Plate assay for determination of DNA concentration

A fairly accurate, rapid assay of DNA concentration can be obtained by UV visualization of samples spotted onto ethidium bromide-containing agarose plates.

1) Prepare 0.8% (w/v) agarose/ethidium bromide plates by melting 0.8g agarose in 100ml 1 x TAE buffer (50 x TAE: 2M Tris-acetate, 50mM EDTA), allowing agarose to cool to approximately 50°C and adding 10ul of a 10mg/ml ethidium bromide stock solution (final concentration was 1ug/ml). Plates can be stored for up to 1 month at 4°C in the dark.

2) Prepare standard DNA solutions of known concentrations to cover the concentration range of 10ng/ul to 200ng/ul in distilled water or TE buffer.

3) Spot standards (1ul) carefully onto the surface of a plate in duplicate followed immediately afterwards by the DNA sample of unknown concentration (1ul).

4) Allow spots to absorb for 10 to 15 minutes.

5) Visualise DNA by illumination using a shortwave UV light box.

The concentration of DNA in the unknown sample can be approximated by comparison with the standards.

Dr. Simon Dawson,
Department of Biochemistry,
University of Nottingham,
The Medical School ,
Q.M.C. ,
Clifton Boulevard ,
Nottingham,
NG7 2UH,
U.K..