Absorption of Haemoglobins Inside and Outside the Red Blood Cell 



the nature of the protein carrier, and possibly upon the manner of 

 linkage between the protein and the haem. Thus the visible and 

 Soret absorption bands of mammalian red cell haemoglobins he at 

 slightly shorter wavelengths than do those of the corresponding muscle 

 haemoglobins {Table I). This is probably not due to the different 

 molecular weights of the red cell haemoglobins (67,000) and those 

 from muscle (17,000) as no changes can be detected in the spectral 

 absorption of red cell haemoglobins under conditions such as strong 

 salt concentration or high haemoglobin dilution when many haemo- 

 globin molecules are known to split into smaller units 3 ' 4 . On the 

 other hand the Soret band wavelengths and molar extinction co- 

 efficients of red cell haemoglobins remain remarkably constant over a 

 great range of species — adult and foetal in man, sheep, pig, and rat, 

 and adult in horse, ox, rabbit, frog, salamander, and many birds — 

 representing a wide variety of amino-acid composition and molecular 

 shape of protein. The relation between the nature of the protein and 

 the wavelength and intensity of these absorption bands due to the 

 haem group may prove to be related to the nature of the linkage 

 between the haem and the protein, and its further study may help to 

 clarify this problem. These Soret band data are summarized in 

 Table I. 



Table I 



Wavelengths (in m\x) of Soret bands of haemoglobins 

 of red cells and muscle 



HbOo HbCO MetHb Hb 



Red cell haemoglobins : Mam- 

 malian, amphibian, and 

 avian (Jope, unpublished) 



414-5 420 406 425 



Muscle haemoglobins : horse 

 heart and man (Theorell 

 1934) 



418 424 407 435 



As a preliminary to the spectral study of haemoglobins in bio- 

 chemical and biological systems it has been necessary to accumulate 

 data on variations in their spectral absorption with controllable 



207 



