Importance of Length and Sequence Order on Magnesium Binding to Surface-Bound Oligonucleotides Studied by Second Harmonic Generation and Atomic Force Microscopy

Holland, Joseph G.; Geiger, Franz M.

doi:10.1021/jp301573g

Cited by 9 publications

(27 citation statements)

References 72 publications

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“…The surface coverage is defined by the Langmuir model as follows. θ = K ads [ C metal ] 1 + K ads [ C metal ] Here, K ads is the binding constant and C metal is the analyte concentration. The assumptions, parameter sensitivities, and full derivations of these equations are discussed in detail in our previously published work. − …”

Section: Background and Theorymentioning

confidence: 99%

Interaction of Cr(III) and Cr(VI) with Hematite Studied by Second Harmonic Generation

et al. 2013

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The fate of chromium in the environment relies heavily on its redox chemistry and interaction with iron oxide surfaces. Atomic layer deposition was used to deposit a 10 nm film of polycrystalline α-Fe2O3 (hematite) onto a fused silica substrate which was analyzed using second harmonic generation (SHG), a coherent, surface-specific, nonlinear optical technique. Specifically, the χ(3) technique was used to investigate the adsorption of Cr(III) and Cr(VI) to the hematite/water interface under flow conditions at pH 4 with 10 mM NaCl. We observed partially irreversible adsorption of Cr(III), the extent of which was found to be dependent on the concentration of Cr(III) ions in solution. This result was confirmed using X-ray photoelectron spectroscopy. The interaction of Cr(III) with hematite is compared with the adsorption of Cr(III) to the silica/water interface, which is the substrate for the ALD-prepared hematite films, and found to be fully reversible under the same experimental conditions. The observed binding constant for Cr(III) interacting with the silica surface was found to be 4.0(6) × 103 M–1, which corresponds to an adsorption free energy of −30.5(4) kJ/mol when referenced to 55.5 M water. The surface charge density at maximum metal ion surface coverage was found to be 0.005(1) C/m2, which corresponds to 1.0 × 1012 ions/cm2 assuming a +3 charge for chromium. In contrast, the observed binding constant for Cr(III) interacting reversibly with the hematite surface was calculated to be 2(2) × 104 M–1, corresponding to an adsorption free energy of −35(2) kJ/mol when referenced to 55.5 M water. The surface charge density at maximum metal ion surface coverage was found to be 0.004(5) C/m2 for the reversibly bound chromium species, which corresponds to 8.3 × 1011 reversibly bound ions per cm2, again assuming a +3 charge of chromium. The data also allows us to estimate that about 6.7 × 1012 Cr(III) ions are irreversibly bound per cm2 hematite at saturation coverage. The results of this investigation suggest that the use of hematite in permeable reactive barriers, for cost-effective chromium remediation, allows for Cr(III) remediation at very low concentrations through adsorptive and redox processes but quickly renders the barriers ineffective at high chromium concentrations due to surface saturation.

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Section: Background and Theorymentioning

confidence: 99%

Interaction of Cr(III) and Cr(VI) with Hematite Studied by Second Harmonic Generation

et al. 2013

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“…Tracking the change of I SHG with increasing electrolyte concentration can produce valuable interface specific parameters, such as surface charge density, interfacial potential, and subsequently thermodynamic binding parameters. By applying an appropriate surface complexation model, the χ (3) method has been successfully utilized to determine these important interface specific parameters for a variety of systems including oxides, ,,,− DNA, − and lipid bilayers …”

Section: Introductionmentioning

confidence: 99%

Interaction of Magnesium Ions with Pristine Single-Layer and Defected Graphene/Water Interfaces Studied by Second Harmonic Generation

