A New Turn on Fluorescent Probe for Selective Detection of Cysteine/Homocysteine.

A new fluorescent probe (probe 1) was developed for recognition of cysteine (Cys) and homocysteine (Hcy). Probe 1 exhibited a large absorption peak blue-shift (107 nm) as well as enhanced fluorescence responses to Cys/Hcy based on cyclization of thiol containing amino acids with aldehydes, inhibiting the C = N isomerization-induced quenching process by an intramolecular hydrogen bond. The detection mechanism was proved by (1)H NMR and mass spectrometry analysis.