Studies on Human Adult and Foetal Haemoglobins 



A distinction between human adult and foetal haemoglobins is also 

 clearly seen. They crystallize in different systems, and the difference 

 between them is also evident from a comparison of the solubilities of 

 their three derivatives HbCO, Hb0 2 and MetHb. Adult HbCO, 

 HbO> and MetHb have solubility-temperature curves, in 2M phos- 

 phate buffer pH 6-7, with a form often shown by proteins in strong 

 salt solutions (Figure 12 curves 1-3). Foetal HbCO (Hb0 2 and MetHb) 

 has a solubility-temperature curve, in the same solvent, more charac- 

 teristic of proteins in dilute salt solutions (Figure 12 curve 5). Adult 

 and foetal Hb's are, however, alike in having very similar solubilities 

 in this solvent ; both solubilities are unaffected by temperature. 



It seems opportune to summarize here the differences which have 

 so far been observed between human adult and foetal haemoglobins. 



1 . Crystal form : described here. 



2. Solubility behaviour : described here. 



3. Electrophoretic mobility : H. Hoch 14 has shown that between 

 pH 7 and pH 8 human adult HbO a moves slightly faster than human 

 foetal Hb0 2 . These more recent experiments do not confirm the 

 results of M. A. Andersch, D. A. Wilson and M. L. Menten 15 

 although their buffer conditions are reproduced exactly. 



4. Spectral absorption : although the wave lengths of the visible and 

 Soret absorption bands are identical in human adult and foetal Hb0 2 

 and HbCO, the prominent fine structure band due to the trytophan in 

 the protein appears at 289-8 mji in foetal human haemoglobin, whereas 

 human adult haemoglobin exhibits this band at 291-0 mjx, the position 

 normal for most proteins. This is not a general difference between 

 mammalian foetal and adult haemoglobins as sheep and rat foetal 

 haemoglobins exhibit this band in the normal protein position, 

 291-0 ma 16 . 



5. Amino acid composition : R. R. Porter and F. Sanger 17 have 

 shown that human adult haemoglobin contains 5 terminal valyl 

 residues per molecule compared with 2-6 in human foetal haemo- 

 globin, assuming a molecular weight of 66,000 in each case. 



6. 2 dissociation : in the red cell adult Hb has a lower affinity for 

 2 than has foetal Hb. In dilute solution this difference is reversed 6 . 



7. Resistance to alkali : foetal haemoglobin is much more resistant 

 to alkali than adult haemoglobin 18 . 



8. Immunological behaviour : R. R. Darrow, S. Nowakovsky and 

 M. H. Austin 19 have shown that human adult and foetal haemo- 

 globins are distinguishable immunologically. 



9. Molecular weight : E. F. McCarthy and G. Popjak 20 have 

 suggested on a basis of osmotic pressure measurements at varying 

 haemoglobin concentrations that sheep foetal haemoglobin has a 



275 



