Plasma proteins preservation

Figure 46-8. Fusion of a vesicle with the plasma membrane preserves the orientation of any integral proteins embedded in the vesicle bilayer. Initially, the amino terminal of the protein faces the lumen, or inner cavity, of such a vesicle. After fusion, the amino terminal is on the exterior surface of the plasma membrane. That the orientation of the protein has not been reversed can be perceived by noting that the other end of the molecule, the carboxyl terminal, is always immersed in the cytoplasm. The lumen of a vesicle and the outside of the cell are topologically equivalent. (Re drawn and modified, with permission, from Lodish HF, Rothman JE The assembly of cell membranes. Sci Am [Jan] 1979 240 43.)...

HSA is used therapeutically as an aqueous solution it is available in concentrated form (15-25 per cent protein) or as an isotonic solution (4-5 per cent protein). In both cases, in excess of 95 per cent of the protein present is albumin. It can be prepared by fractionation from normal plasma or serum, or purified from placentas. The source material must first be screened for the presence of indicator pathogens. After purification, a suitable stabilizer (often sodium caprylate) is added, but no preservative. The solution is then sterilized by filtration and aseptically filled into final sterile containers. The relative heat stability of HSA allows a measure of subsequent heat treatment, which further reduces the risk of accidental transmission of viable pathogens (particularly viruses). This treatment normally entails heating the product to 60 °C for 10 h. It is then normally incubated at 30-32 °C for a further 14 days and subsequently examined for any signs of microbial growth. 

Membranes are structurally and functionally asymmetric, as exemplified by the restriction of sugar residues to the external surface of mammalian plasma membranes. Membranes are dynamic structures in which proteins and lipids diffuse rapidly in the plane of the membrane (lateral diffusion), unless restricted by special interactions. In contrast, the rotation of lipids from one face of a membrane to the other (transverse diffusion, or flip-flop) is usually very slow. Proteins do not rotate across bilayers hence, membrane asymmetry can be preserved. The degree of fluidity of a... 

These observations have several important practical implications. First, hospitals must store red blood cells in a plasma solution which has the correct proportions of salts and proteins. The plasma solution is made to be slightly hypertonic to the red cells so that the integrity of the cells is preserved and hemolysis is prevented. Second, when doctors inject a drug intravenously into a patient, the drug is suspended in a saline solution which is slightly hypertonic to red blood cells. Intravenous injection of a drug in pure water will cause some of the patient s red blood cells to hemolyze because water is hypotonic to the red blood cells. 

The PhEur 2005 similarly describes albumin solution as an aqueous solution of protein obtained from human plasma see Section 13. It is available as a concentrated solution containing 150-250 g/L of total protein or as an isotonic solution containing 35-50 g/L of total protein. Not less than 95% of the total protein content is albumin. A suitable stabilizer against the effects of heat, such as sodium caprylate (sodium octanoate) or N-acetyltryptophan or a combination of these two at a suitable concentration, may be added, but no antimicrobial preservative is added. 

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