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Monitoring the presence of ionic mercury in environmental water by plasmon-enhanced infrared spectroscopy.

Hoang CV, Oyama M, Saito O, Aono M, Nagao T - Sci Rep (2013)

Bottom Line: Here, we adopted single-stranded thiolated 15-base DNA oligonucleotides that are immobilized on the Au surface and show strong specificity to Hg²⁺.The mercury-associated distinct signal is located apart from the biomolecule-associated broad signals and is selectively characterized.For example, with natural water from Lake Kasumigaura (Ibaraki Prefecture, Japan), direct detection of Hg²⁺ with a concentration as low as 37 ppt (37 × 10⁻¹⁰%) was readily demonstrated, indicating the high potential of this simple method for environmental and chemical sensing of metallic species in aqueous solution.

View Article: PubMed Central - PubMed

Affiliation: WPI Center for Materials NanoArchitectonics-MANA, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan. Hoang.ChungVu@nims.go.jp

ABSTRACT
We demonstrate the ppt-level single-step selective monitoring of the presence of mercury ions (Hg²⁺) dissolved in environmental water by plasmon-enhanced vibrational spectroscopy. We combined a nanogap-optimized mid-infrared plasmonic structure with mercury-binding DNA aptamers to monitor in-situ the spectral evolution of the vibrational signal of the DNA induced by the mercury binding. Here, we adopted single-stranded thiolated 15-base DNA oligonucleotides that are immobilized on the Au surface and show strong specificity to Hg²⁺. The mercury-associated distinct signal is located apart from the biomolecule-associated broad signals and is selectively characterized. For example, with natural water from Lake Kasumigaura (Ibaraki Prefecture, Japan), direct detection of Hg²⁺ with a concentration as low as 37 ppt (37 × 10⁻¹⁰%) was readily demonstrated, indicating the high potential of this simple method for environmental and chemical sensing of metallic species in aqueous solution.

No MeSH data available.


(a) Schematic of the structural deformation of DNA owing to the bridge-site adsorption of Hg2+ in the presence of different biomolecules occupying the in-gap space near the folded DNA. Two thymine bases are bridged by an Hg2+ ion after releasing two imino protons. Subsequently the neighboring bonds around the N atoms in the imide structures (marked by red dotted frame) will modify its dipole moment and gives rise to the IR signal change. (b) Evolution of the intensity of the DNA peak (related to the imide bond in thymine) at ω = 1400 cm−1 and biomolecule-related ones at α: 1558 cm−1, β: 1650 cm−1 and γ: 3300 cm−1, by varying the Hg2+ concentration.
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f5: (a) Schematic of the structural deformation of DNA owing to the bridge-site adsorption of Hg2+ in the presence of different biomolecules occupying the in-gap space near the folded DNA. Two thymine bases are bridged by an Hg2+ ion after releasing two imino protons. Subsequently the neighboring bonds around the N atoms in the imide structures (marked by red dotted frame) will modify its dipole moment and gives rise to the IR signal change. (b) Evolution of the intensity of the DNA peak (related to the imide bond in thymine) at ω = 1400 cm−1 and biomolecule-related ones at α: 1558 cm−1, β: 1650 cm−1 and γ: 3300 cm−1, by varying the Hg2+ concentration.

Mentions: Figure 5(a) shows a schematic of the DNA aptamers after the absorption of Hg2+, according to the model reported in the literature348. Owing to the absorption of Hg2+, the DNA aptamers can fold their shape from straight to hairpin-like geometry, giving rise to the distortion of their straight and highly anisotropic feature. The microscopic driving force of this change is the connection of two thymine bases bridged by a Hg2+ ion. As shown in Fig. 5(a) (right) the new N-HgII-N bond is formed by releasing two imino protons into the solution4. This process accompanies with the substantial charge re-distribution near the two N atoms in the imide structures (surrounded by red dotted square), and subsequently leads to the intensity change of the vibrational peak at ωT = 1400 cm−1. Since this mode involves large displacement of the N atom in the imide structure181920, the observed antiabsorption peak at ωT = 1400 cm−1 is most possibly associated with the vibrational mode involving this N atom which sensitively reflects the dipole moment change owing to the formation of N-HgII-N bonds. On the other hand, C = O related band at ω = 1724 cm−1 in the same imide structure shows only slight increase in the absorption intensity (indicated by small red arrows in Fig. 4) suggesting that very small charge re-distribution occurs for the atoms further than the second nearest-neighbor from the HgII atom.


