Use Thermo Scientific Pierce Recombinant Protein A to probe and detect rabbit and human antibodies, especially IgG isotypes, in Western blotting, ELISA, IHC and other immunoassay protocols.

Features of Recombinant Protein A include:

• Contains four Fc-binding domains per protein
• Better than Protein G for polyclonal IgG from rabbit, pig, dog and cat serum
• Poorer than Protein G for mouse IgG1, human IgG3 and rat, goat and cow antibodies

Protein A is a cell wall component produced by several strains of Staphylococcus aureus that consists of a single polypeptide chain and contains little or no carbohydrate. Recombinant Protein A is produced in E. coli and functions essentially the same as native Protein A. The Protein A molecule contains four high-affinity binding sites capable of interacting with the Fc region from IgG of several species including human and rabbit. Optimal binding occurs at pH 8.2, although binding is also effective at neutral or physiological conditions (pH 7.0 to 7.6).

Properties of Recombinant Protein A

• Source: E. coli
• Molecular Weight: ∼44,600 (Apparent MW by SDS-PAGE: 45,000)
• Form: salt-free powder
• A280 of 0.1% solution: ∼0.165
• Isoelectric point (pI): 4.7–4.8

The interaction between Protein A and IgG is not equivalent for all species. Even within a species, Protein A interacts with some subclasses of IgG and not others. For instance, human IgG1, IgG2 and IgG4 bind strongly, while IgG3 does not bind. There are also many instances in which monoclonal antibodies do not bind to Protein A, especially the majority of rat immunoglobulins and mouse IgG1.