71 



electrons which could transport energy, the purine having its 

 system of conjugated double bonds and the phosphate the O's 

 with their nonbonded lone pairs of electrons. The P — O — P, 

 which represents the (£), could merge thus with the adenine in 

 one extensive system of mobile electrons. 



This opens the possibility that when such a double chelate is 

 formed and the metal attracts electrons from the phosphates, it 



V^v^ 



Fig. 19. Mg chelate of c-phenylenediamine and naphthoquinone. 



decreases the energy^ and strength of the P — O — P bond, which 

 then falls prey to hydrolytic splitting while its energy appears in 

 the purine ring as E* , completing the (E) -> £* transformation. 



That Mg can actually facilitate the passage of electrons from 

 one substance to another with which this metal forms complexes 

 can be demonstrated by mixing an alcoholic solution of 1,2-naph- 

 thoquinone and (9-phenylenediamine (Fig. 19). In this system the 

 quinone oxidizes the diamine very slowdy, electrons passing from 

 the latter to the former. This reaction is greatly speeded up by Mg, 

 in analogy to the ATP-ase activity of myosin, which also can occur 

 without Mg, but is greatly accelerated by the metal. The reaction 

 between quinone and diamine is indicated by the darkening of the 

 solution (w^hich can readily be reverted by reducing agents such 

 as ascorbic acid ) . 



One attractive feature of this theory of ATP-ase activity is that 

 it is analogous to E. L. Smith's theory of peptidase activity. 



