labeling on southern, northern and western blot - (May/02/2001 )

What is the commonly use label (except radioactive thing) for probe for Southern, Northern and Western blot today? And how the label expose to a hard copy?

For the most part, Southerns and Northerns still rely on radioactivity. It is possible to generate probes using either biotinylated or digoxigenin labeled nucleotides. In this case, you would detect the biotin using streptavidin-HRP and the digoxigenin with an anti-digoxigenin antibody (conjugated to HRP). In all three cases (Southern, Northern and Western) using the non-radioactive approaches, a chemilumenescent substrate can be added which when cleaved by the HRP (or enzyme of choice) gives off a pulse of light that can be captured on standard X-ray film.