HEMATINS 



173 



Bond type. According to Pauling and co-workers {2126,2127,2129), 

 the linkage between iron and porphyrin is essentially ionic (with five 

 unpaired electrons on the iron) in crystalline hemin, or in solutions 

 of hematin in alkali in the presence of sucrose, or in anhydrous 

 pyridine. While confirming the result of Pauling for alkaline solution 

 in the presence of sucrose, Rawlinson {2219) found in the absence of 



TABLE II 



Spectropliotometric Data for Acid and Alkaline Hematin 



"The absorption spectra of hemin and hematin in glacial acetic acid appear to be 

 identical. 



''The shift of the Soret band and its reduced intensity under these conditions inflicate 

 some association (Hicks and Holden, 1270). 



'^The higher value for the extinction of the Soret Band found by Hogness and col- 

 laborators (1307) may be due to greater dilution of their solutions. Note also 

 that the curves given by these workers are for dimeric hematin. 



''The explanation of the shift of the bands toward shorter wavelengths at pH values 

 below 1 1 is not clear, but may be due to dissociation of the hydroxyl ion of the 

 hematin in this region. 



the latter a smaller magnetic susceptibility, indicating only three 

 unpaired electrons. An alkaline solution of hematin may, therefore, 

 contain hematin compounds with covalent bonds; this may be con- 

 nected with polymerization, occurring by covalent bond formation 



