Flavin-sensitized electrode system for oxygen evolution using photo-electrocatalysis

Sarma, Rupam; Sloan, Madison JoAnne; Miller, Anne‐Frances

doi:10.1039/c6cc01479h

Cited by 8 publications

(7 citation statements)

References 37 publications

(51 reference statements)

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“…However, flavin's utility has already been appreciated based on empirical efforts, and elegant studies have employed flavins immobilized on electrodes or carbon nanotubes 85 as well as in a mobile phase of batteries. 86 Moreover, the electronic transitions we calculated are also being exploited in cases where flavins are in use as sensitizers for photochemical cells 85,87,88 or sensors. 89 While proteins tune flavin reactivity via multiple noncovalent interactions, we have demonstrated that even modification at a single position can change the way electron density is redistributed within the molecule as well as the associated energies.…”

Section: Concluding Remarks and Implications For Applicationsmentioning

confidence: 99%

Tuning the Quantum Chemical Properties of Flavins via Modification at C8

et al. 2021

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Flavins are central to countless enzymes but display different reactivities depending on their environments. This is understood to reflect modulation of the flavin electronic structure. To understand changes in orbital natures, energies, and correlation over the ring system, we begin by comparing seven flavin variants differing at C8, exploiting their different electronic spectra to validate quantum chemical calculations. Ground state calculations replicate a Hammett trend and reveal the significance of the flavin π-system. Comparison of higher-level theories establishes CC2 and ACD(2) as methods of choice for characterization of electronic transitions. Charge transfer character and electron correlation prove responsive to the identity of the substituent at C8. Indeed, bond length alternation analysis demonstrates extensive conjugation and delocalization from the C8 position throughout the ring system. Moreover, we succeed in replicating a particularly challenging UV/Vis spectrum by implementing hybrid QM/MM in explicit solvents. Our calculations reveal that the presence of nonbonding lone pairs correlates with the change in the UV/Vis spectrum observed when the 8-methyl is replaced by NH2, OH, or SH. Thus, our computations offer routes to understanding the spectra of flavins with different modifications. This is a first step toward understanding how the same is accomplished by different binding environments.

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Section: Concluding Remarks and Implications For Applicationsmentioning

confidence: 99%

Tuning the Quantum Chemical Properties of Flavins via Modification at C8

et al. 2021

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“…Reduction potentials were determined by cyclic voltammetry of 1 mM solutions of PAB, AB, and BA using a glassy carbon working electrode, platinum wire counter electrode, and Ag/AgCl reference electrode (catalog nos. CH104, CHI115, and CHI111 from CH Instruments Inc., Austin, TX) in 5 ml of 500 mM potassium phosphate, 100 mM KCl, pH 7.0 (47). Saturated quinhydrone in the same buffer was also analyzed to calibrate the system at 84 Ϯ 10 mV and 22°C (48).…”

Section: Reduction Potentials Of Exogenous Donorsmentioning

confidence: 99%

Equilibrium and ultrafast kinetic studies manipulating electron transfer: A short-lived flavin semiquinone is not sufficient for electron bifurcation

Hoben

Lubner

Ratzloff

et al. 2017

Journal of Biological Chemistry

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Flavin-based electron transfer bifurcation is emerging as a fundamental and powerful mechanism for conservation and deployment of electrochemical energy in enzymatic systems. In this process, a pair of electrons is acquired at intermediate reduction potential ( intermediate reducing power), and each electron is passed to a different acceptor, one with lower and the other with higher reducing power, leading to "bifurcation." It is believed that a strongly reducing semiquinone species is essential for this process, and it is expected that this species should be kinetically short-lived. We now demonstrate that the presence of a short-lived anionic flavin semiquinone (ASQ) is not sufficient to infer the existence of bifurcating activity, although such a species may be necessary for the process. We have used transient absorption spectroscopy to compare the rates and mechanisms of decay of ASQ generated photochemically in bifurcating NADH-dependent ferredoxin-NADP oxidoreductase and the non-bifurcating flavoproteins nitroreductase, NADH oxidase, and flavodoxin. We found that different mechanisms dominate ASQ decay in the different protein environments, producing lifetimes ranging over 2 orders of magnitude. Capacity for electron transfer among redox cofactors charge recombination with nearby donors can explain the range of ASQ lifetimes that we observe. Our results support a model wherein efficient electron propagation can explain the short lifetime of the ASQ of bifurcating NADH-dependent ferredoxin-NADP oxidoreductase I and can be an indication of capacity for electron bifurcation.

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“…This plot shows three anodic (A′, B′, and C′) and three cathodic (A, B, and C) peaks. These correspond to the oxygen evolution process (A-A′) [ 28 ], the ferricyanide/ferrocyanide redox couple (B–B′) [ 26 ], and the reduction of oxygenated species (C–C′) [ 29 ] on the working electrode, as reported in the literature. The reversibility of these reactions relates to their voltammogram features: peaks A-A′ represent an irreversible reduction reaction, peaks B–B′ show a quasi-reversible reaction, and the C–C′ peaks, an irreversible oxidation reaction.…”

Section: Resultsmentioning

confidence: 95%

Low-cost smartphone-controlled potentiostat based on Arduino for teaching electrochemistry fundamentals and applications

Cordova-Huaman

Jauja-Ccana

Rosa-Toro

2021

Heliyon

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Accessibility to potentiostats is crucial for research development in electrochemistry, but their cost is the principal drawback for their massive use. With the aim to provide an affordable alternative for resource-constrained communities, we present a low-cost, portable electrochemical workstation that integrates an open-source potentiostat based on Arduino and a smartphone application. This graphical user interface allows easy control of electrochemical parameters and real-time visualization of the results. This potentiostat can perform the most used electrochemical techniques of cyclic and linear voltammetry and chronoamperometry, with an operating range of AE225 μA and AE1.50 V, and results that are comparable with those obtained with commercial potentiostats. Three applications reported here demonstrate the capacity and the good performance of this low-cost potentiostat as a teaching tool: identification of redox pairs, electrochemical characterization of pencil graphite electrodes, and detection of heavy metals using an electrodeposited film of bismuth on the pencil graphite electrode. Furthermore, detailed schemes of the device and its software are entirely available, expecting to provide an open-source potentiostat easy to replicate to further support education in electrochemical fundamentals and instrumentation.

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Flavin-sensitized electrode system for oxygen evolution using photo-electrocatalysis

Cited by 8 publications

References 37 publications

Tuning the Quantum Chemical Properties of Flavins via Modification at C8

Tuning the Quantum Chemical Properties of Flavins via Modification at C8

Equilibrium and ultrafast kinetic studies manipulating electron transfer: A short-lived flavin semiquinone is not sufficient for electron bifurcation

Low-cost smartphone-controlled potentiostat based on Arduino for teaching electrochemistry fundamentals and applications

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