Protein Blotting: Principles and Applications

Protein blotting was initially introduced in the late 1970s to identify protein antigens that bound to spectfic antibodies (1 ,2 ) In this procedure, a complex protein fraction was separated by electrophoresis and the proteins transferred and bound to a membrane, which was then probed with a radiolabeled antibody This concept and procedure were based on blotting and hybridization methods developed for DNA by Southern (3 ) (and logically called Southern blotting), which was subsequently modified for RNA (4 ) (less logtcally called Northern blotting by some authors). It is, therefore, not surprising that the protem/antibody procedure was called Western blotting (2 ), and that Southwestern (protein/DNA) and Far Western (or West Western) (protem/protem) procedures have since been developed In addition, it is possible to apply proteins to the membrane in solution (dot-blotting), or to transfer them directly from tissues (squash blots and tissue prints), whereas the development of microscale protein sequencing and ammo-acid analysts has allowed the use of blotting to purify and characterize individual components of highly complex mixtures