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



homogeneous, it is possible to calculate the gyration radius of the 

 adopted model and to test if it coincides with the gyration radius 

 deduced from the x-ray scattering measurements. 



HAEMOGLOBIN 



The curve of Figure 1 represents the variation of the scattered intensity 

 with the angle of scattering for haemoglobin. It was deduced from the 

 microphotometric recording of the x-ray photograph. The calculated 

 gyration radius is equal to 23 A db 1. This same value is found either 

 with recrystallized horse haemoglobin dissolved in saline or with the 

 crude contents of the red cell after lysis and dilution with saline. The 

 same value was also found whatever the concentration, this varying 

 between 1-2 and 12 per cent. 



Figure 1. Variation of the scattered intensity 

 with the angle of scattering. Haemoglobin 



lx!Q 2x/0 e 3x10' 

 Rod ion 



A gyration radius of 23 A may be attributed to a variety of forms 

 of particles. Thus, if a spherical form were assumed for the haemo- 

 globin molecule in solution, this value of the gyration radius would 

 correspond to a sphere of 59 A diameter. The interest of this result is 

 that if we assume that the haemoglobin molecule in solution has the 

 flat cylindrical form proposed by one of us 4 as the general shape of 

 protein molecules in solution and if we take for this form the dimensions 

 found by M. F. Perutz et a! 5 for the molecule in the crystal of haemo- 

 globin, i.e. 57 A diameter and 34 A height, the gyration radius calculated 

 is found equal to 23 A, coinciding with the value deduced from the 

 scattering intensity variation curve. 



From the type of variation of the scattering intensity it is possible to 

 conclude that haemoglobin solutions are monodisperse, i.e. containing 

 mainly particles of the same size. In fact, the study of other protein 

 solutions with the same method shows that solutions of serum globulins 

 for example behave as mixtures of particles having different sizes. On 

 the contrary, solutions of serum albumin do behave as if they were 

 monodisperse. 



HAEMOCYANIN 



While the intensity curve slopes down regularly with haemoglobin, 

 with haemocyanin there appears a well marked hump as is seen on 



132 



