50 



David Shemin and Jonathan Wittenberg 



blood of each duck was divided into two parts; half was 

 incubated with the methyl labelled acetate and the other half 

 with the carboxyl labelled acetate. This was done so that the 

 results of the two experiments could be compared, since the 

 dilution of acetate would be the same, and presumably also 

 the rate of synthesis in each of the experiments would be the 

 same. Indeed, that the rate of synthesis was the same was 

 demonstrated experimentally by including ^^N labelled glycine 

 in the incubation mixture. The ^^N concentration of the 

 haemin in the methyl labelled acetate experiment was found 

 to be the same as that of the haemin in the carboxyl labelled 

 acetate experiment. Results of the two experiments are 

 therefore strictly comparable. 



The ^*C labelled hsemin samples from these experiments 

 were degraded and the activities of the fragments and 

 individual carbon atoms determined. Before discussing the 

 individual activities of the carbon atoms we may come to 

 some conclusions by examining the ^^C activities of some of 

 the fragments. It can be seen from Table III (Shemin and 



Table III 



^*C Activity of Fragments of Protoporphyrin Molecule 

 (Shemin and Wittenberg, 1951) 



•Addition of activities found for pyrrole rings A + B and C + D. 



tThe activity of the methylethylnialeimide fragment (haematinic acid minus the carboxyl 

 group) of Rings C and D equals 450 cpm. 



