HEMATINS C 203 



oxidized to azaherajglobin. The spectrum of azahem/globin shows httle 

 diflFerence from that of denatured globin azahem /chrome. 



Azahem/globin at pH 6 has no band in the orange comparable with that 

 of hem/globin. 



The ease with which yerdohemochrome is transformed into monoaza- 

 hematin compounds makes it appear hkely that the latter should be found 

 in nature; in fact to judge from its absorption spectrum (hemochrome band 

 570 m/x, hem?chrome 6'-25 mju), the hemochrome found by Ball and Meyerhof 

 (125) in the eggs of Limulus poh/phenu/s may be an azahemochrome. 



8.3. Oxyporphyrin Heraatin Compounds 



These compounds were first obtained by Lemberg and collaborators 

 (1698) by treatment of pyridine hemochrome with very dilute hydrogen 

 peroxide in the presence of ascorbic acid; they were also later found by 

 Libowitzky and Fischer (1731,1732). Their structure has been discussed in 

 Chapter III. The red oxyprotohemochrome has two absorption bands iden- 

 tical in position with those of pyridine protohemochrome, but the |(3-band is 

 the stronger. Oxygen transforms it to the green oxyprotohemichrome 

 (absorption band 040 m^), which is unstable. In the presence of ascorbic 

 acid and atmospheric oxygen, it is readily converted into verdohemochrome, 

 but even with oxygen alone it is further oxidized. The hematin of oxypor- 

 phyrin in ether is also unstable and changes into brown compounds of 

 unknown structure which no longer give hemochromes with pyridine (1731, 

 1732). 



Holden and Lemberg (1324) have studied the ultraviolet absorption of 

 oxyhemochromes. A moderately strong Soret band was found: pyridine 

 oxyferroprotoporphyrin e^^^ = 40, carbon monoxide pyridine oxyferroproto- 

 porphyrin:«^^^j = 76. 



Oxyhemochromes are mainly of interest as the first intermediates in the 

 formation of bile pigments from hematin compounds; this aspect will receive 

 further discussion in Chapter X. 



8.4. Hematins c 



The term "hematin c," which is used to describe a number of 

 compounds of only distant relationship, arises from the fact that 

 these substances have been studied mainly in order to gain some 

 insight into the nature of cytochrome c. The phenomena of their 

 production have in common the transformation of protohematin into 

 water-soluble, ether-insoluble compounds, the hemochromes of which 

 have spectra of the meso rather than the proto type. This spectral 

 change indicates that addition has occurred to the unsaturated vinyl 

 side chains, and the hydrophilic nature of the product may be 

 ascribed to the hydrophilic nature of the added groups. 



It is also possible, in some instances, for such groups to enter the 



