Western blotting is a laboratory technique used to detect a specific protein in a blood or tissue sample. The method involves using gel electrophoresis to separate the sample's proteins. The separated proteins are transferred out of the gel to the surface of a membrane. The membrane is exposed to an antibody specific to the target protein. Binding of the antibody is detected using a radioactive or chemical tag. A western blot is sometimes used to diagnose disease.
Western blot. In the laboratory we often want to measure whether a specific protein is expressed in a sample. We can do this by taking the material from the sample and running it on a gel, and then transferring the resolved proteins onto a special piece of membrane--of paper, if you will--and then probe that paper with an antibody to the specific protein of interest. Because the antibody is labeled with a molecule that we can then visualize, we can ask whether the protein of interest is expressed in this sample and have an idea of how abundant it is, as well as understanding what size the protein is.