Solvent effects on the redox potentials of benzoquinone

Wilford, J. H.; Archer, Mary D.

doi:10.1016/0022-0728(85)80094-2

Cited by 40 publications

(31 citation statements)

References 27 publications

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“…The oxidation potentials of the nucleobase G and the nucleoside d G in water are 1.53 and 1.19 V ( vs NHE), respectively (21). Although provides in principle the formalism to calculate the change in free energy for the reaction, the fact that the cyclic voltammograms of most dyes are not fully reversible (54–56), and that that potentials are strongly dependent on solvent (21,57,58), makes it difficult to calculate ΔG values with accuracy. A survey of literature reports shows that fluorescent dyes with an excited state reduction potential ( E * red = E A red + E 0,0 ) above approximately 1.5 V ( vs NHE) are quenched efficiently by guanine.…”

Section: Discussionmentioning

confidence: 99%

Probing the Interaction Between Fluorophores and DNA Nucleotides by Fluorescence Correlation Spectroscopy and Fluorescence Quenching^†

Ranjit

Levitus

2012

Photochem & Photobiology

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We have investigated the association interactions between the fluorescent dyes TAMRA, Cy3B and Alexa-546 and the DNA deoxynucleoside monophosphates by means of fluorescence quenching and fluorescence correlation spectroscopy (FCS). The interactions of Cy3B and TAMRA with the nucleotides produce a decrease in the apparent diffusion coefficient of the dyes, which result in a shift toward longer times in the FCS autocorrelation decays. Our results with Cy3B demonstrate the existence of Cy3B-nucleotide interactions that do not affect the fluorescence intensity or lifetime of the dye significantly. The same is true for TAMRA in the presence of dAMP, dCMP and dTMP. In contrast, the diffusion coefficient of Alexa 546 remains practically unchanged even at high concentrations of nucleotide. These results demonstrate that interactions between this dye and the four dNMPs are not significant. The presence of the negatively charged sulfonates and the bulky chlorine atoms in the phenyl group of Alexa 546 possibly prevent strong interactions that are otherwise possible for TAMRA. The characterization of dye-DNA interactions is important in biophysical research because they play an important role in the interpretation of energy transfer experiments, and because they can potentially affect the structure and dynamics of the DNA.

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Section: Discussionmentioning

confidence: 99%

Probing the Interaction Between Fluorophores and DNA Nucleotides by Fluorescence Correlation Spectroscopy and Fluorescence Quenching^†

Ranjit

Levitus

2012

Photochem & Photobiology

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“…[73,74] It has been observed for many quinones as early as the 1960s that the reduction potential of both one‐electron processes shift to more positive potentials as water is added to the solvent. [73–96] The affect is attributable to strong hydrogen bonding of the reduced compounds with water (or other H‐bonding additives). EPR and UV/Vis spectroscopic experiments on solutions containing reduced quinones also support the hydrogen‐bonding interactions.…”

Section: Discussionmentioning

confidence: 99%

Voltammetry of the liposoluble vitamins (A, D, E and K) in organic solvents

Webster

2011

The Chemical Record

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A review summarizing the voltammetric literature of the liposoluble vitamins A, D, E and K in organic solvents containing supporting electrolyte is presented. Electrochemical studies that were performed by attaching the vitamins to electrode surfaces and performing voltammetric scans in aqueous solutions are also summarized. Vitamins A (retinol and retinal) and D (cholecaliferol and ergocalciferol) undergo chemically irreversible voltammetric oxidation processes in organic solvents to form complicated or unknown compounds that cannot be electrochemically converted back to the starting materials. In contrast to vitamins A and D, vitamins E and K undergo chemically reversible electron-transfer processes that are often coupled to proton-transfer reactions. Vitamin E (a phenol) is voltammetrically oxidized in aprotic organic solvents in a -2e(-)/-H(+) process to form a diamagnetic cation, which is unusually long-lived compared to the analogous cations produced during the oxidation of other phenols. In an aqueous environment, vitamin E is electrochemically oxidized to the hydroquinone in a chemically irreversible -2e(-) process. In low moisture content aprotic solvents, vitamin K (a quinone) is reduced in two one-electron chemically reversible steps to form first a radical anion (semiquinone, at E(1)) and then at more negative potentials a dianion is formed (at E(2)). The dianion is especially prone to strong hydrogen-bonding interactions with trace water present in the organic solvents, resulting in a shift in the formal reduction potential of E(2) to more positive potentials as more water is added to the solvent.

