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Issue 10, 2013
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Chromenoquinoline-based thiol probes: a study on the quencher position for controlling fluorescent OffOn characteristics

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Abstract

The design, synthesis and thiol sensing ability of chromenoquinoline-based fluorescent probes 4, 5 and 6 are reported here. The relative position of the maleimide moiety was varied along the chromenoquinoline fluorophore to decrease the background fluorescence. Lower background fluorescence in probes 4 and 6 was rationalized by the smaller kr/knr values compared to that of probe 5. An intramolecular charge transfer (ICT) mechanism was proposed for quenching and the extent was dependent on the position of the maleimide quencher. Fluorescent OffOn characteristics were evaluated by theoretical calculations. All probes were selective only towards thiol containing amino acids. Thiol sensing by probes 4 and 6 were much better compared to 5. Probe 4 displayed a better fluorescence response for less hindered thiol (185-, 223- and 156-fold for Hcy, Cys and GSH, respectively), while for probe 6, a higher enhancement in fluorescence was observed with more hindered thiols (180-, 205- and 245-fold for Hcy, Cys and GSH, respectively). The better response to bulkier thiol, GSH by probe 6 was attributed to the steric crowding at the C-4 position and bulkiness of the GSH group which force the succinimide unit to be in a nearly orthogonal conformation. This spatial arrangement was important in reducing the fluorescence quenching ability of the succinimide moiety. The application of probes 4, 5 and 6 was demonstrated by naked eye detection thiols using a 96-well plate system as well as by live-cell imaging.

Graphical abstract: Chromenoquinoline-based thiol probes: a study on the quencher position for controlling fluorescent Off–On characteristics

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Publication details

The article was received on 10 Nov 2012, accepted on 02 Jan 2013 and first published on 03 Jan 2013


Article type: Paper
DOI: 10.1039/C2OB27192C
Citation: Org. Biomol. Chem., 2013,11, 1691-1701
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    Chromenoquinoline-based thiol probes: a study on the quencher position for controlling fluorescent OffOn characteristics

    D. Kand, A. M. Kalle and P. Talukdar, Org. Biomol. Chem., 2013, 11, 1691
    DOI: 10.1039/C2OB27192C

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