Transfer of small plasmid DNA fragments from polyacrylamide gels onto nitrocellulose paper

The incorporation into a 7% polyacrylamide gel of a nucleic acid-specific photochemical reagent 4,5',8-trimethylpsoralen at a concentration of 1 mg/dl of acrylamide solution improves both the sensitivity and the efficiency of the transfer of plasmid DNA fragments from the gel onto nitrocellulose filters. This improvement allows detection by blot hybridization of DNA fragments as small as 57 bp long.