DANIEL I. ARNON 



525 



Fig. 13. Electron micrograph of isolated sjDinach grana fixed in formaldehyde. 

 Whole chloroplasts were disrupted by sonic vibration treatment for 10 sec. The 

 grana were isolated by differential centrifugation and filtration through a double 

 layer of Whatman \o. 2 filter paper. J'he isolated grana were fixed for 2 hr in 

 6f/f formaldehyde at jM (3.."). .\ comparison with similar particles prepared by 

 the freeze-drying technique (Fig. 12) shows that the grana have collapsed in the' 

 formaldehyde treatment. Fhe backgroimd in the formaldehyde treatment is free 

 from salt (compare with Fig. 12). Magnification: lO.OOO \ Midler Steere and 

 Arnon, 110). 



The close structural association, in both chloroplasts and bacterial 

 chromatophores, of phosphorylating activity with the chlorophyll 

 pigments suggests that the harnessing of light energy in photosynthesis 

 is more closely associated with ATP forination than with CO, assimi- 



