Carbohydrates usually bind to the CH2 region of the heavy chain. FC segment only includes the constant region (CH) of heavy chain, but the Fab segment combined with antigen includes a constant region, a variable region of heavy chain and a variable region of light chain (VH and VL). The heavy chain of immunoglobulin is also glycosylated, especially the CH2 region and Fc fragment, and there may be polysaccharide near the antigen binding site.

Using the polysaccharide chain on the CH2 domain on the Fc fragment, the residues of the polysaccharide can be oxidized by the periodate to form an aldehyde group. Crosslinking agents and modifying agents containing hydrazide groups can be targeted to recognize aldehyde groups to link other molecules. This method can use complete antibody molecules, avoid the blocking of antigen binding sites, and retain the antigen binding activity to the greatest extent after coupling. However, it should be noted that the region near the antigen binding site will be glycosylated, which may affect the coupling process.

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