322 



ELECTRON TRANSPORT 



350 



4 00 450 500 



WAVELENGTH (mp) 



550 



6 00 



Fig. 3. Spectra of reduced and photooxidized ChromatiiDU iron protein. The 

 photooxidation was performed with an anaerobic reaction mixture containing 

 washed, dialyzed Chromatium chromatophores (7 //M in bacteriochlorophyll) 

 plus 0.4 mg/ml reduced iron protein in 50 mM phosphate buffer, pH 7. The iron 

 protein was omitted from the reference cell. The sample cuvette was illuminated 

 for 45 minutes with far-red light from a 100- watt tungsten filament lamp, fil- 

 tered through 3 cm distilled water and a Wratten 88A filter which transmitted 

 light of wavelength longer than 720 m/i. The incident light intensity at the cuvette 

 was 10 mwatt/cm2. 



photooxidation in the presence of illuminated chromatophores, and in 

 the dark after illumination the photooxidized protein was reduced back 

 to the original state. 



The photooxidation of Chrouiatium iron protein could not be demon- 

 strated when chromatophores of/?, nihnini, Rps . spheroides or Rps. 

 pains tris were tested. 



Interaction between reduced iron protein and Chromatium chroma- 

 tophore cytochrome (s) was observed spectrophotometrically. Of the 

 total particle-bound cytochromes detected by a difference spectrum 

 of dithionite reduced-minus-oxidized chromatophores, approximately 

 10 per cent was reduced by added excess iron protein. This observa- 

 tion may indicate that there exists in the chromatophore a C9 type 



