164 



David L. Drabkin 



spectra of derivatives of cytochrome c (Figs. 16 and 17) were in the meso- 

 or copro- locations. Hence, this was offered as evidence that the spectrum 

 itself of cytochrome c revealed a structural difference of its haemin in positions 

 2 and 4, namely a vitiation of the unsaturated vinyl bond structure, such as 

 would occur in Theorell's thio-ether linkage (Drabkin, 1942b) 



Fig. 16. Pattern Type 1; absorption spectra of cyanide derivatives of ferro- 

 haems, haemoglobin, and ferrocytochrome c. Curve 1, cyanide ferroprotopor- 

 phyrin. Curve 2, cyanide ferromesopoi"phyrin. Curve 3, cyanide ferrocopropor- 

 phyrin. Curve 4, the reduced cyanide derivative prepared from dog haemoglobin 

 in alkaline solution, probably cyanide ferroprotoporphyrin. Curve 5, the reduced 

 cyanide derivative prepared from cytochrome c in alkaline solution, ferrocyto- 

 chrome c cyanide. See legend to Fig. 15 (Drabkin, 1942b). 



The spectral displacement of the protohaemin complexes toward the 

 longer wavelengths was ascribed (Drabkin, 1942b) to the increase in the 

 conjugated double bonds in the porphyrin system by the presence of 

 the unsaturated vinyl radicals, analogously to the situation disclosed by the 

 systematic studies of Hausser and Kuhn and their collaborators on polyene 

 dyes of the type R— (CH=CH)„— R' (Hausser, 1934; Hausser et al, 

 1935a to e). Incidentally, on the basis of the above analysis, it could be 

 prophesied that the haemin of cytochrome b.^ must be ordinary protohaemin 

 with the vinyl residues intact (Morton, 1958). I believe that in the haemin 

 proteins the influence on spectral location of the maxima in the visible region, 

 evident also in ferrihaemin complexes such as the cyanide derivatives 



