I 



600 



Jagendorf and Hind 



dark and the partial stabilization by ADP made us hope 

 at first that we were observing a phosphorylated 

 intermediate. However our efforts at identification 

 by chromatography, luciferase assay, etc. showed the 

 counts to be in free ATP32 _ presumably arising from 

 endogenous ADP. This ATP^^ is split by the ATPase 

 unless either TCA or a sufficiently inhibitory 

 concentration of ADP is added. 



32 

 Table 1. Breakdown of newly formed ATP 



ADP in ATP^ Recovered After 



dark Dark Incubation (seconds) 



2 17 32 180 



— 3.38* 2.it5 1.64 1.43 .85 



+ — 2.45 1.94 1.85 1.53 



*mumoles P32/mg chlorophyll, adsorbed to charcoal. All 

 samples exposed to light in a syringe, for 30 seconds 

 at 22 C and pH 8. Light stage contained once washed 

 chloroplasts with 250 ugm of chlorophyll, Pyo. .05 mM, 

 MgCl2 5 mM, NaCl 10 mM, NaH2P04 labeled with P-32 0.33 mM, 

 and Tris buffer 17.5 mM; total vol. 1.0 ml. After 

 illumination the samples were kept in the dark for the 

 times indicated, prior to adding to .20 ml of 20% 

 trichloroacetic acid for killing. Injection into ADP 

 in all cases was done after 2 seconds dark in order to 

 allow for decay of X . (ADP, 0.5 mM). 



e 



These experiments cast doubt on the conclusions of 

 Kahn and Jagendorf (l). In the first place, internal 

 ADP was supposed to have been removed in the earlier 

 work by conversion to cold ATP in a preillumination 

 period. Table I shows that any such transition would 

 have been less than permanent, so ADP probably was 

 present. Secondly, the earlier technique involved 

 handling eight samples at a time, with a consequent lack 

 of precise control over the time of addition of various 



