Recombinant Protein G SePharose

Introduction of antibodies and their affinity ligands:

       Antibodies (Ab) are immunoglobulins produced by plasma cells differentiated from B lymphocytes or memory cells in the body's immune system under antigen stimulation, which can specifically bind to corresponding antigens. They are composed of 2 heavy chains and 2 light chains connected by disulfide bonds. Antibodies can be divided into two segments: Fab and Fc. The Fab segment is the fragment ofantigen binding (Fab), consisting of a complete light chainand the VH and CH1 domains of the heavy chain (Fig.1). The Fc segment is the fragment crystallizable (Fc), equivalent to the CH2 and CH3 domains of lg, and is the site where lg interacts with effector molecules or cells.The Fab segment contains the complete variable region and the CH1 region of the constant region. The Fc segment only refers to the CH2 and CH3 regions of the lg constant region. The variable region (V region) of an antibody is where it binds to an antigen, and the composition and arrangement of these variable region amino acids determine the antigen specificity of the antibody.

       Affinity purification is the most important step in the antibody purification process. Fig.1-1 shows the interaction regions between Protein A and Protein G with traditional antibodies. Based on the antibody's species origin, structural form, and other inherent properties, as well as different expression methods, different affinity ligands can be selected for purification(Table 1-1). Genetically engineered antibodies, such as chimeric antibodies and humanized antibodies, generally use Protein A or Protein G affinity purification resins as the capture step. 

Antibody Affinity Resins:

       Protein G is a protein in the cell wall of group G and C streptococci that can specifically bind to the Fc segment of immunoglobulin lgG molecules without affecting the ability of its Fab segment to bind to antigen molecules. Protein G can also bind to the Fab and (ab”)2 segments of certain antibodies. Protein G has a wide range of uses and can be used to isolate andpurify or remove lgG from serum, purify monoclonal antibodies, and separateantigen-antibody complexes. The albumin and cell surface binding domains of natural protein G through sequence design and protein reconstruction are removed to reduce non-specific binding and has better affinity. Based on recombinant protein G and easily eluted protein G, Recombinant Protein G SePharose, which can specifically bind to all human and mouse lgG subtypes has been developed.