SPECTROSCOPIC OBSERVATIONS ON CYTOCHROMES 345 



hemochrome (shifted slightly toward the red), and the somewhat less 

 distinct relationship of ferrocytochrome a to that of a hemochrome 

 with carbonyl groups in the porphyrin side chains is evident from the 

 following comparison of the position of the absorption maxima in m/x: 



In addition to the above-mentioned absorption bands, three bands 

 were found in the far violet at 448-449, 428-432, and 415-417 m/x 

 {1 479 y2951, 2956). These are ascribed to the cytochromes a, b, and c, 

 respectively. It will be seen later that in the presence of carbon 

 monoxide no such simple correlation is possible. Pyridine leaves the 

 c band unaltered, but shifts the a and b bands to shorter wavelengths. 

 These bands were designated a', b', and c' by Keilin. The a' band 

 has now a position close to the first band of pyridine Spirographis 

 hemochrome and the b' band to that of pyridine protohemochrome 

 iU7J^,U75). 



KeiUn {1J^7J^,1J^76,1479,1481,1484.) and other workers, notably 

 Fujita and Kodama (962), have studied a large number of cells of 

 animals, plants, and microorganisms. Only in strict anaerobes and 

 in a few facultative anaerobes (Streptococcus I act is, Lactobacillus 

 delbrueckii, L. acidophilus) are the cytochrome bands entirely missing. 

 While the absorption spectrum described above for bakers' yeast is 

 the one most frequently found, some of the bands are lacking in some 

 species (2625, p. 29) or are replaced by other bands which are ascribed 

 to substances named cytochromes 0.2, ai, and bi. These spectra are 

 more commonly found in microorganisms, but also occur in some 

 invertebrates, plants, and in the cells of a few mammalian tissues. 

 It is necessary to keep in mind that with the exception of cytochrome 

 c the various cytochromes are as yet spectroscopic phenomena rather 

 than definite substances. The position of the bands is given by 

 Fujita and Kodama as follows: 



Cytochrome Band, mfi Cj'tochrome Band, m/i 



aj 635-625 b 567-558 



a 605-600 bi 563-552 



a, 595-587 c 555-547 



