168 David L. Drabkin 



The novel use of curves of the normal frequency form — admittedly agree- 

 able to the writer — need not imply that absorption bands actually possess this 

 shape. Yet, made up as they are (in different spectral regions) of an electronic 

 band, with blurred out vibrational or rotational elements, their shapes may 

 really be similar to those employed in the graphical resolution. It is hoped 

 that methods will be forthcoming which may permit an experimental resolu- 

 tion of the spectra of haemin derivatives at least, if not those of the haemin 

 proteins. Among the possibilities are the spectra at very low temperatures in 

 which interest has been renewed, and which were originally explored in 

 porphyrins by Conant and his colleagues (Conant and Kamerling, 1931). 



SUMMARY 



A graphic-mathematical analysis, using curves of the normal frequency 

 form, has been made of the absorption spectra of haemin chromoproteins. 



The spectra in the near infra-red, visible and ultra-violet regions of all the 

 derivatives examined are fundamentally similar, and represent the summa- 

 tional effect, which can be expressed mathematically, of the a and /5 bands 

 and bands numbers 3 to 11 of an equally spaced frequency distributed series. 



The bands represent a series of electronic transitions and those in the 

 demonstrated spectral series are inferred to originate from the same molecular 

 structure, the resonating conjugated double bond system of the iron- 

 porphyrin unit. 



The special significance of the a and /5 bands, the contributions of porphyrin 

 and protein, and the influence of co-ordinating ligands have been discussed. 



A ckfio 1 vledgemen t 



The writer's investigations of the chromoproteins have been supported by 

 grants from the Office of Naval Research and the Bureau of Medicine and 

 Surgery of the Navy, and, more recently, by a grant from the National 

 Science Foundation, U.S. 



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