What are Northern, Southern, Western, Southwestern Blots?

Southern blotting was the original of the four.
It got its name from the developer, Edwin Southern.
Western blotting was named as a sort of joke. (North, South, East, West).
The rest arose based on these first two.

Southern blotting uses gel electrophoresis for the detection of a specific DNA sequence in a sample of DNA.

Western blotting also uses gel electrophoresis but it is to detect proteins and separate them based on size and shape.

Northern blotting is for the detection of RNA sequences, and so is geared towards detecting gene expression (the technique is very similar to Southern blotting only formaldehyde is used to denature the RNA).

There is no Eastern blot, but there is a southwestern one. It is used to find where proteins (DNA binding proteins) bind to specific sequences of DNA.

Far-western blotting is a molecular biological method which is based on the technique of western blotting. While usual western blotting uses an antibody to detect a protein of interest, far-western blotting uses a non-antibody protein, which can bind the protein of interest. Thus, whereas western blotting is used for the detection of certain proteins, far-western blotting is rather employed to detect protein:protein interactions.

By the way, they all use gel electrophoresis.





Far-Eastern blotting is different from the above. It is a technique developed in the 1990s by T. Taki and colleagues at the Cellular Technology Institute of Otsuka Pharmaceutical Co., Japan for the analysis of lipids separated by high-performance thin layer chromatography (HPTLC). The lipids are transferred from the HPTLC plate to a PVDF membrane for further analysis, for example by enzymatic or ligand binding assays[1] or mass spectrometry[2].

Cholesterol, glycerophospholipids and sphingolipids are major constituents of the cell membrane and in certain cases function as second messengers in cell proliferation, apoptosis and cell adhesion in inflammation and tumor metastasis. Far-eastern blotting was established as a method for transferring lipids from an HPTLC plate to a polyvinyledene difluoride (PVDF) membrane within a minute. Applications of this with other methods have been studied. Far-eastern blotting allows for the following techniques:

* Purification of glycosphingolipids and phospholipids.
* Structural analysis of lipids in conjunction with direct mass spectrometry.
* Binding study using various ligands such as antibodies, lectins, bacterium, viruses, and toxins, and
* Enzyme reaction on membranes.

Not only analysis of lipids but also metabolites of drugs and natural compounds from plants, and environmental hormones are possible by this method.