Western blot

Highly specific method of protein biochemistry for the detection of proteins, e.g. in a blood or tissue sample. It is based on the electrostatic properties of proteins, which are separated electrophoretically in a polyacryalmid gel along a voltage gradient and migrate to different distances depending on their molecular weight (separation). Similarly heavy proteins migrate a similar distance and are deposited as protein bands. The protein bands are then transferred to a stable foil (polyvinylidene fluoride membrane or nitrocellulose membrane) ("blotted"). The blot can now be incubated with antibodies directed against the proteins on the blot. Depending on the desired representation of the proteins in the blot by colorimetry, chemiluminescence, fluorescence or radioactive detection, the antibodies used carry enzymes, dyes or radioactively labelled molecules, which can then be made visible.

The name of the blot process comes from the English "blot" (blot, spot) and the "blotting paper" (= blotting paper). The name Western blot has nothing to do with the direction. The Western blot procedure is similar to another analysis procedure invented by a molecular geneticist named Southern for DNA detection, the Southern blot. Taking this similarity into account, the method has been named Western blot.