400 450 500 550 600 650 

 WAVELENGTH (mM) 



Fig. 4. Spectrum of oxidized (broken line) and reduced (solid line) R. rubnim 



RHP at pH 11-8 (phosphate buffer, 01 m). Relative concentrations for main 



curves and inset curves as in Fig. 1. (Reproduced by permission of the Journal 



of Biological Chemistry.) 



450 500 550 600 

 WAVELENGTH (m;i) 



Fig. 5. Difference spectrum of R. rubnim RHP-CO compound minus reduced 



RHP, at pH 4-75. In A, Q-ll X IQ-^ //mole/ml and in B, 1-1 x IQ-^ /<mole/ml 



were used in 0- 1 m citrate 2-amino-2-hydroxymcthyl-propan- 1 : 3-diol (Tris)-buffer. 



Gas phase in the experimental cuvette was pure CO. 