Monitoring the presence of ionic mercury in environmental water by plasmon-enhanced infrared spectroscopy.

Hoang CV, Oyama M, Saito O, Aono M, Nagao T - Sci Rep (2013)

(a) Schematic of the structural deformation of DNA owing to the bridge-site adsorption of Hg2+ in the presence of different biomolecules occupying the in-gap space near the folded DNA. Two thymine bases are bridged by an Hg2+ ion after releasing two imino protons. Subsequently the neighboring bonds around the N atoms in the imide structures (marked by red dotted frame) will modify its dipole moment and gives rise to the IR signal change. (b) Evolution of the intensity of the DNA peak (related to the imide bond in thymine) at ω = 1400 cm−1 and biomolecule-related ones at α: 1558 cm−1, β: 1650 cm−1 and γ: 3300 cm−1, by varying the Hg2+ concentration.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3569543&req=5

f5: (a) Schematic of the structural deformation of DNA owing to the bridge-site adsorption of Hg2+ in the presence of different biomolecules occupying the in-gap space near the folded DNA. Two thymine bases are bridged by an Hg2+ ion after releasing two imino protons. Subsequently the neighboring bonds around the N atoms in the imide structures (marked by red dotted frame) will modify its dipole moment and gives rise to the IR signal change. (b) Evolution of the intensity of the DNA peak (related to the imide bond in thymine) at ω = 1400 cm−1 and biomolecule-related ones at α: 1558 cm−1, β: 1650 cm−1 and γ: 3300 cm−1, by varying the Hg2+ concentration.
Mentions: Figure 5(a) shows a schematic of the DNA aptamers after the absorption of Hg2+, according to the model reported in the literature348. Owing to the absorption of Hg2+, the DNA aptamers can fold their shape from straight to hairpin-like geometry, giving rise to the distortion of their straight and highly anisotropic feature. The microscopic driving force of this change is the connection of two thymine bases bridged by a Hg2+ ion. As shown in Fig. 5(a) (right) the new N-HgII-N bond is formed by releasing two imino protons into the solution4. This process accompanies with the substantial charge re-distribution near the two N atoms in the imide structures (surrounded by red dotted square), and subsequently leads to the intensity change of the vibrational peak at ωT = 1400 cm−1. Since this mode involves large displacement of the N atom in the imide structure181920, the observed antiabsorption peak at ωT = 1400 cm−1 is most possibly associated with the vibrational mode involving this N atom which sensitively reflects the dipole moment change owing to the formation of N-HgII-N bonds. On the other hand, C = O related band at ω = 1724 cm−1 in the same imide structure shows only slight increase in the absorption intensity (indicated by small red arrows in Fig. 4) suggesting that very small charge re-distribution occurs for the atoms further than the second nearest-neighbor from the HgII atom.

Bottom Line: Here, we adopted single-stranded thiolated 15-base DNA oligonucleotides that are immobilized on the Au surface and show strong specificity to Hg²⁺.The mercury-associated distinct signal is located apart from the biomolecule-associated broad signals and is selectively characterized.For example, with natural water from Lake Kasumigaura (Ibaraki Prefecture, Japan), direct detection of Hg²⁺ with a concentration as low as 37 ppt (37 × 10⁻¹⁰%) was readily demonstrated, indicating the high potential of this simple method for environmental and chemical sensing of metallic species in aqueous solution.

View Article: PubMed Central - PubMed

Affiliation: WPI Center for Materials NanoArchitectonics-MANA, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan. Hoang.ChungVu@nims.go.jp

ABSTRACT
We demonstrate the ppt-level single-step selective monitoring of the presence of mercury ions (Hg²⁺) dissolved in environmental water by plasmon-enhanced vibrational spectroscopy. We combined a nanogap-optimized mid-infrared plasmonic structure with mercury-binding DNA aptamers to monitor in-situ the spectral evolution of the vibrational signal of the DNA induced by the mercury binding. Here, we adopted single-stranded thiolated 15-base DNA oligonucleotides that are immobilized on the Au surface and show strong specificity to Hg²⁺. The mercury-associated distinct signal is located apart from the biomolecule-associated broad signals and is selectively characterized. For example, with natural water from Lake Kasumigaura (Ibaraki Prefecture, Japan), direct detection of Hg²⁺ with a concentration as low as 37 ppt (37 × 10⁻¹⁰%) was readily demonstrated, indicating the high potential of this simple method for environmental and chemical sensing of metallic species in aqueous solution.

No MeSH data available.