NEP, a turn-on fluorescent probe employing the intramolecular charge transfer (ICT) mechanism, facilitates the detection of vicinal dithiol-containing proteins (VDPs). Notably, NEP exhibits exceptional selectivity towards VDPs in live cells and in vivo and manifests a robust green fluorescence signal at λ ex λ em =430 535 nm. Furthermore, NEP bears promise for the potential diagnosis and study of parkinsonism.