Affinity chromatography deals with the

Methods for Separating and Purifying Biomolecules1Salt fractionation (eg, precipitation of proteins with ammonium sulfate)Chromatography: Paper, ion exchange, affinity, thin-layer, gas-liquid, high-pressure liquid, gel filtrationElectrophoresis: Paper, high-voltage, agarose, cellulose acetate, starch gel, polyacrylamide gel, SDS-polyacrylamide gelUltracentrifugationAffinity chromatography exploits the high selectivity of most proteins for their ligands. Enzymes may be purified by affinity chromatography using immobilized substrates, products, coenzymes, or inhibitors. In theory, only proteins that interact with the immobilized ligand adhere. Bound proteins are then eluted either by competition with free, soluble ligand or, lessselectively, by disrupting protein-ligand interactions using urea, guanidine hydrochloride, mildly acidic pH, or high salt concentrations. Commercially available stationary phase matrices contain ligands such as NAD+ or ATP analogs. Purification of recombinantly expressed proteins is frequently facilitated by modifying the cloned gene to add a new fusion domain designed to interact with a specific matrix-bound ligand