CYTOCHROME SPECTRA 493 



differentiated 6-type ferro-minus-ferri- difference spectrum with 

 peaks at approximately 560 and430m/i. With/?, rnbrum, a cytochrome 

 b component is less obvious. Interfering pigments are first removed 

 by washing cells or chromatophore preparations with acetone, and the 

 residue is suspended in alkaline pyridine. After dithionite is added to 

 reduce the heme derivatives, a distinct pyridine hemochromogen spec- 

 trum of a 5-type cytochrome can be seen, with an a peak at 556 m^ 

 (11). With Chromatin})! as well as with Chlorobium thiosulphatophilum 

 (8) even this strategem is fruitless, and perhaps no &-type cytochrome 

 is present in these species. Possibly cytochromoid C may be mistaken 

 for cytochrome b in whole cells or particle preparations because 

 ferro-minus-ferri- difference spectra of both types of cytochromes 

 produce marked peaks or shoulders in the region of 560 rafi and 430 

 m^. A small amount of soluble cytochrome b has been isolated from 

 Rps. spheroides (6), but in general the cytochrome remains tightly 

 bound to the cellular particles of several species that have been ex- 

 amined. 



REFERENCES 



1. The Classification and Nomenclature of Cytochromes, p. 24 in Report of 

 the Commission on Enzymes of the International Union of Biochemistry. 

 Pergamon Press, New York, 1961. 



2. Horio, T., and Kamen, M. D., Preparation and properties of three pure 

 crystalline bacterial haem proteins. Biochi)n. Bioplivs .Acta, 48, 266 (1961). 



3. Bartsch, R. G., and Kamen, M. D., Isolation and properties of two soluble 

 heme proteins in extracts of the photoanaerobeC/zro^j?<7/?"?r;;?. J. Biol. Chem., 

 235, 825 (1960). 



4. Morita, S.,and Conti, S. F., Localization and nature of the cytochromes of 

 Rhodomicrobiiim vawiielii. Arch. Biochem. Biophys., 100,302 (1963). 



5. Orlando, J. A., Rhodopseudomonas spheroides cytochrome 553. Biochim. 

 Biophys. Acta, 57, 373 (1962). 



6. Orlando, J. A., and Horio, T., Observations on a b-tj^e cytochrome from 

 Rhodopseudomonas spheroides . Biochim. Biophys. Acta, 50, 367 (1961). 



7. Morita, S., Crystallization of Rhodopseudomonas paliistris cytochrome 552. 

 J. Biochem. (Tokyo), 4S, 870 (1960). 



8. Gibson, J., Cytochrome pigments from the green photosynthetic bacterium 

 Chlorobium thiosidphatophilnm. Biochem. J., 75,151 (1961), 



9. Drabkin, D., Structural interpretation of the spectra of cyanide, pyridine 

 and carbon monoxide derivatives of cytochrome c and hemoglobin. J. Biol. 

 Chem., 146, 605 (1942). 



10. Paleus, S., and Tuppy, H., A hemopeptide from a tryptic hydrolysate of 

 Rhodospirillum rnbruni cytochrome c. Acta Chem Scand., 13, 641 (1959). 



11. Vernon, L. P., and Kamen, M. D., Hematin compounds in photosynthetic 

 bacteria. J. Biol. Chem., 211, 643 (1954). 



12. Chance, B., and Smith, L., Respiratory pigments oi Rhodospirillum rubrum. 

 Nature, 175, 803 (1955). 



13. Bartsch, R. G., Properties of c-tj^e cytochromes of Chromatium. Fed. 

 Proc, 20, 43 (1961). 



