ANALYSIS AND INTERPRETATION OF ABSORPTION 

 SPECTRA OF HAEMIN CHROMOPROTEINS 



By David L. Drabkin 



Department of Biochemistry, Graduate School of Medicine, 

 University of Pennsylvania, Pennsylvania 



The molecular spectra of various common haemin chromoproteins, their 

 derivatives, and such related compounds as the haemochromes (nitrogenous 

 ferro- and ferriporphyrins) exhibit selective absorption over the broad spectral 

 range of 1000 to 200 m/t. The spectrum may be conveniently subdivided into 

 four regions, in which individual maxima have a 500-fold difference in 

 density (see Fig. 1). The most frequently examined region is the visible (2 in 

 Fig. 1), the location of the a and /5 bands, as they have been designated 

 historically. The selective absorption in this region is very different for the 

 different haemin chromoproteins and some of their derivatives, whereas the 

 absorption in regions 3 and 4 (Fig. 1), respectively the location of the y 

 band (Soret, 1878, 1883a and b; Grabe, 1892) and the ultra-violet, is more 

 generally similar for the different chromoproteins. Although the differences 

 in absorption, as in the visible and near infra-red regions, form a very 

 convenient and accurate basis for the quantitative determination of the various 

 pigments (Drabkin, 1950; Gordy and Drabkin, 1957), they yield little obvious 

 information concerning the relationship of the absorption to structures in 

 the complex molecules. 



Dhere's finding that haemoglobin, like other proteins, had an absorption 

 maximum in the vicinity of 275 m/< led him to conclude that the haemin 

 nucleus v/as responsible for the absorption in the visible region, while the 

 globin caused the absorption in the y band and ultra-violet regions (Dhere, 

 1906). In an early attempt to analyse the spectra of haemoglobin derivatives. 

 Vies (1914) presumably accepted Dhere's earlier generalization, which has 

 persisted to the present day. An examination of the spectrum curves of several 

 haemoglobin derivatives led me to deduce about a quarter of a century ago 

 that all the maxima (which represent bands) in the ultra-violet and some in 

 the visible region were spaced at approximately equal frequency distances 

 from each other (Drabkin, 1934). This was a potentially important discovery, 

 since it materially simplified the interpretation of the complex spectrum from 

 the viewpoint of its origin in the molecular structure. Before this work such 

 a distribution of integrally related absorption bands, belonging to a spectral 



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