230 



METABOLISM AND PHYSIOLOGY 



200 400 600 800 



LIGHT INTENSITY , FOOT CANDLES 



1000 



Fig. 6. Effect of light intensity on photophosphorylation by R. 

 rnhrum chromatophores in the presence of the factor isolated from 

 R. nibrnm. 



Chromatium (5), It is pertinent to point out that photosynthetic phos- 

 phorylation by spinach chloroplasts does not show proportionality with 

 light intensity below about 50 foot- candles (11), A broad pH optimum 

 between 7.4 and 8,4 has also been observed with chromatophores in 

 the presence of the factor, 



Horio and Kamen (12) have reported that the low photosjmthetic 

 phosphorylation capacity of "washed chromatophores" could be restored 

 to a maximal rate by the addition of "chromatophore washings," One 

 component of the "chromatophore washings" was identified as cyto- 

 chrome 02- Heating, aerating, or freezing the "chromatophore wash- 

 ings" resulted in a loss of photosynthetic phosphorylation-activation 

 capacity. The factor reported in this paper does not appear to be the 

 same as those studied by Horio and Kamen, since it is not destroyed 

 by these treatments and does not contain cytochrome c^. 



