338 



M. Morrison and E. Stotz 



vinyl group as two groups in resonance witli the porphyrin a nucleus 

 (Dannenberg and Kiese, 1952; Lemberg, 1953; Kiese and Kurz, 1953; 

 Warburg, Gewitz and Volker, 1955). Table 1 supplies such evidence. Haemin 



A = actio, R = rhodo, O = oxorhodo. 



a reacts with dimedon to form a methone derivative; bromine adds to 

 haemin a to form a product of which the haemochrorae band is shifted 5 m/t 

 towards the blue. These observations confirm the presence of a formyl and 

 a vinyl substituent. 



The third group removed in the resorcinol melt of haemin a may be an 

 a-ketoalkyl group on the following grounds : the infra-red spectrum indicates 

 the presence of two carbonyl groups other than the carboxyl-carbonyls ; 

 one of these is the formyl group, while the other must be present in the third 

 group. The long aliphatic side chain is probably present in the a-ketoalkyl 

 side chain rather than on the vinyl, since oxidation with permanganate 

 yielded no long chain aliphatic acid or aldehyde. From our studies, the 

 molecular weight of chlorohaemin a based on iron determination is 880. By 

 difference, the alkyl group must account for 213 of the molecular weight. 



The significance of the long aliphatic chain and the aldehyde and ketone 

 groups in the functioning of the cytochromes a and ^3 is not apparent. It is 

 clear that the long chain aliphatic group can help supply a non-polar environ- 

 ment. In view of the findings of Wang (1958) and Corwin and Bruck (1958), 

 it could be suggested that the 'aliphatic' environment makes possible a 

 haem-oxygen combination equivalent to that which takes place in the 

 haemoglobin molecule and that the subsequent oxidation of the iron requires 

 the transfer of an electron from a co-ordinating group on the protein. 



CYTOCHROMES AND PHOSPHORYLATION 



The clarification of the mechanism of oxidative phosphorylation in chemical 

 terms is a second outstanding problem in understanding biological oxidation. 

 This problem can be approached in a number of diflFerent ways. It has been 

 investigated by spectrophotometric study (Chance and Williams, 1957) of 

 the kinetics of interaction of the various cytochromes, flavoproteins and 



