ABSTRACT
The selective precipitation of a given protein from a mixture of proteins is a function of those unique physicochemical properties that differentiate it from the other proteins in the mixture. Euglobulins are those proteins insoluble in water but soluble in salt solutions. Maximum insolubility in water occurs at the isoelectric point of the protein. A number of water-soluble uncharged polymers of varying molecular weights have been used for the precipitation of proteins. Alcohols, acetone, ether, and other water-miscible organic reagents have been used by analytical chemists to precipitate proteins since the early part of the last century. Protamines, a group of highly basic proteins rich in arginine, have been used to precipitate selectively fibrinogen from plasma. A number of studies of the nucleation process during protein precipitation and crystallization have been reported in the literature. Aging a protein precipitate by gentle agitation for an extended period of time improves its physicochemical characteristics with regard to liquid/solids separations.
