X-Ray Investigation of Haemoglobin and Haemocyanin 



Figure 2. Variation of the scattered intensity S 

 with the angle of scattering. Haemocyanin •$ 



1x10 2x10 3x10 

 Radian 



Figure 2. The angle at which this hump appears does not vary with the 

 dilution of the haemocyanin solution. The conclusion is therefore that 

 the singularity is due to an internal structure of the particles. 



If Bragg's law is assumed, the value of the angle at which the hump 

 occurs corresponds to a period of 220 A. This, as said above, appears 

 to be an internal spacing of the particles in solution. But, in contrast 

 to the case of haemoglobin, the particular form of the experimental 

 curve does not permit the use of the above mentioned simple theory to 

 obtain information about the size of the entire particle of haemocyanin. 



O. Kratky 2 found with haemocyanin a similar scattering curve 

 showing a hump. The deduced spacing was 260 A, but apparently this 

 author has not examined solutions at different dilutions. Kratky thinks 

 that it is plausible to conclude that the primary particles are really 

 spherical and that the value of 260 A corresponds to the diameter of 

 these particles. This dimension should be compatible with the molecular 

 weight of 89 . 10 6 found by ultra-centrifugation. According to 

 Kratky these spheres would be capable of forming threadlike aggre- 

 gates responsible both for flow birefringence and for the hump in the 

 x-ray scattering diagram. 



According to the electron micrographs obtained by A. Polson and 

 R. W. G. Wyckoff 6 with haemocyanin preparations (although the 

 haemocyanin was from Busy con canal iculatum), each haemocyanin 

 particle appears to consist of rod-like sub-units stacked together. The 

 dimensions of these sub-units, which can be appreciated from the 

 picture of Poison and Wyckoff, are of the same order of magnitude as 

 the 220 A found in the present work. Nevertheless, a model formed of 

 four ellipsoids stacked together does not fit with the complete curve 

 of scattering intensity. 



ACTION OF UREA 



By the same method of x-ray scattering, solutions of haemoglobin or 

 haemocyanin containing different concentrations of urea were studied. 

 Urea was added up to a concentration of 25 per cent and left in contact 

 with the protein from a few hours to 24 hours. With haemoglobin, the 



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