Staphylococcal Protein A binds strongly and specifically to the Fc region of immunoglobulin molecules, particularly IgG. The product contains five high-affinity binding sites capable of interacting with the Fc region of IgG in humans, rabbits, pigs, and other species. Biotin-Protein A, which is produced by covalently linking biotin to protein A, can be used in immunodetections, such as immunoblotting (western or dot blot), ELISA, and immunohistochemistry.