KINETICS OF HEMOGLOBIN REACTIONS 283 



and more work was promised. The slight effect of varying pH was 

 unexpected in view of the sensitivity of the oxyhemoglobin dissocia- 

 tion to alterations of this variable in the absence of carbon monoxide. 

 We will postpone discussion of this anomaly until Section 7.3.1. 



6.2.6. HbCO + 02-^ Hb02 + CO. This reaction was studied 

 {2357) as far down as 30% carboxy hemoglobin. It is described by 

 the equation : 



- 4HbC0]M = - k^f^^Ui^^ + k, [HbCO] 



[o 



Roughton endeavored to reduce the effect of the back reaction by 

 increasing the concentration of oxygen until it produced no further 

 increase in the rate of reaction. This condition was not quite attained 

 when the partial pressure of the oxygen reached one atmosphere, 

 but the rate of alteration in velocity at this oxygen concentration 

 was sufficiently slight for extrapolation to be made to the desired 

 condition. He found the reaction to be of the first order with respect 

 to [HbCO]. In spite of the sensitivity of the equilibrium between 

 carbon monoxide, hemoglobin, and oxyhemoglobin to changes in the 

 hydrogen ion concentration, the rate proved to be insensitive to 

 changes in pH between 6.2 and 10, behaving in the same anomalous 

 fashion as the reaction CO + HbOs ^ HbCO + O2. 



In this instance the ratio of the association and dissociation reac- 

 tions of carbon monoxide, k2/ki, refers to the equation: 



CO + Hb02 ^ HbCO + O2 



where A', the partition constant is defined by: 



[Hb02] [CO] 



K 



[HbCO] [O2 



This equilibrium was measured for the samples of hemoglobin used 

 in the kinetic experiments and the value found compared with those 

 calculated from the two velocity constants. 



"Question mark in original. 



