title: Ethynyl and π-stacked thymine-Hg2+-thymine base pairs enhanced fluorescence quenching via photoinduced electron transfer and simple and sensitive mercury ion sensing.
abstract: Ethynyl triggered enhanced fluorescence quenching effect was first reported based on photoinduced electron transfer (PET) between fluorophore and ethynyl. Ethynyl and 6-carboxyl-fluorescein (FAM) were labeled at the 5'- and 3'-termini of a poly d(T) sequence containing three thymine units, respectively. In the presence of Hg(2+), Hg(2+) binds to two thymine residues through T-Hg(2+)-T interactions and the formed T-Hg(2+)-T base pairs bring FAM and ethynyl from two matched sequences into close proximity. On the one hand, π-stacked T-Hg(2+)-T mediates and accepts electron transfer of the excited state of FAM and quenches the fluorescence through PET. On the other hand, π-stacked interactions between ethynyl and FAM also provide a de-excitation process for the excited state of FAM via PET and trigger an enhanced fluorescence quenching. On the basis of fluorescence quenching, a simple, rapid, and sensitive Hg(2+) sensor was constructed; under optimum conditions, a good linear relationship was obtained over the concentration range of 5-150 nM for Hg(2+) and a very low detection limit (0.42 nM) was reached. The developed system was further designed as a cysteine (Cys) sensor based on fluorescence recovery resulted from the strong interaction between Cys and Hg(2+); the proposed Cys sensor has a linear range of 10-550 nM and a detection limit of 2.5 nM. The two sensors were used for analysis of real samples and the satisfactory results were achieved.
authors.affiliation: Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, PR China.
authors.forename: Jian Rong
authors.initials: JR
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, PR China.
authors.forename: Wei Tao
authors.initials: WT
authors.lastname: Huang
authors.affiliation: Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, PR China.
authors.forename: Ai Lian
authors.initials: AL
authors.lastname: Zeng
authors.affiliation: Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, PR China. Electronic address: luohq@swu.edu.cn.
authors.forename: Hong Qun
authors.initials: HQ
authors.lastname: Luo
authors.affiliation: Key Laboratory of Eco-environments in Three Gorges Reservoir Region (Ministry of Education), School of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, PR China. Electronic address: linb@swu.edu.cn.
authors.forename: Nian Bing
authors.initials: NB
authors.lastname: Li
mesh_terms: D015374:Biosensing Techniques / Q000379:methods*; D003545:Cysteine / Q000032:analysis* / Q000737:chemistry; D007477:Ions; D008628:Mercury / Q000032:analysis* / Q000737:chemistry; D009841:Oligonucleotides / Q000737:chemistry*; D013050:Spectrometry, Fluorescence / Q000379:methods*; D013941:Thymine / Q000737:chemistry*
chemical_list: D007477:Ions; D009841:Oligonucleotides; D008628:Mercury; D003545:Cysteine; D013941:Thymine
keywords: Enhanced fluorescence quenching; Ethynyl; Photoinduced electron transfer; Thymine–Hg(2+)–thymine