Loading Dyes | DNA Electrophoresis Buffers

Using the correct loading dyes and DNA electrophoresis buffers in your gel electrophoresis setup is critical for obtaining accurate and reliable results. View recommendations for Thermo Scientific loading and tracking dyes and buffers.

Loading dyes are used to prepare DNA samples for loading on agarose or polyacrylamide gels. Loading dyes serve multiple purposes in gel electrophoresis:

1. To make the DNA samples visible during the loading process, making it easier to verify that the sample is in the well
2. To increase the density of the sample to make it sink into the wells of the gel, preventing loss of sample
3. To visualize the progress of sample migration through the gel, allowing the operator to determine when optimal separation is achieved

Ready-to-use (RTU) DNA ladders come prepackaged with a loading dye.

Loading dyes in gel electrophoresis consist of:

• Glycerol, to help ensure that the sample easily sinks into the well and remains there until electrophoresis begins
• EDTA, which binds divalent metal ions that may interfere with electrophoresis. EDTA also stops metal-dependent enzymatic reactions such as DNA degradation by nucleases
• Tracking dyes (bromophenol blue, xylene cyanol FF, and/or orange G), which help monitor the progress of electrophoresis by the migration of the dyes

Loading dye	Description of tracking dyes		Format
		Two-color tracking Contains bromophenol blue and xylene cyanol FF	6X DNA loading dye Order here 6X DNA loading dye with SDS Order here
		Single color tracking Contains bromophenol blue	6X MassRuler Loading Dye Order here
		Two-color tracking Contains xylene cyanol FF and orange	6X Orange DNA Loading Dye Order here
		Three-color tracking Contains bromophenol blue, xylene cyanol FF and orange G	6X TriTrack Loading Dye Order here

Orange G: Apparent MW in TAE <50 bp; apparent MW in TBE <50 bp
Bromophenol blue: Apparent MW in TAE <370 bp; apparent MW in TBE <220 bp
Xylene cyanol FF: Apparent MW in TAE <4,160 bp; apparent MW in TBE <3,030 bp

We offer two Thermo Scientific buffers for DNA electrophoresis: Tris-acetate-EDTA (TAE) and Tris-borate-EDTA (TBE).

• TAE buffer is generally used for electrophoresis of longer nucleic acid fragments of >1 kb. It is compatible with enzymatic reactions and recommended for preparative gel electrophoresis.
• TBE buffer is commonly used with small DNA fragments, as it provides better separation for sizes of <1 kb.