PHOTOSYNTHETIC PHOSPHORYLATION AND THE ENERGY CONVERSION PROCESS 347 



Frenkel's findings were followed by those of Williams [59] who 

 demonstrated photosynthetic phosphorylation in cell-free preparations of 

 the obligately anaerobic photosynthetic bacteria, Chromatium and Chloro- 

 bitim. It thus became clear that a common anaerobic mechanism for a light- 

 induced phosphorylation, that does not depend on an exogenous chemical 

 substrate or on oxygen consumption, is shared by both green plants and 

 photosynthetic bacteria. The energy conversion process proper seemed to 

 be fundamentally independent of oxygen although it was still possible 

 that details of mechanisms were diiferent in green plants and photo- 

 synthetic bacteria. 



The discovery of photosynthetic phosphorylation in chloroplasts by 

 Arnon et al. [13] and in bacterial particles by Frenkel [57] was confirmed 

 and extended in a number of laboratories. Photosynthetic phosphorylation 

 in isolated chloroplasts was observed by Avron and Jagendorf [60, 61], 

 Wessels [62], and Vennesland and her associates [63, 56]; in algae by 

 Thomas and Haans [64] and Petrack [65] ; and in photosynthetic bacteria 

 by Geller [66], Kamen, and Newton [67] and Anderson and Fuller [68]. 

 In later experiments Whatley et al. [22, 23] have shown that photo- 

 synthetic phosphorylation by chloroplasts, which had previously been 

 almost entirely limited to observations on chloroplasts isolated from one 

 species, viz. spinach, is also operating in chloroplasts isolated from several 

 other species of higher plants.* It now seems well established, therefore, 

 that all photosynthetic organisms contain a phosphorylating system that is 

 intimately associated with, and structurallv bound to, the chlorophyll 

 pigments. 



Soon after the demonstration of photosvnthetic phosphorylation in 

 isolated chloroplasts attempts were made to compare its rate with that of 

 COo assimilation bv illuminated whole cells. Since, as with most newly 

 isolated processes in cell-free systems, f the rates of photosynthetic 

 phosphorylation were rather low, there was little inclination at first to 

 accord this process quantitative importance [72, pp. 292, 345] as a 

 mechanism for converting light into chemical energv. 



With further impro\ement in experimental methods we obtained rates 

 of photosynthetic phosphorylation up to 170 times higher [73] than those 



* Other accounts of the discovery of COo assimilation and photosynthetic 

 phosphorylation by isolated chloroplasts are given by Calvin. In 1956 he ascribed 

 (69, p. 31) the discovery of COo assimilation by isolated chloroplasts to Boychenko 

 and Baranov (70) and in 1959 he ascribed the discovery of both CO., assimilation 

 by isolated chloroplasts and photosynthetic phosphorylation to his own laboratory 

 (71, p. 152). 



t The most recent instance of this kind is the cell-free synthesis of DN.A 

 investigated by Kornberg. "The first positive results represented the conversion 

 of only a very small fraction of the acid-soluble substrate into an acid-insoluble 

 fraction (50 or so covmts out of a million added)" [3]. 



