PHOTOOXIDATION AND PHOTOREDUCTION REACTIONS 259 



these inhibitor studies are not valid. However, one cannot resolve 

 this problem at present, since it is not possible to detect and experi- 

 mentally manipulate such high energy intermediates. 



ELECTRON TRANSFER SEQUENCE 



Since there is considerable information becoming available on the 

 various photooxidation and photo reduction reactions catalyzed hy R. 

 rubrum, it would be well to attempt to correlate all this information. 

 Figs. 16, 17, and 18 are an attempt to do this and are presented here 

 not with the intent of being an authoritative statement on this matter, 

 but rather with the idea of using this means to bring the information to 

 the attention of workers in the field with the hope that it may stimulate 

 thinking and experimentation to solve some of the problems which now 

 face us. Fig. 16 is a representation of the components of the chroma- 

 tophore electron transfer system arranged in a probable sequence for 

 electron transfer. Fig, 17 has imposed upon this basic electron trans- 

 fer system the sites of action of the various compounds known to be 

 effective in photooxidation and photo reduction reactions. Fig, 18 lists 

 the possible sites of action of the inhibitors known to affect the photo- 

 chemical reactions in R. rubnini chromatophores. 



It immediately becomes apparent that the various photochemical 

 reactions demonstrated by R. rubnim chromatophores are couched in 

 terms of only one electron transfer system. In discussing Fig. 17 it 

 will be pointed out that a portion of this electron transfer scheme could 

 be operative in the respiratory reactions which take place in the dark 

 with this organism. 



ELECTRON TRANSFER COMPONENTS 

 in Ki rubrum 



e^- Cy^to. C2 



I Cyto. b 



Light ▼ t 

 ^vN~v-*.B. Chi. RHP ►02 



Ubiquinone "* » 



A, /t 



Ferredoxin-*-Flavo-"*z:z^ nao 

 Protein 

 (FMN) 



Fig. 16. Electron transfer components and sequence 

 of reaction in R. riibnoji chromatophores. 



