Protein purification technolog problems

For every protein purification problem there is always an affinity solution, but cost and safety considerations may render these solutions impractical. As an example, antibodies are widely used for analysis, where only relatively small amounts are usually required, but their production and purification on a large scale for preparative-scale chromatography may be difficult to justify economically. In some cases, Hhybridoma technology may be able to address this problem. Even if production costs are acceptable, the immobilized antibodies may be unstable over the sequence of sample application, elution, and sanitation required for multiple use of the affinity adsorbent. For these reasons, while biological ligands (antibodies, enzymes, receptors, lectin. 

The practical achievement of this goal was held up for 18 years, primarily because of the great difficulty in isolation and purification of single-species proteins from the immune repertoire. During that time, many attempts to elicit catalysis by inhomogeneous (i.e. polyclonal) mixtures of antibodies were made and failed (e.g. Raso and Stollar, 1975 Summers, 1983). The problem was resolved in 1976 by Kbhler and Milstein s development of hybridoma technology, which has made it possible today both to screen rapidly the complete immune repertoire and to produce in vitro relatively large amounts of one specific monoclonal antibody species (Kohler and Milstein, 1975 Kohler et al., 1976). 

In some technological and medical applications protein adsorption and/or cell adhesion is advantageous, but in others it is detrimental. In bioreactors it is stimulated to obtain favourable production conditions. In contrast, biofilm formation may cause contamination problems in water purification systems, in food processing equipment and on kitchen tools. Similarly, bacterial adhesion on synthetic materials used for e.g. artificial organs and prostheses, catheters, blood bags, etc., may cause severe infections. Furthermore, biofilms on heat exchangers, filters, separation membranes, and also on ship hulls oppose heat and mass transfer and increase frictional resistance. These consequences clearly result in decreased production rates and increased costs. 

At present, these technologies have rendered possible the production of virtually unlimited quantities of important new biologies which were previously available only in minutest quantities. Human insulin, interferon, human growth hormone, foot and mouth disease vaccine are but a few examples. For the purpose of this symposium it should be emphasized that these proteins are often first obtained in the form of crude extracts, heavily contaminated by extraneous matter, derived from the host organism. The purification of the desired end product is essential if it is to be used as a pharmaceutical. The magnitude of the problem can best be comprehended if one realizes that the host cell, i.e. the modified microorganism or the hybridoma cell, may contain well over 5,000 different proteins, only one of which may be the desired active principle. 

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