FERRIHAEMOPROTEIN HYDROXIDES: A 



CORRELATION BETWEEN MAGNETIC AND 



SPECTROSCOPIC PROPERTIES 



By P. George, J. Beetlestone and J. S. Griffith 

 Department of Chemistry, University of Pennsylvania, Philadelphia, U.S.A. 



INTRODUCTION 

 Ferrihaemoglobin, ferrimyoglobin, ferriperoxidase and ferricytochrome c 

 all undergo ionizations in alkaline solution that are accompanied by signifi- 

 cant changes in absorption spectra and magnetic susceptibiUty. These 

 reactions can be represented simply as 



Acidic form ^-^ Alkaline form + H+ 



(1) 



That of ferrihaemoglobin, where the colour changes from chocolate brown to 

 wine red, is the most familiar, and has been known from the earliest days of 

 spectroscopic observations on haemoglobin and haemin by Hoppe-Seylet, 

 Stokes and Gamgee (Gamgee, 1868). The pA: values which characterize these 

 reactions are hsted in Table 1. Ferricatalase, which in complex formation 



• In this case the value of 'n' for the titration was found to be greater than 1, i.e. 1-64, which may be an 

 indication of additional reactions occurring in the very alkaline solution, 



with many ligands resembles the other ferrihaemoproteins, is an exception for 

 no such ionization has been observed. It may well be that the ipK is so high 

 that protein denaturation sets in before the ionization can take place. 



It is generally accepted that these reactions involve the bonding of the 

 hydroxyl ion to the ferriporphyrin iron atom, but the evidence is circumstan- 

 tial. First, there are many ionizations of aquo-ions and simple co-ordination 



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