ANDRE r. JAGENDORI- AND GIORi.lO lORTJ bid 



CMU CONCENTRATION 



I"ig. 1. Inhibition of phosphorylation by CMU (/>chlorophenyl dimethyl urea) 

 with different cofactors. FMN, PMS (phenazine methosulfate) or pyocyanine pres- 

 ent as indicated at 3 X ^^'^ '^^- Ot'ier reaction conditions essentially those de- 

 scribed under Table 1. The reactions were all flushed with nitrogen containing a 

 small amount of oxygen. Each curve represents the average of from 6 to 12 experi- 

 ments; the vertical lines represent twice the standard deviation. Specific activities 

 of the control flasks ranged from 50 to 150 ^moles ATP formed/mg chloro- 

 phyll/hour with FMN; from 310 to 640 for pyocyanine; from 300 to 650 for PMS. 



cation was proposed by Anion, Bove, and Whatley in connection with 

 similar data obtained on studying chloride-deficient chloroplasts 

 (1). In both cases the elaboration no longer seems necessary; the 

 data do not really require us to go beyond the first five equations 

 listed above. 



The intermediate inhibition observed with pyocyanine (middle 

 curve in Fig. 1) turned out to be an artifact, caused by a small amount 

 of oxygen left in the nitrogen we used to eliminate air from the 

 reaction flasks. After improving the preliminary oxygen-trapping sys- 

 tem on our nitrogen gassing line, and increasing the length of time of 

 flushing with nitrogen, the results shown in Table 1 were obtained. 

 With sufficient removal of oxygen, the pyocyanine-catalyzed phos- 

 jjhorylation becomes resistant to CMU. This is especially true if, 

 as in the second column, the oxygen is removed prior to addition of 

 the CMU. 



