NEP (VDP-green (NEP)) is a turn-on fluorescent probe based on the intramolecular charge transfer (ICT) mechanism for sensing vicinal dithiol-containing proteins (VDPs). NEP exhibits high selectivity toward VDPs in live cells and in vivo and displays a strong green fluorescence signal (λ ex /λ em =430/535 nm). NEP has the potential for parkinsonism.