The Osmotic Pressure of Haemoglobin in 

 Strong Salt Solutions 



H. GUTFREUND 



In the introduction previous studies on the size and molecular 

 dissociation of mammalian haemoglobin in solutions are sum- 

 marized. The influence of dissociation phenomena and of 

 solvent-solute and solute interaction phenomena on the osmotic 

 pressure of solutions is discussed, and the procedure of dif- 

 ferentiating between the two effects is described. 

 Data of measurements of osmotic pressures of solutions of 

 horse and human haemoglobin in phosphate, sodium chloride 

 and lithium chloride solutions of varied concentrations are 

 recorded. The results of these experiments show that high salt 

 concentrations increase the interaction phenomena at high 

 protein concentration and cause dissociation of horse and human 

 haemoglobin at low protein concentration. 



The results of osmotic pressure measurements described by G. S. 

 Adair 1 " 5 showed that the molecular weight of haemoglobin from man, 

 horse, ox and sheep is 66,700, or four times the equivalent weight 

 calculated from the iron contents of these proteins. Studies of the 

 osmotic pressure of adult and foetal goat haemoglobin 6 , foetal sheep 

 haemoglobin 7 and foetal human haemoglobin (Gutfreund, un- 

 published observations) showed that these proteins too have a 

 molecular weight of 66,000-67,000. 



Recent careful reinvestigation of the sedimentation constants of 

 horse, adult and foetal human and adult and foetal sheep haemoglobin 

 (Cecil and Gutfreund, unpublished observations) showed these to 

 be almost identical. This indicates that not only the molecular weight 

 but also the shape of haemoglobins from these species is the same. 

 The sedimentation constant is dependent on the molecular weight, 

 shape and hydration, but the latter (0-3 g per g of protein) is not 

 likely to differ significantly from one haemoglobin to another. The 

 similarity of size and shape of various haemoglobins is in marked 

 contrast with the great differences observed in their chemical com- 

 position, number and type of free amino groups as well as in their 

 physiological, solubility and electrophoretic behaviour. 



The dissociation of horse haemoglobin in very dilute solutions was 

 first observed by A. Tiselius and D. Gross 8 from measurements of 

 the diffusion constant and T. Svedberg and K. O. Pedersen 9 reported 



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