How does affinity chromatography function in the protein purification process?

• A. It relies on pH adjustments
• B. It uses a bound receptor or ligand
• C. It separates proteins based on size
• D. It utilizes electric fields for separation

Answer: (B)

Affinity chromatography is a powerful technique in protein purification that specifically takes advantage of the strong, non-covalent interactions between proteins and their specific ligands or receptors. In this method, a stationary phase is designed to contain a ligand that is complementary to the target protein. As the protein solution flows through the chromatography column, the target proteins will bind to the ligand due to this specific affinity, while other proteins that do not bind effectively will wash through the column. After unbinding the non-specific proteins, the target proteins can be eluted from the column by altering the conditions, such as the concentration of a competing ligand, pH, or ionic strength. This specificity allows for a highly efficient and effective purification of the desired protein from a complex mixture.

While other techniques mentioned, such as size exclusion or electric field applications (like in gel electrophoresis), focus on different properties of proteins, affinity chromatography stands out for its selective binding approach, making it a key method in protein purification.