DNA Load Dye

Purpose: many commercially-prepared DNA loading dyes contain ridiculously high concentrations of xylene cyanol and bromophenol blue.  The intense dye bands can obscure faint DNA bands.  We therefore prepare separate DNA load dyes containing lower amounts of either xylene cyanol or bromphenol blue.  The separate dye preparations make it possible to choose the dye least likely to obscure particular bands of interest.

Prepare in water

15% (w/v) Ficoll 400 (Sigma# F2637)

200 mM EDTA

200 mM Tris pH 8

0.015% (w/v) xylene cyanol or bromophenol blue

The resulting load dye is 6x.

We usually prepare about 40 ml of load dye for the whole lab roughly once every four years.