What is a Western Blot?

A Western Blot is an analytical technique used to detect and measure targeted proteins within a sample.

This method uses a conjugated primary antibody to bind to the protein of interest and allow detection. Typical detection methods include selected colorimetric, fluorescent, and chemiluminescent antibody tags, to visualize the experimental results. During gel electrophoresis, the proteins within the sample will migrate at varying rates according to their size. The gel will then be stained and either examined by eye or photographed using selected filters, depending on the sensitivity of the blot. These results are compared to a standardized ‘ladder’ made up of bands of known protein sizes. See Figure 1 below: 

Figure 1: Virtual Western Blot results. Notice the comparative 'ladder' of the Markers lane on the leftmost portion of each gel.

Image courtesy of Researchgate.net

The applications of this test are often used to simply identify the presence of a protein or antibody, such as in medical diagnostics, but are also common in biochemical labs for quantification of experimental results.

For more information on Western Blots and other biochemical assays, see Additional Resources below.