46065 Sigma-Aldrich

Ethidium bromide

for fluorescence, ≥95.0% (HPLC)

Synonym: 3,8-Diamino-5-ethyl-6-phenylphenanthridinium bromide, EtBr, Homidium bromide

  • CAS Number 1239-45-8

  • Empirical Formula (Hill Notation) C21H20BrN3

  • Molecular Weight 394.31

  •  Beilstein/REAXYS Number 3642536

  •  EC Number 214-984-6

  •  MDL number MFCD00011724

  •  PubChem Substance ID 57650683



Related Categories Biochemicals and Reagents, Detection, Fluorescent Enzyme Substrates, Fluorescent Enzyme Substrates for Electrophoresis, Fluorescent Probes, Labels, Particles and Stains,
grade   for fluorescence
assay   ≥95.0% (HPLC)
mp   260-262 °C (dec.) (lit.)
solubility   H2O: 10 mg/mL, opaque, very dark red
fluorescence   λex 480 nm; λem 620 nm in H2O
  λex 530 nm; λem 600 nm in 50 mM phosphate buffer pH 7.0 (upon binding to DNA)


General description

Ethidium bromide (EtBr) undergoes complexation with nucleic acids (DNA and RNA) specifically to the saturated sites. These complexes decomposes by employing a cation-exchange resin. It has been reported to inhibit the production of mitochondrial RNA in HeLa cells. On interaction with helical polynucleotides under high salt medium, it forms fluorescent complex (having high fluorescence quantum yield).


Ethidium bromide (EtBr) is the most commonly used nucleic acid stain for PAGE or agarose gel electrophoresis. The fluorescence of EtBr increases 21-fold upon binding to double-stranded RNA and 25-fold on binding double-stranded DNA so that destaining the background is not necessary with a low stain concentration (10 μg/ml). Ethidium bromide has been used in a number of fluorimetric assays for nucleic acids. It has been shown to bind to single-stranded DNA (although not as strongly) and triple-stranded DNA. Because of its ability to bind to DNA, EtBr is an inhibitor of DNA polymerase.

Frameshift mutagen which intercalates double-stranded DNA and RNA.

Ethidium bromide has been used to prepare fluorescent stock solution for the evaluation of cell viability during the live/dead assay of adipose-derived stem cells (ADSCs) seeded on irradiated hydrogels.

Biochem/physiol Actions

Ethidium bromide intercalates double-stranded DNA and RNA and acts as a frameshift mutagen. It can also be used in conjunction with acridine orange to differentiate between viable, apoptotic and necrotic cells.


For staining a gel after electrophoresis, dilute a sample of the stock solution to 0.5 μg/ml with water and incubate the gel for 15-30 min. Destaining is usually not needed but can be carried out in water for 15 min if decreased background is necessary. The DNA bands can then be detected on a UV light box (254 nm wavelength). Ethidium bromide can also be incorporated into the gel and running buffer at 0.5 μg/ml and visualized immediately after electrophoresis.

Other Notes

Intercalating agent and fluorescent label for DNA. Review; Destruction and decontamination of solutions

Safety & Documentation

Safety Information

Signal word 
Hazard statements 
UN 2811PIH 6.1 / PGI
WGK Germany 


Certificate of Analysis (COA)

Please Enter a Lot Number
Protocols & Articles


Nancy-520 for DNA Detection and Quantitation

Nancy-520 is a fluorescent stain for double stranded DNA (dsDNA) on agarose electrophoresis gels, with higher sensitivity than ethidium bromide and an easy, fast, and robust staining procedure. It is...
Monika Baeumle
BioFiles 2009, 4.1, 4.
Keywords: Catalytic combustion detector, Electrophoresis

Peer-Reviewed Papers


Related Products

related product

Product #


Add to Cart

01494 Nancy-520, suitable for RT-PCR, ≥97.0% (HPCE)

Technical Service:

Our team of scientists has experience in all areas of research including Life Science, Material Science, Chemical Synthesis, Chromatography, Analytical and many others.

Bulk Ordering & Pricing:

Need larger quantities for your development, manufacturing or research applications?