176 



J. M. OLSON 



-oe 



O20i 



-04- 



• +£I4 



400 420 4 40 



Wavelength imy) 



460 



520 540 560 



Wavelength (my) 



580 



Fig. 2. Changes in optical density of anaerobic Chromatium suspensions 

 upon irradiation with near infrared. Curve A is the difference between the final 

 irradiated stead,v state and the dark steady state. Curve B is the difference be- 

 tween the intermediate irradiated steady state and the dark steady state. Curve 

 C is the difference between the final steady state and the intermediate steady state 

 during irradiation. Curve C lies above curve B at 553 mju, but lies below curve 

 B at 423 m/x, because a different sample was used for the wavelength interval, 

 510 to 580 m/i, than was used for the interval, 390 to 460 m/i. 



dark. The existence of a CO-binding pigment similar to that found in 

 Rhodo spirillum rubrum (2) was shown by the addition of carbon 

 monoxide to a suspension in which the cytochromes had been re- 

 duced by sodium dithionite. The spectrum of the difference between 



TABLE I. Peaks and Troughs of Difference Spectra. Positions of Shoulders 



Are Shown in Parentheses 



