204 V. HEMATIN COMPOUNDS 



methene groups of the porphyrin nucleus; in this manner, meso- 

 hematin can also be transformed into a hematin c. 



Preparation. Keilin {H7(')) observed that by alternate reduction and 

 oxidation of protohematin with sodium dithionite and ferricyanide, respec- 

 tively, a hematin c was obtained. Zeile {31-JO) found that the ether-insoluble 

 porphyrin c obtained from this by acifl contained three to four sulfonic acid 

 groups. Since mesohematin gives similar products, the porphyrin nucleus is 

 also substituted. These compounds are thus not related to the compounds 

 derived from cytochrome c, from which they differ also by losing their iron 

 much more readily on treatment with acids, yielding "porphyrin c" {^30S), 

 and by not being transformed into hematoporphyrin by hydrobromic acid 

 in glacial acetic acid iJ708,31o9). With native globin they unite, giving a 

 heuKchrome, not a hem/globin (2306). 



These facts should be a warning that sodium dithionite, which is frequently 

 used as a reducer in hematin andhemoglobin investigations, is by no means 

 harmless, and can cause unexpected side reactions (cf. Chapter \TII, Section 

 S.S.'^.). 



A similar ether-insoluhle porphyrin c is obtained from hematin after 

 treatment with sulfur dioxide, particularly on irradiation {317(>). Hemo- 

 globin under these conditions yields a porphyrin peptide containing one to 

 two sulfur atoms, which cannot be .split by pepsin or trypsin, probably 

 liecause it contains a stable — SO2 — linkage between the peptide residue 

 and the prosthetic group. On treatment with hydrochloric acid, a porphyrin 

 c is obtained. By peptic digestion of sulfhemoglobin, Haurowitz obtained a 

 "sulfheminproteose" (11(10), which is evidently of the same type, whereas 

 the heminproteose of Waelsch (2002) differs in yielding hematopdrphyrin 

 on splitting. 



Hematins c of a different type have been obtained by Zeile (3159,3169) 

 by addition of amino acids, amines, and (juaternary bases to the vinyl side 

 chains of protohematin. The hematins c so formed have side chains such as: 



CH3 CH3 CH3 



— CHNHCH2CO2R CHN(CH3)2 — CH — N 



a be 



Of these, the third type (c) alone yields hematoporphyrin on treatment with 

 hydrobromic acid. They all combine with native globin to form hemoglobins 

 {230H). During the peptic digestion of hemoglol)in, addition of amino acids 

 to the vinyl side chains may occur, giving artifacts, which on acid treatment 

 yield a hematin c and porphyrin c of this type (160,2433). 



A special type of hematin c is that in which combination takes place with 

 cysteine. Here, linkage is through the sulfur instea<l of the nitrogen. This 

 sulfur-containing compound is the only type of hematin c (or porj)hyrin c) 



