Post-illumination phosphorylation

When chloroplasts are pre-illuminated in the absence of a phosphorylation component under conditions in which massive proton uptake occurs, ATP synthesis can be observed in the dark in the post-illumination period when the missing component is added [17]. The amount of ATP synthesized is a function of the number of protons stored in the inner thylakoid compartment during the pre-illumination period, which is in turn a function of the intrathylakoid buffer capacity, and the pH gradient sustained [14]. 

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When the rate of ATP synthesis is plotted versus the total electrochemical gradient which serves as its driving force, a non-linear curve is obtained with little or no ATP synthesis until a threshold value of about 120-150 mV is reached, and a close to linear dependence thereafter. This behavior has been demonstrated in all of the ATP-synthesizing systems photophosphorylation, post-illumination phosphorylation and acid-base phosphorylation, and under a variety of energy-limiting conditions such as light intensity, inhibitors, uncouplers, etc. 

Recently the kinetics of acid base phosphorylation was studied using rapid mixing and quenching techniques [44,46]. In contrast with post-illumination phospho-... 

On the other hand, it is possible to create conditions which enable us to catalyze the ATP formation without electron transport. It was demonstrated in the early 1960s that the illumination of chloroplasts in the absence of phosphorylation substrates (ADP and Pi) led to the formation of a certain energized compound (or state), which was capable of providing ATP synthesis in the dark after ADP and Pi addition [17, 18]. This post-illumination ATP synthesis is one of the most explicit demonstrations of the existence in chloroplasts of a high-energy state formed in the light. Later, Jagendorf and... 

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