An X-Ray Investigation of Haemoglobin 

 and Haemocyanin in Aqueous Solution 



D. G. DERVICHIAN, G. FOURNET and A. GUINIER 



The scattering of x-rays at low angles has been used to obtain 

 information on the dimensions of molecules of haemoglobin and 

 haemocyanin in aqueous solutions. A gyration radius of 23 A is found 

 for haemoglobin, which fits with the flat cylindrical model of the 

 molecule (57 A diameter and 34 A height). Haemocyanin shows a 

 spacing of 220 A inside the particle. The same proteins were ex- 

 amined in presence of urea but showed no marked sign of dissociation. 



The method of x-ray scattering at low angles can supply information 

 on the size of particles in solution. In a previous work we investigated 

 the organization of the haemoglobin molecules in the red cell 1 . It was 

 shown that there existed a certain type of regularity in the mutual 

 arrangement of the haemoglobin molecules. In the present article we 

 are concerned with solutions of horse haemoglobin of concentrations 

 much weaker than in the red cell. These concentrations varied from 

 1-2 to 12 per cent. In these conditions organization is absent. But, 

 owing to the relative independence of the molecules it is possible to 

 deduce information on the size of the dissolved haemoglobin mole- 

 cules from the shape of the scattering intensity curve. 



Solutions of haemocyanin (from Helix) were also investigated for 

 concentrations ranging between 0-7 and 3 per cent. They show an 

 internal spacing of the particle in solution in agreement with the value 

 already found by O. Kratky 2 . 



Finally we tried to detect the action of urea on the size of the particles 

 of haemoglobin and haemocyanin. 



Technical details of the method and the theory of the calculation 

 have been given elsewhere by one of us 3 . It should be recalled here 

 that the gyration radius of the scattering particle is calculated from the 

 curve of the logarithm of intensity of scattered x-rays against the square 

 of the angle. This gyration radius p has the same definition as is given 

 in the calculation of moments of inertia, i.e. p represents the radius of 

 a particle having the same moment of inertia as the particle studied 

 but in which the mass of the particle is entirely localized at the 

 distance p. Thus, for example, for a homogeneous sphere, p is equal 

 to 0-78 times the actual radius. By adopting a certain definite shape, 

 e.g. cylindrical, spherical, cubic, etc, and assuming that the particle is 



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