A simple staining method for dna and rna blotted on a membrane using a polyethyleneimine-enzyme conjugate

We describe a new method for the detection of nucleic acids fixed on a membrane involving enzyme-conjugated polyethyleneimine. This method is based on the strong ionic interaction of the cationic polymer, polyethyleneimine (aziridine), with nucleic acids. Sensitivities of 10 pg for DNA and 1 ng for rRNA were achieved in slot-spot blotting experiments. DNA fragments blotted onto a membrane by Southern transfer can be stained after hybridization with a labeled nucleic acid probe. By combining this method with a non-isotopic detection system, the positions of probe hybridized and non-hybridized signals were visualized as distinct colors on the same membrane without superimposing any other image. This technique should have wide application for the detection of nucleic acids fixed on membranes in blot-hybridization experiments.