Detection of small quantities of double stranded DNA by enhanced fluorescence of substituted aldehyde modified polydeoxynucleotide-ethidium bromide complexes.

A method for the detection of small amounts of double stranded DNA by a simple incubation procedure involving the reaction of the nucleotide bases in DNA with chloroacetaldehyde is described. Following incubation, the presence of DNA may be visualized by the orange fluorescence emitted when ethidium bromide (EtBr) is added. Alternatively, the aldehyde/DNA mixture may be separated by agarose gel electrophoresis and individual double stranded DNA visualized by exposing the gel to ethidium bromide and observing the orange ultraviolet light induced fluorescence of the aldehyde modified double stranded ethidium bromide complex (Waring, M.J. (1965) J. Mol. Biol. 13, 269-282). At least a 20-fold increase in the detection of double stranded DNA is possible by this procedure. An important aspect of this method is that the visualization of single stranded DNA is not enhanced.