Agarose gel loading buffer

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).

Material

Density

• Ficoll
• sucrose

Colour

dye	0.5-1.5% agarose	2.0-3.0% agarose*	order # example
xylene cyanol	4000-5000 bp	750 bp	Sigma X4126
bromophenol blue	400-500 bp	100 bp	Sigma B8026
Orange G	<100 bp	?	?

*sieving agarose

Recipes

The precise amount of dye is not important. However, it is crucial that you prevent overlay of dye and expected DNA size. For example, if you are expecting a genotyping band of 200-400nt, you shouldn't use bromophenol blue since it will obscure your product. In this case, you should use a larger dye like xylene cyanol.

Ficoll & Orange G

• Ficoll 400
• 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.

Sucrose & xylene cyanol / bromophenol blue

• 25mg bromophenol blue or xylene cyanol
• 4g sucrose
• H₂O to 10mL

Store at 4°C to avoid mould growing in the sucrose. 10mL of loading buffer will last for years.

Specific recipes

• Knight:Loading dye