186 



METABOLISM AND PHYSIOLOGY 



I 



I 



OJ 



Photoreduction of TPN via DPN 

 ( R. rubrum chromatophores) 



+ DPN 

 (catalytic) 



boiled 

 extract 



TPN only 



9 m 



10 20 30 40 50 

 minutes 



Fig. 1. Photoreduction of TPN via DPN by R. riibnou chromatophores. 

 The reaction mixture included, in a final volume of 3 ml, chromatophores 

 (containing 30 /yg bacteriochlorophyll) and the following (in //moles): tris 

 buffer, pH 7.9, 100; magnesium chloride, 5; sodium ascorbate, 20; 2,6- 

 dichlorophenolindophenol, 0.2; TPN, 2. Also added was 0.05 /ymole DPN 

 or boiled extract (see text) as indicated. The reaction was carried out in 

 Thunberg type cuvettes at 20°C. TPN reduction was measured at 15 min 

 intervals as the increase in optical density at 340 m//. Illumination, 

 10,000 lux. 



