166 



V. HEMATIN COMPOUNDS 



3. HEMES, HEMINS, AND HEMATINS 



3.1. Hemes 



While earlier worker.s had considered "hemochromogen" to be the 

 pro.sthetic group of hemoglobin, An.son and Mirsky (65,69, cf. also 

 Keilin, IJf'^o) recognized that it was a more complex compound (cf. 

 Chapter VI). The true prosthetic group, iron protoporphyrin, was 

 later called heme. Hemes are rather unstable and easily oxidizable 

 substances which are obtained when a solution of hematin in alkali 

 is reduced in the absence of nitrogenous substances. In this way it 

 was probably first obtained by Bertin-Sans and de Moitessier {251), 

 and in crystalline form by Dhere and co-workers {57 J^). Protoheme 

 is unstable and rapidly oxidized in contact with air. The more 

 stable etioheme has been prepared in pure crystalline form and has 

 been analyzed by Fischer, Treibs, and Zeile {886). Magnetochemical 

 investigations {2127,3219) indicate ionic linkage (four unpaired elec- 

 trons) of the iron, in solutions of heme in dilute aqueous sodium hydrox- 



700 660 620 580 540 500 

 WAVELENGTH, m/x 



460 



420 



fig. 1 . Absorption curve of heme {S9S) 



ide. With solvents containing carbonyl or hydroxyl groups, such as 

 acetone and alcohol, hemes combine to form loose compounds {1120). 



