Properties of Cytochrome c

A STRONG solution of pure cytochrome c obtained by the method which we have previously described1 shows in the oxidized state an absorption spectrum of the parahaematin type. In a very much higher concentration and in a thick layer this compound reveals the two additional feeble absorption bands at about 695 mμ and 625 mμ discovered by Yakushiji2. The absorption spectrum of oxidized cytochrome c changes with the hydrogen ion concentration2,3. In this respect, cytochrome c resembles other trivalent haeematin compounds such as methaemoglobin, parahaematin and haeematin. It is known, for example, that a parahaematin compound has a characteristic absorption spectrum only within a certain limited range of hydrogen ion concentration4. On acidifying it or on making it alkaline the absorption spectrum of parahaematin changes respectively to those of free acid and free alkaline haematins.