title: Highly selective DNA-based sensor for lead(II) and mercury(II) ions.
abstract: We have developed a technique for the highly selective and sensitive detection of Pb(2+) and Hg(2+) using a thrombin-binding aptamer (TBA) probe labeled with the donor carboxyfluorescein (FAM) and the quencher 4-([4-(dimethylamino)phenyl]azo)benzoic acid (DABCYL) at its 5' and 3' termini, respectively. The TBA has a random coil structure that changes into a G-quartet structure and a hairpin-like structure upon binding Pb(2+) and Hg(2+) ions, respectively. As a result, the fluorescence decreases through fluorescence resonance energy transfer (FRET) between the fluorophore and quencher. These changes in fluorescence intensity allow the selective detection of Pb(2+) and Hg(2+) ions at concentrations as low as 300 pM and 5.0 nM using this TBA probe in the presence of phytic acid and a random DNA/NaCN mixture, respectively. The linear correlation existed between the fluorescence intensity and the concentration of Pb(2+) and Hg(2+) over the range of 0.5-30 nM (R(2) = 0.98) and 10-200 nM (R(2) = 0.98), respectively. To the best of our knowledge, this is the first example of a single DNA-based sensor that allows the detection of both Hg(2+) and Pb(2+) ions. This simple and cost-effective probe was also applied to separately determine Pb(2+) in soil samples and spiked Hg(2+) in pond samples.
authors.affiliation: Department of Chemistry, National Taiwan University, 1, Section 4, Roosevelt Road, Taipei, Taiwan.
authors.forename: Chi-Wei
authors.initials: CW
authors.lastname: Liu
authors.forename: Chih-Ching
authors.initials: CC
authors.lastname: Huang
authors.forename: Huan-Tsung
authors.initials: HT
authors.lastname: Chang
mesh_terms: D052157:Aptamers, Nucleotide / Q000737:chemistry; D004247:DNA / Q000737:chemistry*; D005452:Fluoresceins / Q000737:chemistry; D031541:Fluorescence Resonance Energy Transfer; D007477:Ions / Q000737:chemistry; D007854:Lead / Q000032:analysis*; D008628:Mercury / Q000032:analysis*; D010833:Phytic Acid / Q000737:chemistry; D013050:Spectrometry, Fluorescence / Q000379:methods*
chemical_list: D052157:Aptamers, Nucleotide; D005452:Fluoresceins; D007477:Ions; C081676:thrombin aptamer; D007854:Lead; C024098:6-carboxyfluorescein; D010833:Phytic Acid; D004247:DNA; D008628:Mercury