affinity chromatography

Affinity chromatography is a method used to isolate and purify macromolecules, such as proteins. It works by passing a solution containing the target molecule through a column packed with a substance that has a specific ligand. This ligand has an affinity for the target molecule, causing it to bind to the column while other substances pass through.1

This technique exploits very specific intermolecular interactions, often described as a "lock and key" mechanism, which are common in biochemistry. For example, an enzyme might bind to a specific structural feature of a protein. In affinity chromatography, a ligand with the desired binding capability is attached to a support material. This ligand then selectively retains the solute with the compatible structural feature, allowing other components of the mixture to be washed away. The desired solute can then be released from the column by changing the mobile phase, for instance, by adding a competing solute or altering the acidity or ionic strength.2