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Ethidium Monoazide Bromide (EMA)

Ethidium monoazide bromide is a fluorescent nucleic acid binding dye. The dye, after photolysis, binds covalently to nucleic acids. It can be used for viability PCR.

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5 mg
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Product Description

Ethidium monoazide bromide (EMA) is a fluorescent nucleic acid stain with a photoaffinity label. The dye, after photolysis, binds covalently to nucleic acids.The dye has been used to footprint drug binding sites on DNA2, to modify plasmid DNA,3,4 and for labeling yeast cells for leukocyte phagocytosis assays5. A particularly useful application of the dye is to label dead cells in a mixed population of live and dead cells. Because EMA is relatively impermeant to live cells, it selectively binds DNA in dead cells. Photolysis renders the dead cell DNA covalently labeled with the dye. One can then wash and fix the cell preparation for analysis by microscopy, fluorescence plate reader or flow cytometry. The major advantage of this method is that researchers can avoid extensive manipulation of live pathogenic organisms.7

EMA has been used to differentiate between viable and dead bacteria by 5′-nuclease PCR.8

For viability PCR applications, Biotium also offers propidium monoazide iodide (PMA, catalog numbers 40013 and 40019) as well as our new and improved viability PCR dye, PMAxx™ (catalog number 40069). PMA and PMAxx™ are less membrane permeant than EMA and therefore more selective for dead cell labeling for qPCR quantitation of viable bacteria.9

For photoactivation of PMA, PMAxx™ or EMA dye, we recommend the use of Biotium’s PMA-Lite™ LED Photolysis Device (E90002), which is designed to conduct photolysis under controlled conditions.

  • Absorption (pH 3) = 464 nm
  • λExEm (after photocrosslinking to nucleic acid) = 510/600 nm6
  • Orange solid soluble in DMF, or ethanol
  • Store desiccated at 4oC or -20oC and protect from light, especially in solution
  • C21H18BrN5
  • MW: 420
  • [58880-05-0]



1. J Mol Biol 92, 319 (1975).

2. Euro J Biochem 182, 437 (1989).

3. J Biol Chem 257, 13205 (1982).

4. J Biol Chem 259, 11090 (1984);.

5. Cytometry 11, 610 (1990).

6. For excitation and emission of the dye before and after binding to DNA/RNA and photolysis, please see Nucleic Acids Res.5, 4891 (1978).

7. Cytometry, 12, 133 (1991).

8. Biotechniques, 34, 804 (2003)

9. J. Microb. Meth., 67, 310 (2006).


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