E. M. JOPE 



band (Figure 8), the observed curve being probably due to the super- 

 position of the variations with wavelength of both absorption and 

 refraction within the red cells, and reflexion and scattering from their 

 surfaces. The slight changes in the curve as a result of alterations 

 in the size and internal haemoglobin concentration of the red cells 

 due to suspending them in varying strengths of saline may be noted 

 (Figure 8). 



Figure 8. Spectral absorption 

 of a solution of human haemo- 

 globin of a concentration of 

 0-03 per cent, in OS cm. layers 

 (Curve A) and spectral absorp- 

 tion of human red cells sus- 

 pended in 0*65 per cent, 0*9 

 per cent and 2 per cent sodium 

 chloride (Curve B). 



320 360 400 440 



Wavelength in rr>u 



480 



Although the wavelength of the Soret absorption peak remains 

 unchanged in solutions up to 38 per cent, and also in the red cells 

 themselves, examination of the spectrograms of these suspensions of 

 red cells obtained using a tungsten ribbon filament lamp as a con- 

 tinuous spectral source shows the presence of an extra absorption 

 band at 378 m.\x in human red cells (Figures 6 and 7) which cannot 

 be detected in the spectrograms from strong solutions of haemoglobin 

 prepared from these cells (Figure 9). This extra band is quite sharp 

 and represents about 2-3 per cent of the Soret band intensity. It has 

 not been possible so far to detect this band in any preparation of red 

 cell ghosts — the insoluble remains after haemolysis — and it was thought 

 to be due to some optical effect such as a reflexion spectrum from 

 the red cell interface. But the presence of this extra band at 378 m\i 

 was confirmed in examining the central region of a single human red 

 cell (see below), and its wavelength could not be shifted by altering 

 the refractive index change at the interface by suspending the cells in 

 different strengths of saline, or even in 60 per cent dextrin. On the 

 other hand it is difficult to see what compound with such an absorption 

 spectrum could be present in red cells in sufficient amounts, and yet 

 remain undetectable after haemolysis. This problem is at present 

 under further investigation. 



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