Protein A beads

Protein A is a cell wall surface protein found in Staphylococcus aureus, with a molecular weight of 42 kDa, that specifically binds to the Fc region of mammalian immunoglobulin (Ig) and also to the Fab region of the human VH3 family. This product is a modified recombinant Protein A (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 the corresponding antibodies, such as human IgG1, IgG2, IgG4, mouse IgG2a, IgG2b and rabbit IgG, etc. Each Protein A molecule can bind to 5 IgG molecules, mainly for immunoprecipitation (IP), co-immunoprecipitation (Co-IP) or chromatin immunoprecipitation (Chromatin). Immunoprecipitation, Ch-IP), and 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 offers significant advantages. First, high content and binding specificity of the binding antibody can be achieved. Compared with traditional Protein A agarose gels, this product has a smaller pore size, is less prone to non-specific adsorption, and has a high binding amount. The 1ml magnetic bead suspension of this product contains about 10 mg of magnetic beads, not less than 0.6 mg of recombinant Protein A, and the 5 Fc binding domains contained in a single recombinant Protein A can bind to not less than 0.7 mg Human IgG, and the specific maximum binding amount is related to the type of antibody and the target protein. For experiments, efficient immunoprecipitation experiments are usually performed on 500 μl samples using 10-20 μl Protein A bead suspension. Second, ultra-rapid binding of antibodies or antibody complexes can be achieved. Protein A 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 beads.