THE PHOTOCHEMICAL ABSORPTION SPECTRUM 19 



was developed by Warburg in the course of his studies of the respira- 

 tory ferment. His experiments on the inhibition of the respiration 

 of yeast and other cells showed that cyanide and carbon monoxide 

 are effective inhibitors and that the carbon monoxide inhibition is 

 reduced by irradiation, due to dissociation of the carbon monoxide 

 compound of the catalyst. 



If certain conditions are fulfilled, the rate of respiration can be 

 assumed to be proportional to the concentration of active catalyst. 

 The degree of inhibition by carbon monoxide then becomes a meas- 

 ure of the ratio of carbon monoxide-combined enzyme to total 

 enzyme. This ratio, and with it the degree of inhibition of respira- 

 tion by carbon monoxide of a given partial pressure, is altered by the 

 illumination, the magnitude of the effect being a function of the 

 energy of the light and of the absorption coefficient of the light- 

 sensitive carbon monoxide compound. If light of the same energy, 

 but of different wavelengths, is used, it will then be possible to map 

 the relative absorption curve of the carbon monoxide compound of 

 the enzyme. Only a short summary of the mathematical treatment 

 can be given; for greater detail the reader is referred to Warburg's 

 original papers (c/. Chapter VIII, also 292 J^, 2928, 2930, 903). 



Let A be the respiratory rate of tlie cells in the absence of carbon monoxide. 

 Ax the same in the presence of carbon monoxide in the dark. [FeOa] and 

 [FeCO] the concentrations of inicombined and carbon monoxide-combined 

 enzyme, respectively. K the dissociation constant of the carbon monoxide- 

 compound in the dark, n the "residual respiration." and [O2] and [CO] the 

 partial pressures of oxygen and carbon monoxide. Tlien we have: 



A,_ [FeOo] 



A,~ "" ~ [FeO,] + [FeCO] 



(1) 



n [FeO.] __j,[0^] ^^, 



1 - n [FeCO] [CO] 



From these equations the relative affinity of the respiratory ferment for 

 oxygen and carbon monoxide can be found. 



Further, if B is the velocity constant of the formation, Z of the decompo- 

 sition of the oxygen compound, and b and z the corresponding constants for 

 the carbon monoxide compound, while Zr is a term corresponding to the dis- 

 appearance of the oxygen compound by respiration, we may write: 



