Southwestern blotting

Western Blotting A method for identifying proteins after electrophoretic separation involving a specific probe, usually an antibody. It was derived from the earlier development of southern blotting and northern blotting. See also Northwestern Blotting, Southwestern Blotting. See Radka, S.P., Monoclonal... 

Western, northern, and southwestern blotting are likely spoofs on the term Southern blotting. All follow the same basic technique. The initial step is the separation of a class of compounds, such as DNA, RNA, or proteins from the mixture. Electrophoresis is performed on the class to separate the individual compounds, which then are blotted. The blotting membranes can be treated to retain different compounds. 

Southwestern blotting is used to retain DNA bound to proteins. 

The term Southern blotting is used because the method was developed by E. M. Southern and the term northern blotting was introduced for RNA blots to distinguish them from DNA blots. More recently, protein chemists have gotten into the act by blotting electrophoresed proteins to a membrane and detecting specific protein molecules with antibodies, which is known as western blotting. Finally, southwestern blots (a renatured protein blot and a DNA probe) are used to study protein-DNA interactions. 

Figure 11. Southwestern blotting experiment showing the size and specificity of plat-inum-DNA binding factor. In (a), unmodified DNA was used as a probe In (b), DNA platinated with cis-DDP at a (D/N), of 0.04.3 was used as a probe. Lane 1, HcLa whole cell extract lane 2, extract from E. coli ly-sogen from Xgtll with no insert lane 3, extract from E. coli lysogen from XPt2 lane 4, extract from E. coli lysogen from XPtl. Reproduced with permission from Ref. 128.

These blotting techniques are known by the names of compass directions (Southern, Northern, Western). Since Southern is a person s name, there s no logic in how the different blots were named. Southern developed a blot in which DNA on the blot is detected by a labeled DNA probe. It was then fairly logical that the next technique developed, detecting RNA on the blot with a DNA probe, should be called a Northern blot. Then things got carried away with the Western, and now the Southwestern, and so on and so on. 

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