"Southwestern blot mapping" is a time-efficient way of identifying DNA-binding proteins and specific sites on the genomic DNA that they interact with.
# First, proteins are prepared with a mixture that exposes them to the denaturing sodium dodecyl sulfate (SDS) agent. This exposure not only converts the proteins from a folded conformation to an unfolded conformation but also establishes uniform charge among them as well contributing to the ease of separation on a size basis using polyacrylamide gel (PAGE). 
# Second, in contrast to the previous step, proteins on the resulting gel are to be renatured by removal of SDS. This serves to bring the proteins back to the form that ideally  maximizes interactions later on in the procedure.
# Third, blotting takes place onto nitrocellulose membranes using methods for and properties of diffusion. 
# Fourth, shifting to probe creation, particular restriction enzymes are chosen and used on the region of DNA under study to produce fragments of appropriate but different sizes.
# Fifth, the fragments are radioactively labeled and given appropriate time for binding to previously prepared blots. Once this time has elapsed, the blots are washed to remove any DNA that was not able to bind.   
# Finally, the specifically-bound DNA is eluted from each individual protein-DNA complex and analyzed by another application of polyacrylamide gel electrophoresis.