Analysis and Interpretation of Absorption Spectra of Haeniin Chromoproteins 165 



(Drabkin, 1942a), represents the major contribution of the structure of the 

 porphyrin nucleus to the spectra, although it is tempting to draw analogies 

 between the band distribution and location in the spectra of porphyrins and 



/"xlO^^ 



Fig. 17. Pattern Type 2. Absorption spectra of denatured globin (globan) 

 derivatives of ferrohaemins (reduced haemochromogens) and the spectra of 

 haemoglobin and ferrocytochrome c in alkaline solutions. Curve 1, globan 

 ferroprotoporphyrin, prepared from human globin and protohaemin. Curve 2, 

 globan ferromesoporphyrin, prepared from human globin and mesohaemin. 

 Curve 3, globan ferrocoproporphyrin, prepared from human globin and copro- 

 haemin. Curve 4, globan ferroprotoporphyrin, prepared from haemoglobin of 

 man. Curve 5, ferrocytochrome c in alkaline solution. See legend to Fig. 15 and 

 for details see Drabkin, 1942b. 



their two-banded hydrochlorides and in haemin derivatives (Williams, 1956). 

 Nevertheless, this is a matter of predilection, and Williams' interpretation 

 that in porphyrins (see Fig. 5) the near ultra-violet band ('Soret band') is 

 accounted for by a tt -> 77' electron transition, and the visible bands, I, II, III 

 and IV by a second -n electron transition may be valid for porphyrin spectra 

 (Williams, 1956). 



DISCUSSION 



Theory of Absorption Spectra. In general the absorption of light energy by 

 atoms and molecules may be considered to be the reverse of emission. 



