affinity chromatography

A bio­chemical technique for purifying nat­ural polymers, especially proteins. It functions by attaching a specific lig­and by covalent bonding to an insolu­ble inert support. The ligand has to have a specific affinity for the poly­mer, so that when a solution contain­ing the ligand is passed down a column of the material it is specifi­cally retarded and thus separated from any contaminating molecules. An example of a suitable ligand is the substrate of an enzyme, provided that it does not change irreversibly during the chromatography.