601 



Jagendorf and Hind 



reagents. As a matter of fact, TCA-only addition was 

 generally made several seconds later than ADP addition. 

 The shifting control values in Table I show that such 

 a procedure is dangerous. ADP can lead to recovery of 

 more ATP^^ because it stabilizes some of the light 

 product, rather than because it leads to the formation 

 of new ATP32 i^ a dark reaction. Finally, if ADP is 

 added soon enough it can also pick up the last remnants 

 of the non-phosphorylated intermediate. Although a high 

 energy phosphorylated intermediate may truly exist, the 

 previous experiments can not be considered to have 

 demonstrated it critically. More powerful and direct 

 techniques - perhaps those of Hinkson and Boyer (7) will 

 be needed for a more definitive demonstration. 



The ATPase that forms in the light, in our case, 

 has been shown to be particulate and transient (manuscript 

 in preparation). Trace amounts of ATP32^ whether 

 formed in the light or added later, can be broken down 

 by properly activated chloroplasts. Activation consists 

 of incubation in the light with a trace of ADP, and 

 pyocyanine. Interestingly, the time course for 

 activation appears to be identical with that for 

 phosphorylation if some phosphate is present as well as 

 ADP, (See Figure l). 



MINUTES 



