Limits...
A Decaheme Cytochrome as a Molecular Electron Conduit in Dye-Sensitized Photoanodes.

Hwang ET, Sheikh K, Orchard KL, Hojo D, Radu V, Lee CY, Ainsworth E, Lockwood C, Gross MA, Adschiri T, Reisner E, Butt JN, Jeuken LJ - Adv Funct Mater (2015)

Bottom Line: The system is assembled by forming a densely packed MtrC film on an ultra-flat gold electrode, followed by the adsorption of approximately 7 nm TiO2 nanocrystals that are modified with a phosphonated bipyridine Ru(II) dye (RuP).The step-by-step construction of the MtrC/TiO2 system is monitored with (photo)electrochemistry, quartz-crystal microbalance with dissipation (QCM-D), and atomic force microscopy (AFM).Photocurrents are dependent on the redox state of the MtrC, confirming that electrons are transferred from the TiO2 nanocrystals to the surface via the MtrC conduit.

View Article: PubMed Central - PubMed

Affiliation: School of Biomedical Sciences, University of Leeds Leeds, LS2 9JT, UK E-mail: L.J.C.Jeuken@leeds.ac.uk ; The Astbury Centre for Structural Molecular Biology, University of Leeds Leeds, LS2 9JT, UK.

ABSTRACT

In nature, charge recombination in light-harvesting reaction centers is minimized by efficient charge separation. Here, it is aimed to mimic this by coupling dye-sensitized TiO2 nanocrystals to a decaheme protein, MtrC from Shewanella oneidensis MR-1, where the 10 hemes of MtrC form a ≈7-nm-long molecular wire between the TiO2 and the underlying electrode. The system is assembled by forming a densely packed MtrC film on an ultra-flat gold electrode, followed by the adsorption of approximately 7 nm TiO2 nanocrystals that are modified with a phosphonated bipyridine Ru(II) dye (RuP). The step-by-step construction of the MtrC/TiO2 system is monitored with (photo)electrochemistry, quartz-crystal microbalance with dissipation (QCM-D), and atomic force microscopy (AFM). Photocurrents are dependent on the redox state of the MtrC, confirming that electrons are transferred from the TiO2 nanocrystals to the surface via the MtrC conduit. In other words, in these TiO2/MtrC hybrid photodiodes, MtrC traps the conduction-band electrons from TiO2 before transferring them to the electrode, creating a photobioelectrochemical system in which a redox protein is used to mimic the efficient charge separation found in biological photosystems.

No MeSH data available.


Related in: MedlinePlus

QCM-D results with frequency (black line, left axis) and dissipation (gray line, right axis) against time for a gold crystal at 21 °C. The gold surface is modified with 8-OH/8-NH3+ (ratio 80/20) SAM prior to the experiments. The plots shown are representative of triplicate experiments. As indicated, the gold crystal is consecutively incubated with: MtrC (0.87 × 10−6m) in buffer (20 × 10−3m MOPS, 30 × 10−3m Na2SO4 at pH 7.4); buffer only; EDTA (25 × 10−3m EDTA at pH 7.4); RuP-TiO2 (0.2 mg mL−1) in EDTA and, finally, EDTA.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4493899&req=5

fig05: QCM-D results with frequency (black line, left axis) and dissipation (gray line, right axis) against time for a gold crystal at 21 °C. The gold surface is modified with 8-OH/8-NH3+ (ratio 80/20) SAM prior to the experiments. The plots shown are representative of triplicate experiments. As indicated, the gold crystal is consecutively incubated with: MtrC (0.87 × 10−6m) in buffer (20 × 10−3m MOPS, 30 × 10−3m Na2SO4 at pH 7.4); buffer only; EDTA (25 × 10−3m EDTA at pH 7.4); RuP-TiO2 (0.2 mg mL−1) in EDTA and, finally, EDTA.

Mentions: The binding of MtrC onto the modified gold was further characterized using quartz-crystal microbalance with dissipation (QCM-D, Figure5), which provides information on both the mass and viscoelastic properties of the adsorbed protein layer through the frequency shift and the energy dissipation of the resonating crystal. MtrC adsorption saturates at −19 ± 1 Hz, which, according to the Sauerbrey equation, corresponds to ca. 0.34 ± 0.02 μg cm−2. Rinsing with buffer does not remove MtrC, indicating it is irreversibly adsorbed on the surface. Assuming the mass of MtrC is increased by about 25% due to water entrapped within the protein matrix,[37] the MtrC coverage can be estimated at 3.6 ± 0.2 pmol cm−2. The dimensions of MtrC are predicted to be 3.5 nm × 6 nm × 7 nm by comparison to the structure of the close homologue MtrF for which a crystal structure is available.[31] Depending on the orientation of MtrC on the surface, a closely packed monolayer would consist of 6.0 pmol cm−2 (upright orientation) or 3.0 pmol cm−2 (prone orientation).


