250 



ELECTRON TRANSPORT 



two systems are involved, one for NAD and one for fumarate. Quina- 

 crine has been shown to have potent effects upon electron transfer 

 systems in photo synthetic bacteria. Baltscheffsky has shown that this 

 compound is an inhibitor of the photophosphorylation process (38). 

 Furthermore, the inhibition observed in his experiments was partially 

 relieved by the addition of FAD, while FMN was less active. It should 

 be noted, however, that extremely high concentrations of FAD and 

 FMN were required for these reactivations, and at such high concen- 

 trations the flavin nucleotides are active in nonenzymatic reactions. 



I 2 3 



MINUTES 



Fig. 13. The effect of 2 x lO'^ M quinacrine on DPIPH2 

 photooxidation by R. ruhrum chromatophores. The ex- 

 perimental conditions employed for Fig. 1 were used with 

 0.21 mg of BChI present. 



The experiments of Ash et al. (17) show that quinacrine has a strik- 

 ing effect upon the photo reduction of methyl red and tetrazolium blue 

 by R. riihnun chromatophores. The stimulating effect of quinacrine on 

 a very similar system has been found by Bose and Gest (39). In their 

 experiments, R. mbntin chromatophores catalyzed the photoreduction 

 of fumarate by hydrogen gas. This photoreduction required the presence 

 of DPIP, which was reducedenzymaticallyby the hydrogen gas. There- 

 fore, the two systems are essentially the same, consisting of DPIPH2 

 and fumarate. In both cases DPIPH2 is photooxidized and fumarate is 

 reduced, and in both cases quinacrine markedly stimulates the reac- 

 tions. 



