Ethidium homodimer

Ethidium homodimer (EthD-1) is a high-affinity fluorescent nucleic acid dye commonly used to stain mammals, bacteria, yeast, and fungi. Ethidium homodimer binds to DNA or RNA, enhancing fluorescence more than 30 times. The Ethidium homodimer has a strong positive charge, so it cannot cross cell membranes and stain living cells; But the Ethidium homodimer can cross the disordered region of the dead cell membrane to reach the nucleus and embed the DNA double strand to produce red fluorescence. Therefore, Ethidium homodimer is a relatively sensitive nucleic acid stain that can accurately detect nucleic acids in solution or in decomposing cells. Ethidium homodimer binds DNA, Ex/Em=528/617 nm[1].