Loading dye is mixed with DNA samples for use in agarose gel electrophoresis. It generally contains a dye to assess how "fast" your gel is running and a reagent to render your samples denser than the running buffer (so that the samples sink in the well).
Here's a sample recipe for loading dye.
- Ficoll 400 (in 68-558F)
- Deionized water
- Orange G dye
Dissolve 1.5 g of Ficoll in 10 mL of deionized water. Add very small amounts of Orange G dye such that the loading dye is dark orange. Store in small aliquots at 4°C (room temperature is okay too). To use, add and mix 1/5th volume of loading dye to DNA solutions prior to loading into the wells of gels.
- Orange G: generally runs very fast (<100 bp)
- Bromophenol blue: purple, generally runs at ~500bp (depending on percentage agarose)
- Xylene cyanol: blue, runs at ~4kb