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Jagendorf and Hind 



yet whether it is an obligate intermediate in the usual 

 process of ATP formation, or some side pool of extra 

 energy. If the latter were the case (and this is 

 suggested but not proven by the large amount and rather 

 slow rate of formation) perhaps its true significance 

 lies in ion transport, or reverse electron flow, or even 

 more directly in CO. fixation itself. Indeed, perhaps 

 it is a reservoir or energy that can be used in any of 

 several different ways depending on the circumstances. 

 In the larger view of photosynthesis, an energy reservoir 

 of major proportions in which each unit is of the order 

 of 9,000 calories per mole could be a method of 

 achieving a more flexible use of the total energy of 

 45,000 calories available from each light quantum. 



No matter what the precise relations are between 

 phosphorylation and our three phenomena, it seems fairly 

 safe to guess even now that the ion transport and 

 structural changes in the chloroplast membranes are 

 likely to be intimately linked to the existence and 

 function of high energy intermediates, either on the 

 pathway of or in equilibrium with photophosphorylation. 

 The direction of our future research must be towards 

 finding out the degree of intimacy of these relationships, 

 and which if any of the three is causal for the others. 



ACKNOWLEDGEMENTS 



This paper represents contribution number k02 from 

 the McCollum-Pratt Institute. The work was supported in 

 part by a grant for equipment from the Kettering 

 Foundation, and in part by grant RG 5923 from the 

 National Institutes of Health. The excellent technical 

 assistant of Marie Smith is gratefully acknowledged. 



BIBLIOGRAPHY 



1. Kahn, J. S,, and Jagendorf, A. T. Biochem.Biophys. 



Res. Communs. 2:259-263 (i960). 



2. Hind, G. and Jagendorf, A. T. Proc. Nat. Acad. Sci. 



(U.S.) 42:715-722 (I963). 



5. Hind, G. and Jagendorf, A. T. Z, Naturforsch, 

 (In Press, I963). 



