Purification of plasma protein.
The purification of coagulation proteins from plasma milieu is a complex and sometimes difficult task. Most clotting factors are present in plasma in trace amounts. They are sensitive to proteolytic degradation and adsorption to surfaces. Thus for most coagulation proteins it was not until the seventies that highly purified preparations were available. Nowadays, most coagulation proteins are isolated from plasma using combinations of ion exchange, molecular sieve and affinity chromatographies. Sometimes, e.g. for Vitamin K dependent factors, specific adsorption properties are utilized. During affinity chromatography, proteins may be bound to specific immobilized receptors, antibodies, substrates, or inhibitors. An example for the latter is the use of bezamidine-Sepharose for the purification of thrombin. Immunoadsorption to immobilized monoclonal antibodies allowed the isolation of highly purified factor VIII:C. For factor XI and prekallikrein the binding of these proteins to the immobilized cofactor high molecular weight kininogen is utilized for an effective separation of contaminations. Antithrombin III can be isolated by linkage to its cofactor, heparin, on heparin-Sepharose. Using affinity chromatography on lysine-Sepharose it is possible to isolate plasminogen from plasma, serum or urine in a one step procedure with high yield and quality. This, of course, is an ideal situation, where the goal of a purification, namely the separation of a highly purified, biologically active product with high yield can be accomplished in a simple, fast procedure.