Antibodies that are used in immunoassays belong to the IgG class of immunoglobulins and have a molecular weight of some one hundred and fifty thousand. Structurally, the antibodies are composed of two ΓÇÿheavyΓÇÖ and two ΓÇÿlightΓÇÖ peptide chains, which are linked together by disulphide bonds; their structure resembles a large ΓÇÿYΓÇÖ (Fig. 22.4). The amino-terminal part of the heavy and the light chains is involved in the binding with the antigen.
