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Protein A Affinity Chromatography

Protein A Chromatography relies on the specific and reversible binding of antibodies to an immobilized protein A ligand. Protein A is a 56 kDa surface protein native to the cell wall of the bacterium Staphylococcus aureus. It is composed of five immunoglobulin-binding domains, each of which are able to bind proteins from many mammalian species, most notably Immunoglobulin G (IgG) through the heavy chain within the Fc region. While the native form of Protein A was used as the ligand for first generation Protein A resins, the recombinant form (rProtein A) produced in E. coli is the most prevalent today. Modifications to the protein structure of the ligand, the advent of ligands composed of single domain multimers, and multipoint attachment have given rise to the caustic stable, high capacity and extremely robust Protein A resins in use today.

Applications

Protein A resins are the most frequently used affinity resins in biomanufacturing. Protein A chromatography is a very robust purification procedure and is used as a capture step due to its specificity. Today Protein A chromatography is the standard technique for capturing recombinant monoclonal antibodies. Depending on the intended use for the target molecule (antibodies for diagnostic testing) Protein A capturing might be the only chromatographic step required to achieve adequate product purity.

TOYOPEARL Protein A Resins

Tosoh Bioscience offers two Protein A affinity resins, both based on alkaline stable, recombinant ligands coupled to the proven TOYOPEARL polymethacrylate matrix. Both ligands are recombinant protein A variants expressed in E. coli. They are derived from one of the IgG binding domains of protein A. The ligand of TOYOPEARL AF-rProtein A-650F consists of a tetramer of theses modified protein A C domains. For the ultra-high capacity TOYOPEARL AF-rProtein A HC-650F, this domain was further optimized and expressed as a hexamer in order to further increase IgG binding capacity. Multipoint attachment of the ligands to the TOYOPEARL matrix enhances the chemical and thermal stability of the resins.

Both resins are based on the TOYOPEARL HW-65F base bead with a particle size of 45 μm and exhibit excellent pressure-flow characteristics. The new ultra-high capacity TOYOPEARL AF-rProtein A HC-650M excels all other commercially available protein A media with regard to its IgG binding capacity of >65 g IgG/L resin.

The ultra-high capacity TOYOPEARL AF-rProtein A HC-650F exceeds all other commercially available protein A media with regard to its IgG binding capacity of more than 65 g IgG/L resin at residence times of 5 minutes. Its IgG capacity still exceeds 50 g/L at 2 minutes residence time with feed stock concentrations from 1.0 g/L to 10.0 g/L. Improved mass transfer characteristics allow it to maintain a larger percent of its capacity at lower residence times relative to agarose based, caustic stable resins.

The standard TOYOPEARL AF-rProtein A-650F resin binds human and mouse immunoglobulin G, IgM, and Fab fragments. It provides a static IgG binding capacity of more than 45 g/L and a typical dynamic IgG binding capacity of more than 30 g/L at 2 minutes residence time (1 g/L protein load). Fast mass transfer kinetics support high binding capacities at high flow rates.

TOYOPEARL AF-rProtein A-650F is also stable in ethanol, 6 mol/L urea, 6 mol/L guanidinium chloride, and 1% phosphoric acid, respectively. Static binding capacity of the resin is not impaired when heated for 30 minutes to temperatures of up to 90 °C.