316 ELECTRON TRANSPORT 



TABLE 1. 



Spectroscopic properties of Chromatium iron protein 

 Extinction coefficients- (E mg/ml, d 1.0 cm) 



- Spectra were measured in 50 mM phosphate buffer, 

 pH 7, d = 1.0 cm, with a Gary Model 14 spectro- 

 photometer. 



tographed on a DEAE-cellulose column previously equilibrated with 

 20 mM Tris, pH 8. The greenish-brown colored iron protein was eluted 

 with buffer plus 40 mM NaCl. Two cytochromes were eluted at higher 

 salt concentrations; RHP with buffer plus 80-100 mM NaCl, and cyto- 

 chrome 552 with buffer plus 140-160 mM NaCl, In one preparation 

 these three proteins were recovered in the following approximate 

 yields per 100 g dry weight of cells: 



Iron protein 15 ^moles (10,000 MW, assumed) 



RHP 6 " (36,000 MW) 



Cytochrome 552 2 " (97,000 MW) 



A pooled sample containing 1300 mg iron protein, purity index 

 A283/A33g = 3, was rechromatographed as above, but onA-25DEAE- 

 Sephadex. The main fraction, which was concentrated on a short 

 DEAE-cellulose column and then desalted on a G-25Sephadex column, 

 yielded 1200 mg iron protein, purity index = 2.52. At this stage the 

 protein appeared to be homogeneous by the criteria listed below. 



The three CJiroDiatiui)} proteins were recovered in about the same 

 proportions from an acetone powder of washed small chromatophores 



