The background fluorescence is greatest when viewing EtBr-stained gels with a DR transilluminator. As a result, the DR is not as sensitive as a UV device for the detection of EtBr-stained DNA.
The background problem can be minimized by using a lower concentration of EtBr to stain the gel. We have found that staining a gel with an EtBr solution of 0.1 ug / mL (rather than the typical 1.0 ug / mL) significantly enhances the viewability of DNA bands. Using these conditions it is possible to see about 5 ng of dsDNA by eye and about 600 pg using a CCD or Polaroid camera. The best viewability by eye is achieved in a well darkened room and a few seconds should be allowed for the eyes to adjust to the low light levels.
Shown below are 2 images of a DNA gel stained with EtBr using our modified protocol and viewed on a DR transilluminator.
