496 X. BILE PIGMENT FORMATION, ETC. 



prepared his sulfhemoglobin in a more cautiotis manner than in his first, the 

 long exposure (ten hours) to mixtures of hydrogen sulfide and oxygen, and 

 particularly the subsequent digestion of the protein by pepsin in hydrochloric 

 acid, may well have produced secondary changes, with an alteration of the 

 type of linkage of the prosthetic group. The "sulfhemin proteose" obtained 

 by the action of pepsin was converted into a porphyrin by heating at 100° C. 

 with concentrated hydrochloric acid. The elementary analysis of this ether- 

 insoluble porphyrin gave C34H36N4O4S2. Since, upon titration, no free acid 

 (SO3H) groups were found to be present, Haurowitz assumes that the sulfur 

 and the additional oxygen atoms are present as sulfone groups in rings 

 between the vinyl side chains and the methene group (Fig. 10). This is, 



H 



N C 



SO, 



Fig. 10. Porphyrin from sulfhemin proteose (Haurowitz). 



however, in contradiction to his observation that the vinyl groups can be 

 removed by the resorcinol melt. Moreover, a sulfhemoglobin is also formed 

 from mesohemoglobin with saturated side chains {1170) and from hemato- 

 hemoglobin {Idlfo). According to Haurowitz, the prosthetic group of 

 sulfhemoglobin is not detached from the protein by boiling acetic acid or by 

 oxalic acid in acetone. Tliere can be little doubt that Haurowitz's porphyrin 

 is not closely related to the original prosthetic group. 



Fig. 11. Structure of sulfhemoglobin suggested by Nijveld (2054). 



Nijveld suggests the structure of Figure 11 for sulfhemoglobin and 

 a similar structure with CO instead of CS for choleglobin. Such 

 structures with allene carbon (=C=) in the ring are stereochemically 

 impossible. This formula for sulfhemoglobin also fails to explain the 



