PHOTOOXIDATION AND PHO TOR EDUCTION REACTIONS 243 



rate of photooxidation could easily be balanced by reduction reactions 

 from the photoreduced chromatophore components. 



One of the early reactions observed with /?, rubnim chromsitophores 

 was the photooxidation of ascorbate in the presence of DPIP and molec- 

 ular oxygen (3), The ability of chromatophores to photooxidize re- 

 duced dye in the presence of oxygen is shown in Fig. 6. The oxidation 

 of the dye in the presence of oxygen is a very stable reaction and is 

 not appreciably influenced by heating the chromatophores to 60°C. The 

 stability of this system has been studied by Lindstrom (6), By de- 

 creasing the chromatophore content in the reaction system, it was 

 possible to observe the usual biphasic reaction shown for the other 

 photooxidations. It is interesting, however, that the initial photooxida- 

 tion rate in the presence of oxygen was significantly lower than that 

 observed under anaerobic conditions. The reason for this is not im- 

 mediately apparent. 



PHOTOOXIDATION REACTIONS CATALYZED BY CHROMATIUM 

 AND RHODOPSEUDOMONAS SPHEROIDES CHROMATOPHORES 



Other photosynthetic bacteria were investigated to see if their 

 photosynthetically active particles could also photooxidize DPIPH2 in a 

 manner similar to that observed with R. nibnim. Fig. 7 presents the 



Fig. 7. Photooxidation of DPIPH2 by Chromatium chromato- 

 phores. The experimental conditions given for Fig, 1 were em- 

 ployed with Chromatium chromatophores being used at a con- 

 centration equal to 0.264 mg BChl. 



