621 



Thomas Punnett 



1.0 

 ATP 



MC CHI 



HR 



0.5 



400 



200 



FECN 



M6 CHL 

 HR 





 60 



no 



•200 



X= ADP STIM. REDUCT. 

 0=/\y P 



220 



1100 



FECN {yM/D 



100 



ATP 



M6 CHL 

 HR 



Jo 



220O 



Fig. 2- ATP/2e- ratio as a function of the ferricyanide con- 

 centration . 



P-QUINONE PHOSPHORYLATION 



Another finding was that the quinone Hill reaction is accompanied by a non- 

 cyclic phosphorylation. It was necessary to use a low concentration of 

 oxidant (0.11 mM/L quinone) as was the case in Avron's (8) and in Kilter's (9) 

 studies of dye-induced photophosphorylation. One unusual feature of this 

 reaction was that the rate of quinone reduction was not affected by the 

 addition of ADP at any pH. In this case, too, the "corrected" ATP/2e- ratios 

 would have been infinite. The ATP/2e- (total) varied from 0.3 to 0.7 over the 

 pH range 6.8 to 8.4, with the maximum ratio occurring at pH 7.6 to 8.0. (Fig. 

 3). This ratio was neither as high nor as constant as that obtained in the 

 ferricyanide reaction, probably because of the instability of p-quinone. The 

 quinone ATP/2e- ratio was fairly constant from 5 ^M/L to 110 ^M/L, while at 

 higher concentrations uncoupling became progressively greater. 



With both the quinone and ferricyanide Hill reactions, care must be taken 

 to add C0„ to the reaction mixture if the oats are grown during the winter. 

 The added CO2 increased the reaction rates and the ATP/2e- ratios apparantly 

 because it reacted directly with the phosphorylating step. 



