he proteins are extracted from an overnight culture and purified using Immobilized Metal Affinity Chromatography (IMAC). Naturally occurring proteins do not exhibit an affinity for chelated cobalt or nickel ions on the resin, but our scFv-AP fusion proteins do because their C-terminus contains a 6-His tag. Purification occurs in three main phases: binding of the cell lysate to the beads, washing away the unbound proteins, and selective eluting of the bound scFv-AP fusion protein. Imidazole is used to elute the captured protein off of the beads because it competes with the His-tag proteins for binding to the chelated Nickel ions. The yield and purity of the purified scFv-AP fusion proteins are measured by polyacrylamide gel electrophoresis.