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The F(ab) fragment is an antibody structure that still binds to antigens but is monovalent with no Fc portion. An antibody digested by the enzyme papain yields two F(ab) fragments of about 50 kDa each and an Fc fragment.
In contrast, F(ab')2 fragment antibodies are generated by pepsin digestion of whole IgG antibodies (See below IgG structure) to remove most of the Fc region while leaving intact some of the hinge region. F(ab')2 fragments have two antigen-binding F(ab) portions linked together by disulfide bonds, and therefore are divalent with a molecular weight of about 110 kDa.
Figure legend: The light chain (LH) folds into a variable domain (VL) and a constant domain (CL) whereas the heavy chain is composed of one variable domain (VH) and three (IgG and IgA or four constant domains (IgE).
Choosing a F(ab) fragment
Choosing a F(ab')2 fragment
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