et al. 2014

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This work reports thermodynamic and electrostatic parameters for fused silica/water interfaces containing cm(2)-sized graphene ranging from a single layer of pristine graphene to defected graphene. Second harmonic generation (SHG) measurements carried out at pH 7 indicate that the surface charge density of the fused silica/water interface containing the defected graphene (-0.009(3) to -0.010(3) C/m(2)) is between that of defect-free single layer graphene (-0.0049(8) C/m(2)) and bare fused silica (-0.013(6) C/m(2)). The interfacial free energy of the fused silica/water interface calculated from the Lippmann equation is reduced by a factor of 7 in the presence of single-layer pristine graphene, while defected graphene reduces it only by a factor of at most 2. Subsequent SHG adsorption isotherm studies probing the Mg(2+) adsorption at the fused silica/water interface result in fully reversible metal ion interactions and observed binding constants, Kads, of 4(1) - 5(1) × 10(3) M(-1) for pristine graphene and 3(1) - 4(1) × 10(3) M(-1) for defected graphene, corresponding to adsorption free energies, ΔGads, referenced to the 55.5 molarity of water, of -30(1) to -31.1(7) kJ/mol for both interfaces, comparable to Mg(2+) adsorption at the bare fused silica/water interface. Maximum Mg(2+) ion densities are obtained from Gouy-Chapman model fits to the Langmuir adsorption isotherms and found to range from 1.1(5) - 1.5(4) × 10(12) ions adsorbed per cm(2) for pristine graphene and 2(1) - 3.1(5) × 10(12) ions adsorbed per cm(2) for defected graphene, slightly smaller than those of for Mg(2+) adsorption at the bare fused silica/water interface ((2-4) × 10(12) ions adsorbed per cm(2)), assuming the magnesium ions are bound as divalent species. We conclude that the presence of defects in the graphene sheet, which we estimate here to be around 1.3 × 10(11) cm(2), imparts only subtle changes in the thermodynamic and electrostatic parameters quantified here.

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“…Because the initial surface charge density of a 20-mer of DNA was unknown, salt screening experiments, as described in our previous work, were performed. 59 Additionally, tapping mode AFM studies under aqueous conditions, similar to those described in our previous work, 60 were performed to assess the height profiles of the guanine oligonucleotides pre-and post-Y(III) adsorption.…”

Section: Methodsmentioning

confidence: 99%

“…The use of the Gouy− Chapman model to interpret SHG data has been previously explained in terms of detailed sensitivity analyses in our previous work. 55,60 "Salt screening" experiments monitor the electric field of the second harmonic signal (E SHG ) as a function of the bulk NaCl concentration. First, under flow conditions, the number of SHG photons per second, or SHG intensity, I SHG , was measured for a background solution of Millipore water (18.2 MΩ) at constant pH and temperature (pH 5.7, 298 K).…”

Section: Methodsmentioning

confidence: 99%

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Y(III) Interactions with Guanine Oligonucleotides Covalently Attached to Aqueous/Solid Interfaces

Holland

Geiger

2013

J. Phys. Chem. B

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The binding of Y(III) ions to surface-immobilized single-stranded 20-mers of guanine was studied using the Eisenthal χ((3)) technique and AFM. The free energy of binding for Y(III) to the G(20) sequence was found to be -39.5(8) kJ/mol. Furthermore, yttrium binds much more strongly to surface-immobilized oligonucleotides than the divalent metals previously reported. At maximum surface coverage, Y(III) ion densities range between one to three ions bound per strand. Comparatively, Mg(II) binds to the G(20)-functionalized interface in much higher ion densities. This result may be explained, in part, by the larger hydration sphere radius of Y(III) compared to that of Mg(II). The ion loading and binding free energy results, in conjunction with other surface and bulk aqueous phase studies, suggest that a fully hydrated +2 or +3 yttrium ion binds to the oligonucleotides through an outer-sphere mechanism. Tapping mode AFM results indicate that oligonucleotide height does not appreciably decrease following Y(III) binding. These results, together with the low ion densities for Y(III) ions, indicate that Y(III) strand loading may not significantly decrease the intrastrand Coulombic repulsions in order to cause a significant decrease in oligomer height.

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Importance of Length and Sequence Order on Magnesium Binding to Surface-Bound Oligonucleotides Studied by Second Harmonic Generation and Atomic Force Microscopy

Cited by 9 publications

References 72 publications

Interaction of Cr(III) and Cr(VI) with Hematite Studied by Second Harmonic Generation

Interaction of Cr(III) and Cr(VI) with Hematite Studied by Second Harmonic Generation

Interaction of Magnesium Ions with Pristine Single-Layer and Defected Graphene/Water Interfaces Studied by Second Harmonic Generation

Y(III) Interactions with Guanine Oligonucleotides Covalently Attached to Aqueous/Solid Interfaces

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