Merck, SML1961-5MG, EF5

Biochem/physiol Actions
A 2-nitroimidazole-based hypoxia marker
EF5 is a 2-nitroimidazole-based hypoxia marker corresponding to a pentafluorinated derivative of the hypoxic cell-radiation sensitizer etanidazole. Under low oxygen (hypoxic) condition, reductive activation of its 2-nitroimidazole moiety leads to enhanced EF5 adduct formation with protein thiols and reduced glutathione. The pentafluorination derivatization substantially decreases the proportion of low molecular weight hydrolytic fragmentation of the adducts, making EF5 superior to etanidazole when utilized as a hypoxia marker by immunohistological staining.