A novel near-infrared and naked-eye fluorescence probe with a large stokes shift for specific detection of cysteine and its application in living cells.

• We developed a near-infrared fluorescence probe, TMN-NH 2 -Cys. • The probe exhibited a large stokes shift. • The selective detection of Cys was confirmed by a visible colour change. • The probe exhibited a low cytotoxicity. • It could be applied to the imaging of endogenous Cys with fluorescence enhancement. Cysteine (Cys) is a sulfur-containing nutritional amino acid that plays an important role in the physiological function of living systems. We developed a near-infrared fluorescence probe, TMN-NH 2 -Cys. Upon the treatment with Cys, TMN-NH 2 -Cys exhibited a large Stokes shift (180 nm) and a visible colour change. TMN-NH 2 -Cys can selective detect Cys over homocysteine and glutathione. The probe was synthesised by a simple and high yielding three-step reaction. In addition, the probe exhibited a low cytotoxicity, and could be applied to the imaging of endogenous Cys with fluorescence enhancement. [ABSTRACT FROM AUTHOR]