Fibrinogen precipitation from plasma

Protein samples used to conduct a protein transfer were bovine serum albumin (BSA, 67,000 daltons), chicken egg ovalbumin (Ovalb, 45,000 daltons), and human serum cryo-precipitate. These agents were obtained from plasma containing a mixture of proteins including Fibrinogen (340,000 daltons), human serum albumin (HSA, 67,000 daltons), and immunoglobulin G (IgG, 47,000-56,000 daltons). The cryo-precipitate was diluted with 20 ml of buffer solution prior to separation. 

While erythrocytes have been shown not to absorb albumin from plasma (B28), washed blood platelets absorb and firmly bind radioactive albumin (S5). Although human blood platelets absorb albumin and fibrinogen, specifically from among the plasma proteins, the amount of albumin precipitated on centrifuging platelet-rich plasma is extremely small (B15). 

Sodium chloride can be used to separate some of the proteins most readily salted out from those which require higher ionic strengths than are attainable with its use. The classical example is the use of half saturated sodium chloride solution to precipitate fibrinogen from plasma, a procedure first employed by Hammarsten (87). Potassium chloride is, in general, less suitable than sodium chloride, because of its lower solubility which limits the ionic strengths attainable by its use. 

Cry precipitate is a plasma protein fraction obtainable from whole blood. It is used to treat deficiencies or qualitative abnormalities of fibrinogen, such as that which occurs with disseminated intravascular coagulation and liver disease. A single unit of cryoprecipitate contains 300 mg of fibrinogen. 

Dried human thrombin. A preparation of the enzyme that converts human fibrinogen into fibrin. It is obtained from liquid human plasma and may be prepared by precipitation with suitable salts and organic solvents under controlled conditions of pH, ionic strength, and temperature. 

In the late 1940s, a method was developed (Cohn et al. 1946) for the fractionation of proteins from blood plasma by means of ethanol (an anti-solvent) addition to aqueous solutions at specified conditions of temperature, pH, and ionic strength. Briefly, a series of five successive batch ethanol precipitations were used to prepare fractions of fibrinogens, globulins, and albumin. The conditions used in each step are in Table 11.1 along with the major protein(s) precipitated at each step. More recently, a method employing a series of MSMPR precipitators has been reported (Chang 1988). 

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