Specific proteins in a sample of tissue homogenate or extract.
Western blot. A western blot is a laboratory method used to detect specific protein molecules from among a mixture of proteins. This mixture can include all of the proteins associated with a particular tissue or cell type. The first step in a western blot is to prepare the protein sample by mixing it with a detergent called sodium dodecyl sulfate, which makes the proteins unfold into linear chains and coats then with a negative charge. The immunoblot is a laboratory test that looks for antibodies the body makes against different molecules, or “antigens,” that are part of the Borrelia burgdorferi bacteria. Western Blots were the first type of immunoblot developed for Lyme disease testing.  Western blot. This is an immunoassay test method that detects specific proteins in blood or tissue. It combines an electrophoresis step with a step that transfers (blots) the separated proteins onto a membrane.  Western Blotting. Western blot analysis can detect one protein in a mixture of any number of proteins while giving you information about the size of the protein. It does not matter whether the protein has been synthesized in vivo or in vitro. You will use this antibody as a probe to detect the protein of interest. Western blotting tells you how much protein has accumulated in cells. If you are interested in the rate of synthesis of a protein, Radio-Immune Precipitation (RIP) may be the best assay for you. The proteins are then transferred to a membrane (typically nitrocellulose or PVDF), where they are stained with antibodies specific to the target protein. The gel electrophoresis step is included in western blot analysis to resolve the issue of the cross-reactivity of antibodies. The name western blot was given to the technique by W. Neal Burnette and is a play on the name Southern blot, a technique for DNA detection developed earlier by Edwin Southern. A series of blood screenings are performed to test for HIV. The enzyme-linked immuno assay (ELISA or EIA) is the first test that your doctor will order to screen for HIV. ELISA and the Western blot test detect HIV antibodies in your blood. Antibodies are proteins your immune system produces in response to the presence of foreign substances such as viruses. If you test positive for HIV with the Western blot test, you probably have HIV. Sometimes, HIV does not show up on the ELISA test even though you are infected. This can happen if someone is in the early stages of the infection, and his or her body has not produced enough antibodies to the virus for the tests to detect. Western blot using an antibody that recognizes proteins modified with lipoic acid. The western blot (sometimes called the protein immunoblot) is a widely used analytical technique used to detect specific proteins in a sample of tissue homogenate or extract. It uses gel electrophoresis to separate native proteins by 3-D structure or denatured proteins by the length of the polypeptide. The name western blot was given to the technique by W. Neal Burnette and is a play on the name Southern blot, a technique for DNA detection developed earlier by Edwin Southern. Eastern blotting is an extension of western blotting and is used in the detection of protein post-translational modifications. Eastern blotting is used to detect lipoylated, glycosylated or phosphorylated proteins or proteins with other post translational modifications.  Like the ELISA procedure, the western blot is an antibody detection test. However, unlike the ELISA method, the viral proteins are separated first and immobilized. In subsequent steps, the binding of serum antibodies to specific HIV proteins is visualized. 
http://www.nature.com/scitable/definition/Western-blot-288 http://www.cdc.gov/lyme/diagnosistesting/LabTest/TwoStep/WesternBlot/index.html https://labtestsonline.org/understanding/features/methods/start/3 https://askabiologist.asu.edu/western-blotting https://en.wikipedia.org/wiki/Western_blot http://www.healthline.com/health/elisa-western-blot-tests-for-hiv https://en.wikipedia.org/wiki/Western_blot https://en.wikibooks.org/wiki/Structural_Biochemistry/Proteins/Western_Blotting https://en.wikipedia.org/wiki/Diagnosis_of_HIV/AIDS
what does a western blot detect