h. m. jope and j. r. p. o'brien 



a much lower solubility than the other three haemoglobin derivatives 

 HbCO, Hb0 2 and MetHb. For both adult and foetal haemoglobins 

 also the shape of the Hb curve is almost horizontal, with zero tem- 

 perature coefficient, by contrast with the curves for HbCO, Hb0 2 , 

 and MetHb which vary greatly with temperature ; the curves of adult 

 HbCO, HbO a and MetHb all have a minimum at about 20°C. Foetal 

 HbO a and MetHb behave as if their temperature solubility curves 

 were similar to that of foetal HbCO (curve 5) but no quantitative 

 data have been obtained for these two derivatives owing to a shortage 

 in the supply of foetal blood. Qualitative observations on adult Hb 

 crystallised from dilute sodium chloride solution (about 0-3 per cent) 

 indicate that the solubility in this solvent increases rapidly with 

 temperature. 



DISCUSSION 



No previous study of the solubility of the four main haemoglobin 

 derivatives appears to have been made, although work has been done 

 on the solubility of mammalian HbCO. The striking conclusion 

 from this study is the contrast between Hb and the other three haemo- 

 globin derivatives : the contrast is shown in both the human adult and 

 the foetal haemoglobin series in their crystallography and in their 

 solubility behaviour. This difference in behaviour of Hb from that 

 of the other three haemoglobins cuts across the distinction made by 

 L. Pauling and his co-workers 12 ' 13 , between Hb and MetHb with 

 their unpaired electrons and Hb0 2 and HbCO with no unpaired 

 electrons. It may be noted, however, that the solubility of MetHb 

 lies closest of the three to the solubility of Hb. 



-10 O 10 20 30 40 



Temperature "C 



Figure 12. Solubilities of adult and 



foetal haemoglobins as functions of 



temperature. 



274 



