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Monoclonal Antibiotics




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What Do Antibodies Look Like?

Antibodies are glycoproteins, they have carbohydrate attached to them, and they each share a common Y-shaped structure composed of four protein subunits. These subunits contain two identical light chains and two identical heavy chains. Each light chain consists of about 200 amino acids, which compared to a heavy chains is only about half the size. The variable regions of the antibody are located at the amino terminals, N-Terminals, and it is in this region where the first 100 or so amino acids vary from antibody to antibody. The variable regions determine the antibody's antigen-binding specificity. The constant regions are located on the light and heavy chains and only a few different amino acid sequences are found here. This region determines antibodies' ability to activate other immune system components.

Humans make two different kinds of constant regions for their light chains producing: kappa and lambda light chains. Also they produce five different kinds of constant regions for their heavy chains producing: mu chains (IgM antibodies), gamma chains (IgG), alpha chains (IgA), delta chains (IgD), and epsilon chains (IgE). Each of these five kinds of heavy chains appears to have no particular preference for pairing with the lambda or kappa light chains.

iggantibodya.gif

The diagram above represents the polypeptide chain structure of a molecule of the IgG antibody. The numbers indicate the number of amino acids at that particular spot counting up form the amino terminal. In the actual molecule, the chains are folded to that each cysteine is brought close to the partner with which it forms a disulfide bridge.