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Antibodies are proteins. As such, they are made of chains of amino acids that are folded into a specific shape based on the sequence and properties of the amino acids. Antibodies all have the same basic structure. Each antibody is made of four chains (shown in the image as blue and pink sections). There are two long heavy chains (colored blue) and two shorter light chains (pink/red). The specific binding site is found at the tips of the two arms, in a pocket formed between the light and heavy chain.
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Figure 18.10, Purves's Life: The Science of Biology, 7th Edition (Found: http://www.hammiverse.com/lectures/43/2.html)
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The binding site is composed of several loops in the protein chain that have very different lengths and arrangements of amino acids. Differences in these "hypervariable loops" form the many types of pockets in different antibodies, each of which bind specifically to a different antigen. The rest of the antibody is relatively uniform in structure, providing a constant recognition site for when antibodies interact with the rest of the immune system. In the image to the right you can see the variable region forms a specific shape that can bind with a specific antigen.
Antigens are molecules, such as proteins and carbohydrates, that can fit into the variable region of the antibody. This process is similar to how enzymes have a specific binding sites that match with specific substrates. |
An ELISA (enzyme-linked immunosorbent assay) uses scientifically designed antibodies to detect if a particular substance, such as a viral antigen, hormone, or another specific antibody, is present in a sample.
The protocol involves binding an antigen or an antibody to a well plate. A sample is then added to the well plate. If the well plate was loaded with an antigen then the test will determine if an antibody for that antigen is present in the sample. If an antibody was loaded into the well plate then the test will determine if the antigen for that antibody is present in the sample. |
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