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.

NEP (1-30 μM; 6 hours) has no or little cytotoxicity in HepG2 and PC12 cells[1]. NEP (10 μM; 4 hours) causes the fluorescence intensity to decrease gradually in PC12 cells pretreated with 6-OHDA (0, 50, 100, and 200 μM; for 30 min)[1]. NEP contains a dithiarsolane moiety (five-membered As-S ring) as the receptor of VDPs. In the presence of VDPs, NEP displays a strong green fluorescence signal produced by the cyclic dithiarsolane cleavage and subsequent intramolecular cyclization to liberate the fluorophore. NEP maintains a reliable fluorescence response within the range of pH 7-10[1].

NEP (10 μM; for 4 h) causes the obvious green signal in zebrafishes (4 day old)[1].