66 



is open that by rotation and the consecutive folding the phosphate- 

 and the purine-end of the molecule may approach one another. 

 Naturally, for an energy transfer to take place between the two 

 ends, an "approach" is not enough, since the E of the '^P which 

 has to be transferred is an (£), that is, a bond energy which has 

 no outward action. For the transference of (E) there must be a 

 close fit, point counter point. The atoms which have to touch one 



show no relation, the first consisting of pyrrols, coordinated by a metal, while 

 the latter is built of isoprenes. However, if we eliminate the Mg with the 

 four N's, as well as the longer side chains from the porphyrin, we are left 

 with a chain (Fig. 13b) which is almost identical with the chain of caro- 

 tene, curled up (Fig. I4b). 



If these relations were hitherto not considered, this is probably due to the 

 fact that we have seen the structure formula of pyrrol too often. 



CH 



< 



C — OH, 



y 



HC 

 \ 



C-CH3 

 HC 



> 



HC 



HC 



\CH 

 / 



HX — C 



\ 



XH 



HC 



Fig. 14. a: Central chain of carotene without the ionone rings, b: Same 

 curled up. 



