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Protein purification is a series of processes intended to isolate a single type of protein from a complex mixture. Protein purification is vital for the characterization of the function, structure and interactions of the protein of interest. The starting material is usually a biological tissue or a microbial culture. The various steps in the purification process may free the protein from a matrix that confines it, separate the protein and non-protein parts of the mixture, and finally separate the desired protein from all other proteins. Separation of one protein from all others is typically the most laborious aspect of protein purification. Separation steps may exploit differences in (for example) protein size, physico-chemical properties, binding affinity and biological activity. Contents * 1 Purpose * 2 Strategies * 3 Evaluating purification yield * 4 Methods of protein purification * 5 Extraction * 6 Precipitation and differential solubilization * 7 Ultracentrifugation * 8 Chromatographic methods * 8.1 Size exclusion chromatography * 8.2 Separation based on charge or hydrophobicity * 8.3 Ion exchange chromatography * 8.4 Affinity chromatography * 8.4.1 Metal binding * 8.4.2 Immunoaffinity chromatography * 8.4.3 Purification of a tagged protein * 8.5 HPLC * 9 Concentration of the purified protein * 9.1 Lyophilization * 9.2 Ultrafiltration * 10 Analytical * 10.1 Denaturing-Condition Electrophoresis * 10.2 Non-Denaturing-Condition Electrophoresis * 11 References * 12 External links |
Purification may be preparative or analytical. Preparative purifications aim to produce a relatively large quantity of purified proteins for subsequent use. Examples include the preparation of commercial products such as enzymes (e.g. lactase), nutritional proteins (e.g. soy protein
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