Affinity chromatography is a useful chromatography technique separating proteins in a reversible interaction between the target protein and ligand of bead. The interaction can be biospecific for example antibodies binding to protein A or non-biospecific for example histidine-tagged proteins binding to metal ions.
The chromatography technique provides high selectivity, high resolution and high capacity. High purity can often be achieved in a single step. Large sample volumes can be handled and samples can be applied under conditions that favor specific binding to the ligand. Elution is often performed under gentle conditions which helps preserve bioactivity. The target protein is eluted in a purified and concentrated form by modification of pH, ionic strength, or by introducing a competitive ligand.