The southwestern blot, is a lab technique that involves identifying as well as characterizing DNA-binding proteins [1] by their ability to bind to specific oligonucleotide probes.
Southwestern blotting was first described by Brian Bowen, Jay Steinberg, U.K. Laemmli, and Harold Weintraub in 1979.
To begin, proteins of interest are prepared for the SDS-PAGE technique and subsequently loaded onto the gel for separation on the basis of molecular size.
One membrane filter can be stained to see the protein bands that were created from gel electrophoresis and the other is used in the actual process of hybridizing with prepared 32P radioactively labeled specific oligonucleotide probes.
"Southwestern blot mapping" is a time-efficient way of identifying DNA-binding proteins and specific sites on the genomic DNA that they interact with.