Protein A/G beads

Protein A is a cell wall surface protein found in Staphylococcus aureus with a molecular weight of 42 kDa, which can specifically bind to the Fc region of mammalian immunoglobulin (Ig) and to the Fab region of the human VH3 family. Protein G is an immunoglobulin-binding protein expressed by Streptococcal bacteria that specifically binds to the Immunoglobulin (Ig) Fc region of mammals. This product is a modified recombinant Protein A (25 kDa) and Protein G (25 kDa), covalently coupled with nanoscale amino beads, and only retains the amino acid sequence associated with Fc terminal binding such as IgG, removing the sequence that may lead to non-specific binding except the binding site, which can effectively reduce non-specific binding.

Protein A beads can specifically bind to corresponding antibodies, such as human IgG1, IgG2, IgG4, mouse IgG2a, IgG2b and rabbit IgG, etc., each Protein A molecule can bind 5 IgG molecules, and Protein G beads are suitable for immunoprecipitation human IgG1, IgG2, IgG3, IgG4, mouse IgG1, IgG2a, IgG2b, IgG3, rat IgG1, IgG2a, IgG2b, IgG2c, as well as rabbit, goat polyclonal antibodies, etc., each Protein G molecule can bind to 3 IgG molecules. The product is mainly used for immunoprecipitation (IP), co-precipitation (Co-IP) or chromatin immunoprecipitation (Ch-IP), as well as the purification of antibodies in samples such as serum, cell culture supernatant or ascites. The binding capacity of common immunoglobulin subclasses and the total binding capacity of different species are shown in the following table (Table 1).

This product is configured with Protein A beads and Protein G beads in a ratio of 1:1, which has a variety of significant advantages. First, high content and binding specificity of the binding antibody can be achieved. Compared with traditional Protein A/G agarose gels, this product has a smaller pore size, is not prone to non-specific adsorption, and has a high binding amount. The 1 ml magnetic bead suspension of this product contains about 10 mg of magnetic beads, not less than 0.6 mg of recombinant Protein A/G and can bind to not less than 0.7 mg of Human IgG. The specific maximum binding amount is related to the type of antibody and the target protein. For experiments, efficient immunoprecipitation experiments are typically performed using 10-20 μl of Protein A/G bead suspension for 500 μl of samples. Second, ultra-rapid binding of antibodies or antibody complexes can be achieved. Protein A/G beads (~200 nm) facilitate fast and effective binding of beads to antibodies or antibody complexes due to their large specific surface area. The adsorption process of the antibody or its complex can usually be completed within 10 min, 30 min Complete the immunoprecipitation operation of the protein of interest. Shortening the operation time can effectively avoid the degradation or denaturation of the protein of interest during long-term operation, and fully ensure the activity of the protein of interest. Due to the magnetic separation, IP and Co-IP can save 40% of the time compared to agarose gels per time. Finally, a variety of methods can be used to elute. Depending on factors such as the structure, biological function and design requirements of the protein of interest, a variety of eluents such as acidic solution, SDS-PAGE loading buffer or competitive peptides can be used for elutation. (See Table 2 for specific product parameters).

Table 1 affinity data for Protein A and Protein G for different sources and subtypes of IgG. ++++ = Strong Binding; ++~+++ = Medium Binding; + = Weak Binding; +/- = Weak or No Binding; - = No Binding.

Table 2 The main related indicators of Protein A/G beads.