figure 12, Infrared differ-ence spectrum of carbonyl cytochrome c oxidase vs. oxidized oxidase. Water vapor hand at right used for wavelength calibration. Insert at bottom Soret and visible spectra of the CO derivative in the Cap2 cell used to obtain the infrared spectrum.

The reduction of ring IV in chlorophylls a or b changes the optical absorption spectrum of the molecule dramatically. Whereas the long-wavelength absorption band of a cytochrome is relatively weak (see fig. 14.4), chlorophyll a has an intense absorption band at 676 nm (fig. 14.5). Chlorophyll b has a similar band at 642 nm. Bacteriochlorophylls a and b have strong absorption bands in the region of 770 nm (see fig. 15.5). The chlorophylls thus absorb red or near-infrared light very well. 

Fig. 9. A reductive titration of the crystalline bovine heart cytochrome c oxidase with dithionite. Absolute spectra for each oxidation state are shown for the Soret (A) and visible (B) regions. The difference spectra against the spectrum in the fully reduced state are given for the near-infrared region (C). The insets show titration curves against the electron equivalent per enzyme. The reaction mixture contained 7.5 jlM bovine heart cytochrome c oxidase in 0.1 M sodium phosphate buffer, pH 7.4. The enzyme preparation was stabilized with a synthetic non-ionic detergent, CH3(CH2)ii(0CH2CH2)80H. The light path was 1 cm.

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