EDTA-Tris-DNA solution

Dissolve carrier DNA (e.g., salmon sperm DNA) at a concentration of 50 μg/ml in 50 mM EDTA-Tris (pH 6.0) (i.e., a 1:10 dilution of the 0.5 M EDTA-Tris solution). The DNA used as carrier should be of fairly uniform size and not interfere with the hybridization of the radiolabeled nucleic acid to its target DNA. For most purposes, sonicated or fractionated salmon sperm DNA works well (sonicated salmon sperm DNA 600-5000 bp in length may be prepared as described in Chapter 6, Protocol 10).