46065 Sigma

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 Registry 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: soluble10 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)


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.

Other Notes

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


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.


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.

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).

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Laboratory Gloves
Safety & Documentation

Safety Information

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


Certificate of Analysis

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


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

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