NucPE1, a nuclear-localized fluorescent hydrogen peroxide, is specifically localized to cellular nuclei without appended targeting moieties.

NucPE1 features two major visible region absorptions (λabs=468 nm, ε=27,300 M-1cm-1; λabs=490 nm, ε=26,000 /(M·cm)) and a weak emission (λem=530 nm, Φ=0.117). Reaction of NucPE1 with H2O2 triggers a fluorescence increase upon its conversion to fluorophore NucPE1, which possesses one major absorption band at 505 nm (ε=19,100 /(M·cm)) with enhanced emission (λem=530 nm, Φ=0.626). NucPE1 selectively accumulates in the nuclei of a variety of mammalian cell lines as well as in whole model organisms like C. clegans, where it can respond to subcellular changes in H2O2 fluxes.

NucPE1 imaging reveals a reduction in nuclear H2O2 levels in worms overexpressing sir-2.1 compared to wildtype congeners.