Ethidium Bromide

2,7-diamino-N-ethyl-6-phenyl-phenanthridinium bromide, also given as 2,7-diamino-10-ethyl-6-phenyl phenanthridinium bromide, also given as 2,7-diamino-10-ethyl-9-phenyl phenanthridinium bromide. FW 394.3, C21H20N3Br.

Intercalative DNA stain used in microbiology to stain gels and visualize DNA. It is weakly fluorescent in solution, but its quantum yield increases 30-fold upon binding to DNA. This is likely due to rigid stabilization of the phenyl moiety.