What type of chromatography uses a ligand to bind specific proteins?

Affinity chromatography is a technique that specifically uses a ligand to selectively bind targeted proteins from a mixture. The core principle of this method involves the interaction between the ligand, which is covalently attached to a stationary phase (typically a solid matrix), and the specific protein of interest that has a natural affinity for that ligand.

In this process, the mixture containing various proteins is passed through a column filled with the stationary phase. The protein that binds to the ligand remains attached to the column, while unbound proteins are washed away. To isolate the target protein, a solution with a higher concentration of the free ligand or an elution buffer is applied to the column, which competes with the protein for binding to the ligand. This causes the target protein to detach from the ligand and be eluted from the column.

This specificity is what makes affinity chromatography a powerful tool in protein purification. It allows for the selective separation of a desired protein based on its unique binding properties, rather than relying on size or charge, which are the principles used in other chromatographic techniques.