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“…[1] Nature and chemists alike have been tuning electron-donor and -acceptor sites or their environments to obtain ET rates and relative donor-acceptor stabilities that are optimized for a particular task. [3][4][5][6][7][8][9][10] We employed 1,4-benzoquinone (BQ) and 2,3,5,6-tetramethylbenzoquinone (duroquinone, DQ) in this study.A key step in the understanding of ET reactions was the formulation by Marcus [11,12] of the rate of ET (k ET ) as a function of the reaction free energy DG and l, that is, the sum of the inner (l i ) and outer (l o ) sphere reorganization energies [Eq. This work confirms recent experiments [2] that highlight the role of hydrogen-bonding interactions in ET processes.…”

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From Solvent Fluctuations to Quantitative Redox Properties of Quinones in Methanol and Acetonitrile

2006

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Electron-transfer (ET) reactions are among the most fundamental chemical processes and are crucial in a number of important biological processes, such as photosynthesis and cell respiration. [1] Nature and chemists alike have been tuning electron-donor and -acceptor sites or their environments to obtain ET rates and relative donor-acceptor stabilities that are optimized for a particular task. Herein, we report an atomistic theoretical approach based on molecular-dynamics simulations and density functional theory to predict quantitatively the effects of such modifications on the parameters that control ET. This work confirms recent experiments [2] that highlight the role of hydrogen-bonding interactions in ET processes. We have investigated the redox properties of substituted quinones in methanol (MeOH) as a prototypical hydrogen-bonding solvent and in acetonitrile (MeCN) as a solvent with similar dielectric properties but without the specific hydrogen-bonding interactions. In view of their biological importance, it is not surprising that quinones are often employed in electrochemical experiments and that the effects of the solvent and substituents on the redox properties have been well characterized. [3][4][5][6][7][8][9][10] We employed 1,4-benzoquinone (BQ) and 2,3,5,6-tetramethylbenzoquinone (duroquinone, DQ) in this study.A key step in the understanding of ET reactions was the formulation by Marcus [11,12] of the rate of ET (k ET ) as a function of the reaction free energy DG and l, that is, the sum of the inner (l i ) and outer (l o ) sphere reorganization energies [Eq. (1)], in which k is a proportionality constant that depends on the donor and acceptor quantum coupling, T the temperature, and k B the Boltzmann constant. Furthermore, Marcus also derived an approximate expression for l o that provides insight into the nature of the reorganization energy for simple solutes in a homogeneous environment. Based on continuum theory, it provides the nonspecific solvent reorganization energy l s as a function of the effective radii of the donor and the acceptor (r D and r A ), their distance of separation r, the solvent refractive index n D , and the relative permittivity e r [Eq. (2)]. In this work, we obtain estimates for DG and l beyond the continuum approximation by using atomistic simulations.In simulation, the free-energy difference between the oxidized and reduced states of a system can be computed exactly from ensemble averages on the basis of the vertical ionization energy (DE). [13][14][15][16][17][18][19] Such an ensemble average can be computed by using molecular-dynamics (MD) simulations. Herein, we have employed a computationally straightforward, but approximate formula for the free-energy difference DA. This formula can be derived [13][14][15] if the atomistic equivalent of the parabolic functions derived from Marcus theory, which depict the assumed harmonic dependence of the free energy on the vertical energy gap, is introduced as an approximation. This atomistic equivalent is the premise that DE fl...

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Solvent effects on the redox potentials of benzoquinone

Cited by 40 publications

References 27 publications

Probing the Interaction Between Fluorophores and DNA Nucleotides by Fluorescence Correlation Spectroscopy and Fluorescence Quenching^†

Probing the Interaction Between Fluorophores and DNA Nucleotides by Fluorescence Correlation Spectroscopy and Fluorescence Quenching^†

Voltammetry of the liposoluble vitamins (A, D, E and K) in organic solvents

From Solvent Fluctuations to Quantitative Redox Properties of Quinones in Methanol and Acetonitrile

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Solvent effects on the redox potentials of benzoquinone

Cited by 40 publications

References 27 publications

Probing the Interaction Between Fluorophores and DNA Nucleotides by Fluorescence Correlation Spectroscopy and Fluorescence Quenching†

Probing the Interaction Between Fluorophores and DNA Nucleotides by Fluorescence Correlation Spectroscopy and Fluorescence Quenching†

Voltammetry of the liposoluble vitamins (A, D, E and K) in organic solvents

From Solvent Fluctuations to Quantitative Redox Properties of Quinones in Methanol and Acetonitrile

Contact Info

Product

Resources

About

Probing the Interaction Between Fluorophores and DNA Nucleotides by Fluorescence Correlation Spectroscopy and Fluorescence Quenching^†

Probing the Interaction Between Fluorophores and DNA Nucleotides by Fluorescence Correlation Spectroscopy and Fluorescence Quenching^†