Affinity Chromatography (AFC) offers the greatest potential specificity and selectivity for the isolation or purification of biomolecules. Almost all biological molecules can be purified on the basis of a specific interaction between their chemical or biological structure and a suitable affinity ligand.
In AFC, the target molecule is specifically and reversibly adsorbed by a complementary ligand and immobilized on a matrix. Examples of a complementary ligand include an inhibitor, substrate analog or cofactor, or an antibody which specifically recognizes the target molecule. The selectivity is often based on spatial recognition, a ‘lock-and-key’ mechanism.
The adsorbed molecule is subsequently eluted either by competitive displacement or a conformation change through a shift in pH or ionic strength. Typical molecular pairs are antigens and antibodies, enzymes and coenzymes, and sugars with lectins.
Purification of several thousand-fold may be obtained due to the high selectivity of the affinity interactions. Although affinity chromatography is not specific, in that no enzyme interacts with only one substrate, it is the most selective method for separating proteins.
