title: G-quadruplex DNAzyme-based Hg2+ and cysteine sensors utilizing Hg2+-mediated oligonucleotide switching.
abstract: A simple and sensitive colorimetric Hg(2+) detection method is reported, based on the Hg(2+)-mediated structural switch of an unlabeled oligonucleotide strand. In the absence of Hg(2+), the oligonucleotide strand forms a stem-loop. A G-rich sequence in the strand is partially caged in the stem-loop structure and cannot fold into a G-quadruplex. In the presence of Hg(2+), T-Hg(2+)-T coordination chemistry leads to the formation of another stem-loop structure and the release of the G-rich sequence. The released sequence folds into a G-quadruplex, which binds hemin to form catalytically active G-quadruplex DNAzymes. This is detected as an absorbance increase in a H(2)O(2)-2,2'-azinobis(3-ethylbenzothiozoline)-6-sulfonic acid (ABTS) reaction system using UV-vis absorption spectroscopy. This simple colorimetric sensor can detect aqueous Hg(2+) at concentrations as low as 9.2 nM with high selectivity. Based on the strong binding interaction between Hg(2+) and the sulfur-containing amino acid cysteine (Cys), and the competition between Cys and a oligonucleotide for Hg(2+), the proposed Hg(2+)-sensing system can be further exploited as a Cys-sensing method. The method has a detection limit for Cys of 19 nM.
authors.affiliation: State Key Laboratory of Medicinal Chemical Biology, Nankai University, Tianjin, PR China.
authors.forename: Shu-Min
authors.initials: SM
authors.lastname: Jia
authors.forename: Xiao-Fei
authors.initials: XF
authors.lastname: Liu
authors.forename: Ping
authors.initials: P
authors.lastname: Li
authors.forename: De-Ming
authors.initials: DM
authors.lastname: Kong
authors.forename: Han-Xi
authors.initials: HX
authors.lastname: Shen
mesh_terms: D052160:Benzothiazoles; D015374:Biosensing Techniques; D003124:Colorimetry / Q000379:methods*; D003545:Cysteine / Q000737:chemistry*; D021881:DNA, Catalytic / Q000737:chemistry*; D004785:Environmental Pollutants / Q000032:analysis*; D054856:G-Quadruplexes; D006427:Hemin / Q000737:chemistry; D057230:Limit of Detection; D008628:Mercury / Q000032:analysis*; D009841:Oligonucleotides / Q000737:chemistry; D013451:Sulfonic Acids / Q000737:chemistry; D013844:Thiazoles / Q000737:chemistry
chemical_list: D052160:Benzothiazoles; D021881:DNA, Catalytic; D004785:Environmental Pollutants; D009841:Oligonucleotides; D013451:Sulfonic Acids; D013844:Thiazoles; C002502:2,2'-azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid; D006427:Hemin; D008628:Mercury; D003545:Cysteine