In gel electrophoresis experiment loading dye or buffer is widely used with DNA and RNA to follow the migration of samples. Typical loading buffer composed of two dyes bromophenol blue and xylene cyanol FF. It can be used for both agarose and polyacrylamide gel. Composition of 6x loading dye or buffer:Recipe no 1:
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0.03% bromophenol blue,
10 mM Tris-HCl (pH 7.6),
0.03% xylene cyanol FF,
60% glycerol,
60 mM EDTA.
Recipe no 2:
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25mg bromophenol blue (0.25%),
25mg xylene cyanol (0.25%),
4g sucrose (40%),
adjust volume to 10 ml with H2O.
presence of glycerol or sucrose in the solution ensures that the same sample forms a layer at the bottom of the well and the EDTA included in the solution binds divalent metal ions and inhibits metal dependent nucleases.
In 1% agarose gels bromophenol blue co-migrates with ~300 bp DNA and xylene cyanol FF co-migrates with ~4000 bp DNA. Store at +4°C up to 12 months.
In 5 volumes of DNA sample add 1 volume of 6X DNA Loading Dye.
See also,
http://openwetware.org/wiki/Agarose_gel_loading_dye
