Ethidium bromide (EtBr), identified by its CAS number 1239-45-8, is a synthetic fluorescent intercalating agent that has been fundamental to molecular biology techniques for decades, particularly in the visualization of nucleic acids. Its chemical structure, a planar phenanthridine ring system with an ethylamino group, allows it to intercalate between the base pairs of double-stranded DNA (dsDNA). This intercalation is the key to its utility as a DNA visualization dye.

The fluorescence of Ethidium Bromide is significantly enhanced upon binding to DNA. When EtBr molecules are free in solution, their fluorescence is relatively low. However, upon intercalation into the DNA helix, the molecule becomes more rigid and its environment becomes hydrophobic, shielding it from fluorescence-quenching water molecules. This results in a dramatic increase in fluorescence intensity, typically emitting an orange-red light when excited by ultraviolet (UV) radiation, usually around 300-360 nm. This property makes it an excellent tool for detecting DNA in agarose or polyacrylamide gels after electrophoresis.

Detection of DNA bands stained with EtBr is commonly performed using a UV transilluminator. The gel, typically run in a buffer containing EtBr or stained post-electrophoresis, is placed on the transilluminator. The emitted orange fluorescence from the DNA bands is then captured using photography or a digital imaging system. The sensitivity of EtBr allows for the detection of DNA fragments as small as a few nanograms per band. While highly effective, it's crucial to remember that EtBr is also a known mutagen, and proper handling procedures are essential.

Understanding the excitation and emission spectra of EtBr is vital for selecting appropriate imaging equipment. The absorption maxima are typically observed at 210 nm and 285 nm in aqueous solution, with fluorescence emission peaking around 605 nm when bound to DNA. This specific spectral profile means that standard UV transilluminators and filters are suitable for visualization. Researchers at NINGBO INNO PHARMCHEM CO.,LTD. provide Ethidium Bromide, adhering to quality standards that ensure reliable performance for these critical detection applications. While alternatives exist, the established protocols and cost-effectiveness of EtBr continue to make it a relevant reagent in many laboratories, provided safety measures are rigorously followed.