Fluorescent Probe For Cysteine Research Articles

Exploring cysteine regulation in cancer cell survival with a highly specific “Lock and Key” fluorescent probe for cysteine

To probe the regulatory roles of cysteine (Cys) in cancer cell survival, a highly selective and sensitive fluorescent Cys probe SiR was developed by employing a novel "lock and key" strategy, which allows Cys to be detected without any interference or probe consumption caused by the intracellular high concentration of glutathione (GSH). Using SiR, we confirmed that inhibiting cystine (Cys2) transporter system xc - to deplete intracellular Cys is more efficient than inhibiting glutamate-cysteine ligase GCL to deplete intracellular GSH for sensitizing cancer cells to chemotherapy. Moreover, with the probe, a possible self-protection mechanism of cancer cells was indicated: when extracellular Cys sources are blocked, cancer cells could still survive by multidrug resistance protein transporter (Mrp1)-mediated export of intracellular GSH/GSSG as sources to supply intracellular Cys for resisting detrimental oxidative stress. Based on this finding, we further confirmed that abrogating the self-protection mechanism is an even more efficient strategy for sensitizing cancer cells to chemotherapy.

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A new simple and readily available fluorescent probe for cysteine (Cys) was reported. This probe is based on an excited-state intramolecular proton transfer (ESIPT) dye and uses two acrylate moieties as the Cys reaction sites to promote signal changes. Importantly, this probe shows rapid fluorescent turn-on signal changes for Cys with high selectivity and sensitivity over various analytes including the similar structured homocysteine (Hcy) and glutathione (GSH) in aqueous solution under mild conditions. The detection limit of this probe for Cys was found to be as low as 0.80 μM, which is far below the normal content of Cys (30–200 μM) in cells. This probe was also successfully applied for bioimaging of intracellular Cys in living cells with low cytotoxicity. Besides, a paper test strip system was developed with this probe for a convenient detection of Cys.

A simple and readily available fluorescent turn-on probe for cysteine detection and bioimaging in living cells

A new simple and readily available fluorescent probe for cysteine (Cys) was reported. This probe is based on an excited-state intramolecular proton transfer (ESIPT) dye and uses two acrylate moieties as the Cys reaction sites to promote signal changes. Importantly, this probe shows rapid fluorescent turn-on signal changes for Cys with high selectivity and sensitivity over various analytes including the similar structured homocysteine (Hcy) and glutathione (GSH) in aqueous solution under mild conditions. The detection limit of this probe for Cys was found to be as low as 0.80 μM, which is far below the normal content of Cys (30–200 μM) in cells. This probe was also successfully applied for bioimaging of intracellular Cys in living cells with low cytotoxicity. Besides, a paper test strip system was developed with this probe for a convenient detection of Cys.

Fluorescent Probes for the Selective Detection of Cysteine in Water

Two novel fluorescent chemodosimeters will be presented for the selective detection of cysteine over homocysteine and glutathione in aqueous solvent. First, a rhodamine-based fluorescent probe (1) will be reported. Masked with a para-hydroxybenzyl alcohol (HBA) unit, probe 1 initially showed a weak fluorescence but displayed a strong fluorescence through a series of reactions of Michael addition and intramolecular cyclization of cysteine, followed by deprotection of HBA. The caged probe (1) exhibited a selective and sensitive response toward cysteine over homocysteine and glutathione in HEPES buffer. Secondly, a fluorescein-based fluorescent probe will be discussed. A bromoacetyl functionalized fluorescein chemodosimeter (2) was utilized as a fluorescent probe for cysteine. The probe showed a selective and sensitive response to cysteine over homocysteine and glutathione in aqueous buffer through a rapid cyclization reaction. When cysteine was added, a fast fluorescence turn-on change of 2 was observed and applied to the in-vivo imaging of cysteine.

A squaraine and Hg2+-based colorimetric and “turn on” fluorescent probe for cysteine

A novel squaraine derivative (SQ-1) was synthesized and characterized for the determination of cysteine. Binding with Hg2+ as a fluorescent quencher to SQ-1 leads to absorption and emission turn-off. More significantly, the SQ-1–Hg2+ complex exhibits a dual-channel chromofluorogenic responses to biologically important cysteine with a high sensitivity and selectivity over other natural amino acids, along with a low detection limit of 36.7nM.

Selective detection of cysteine over homocysteine and glutathione by a bis(bromoacetyl)fluorescein probe

A bromoacetyl functionalized fluorescein chemodosimeter (1) was utilized as a fluorescent probe for cysteine. The probe showed a selective and sensitive response to cysteine over homocysteine and glutathione in aqueous buffer through a rapid cyclization reaction. When cysteine was added, a fast fluorescence turn-on change of 1 was observed, thus allowing cysteine to be discriminated from other biothiols and micromolar concentrations of cysteine to be detected by the naked eye.