F. J. W. ROUGHTON, J. W. LEGGE and P. NICOLSON 



have tackled some of these outstanding matters both by means of new 

 experimental work (J. W. L. and F. J. W. R.) and also by further 

 theoretical investigation (P. N. and F. J. W. R.). In this paper we 

 shall summarize the advances which we have recently made in the 

 kinetics of haemoglobin, first in homogeneous solution and secondly 

 in the intact red blood corpuscle. All the work has been done with a 

 modification of the Millikan 8 photo-colorimetric method, and the 

 haemoglobin solutions and corpuscle suspensions have all been pre- 

 pared from sheep blood, since this was the main species used in the 

 previous kinetic work and in the case of adult sheep the haemoglobin 

 is believed not to split into sub-units at the dilutions used (i.e. 1 part 

 of blood to 60 parts buffer solution). 



THE KINETICS OF HAEMOGLOBIN IN SOLUTION 



The earlier work 1-11 seemed to show that the rates of the reactions 

 could be expressed, within the limits of the rather large experimental 

 errors, by the equation put forward by Hartridge and Roughton, 

 namely 



d[X ^ = k' [X][Hb] - k [XHb] ... .(1) 



where [X] = concentration of dissolved 2 or CO 



[XHb] = concentration of oxyhaemoglobin or carboxyhaemo- 

 globin expressed in g mil combined 2 or CO per litre 

 [Hb] = concentration of reduced haemoglobin expressed in 

 same units as [XHb] 

 and k', k are the velocity constants of the reaction. 

 There are several points about equation (1) which call for further 

 thought and inquiry. 



Reconciliation with the intermediate compound hypothesis — Equation 

 (1) suggests that the molecule of mammalian haemoglobin combines 

 reversibly with 1 molecule of X, whereas it has been known for 25 

 years that the haemoglobin molecule actually combines with 4 such 

 molecules. How does (1) fit in with Adair's intermediate compound 

 hypothesis, which is now widely, if not generally, accepted ? On this 

 theory, the reaction proceeds in four stages : — 



Hb 4 + X^ Hb 4 X, — = Ki = equilibrium constant of reaction 



....(2.1) 



/C 2 K% 



Hb 4 X + X^ Hb 4 X 2 , - =K, = equilibrium constant of reaction 



....(2.2) 



68 



/Co K' 



