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In this work, a dicyanoisophorone-based turn-on fluorescent probe, DCIP , for highly selective and sensitive detection of cysteine was designed based on nucleophilic substitution mechanism. Moreover, compared with typical cysteine probes, DCIP showed great selectivity and sensitivity for cysteine over other amino acids including the similar structured homocysteine (Hcy) and glutathione (GSH). Further, the detection limit toward cysteine was calculated to be as low as 0.70 μM. In addition, the utility of DCIP as a bioanalytical molecular tool was demonstrated by fluorescence imaging of biothiols in living cells. [ABSTRACT FROM AUTHOR]

Development of an excited-state intramolecular proton transfer (ESIPT)-based fluorescent probe ( BIHM ) for selective recognition to homocysteine (Hcy) over glutathione (GSH), cysteine (Cys) and other amino acids is described. The distinctive fluorescence response of BIHM to Hcy over Cys is interpreted by density functional theory calculations. Bioimaging experiments of intracellular Hcy detection manifest the great potential utility of the probe. [ABSTRACT FROM AUTHOR]

• 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]

• Four chloroacetate based fluorescent probes were synthesized for a comparative study. • H4 displayed great ratiometric property and selectivity for cysteine. • H4 was applied for real-time cysteine imaging in HeLa cells. The specific detection of cysteine (Cys) over homocysteine (Hcy), glutathione (GSH) and other amino acids is of great significance for studying its biological functions as well as for the diagnosis of related diseases. Chloroacetyl group was often used as a reaction site for cysteine fluorescent probes for its sensitivity and selectivity. However, high background fluorescence and low stability are common problems encountered by such probes. Here, four chloroacetyl group based fluorescent probes (C1 , C2 , C3 , and H4) was synthesized for a comparative study. We found that the inefficient quenching ability of chloroacetyl group turned into an advantage when connected with a ratiometric fluorophore. With the modification of chloroacetyl group, probe H4 displayed excellent ratiometric property and great selectivity for Cys, the stability was also improved. Additionally, the probe was successfully applied for quantitative detection of Cys in fetal bovine serum and real-time imaging in living HeLa cells with low toxicity. [ABSTRACT FROM AUTHOR]