Protein A is a recombinant Fc-binding protein from Staphylococcus aureus, Cowan strain-1 gene. The product is a carboxy truncated material containing 301 amino acid residues. The non-binding regions have been removed to minimise potenial steric interference.

• Binding capacity: 12 to 15 mg of human lgG per mg solid
• Extinction coefficient (E1%): E1% = 1,65 (275 nm) (lit.)
• Isoelectric point (pI): 5,1 (Lit.)

Protein A can be conjugated with various reporter molecules including fluorescent dyes (FITC), enzyme markers (peroxidase, β-galactosidase, alkaline phosphatase), biotin, and colloidal gold without affecting the antibody binding site on the molecule. These conjugates are used to detect immunoglobulins in various immunochemical assays including western blotting, immunohistochemistry, and ELISA applications. In addition, it may be immobilised on a solid support such as agarose or acrylic beads for the purification of either polyclonal or monoclonal immunoglobulins. It is also routinely used for immunoprecipitation assays.