102 MACROMOLECULAR COMPLEXES 



dye could be photoreduced per molecule of chlorophvll per minute; 

 this is preparation-dependent, and the number may not be quanti- 

 tatively significant. When the reaction was followed at 488 m/x 

 (a carotenoid peak), changes in optical density with light or dark- 

 ness suggested that the carotenoid participates in the reaction 

 (Eversole and Wolken, 1958). 



Extracts which actively photoreduced the dye were tested for 

 their ability to cause photolvsis or evolution of oxygen. Photolxsis 

 was measured manometrically in completely anaerobic Warburg 

 vessels with KOH in the center well, and the dye was tipped from 

 a side arm at zero time. The reaction system for photolysis measure- 

 ments was made oxygen-free in order to estimate the oxygen evolved 

 by bacterial bioluminescence. In some preparations of chloroplastin 

 photolysis occurred, yielding 20-30 fA ox\'gen in 2 minutes, with a 

 distinct luminescent glow persisting for almost a minute after a 

 suspension of anaerobic Photobacterium phosphoreum was injected 

 into the experimental vessel in darkness. Controls in the absence of 

 light and those without dye did not evolve oxygen. 



In the experiments in which photolysis occurred, a light-catahzed 

 conversion of inorganic phosphate into labile phosphate ( ATP ) was 

 measurable. The reaction vessels contained 2 ml of chloroplastin 

 (having a chlorophyll concentration of 10""' M), 20 ^umole Mg"^"^, 

 30 yumole keto-glutarate, 0.3 yumole riboflavin-5-phosphate, 0.6 ^amole 

 menadione, 2 /^mole ascorbate, 5 ;ug cytochrome c, 55 /xmole adenosine 

 monophosphate, and 4 ^g inorganic phosphate. These experiments 

 were immediately repeated with the addition of glucose and hexo- 

 kinase, and the glucose-6-phosphate formed was determined by 

 triphosphopyridine nucleotide reduction at 340 m^ in the presence 

 of glucose-6-phosphate dehydrogenase. In this way 80-90 per cent 

 of the inorganic phosphate disappearing was accounted for as labile 

 phosphate. The phosphate conversion occurring in the dark control 

 was only 3-4 per cent of that found in the light. 



Electron Microscopy. When a film of chloroplastin was evap- 

 orated from a digitonin solution on an electron microscope screen, 

 not fixed, and viewed directly in the electron microscope, there was 

 sufficient electron density to reveal particles of an average diameter 

 of 100 A. A digitonin solution alone when examined in the same 

 manner shows no such electron-dense particles. The electron den- 

 sity of the chloroplastin particles is attributable to the Mg^+ of the 



