3-1.3.2 Ethidium Bromide Staining:

The IUPAC name for EtBr is 2, 7-diamino-10-ethyl-9-phenylphenanthridiniumbromide. It is commonly used as a fluorescent dye for nucleic acid staining. It binds as well as intercalates with nucleic acid (mainly with major and minor groove of DNA) and gives orange fluorescence under UV radiation from 500 – 590 nm. Usually EtBr may be added in warm agarose gel before solidification. When DNA or RNA samples are run in agarose gel electrophoresis EtBr molecules will bind with nucleic acids and help in detection under UV light. The post staining can also be done for nucleic acid detection.

Fig 3-1.3.2: Ethidium bromide	Fig. 3-1.3.2.1: Agarose gel stained with EtBr

Ethidium bromide (EtBr) is a potent mutagen and carcinogen. Dyes to stain nucleic acids such as SYBR green, SYBR Safe etc are safer to use instead of EtBr.

Polyacrylamide gel can be used for separation of Nucleic acids and post staining of the gel with EtBr is done for detection. The sensitivity of EtBr staining is of nano-molar level.