ELISA: Enzyme-Linked Immunosorbent Assay

** A way for looking for small quantities of molecules that involves antibodies.

1. A line of wells that are covered on the bottom with antibodies specific for the molecule they are looking for.
2. Pour test substance into the wells, and if the molecule is present, it sticks to the antibodies.
3. Wash the wells with a buffer to ensure that every other molecule besides the ones bound to the antibodies are washed away.
4. Add another solution with a different antibody (that attaches to another epitope of the molecule they are looking for) followed by another buffer wash.
5. Add a 3rd antibody that interacts with an epitope on the second antibody.
6. An enzyme is present on the 3rd antibody that changes colors when treated.
* color change and degree of color change indicates presence of molecule and amount.

This website shows a good schematic diagram about how an ELISA works.

A video explaining this technique is found at this website http://www.idexx.com/production/elisa/

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