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Protein G beads

Catalog No.
Protein G beads commonly used in IP, Co-IP, and Ch-IP
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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 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 G beads are suitable for immunoprecipitation human IgG1, IgG2, IgG3, IgG4, mouse IgG1, IgG2a, IgG2b, IgG3, rat IgG1, IgG2a, IgG2b, IgG2c and each Protein G molecule can bind 3 IgG molecules, mainly 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 offers significant advantages. First, high content and binding specificity of the binding antibody can be achieved. Compared with traditional Protein G agarose gels, this product has a smaller pore size, is less prone to non-specific adsorption, and has a high binding amount. The 1 ml bead suspension of this product contains about 10 mg beads, not less than 0.6 mg of recombinant Protein G, and the 3 Fc binding domains contained in a single recombinant Protein G can bind to not less than 0.7 mg 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 G beads suspension for 500 μl of samples. Second, ultra-rapid binding of antibodies or antibody complexes can be achieved. Protein 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, and the immunoprecipitation operation of the protein of interest can be completed within 30 min. 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).

Species Subclass Protein A binding Protein G binding
Human lgA ++ -
lgD ++ -
IgE ++ -
lgG1 ++++ ++++
lgG2 ++++ ++++
lgG3 - ++++
lgG4 ++++ ++++
lgM ++ -
Mouse lgG1 + ++++
lgG2a ++++ ++++
lgG2b +++ +++
lgG3 ++ +++
lgM +/- -
Rat lgG1 - +
lgG2a - ++++
lgG2b - ++
lgG3 + ++

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.

Characteristics Description
Product content 10mg/ml magnetic beads in specific protective buffer
Beads size ~200nm
Magnetization Superparamagnetic
Coupled protein Recombinant Protein G
M.W. of protein ~25kDa (Protein G)
Antibody concentration ≥0.6mg Protein G per ml beads
Binding capacity ≥ 0.7mg human IgG per ml beads
Specificity Antibodies from many different species, including mouse, human, rabbit, cow, goat and sheep
Elution method Elution with acid, competing peptide or SDS‐PAGE loading buffer
Application IP, Co-IP, Protein purification

Table 2 The main related indicators of Protein G beads.

Quality Control

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Components and Storage

Component K1304-1ml K1304-5*1ml
Protein A beads 1 ml 5*1 ml

Store at 4 °C for two years.