40 PER-AKE ALBERTSSON 



Albertsson: There is not one general method, of course; different methods are 

 used for different materials. One way, for example, is to use adsorption. In the case 

 of the proteins, we have adsorbed the protein on a column of calcium phosphate 

 and the polymers, being non-ionic, pass through and may be washed away. This is 

 a convenient method and a concentration of the proteins is obtained at the same 

 time. Another way is to transfer the substance from a polymer phase to a polymer- 

 free phase. If we are using the dextran-polyethylene glycol system we can, by 

 adding salt, transfer the protein to the top phase which contains polyethylene glycol 

 as the only polymer. This top phase can then be transferred to another tube and 

 mixed with ammonium sulphate (or potassium phosphate) when we get a new phase 

 system consisting of a polyethylene glycol phase in equilibrium with an ammonium 

 sulphate phase, this latter phase containing almost no polyethylene glycol. If one is 

 lucky, the protein is transferred to the ammonium sulphate phase under these 

 circumstances. This method works for some of the serum proteins, for example 

 ceruloplasmins. It is possible to adjust the volumes of the phases so that a concen- 

 tration of the protein is obtained at the same time. 



