Commonly utilized in molecular biology and biochemistry laboratories around the world, ethidium is best known in its bromide form. Though the substance is pharmacologically active, it is most familiar as a nucleic acid stain and a component of electrophoretic gels.

View a second image of Ethidium Bromide

Ethidium bromide, also sometimes referred to as ethobromide, homidium bromide, and dromilac, appears as dark red crystals when it is pure and dry. When utilized in the laboratory, however, and examined under either long or short ultraviolet (UV) wavelengths of light, a reddish-orange fluorescence can be easily detected. A relatively large, flat molecule, ethidium bromide appears somewhat similar to a DNA base pair and can easily insert into strands of the material due to its chemical structure. Thus, when bound to double-stranded DNA molecules, increased fluorescence of ethidium bromide occurs.

Despite the usefulness of ethidium bromide, many other fluorescent dyes have been developed for detecting nucleic acid components in recent years. The reason for this progression is largely due to the fact that ethidium bromide use is plagued by many possible hazards. For instance, although it is not regulated as a hazardous waste, the material is a possible carcinogen with strong mutagenic and poisonous properties, so it should always be handled with great care and be disposed of as a biohazard. Moreover, inhalation of ethidium bromide dust could cause serious side effects since the stain is known to be a severe respiratory irritant. Dermal contact with the substance, which should also be avoided, is easy to detect in the laboratory because a light to deep purple stain that forms on the skin is readily observable.

Questions or comments? Send us an email.

© 1998-2025 by Michael W. Davidson and The Florida State University. All Rights Reserved. No images, graphics, scripts, or applets may be reproduced or used in any manner without permission from the copyright holders. Use of this website means you agree to all of the Legal Terms and Conditions set forth by the owners.

This website is maintained by our
Graphics & Web Programming Team
in collaboration with Optical Microscopy at the
National High Magnetic Field Laboratory.

Last modification: Friday, Nov 13, 2015 at 02:19 PM

Access Count Since January 23, 2004: 14612

All of the images in this gallery were captured with a QImaging Retiga camera system.
For more information on these cameras, use the button below to access
the QImaging website:

For more information on microscope manufacturers,
use the buttons below to navigate to their websites: