KINETICS OF HEMOGLOBIN REACTIONS 



279 



6.2. Kinetics of Individual Reactions 

 with Carbon Monoxide and Oxygen 



6.2.1. Hb02 -^ Hb + O2. This was one of the earhest reactions 

 investigated by Hartridge and Roughton (1H9) and the technique 

 they adopted was the measurement of the rate of disappearance of 

 oxyhemoglobin in the absorption tube when, just prior to entering 

 the tube, it was mixed with a solution of dithionite. When the 

 partial pressure of the oxygen had been reduced sufficiently, the 

 dissociation of the oxyhemoglobin commenced. This was independent 

 of the concentration of reducer. The reaction was found to be of the 

 first order and showed a marked depenJer.^e on pH; see Figure 11. 



< 

 H 



O 



u 



H 

 »— ( 

 U 



s 



> 

 o 



H 



90 



60! 



30 



1 



10 



pH OF SOLUTION 



Fig. 11. pH dependence of rate of dissociation of oxyhemoglobin for two different 

 blood samples (after Hartridge and Roughton, IHS). 



The velocity below pH 5.6 was found to be approximately seven 

 times that found above pH 7.7. The response to changes in pH was 

 found to be virtually instantaneous, no difference being found 

 between the rate of dissociation of oxyhemoglobin at pH 6.3, if the 

 solutions were adjusted to this pH before mixing, or were mixed at 

 different pH values chosen so that the final pH was 6.3. The sig- 

 nificance of their finding a temperature coefficient of Q\o = 3.8 for 

 the reaction is further discussed below. 



6.2.2. Hb +02-^ Hb02. This reaction is investigated by mixing 

 hemoglobin with water containing a known concentration of oxygen 



