Cytocliroines Cooled in Liquid Nitrogen 



445 



the same type of fine band structure of the a- and /^-bands as heart muscle 

 cytochrome c, with some modifications in the location of the maxima. 



Figure 8 presents a comparison of the spectra obtained when samples of 

 heart muscle cytochrome c and yeast cytochrome c are analysed. The spec- 

 trum of the yeast cytochrome c looks similar to that obtained with TCA- 

 denatured or with alkali-denatured heart muscle cytochrome c. It should be 

 noted, however, that the locations of the absorption bands of the denatured 

 material and of the yeast cytochrome c are different. 



Other Types of Cytochrome c 



Some other interesting variations on pigments of the type of cytochrome c 

 are shown by results obtained with cytochrome c^ of Azotobacter vinelandii. 



43 O 460 490 52 O 

 Wavelength , mp 



550 580 



Fig. 9. A comparison of the spectral properties of reduced cytochrome c 

 prepared from heart muscle and cytochrome C4 of Azotobacter vinelandii. 

 Curve A represents the spectrum obtained with cytochrome C4 while curve B 

 is that obtained with heart muscle cytochrome c. Optical depth equals 1 mm. 

 Condition II. 



One sees in Fig. 9 the spectrum of reduced cytochrome q (curve A) compared 

 to that of the heart muscle cytochrome c. Of interest is the fact that even 

 though the fine band structure of the a- and /9-bands are apparently identical 

 in both samples, the location of the maxima of the absorption bands of 

 reduced cytochrome q from bacteria are shifted about 1-5-2 mp, to the red. 

 It was difficult to convince ourselves of the vahdity of this observation, but 

 repeated experiments have proven that this is not an artifact of the machine 

 or the method of carrying out the experiments, but truly a reproducible 

 difference between the two pigments. The multiplicity of Soret bands ob- 

 served with cytochrome c^ prepared from Azotobacter is in contrast to the 



