607 



Jagendorf and Hind 



things show that some change in geometry or refractive 

 index is occurring. Since preliminary experiments 

 using a Coulter counter, have failed to show any change 

 in total volume, the alteration might be one in axial 

 ratio (15) or refractivity. Since the conditions are 

 so different, it is difficult to say yet whether these 

 effects are similar to the light scattering increments 

 observed by Packer (I6) using chloroplasts in a complete 

 phosphorylation mixture. 



Our final observation came when we stopped to think 

 about a rather unusual theory. Peter Mitchell (l?) has 

 advanced the idea that electron flow, in phosphorylating 

 organelles such as mitochondria and chloroplasts, may 

 lead to accumulation of hydrogen ions inside the 

 prerequisite double membranes. Mitchell calculates that 

 a differential of 3 pH units from the outside to the 

 inside has enough potential energy to accomplish the 

 phosphorylation of ADP, given the appropriate enzymes. 

 We reasoned that if this potential could be generated in 

 the absence of phosphorylation it in itself might account 

 for the phenomena we have labelled "X , " Furthermore 

 one consequence of its appearance might be a rise in pH 

 of the medium as hydrogen ions are taken up, or hydroxyl 

 ions secreted, by the particles. -^igure ^ shows that 

 when we looked at chloroplasts in an unbuffered medium 

 brought to pH 6 we did indeed see the predicted change in 

 pH of the medium, 



LIGHT- INDUCED pH RISE 



pH 6.3 



pH 8.0 



0.5pH 



+ PYO 



-PYO 



NO 

 CHLORO- 

 PLASTS 



