11. Riboflavine 



As is generally known, the function of riboflavine- 5 -phosphate 

 (which I will briefly call "riboflavine") is to act as intermediary 

 H-acceptor in the oxidative system, accepting H's coming from the 

 foodstuffs, and passing on electrons to the cytochrome system. 

 This function is in accord with its chemistry. Accepting H's in 

 pairs and giving off electrons one by one, it must be able to form 

 a free radical. The ability to do so can readily be demonstrated by 

 reducing it in a strongly acid medium, whereby the greenish-yel- 

 low color of the oxidized form, turns into the red-brown color of 

 the free radical. 



Naturally, the real function of the substance is not merely to 

 serve as a bridge for the H's or electrons to pass over, but to con- 

 vert the energy, released in its oxido-reduction into ^P's, and our 

 problem here is to find out whether £* is involved in this process. 

 As has been stated earlier, fluorescence tells us that the molecule 

 does not readily dissipate its £*, may thus act as an energy trans- 

 mitter. All fluorescent molecules were also found to be able to go 

 into the triplet state in ice. The well known brilliant greenish- 

 yellow fluorescence of riboflavine may thus be taken as an encour- 

 agement. 



The structure of riboflavine (Fig. 20) has close analogies with 

 that of ATP. We found the structure of ATP more complex than 

 was needed for its alleged function, that of a phosphate carrier. 

 Similarly, the structure of riboflavine is more complex than would 

 be needed for an intermediary H-acceptor. The molecule of ATP 

 is built of three parts : it has phosphate on one end, a heteroxyclic 

 compound with an extensive system of conjugated double bonds 

 on the other, with a pentose connecting the two. Riboflavine has 



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