Modification of the Secondary Structure of Haemoprotein Molecules 83 



in the reaction of haemoglobin and EIC and also that the values of pA^^ and 

 pA^2 of ElC-haemoglobin are the same as those of oxyhaemoglobin. 



Similar experiments with myoglobin have revealed that neither haem-haem 

 interaction nor the Bohr effect exists in the reaction of myoglobin with EIC 

 as would be expected from the reaction of myoglobin with oxygen. 



The absorption spectrum of ElC-haemoglobin is not affected by the 

 addition of 6-0 M-urea. However, it was found that the haem-haem interac- 

 tion was decreased in the presence of 6-0 M-urea. The sigmoid coefficient 

 dropped from 2-4 to 1-4 according to the concentration of urea added. It was 

 also found that the binding affinity of haemoglobin with EIC increased with 

 the increased addition of urea. These data are presented in Tables 1 and 2. 



Table 1. Effect of 60 m urea on the reaction 

 OF reduced haemoglobin and ethyl isocyanide 



pH 60. 



Table 2. Effect of different concentrations 



OF UREA on the HAEM-HAEM INTERACTION («) 



AND THE ETHYL ISOCYANIDE BINDING AFFINITY 



( Yr^ IN THE REACTION OF REDUCED HAEMOGLOBIN 



AND ETHYL ISOCYANIDE. 



pH 6-85. 



From the results in Table 2, it appears that there is no definite relationship 

 between the haem-haem interaction and the ElC-combining affinity ( Y^^. 

 At pH 6-0, 3^50 decreased continuously with increase of urea concentration 



