156 



David L. Drabkin 



Contribution of Protein to the Over-all Spectroscopic Character of the 

 Haemin Chromoproteins. From what has already been said, the affect of the 

 metalloporphyrin complex is dominant throughout the spectral range, and the 

 absorption of the haemoglobins and of cytochrome c in the ultra-violet region, 

 even at the location of the so-called protein band (280-270 m/t ; band number 

 9 in the analysis), cannot be attributed exclusively to the protein moieties. 



Fig, 11. The contribution of the protein moiety, globin, to absorption in the 

 region 275 to 280 m/t (v x 10"^ = 360; band number 9). Curve 1, heavy solid 

 line, oxyhaemoglobin, 1 him/I. (1 milliatom of Fe); curve 2, heavy broken line, 

 carbonyl haemoglobin, 1 mM/1. (1 milliatom of Fe); curve 3, light solid line with 

 open circles, met- or ferrimyoglobin, 1 mM/1. (1 milliatom of Fe); curve 4, light 

 solid line, globin (from haemoglobin), 0-25 mM/1. (reference mol. wt. = 15,850); 

 curve 5, light solid line with black dots, bovine plasma albumin, 1 roM/l. (reference 

 mol. wt. = 68,000); curve 6, broken line with dots, bovine albumin, 0-25 mM/1. 

 (reference mol. wt. = 17,000); curve 7, broken light line, denatured globin, 

 0-25 mM/1.; curve 8, light line with crosses, 1 mM/1. with reference to haemin 

 (protohaemin added to amount of globin used for curve 7). Curves 4 and 6 aflFord 

 a comparison of globin and albumin at approximately similar concentrations by 

 weight. Curves 1 and 2 indicate that, if expressed on a molar basis (mol. wt. = 

 66,000), the absorption in this spectral region would be four times greater for the 

 haemin proteins than for albumin. See the text. 



The spectroscopic data plotted in Fig. 11 substantiates this conclusion. It 

 may be seen that the bands of haemoglobin derivatives and metmyoglobin, 

 though generally similar yet differ slightly from each other (curves 1 to 3). 

 On the other hand, they are broader and smoother than the band of bovine 

 albumin (curve 5). Misleading deductions as to the molecular origin of this 

 band in chromoproteins may have been drawn because of the convention of 

 expressing information on the chromoproteins on a 1-Fe-atom equivalent 

 basis, whereas for proteins like albumin the molecular weight base has been 

 used for reference. If the absorption for the haemoglobin derivatives were 

 to be referred to 1 mM/l., instead of 1 milliatom of Fe/1., its maximum in this 



