Western blotting (protein blotting) An immunoassay for determining very small amounts of a particular protein in tissue samples or cells. The sample is subjected to electrophoresis on SDS-polyacrylamide gel to separate constituent proteins. The resultant protein bands are then `blotted' onto a polymer sheet. A radiolabelled antibody specific for the target protein is added; this binds to the protein, which can then be detected by autoradiography. A variation of this technique is used to screen bacterial colonies containing cDNA clones in order to isolate those colonies expressing a particular protein. The name is derived by analogy to that of Southern blotting.

BLOT, WESTERN

The blot test is a method used to detect and identify DNA or RNA samples, using absorbent paper electrophoresis. The original test in this group was developed by British biologist M. E. Southern in 1975, and is named the Southern blot test. As related tests using the same general method were developed, they were named for the points of the compass. The Western blot test is a specific test that uses paper electrophoresis to detect HIV (human immunodeficiency virus), and it is widely used in screening for HIV infection.

John M. Last

(see also: HIV/AIDS; Laboratory Services; Screening )