Blood: Blood cells make up about 45% of adult blood. These cells include oxygen carrying erythrocytes (red blood cells), immune cells caled leukocytes (white blood cells) and thrombocytes (platelets). Whole blood can be serapted by centrifugation into three layers: (a) the upper plasma layer; (b) the “buffy coat” layer which contains the leukocytes and thrombocytes and (c) the lower layer which contains the erythrocytes. 

Chelators: One hazard in the fractionatation of protein mixtures  is the activation or proteolytic enzymes, whose inactive precursors may be present in the fractions. One means of conteracting such effects is the addition of small amount of chelators such as sodium citrate or ethylene-diaminetetraacetate (EDTA). EDTA also prevents the metal catalyzed oxidation of the lipid moiety of lipoproteins.

pH: Most plasma proteins have their isoelectric point below pH7 so that their solubility will decrease with acidification.

Plasma: makes up 55% of the blood (the other 45% are blood cells), is a straw coloured fluid which contains water, blood plasma proteins (including clotting factors), minerals and dissolved nutrients (such as glucose, amino acids, and fatty acids) and waste produces (such as urea and lactic acid). 

Protein concentration: Another factor to be kept under strict control is the protein concentraiton of the medium. As a rule, the resolving power can be improved by lowering the protein content of the mixture. Some proteins, however, tend to become unstable at very low concentration but this can be countered by the use of stabilizers such as glycine. (Schultz, H.E. “Molecular Biology of Human Proteins” Volume 1: Nature and Metabolism of Extracellular Proteins. 1966, Elsevier Publishing Company, pp. 236-317.

Serum: is the name given to plasma which has had the clotting factors removed. 

Siliceous materials: One technical problem in the isolation of plasma proteins is the sizeable amount of lipoprotiens (8% of the total plasma). It is of advantage to remove the lipoproteins as a preliminary step to any kind of fractionation. For this purpose extensive use is made of the absorbant power of finely idspersed siliceous materials such as glass powder, bentonite and aerosil as well as of calcium phosphate.

Temperature: Proper control of termperature is a critical factor. With fractionation systems employing ethanol, the temperature should not be allowed to rsie above 0, if irreversible denaturation is to be avoided.

Ultrafiltration/Diafiltration:

UF and DF of protein solutions are extensively performed in the course of a manufacturing prcoess for palsma prtoeins, often being sued to concentrate protein solutions or in the exchange of buffers. This may be required to prepare for a subsequent purificaiton step or to adjust protein concentraiton and salt content to the specificaitons required for formulation. Membranes with MWCO of between 10 and 11 kD are widely used. ((Bertolini, “Production of Plasma Proteins for Therapeutic Use” ISBN: 978-0-470-92431-), 512 pages. ).