A Decaheme Cytochrome as a Molecular Electron Conduit in Dye-Sensitized Photoanodes.

Hwang ET, Sheikh K, Orchard KL, Hojo D, Radu V, Lee CY, Ainsworth E, Lockwood C, Gross MA, Adschiri T, Reisner E, Butt JN, Jeuken LJ - Adv Funct Mater (2015)

QCM-D results with frequency (black line, left axis) and dissipation (gray line, right axis) against time for a gold crystal at 21 °C. The gold surface is modified with 8-OH/8-NH3+ (ratio 80/20) SAM prior to the experiments. The plots shown are representative of triplicate experiments. As indicated, the gold crystal is consecutively incubated with: MtrC (0.87 × 10−6m) in buffer (20 × 10−3m MOPS, 30 × 10−3m Na2SO4 at pH 7.4); buffer only; EDTA (25 × 10−3m EDTA at pH 7.4); RuP-TiO2 (0.2 mg mL−1) in EDTA and, finally, EDTA.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493899&req=5

fig05: QCM-D results with frequency (black line, left axis) and dissipation (gray line, right axis) against time for a gold crystal at 21 °C. The gold surface is modified with 8-OH/8-NH3+ (ratio 80/20) SAM prior to the experiments. The plots shown are representative of triplicate experiments. As indicated, the gold crystal is consecutively incubated with: MtrC (0.87 × 10−6m) in buffer (20 × 10−3m MOPS, 30 × 10−3m Na2SO4 at pH 7.4); buffer only; EDTA (25 × 10−3m EDTA at pH 7.4); RuP-TiO2 (0.2 mg mL−1) in EDTA and, finally, EDTA.
Mentions: The binding of MtrC onto the modified gold was further characterized using quartz-crystal microbalance with dissipation (QCM-D, Figure5), which provides information on both the mass and viscoelastic properties of the adsorbed protein layer through the frequency shift and the energy dissipation of the resonating crystal. MtrC adsorption saturates at −19 ± 1 Hz, which, according to the Sauerbrey equation, corresponds to ca. 0.34 ± 0.02 μg cm−2. Rinsing with buffer does not remove MtrC, indicating it is irreversibly adsorbed on the surface. Assuming the mass of MtrC is increased by about 25% due to water entrapped within the protein matrix,[37] the MtrC coverage can be estimated at 3.6 ± 0.2 pmol cm−2. The dimensions of MtrC are predicted to be 3.5 nm × 6 nm × 7 nm by comparison to the structure of the close homologue MtrF for which a crystal structure is available.[31] Depending on the orientation of MtrC on the surface, a closely packed monolayer would consist of 6.0 pmol cm−2 (upright orientation) or 3.0 pmol cm−2 (prone orientation).

Bottom Line: The system is assembled by forming a densely packed MtrC film on an ultra-flat gold electrode, followed by the adsorption of approximately 7 nm TiO2 nanocrystals that are modified with a phosphonated bipyridine Ru(II) dye (RuP).The step-by-step construction of the MtrC/TiO2 system is monitored with (photo)electrochemistry, quartz-crystal microbalance with dissipation (QCM-D), and atomic force microscopy (AFM).Photocurrents are dependent on the redox state of the MtrC, confirming that electrons are transferred from the TiO2 nanocrystals to the surface via the MtrC conduit.

View Article: PubMed Central - PubMed

Affiliation: School of Biomedical Sciences, University of Leeds Leeds, LS2 9JT, UK E-mail: L.J.C.Jeuken@leeds.ac.uk ; The Astbury Centre for Structural Molecular Biology, University of Leeds Leeds, LS2 9JT, UK.

ABSTRACT

In nature, charge recombination in light-harvesting reaction centers is minimized by efficient charge separation. Here, it is aimed to mimic this by coupling dye-sensitized TiO2 nanocrystals to a decaheme protein, MtrC from Shewanella oneidensis MR-1, where the 10 hemes of MtrC form a ≈7-nm-long molecular wire between the TiO2 and the underlying electrode. The system is assembled by forming a densely packed MtrC film on an ultra-flat gold electrode, followed by the adsorption of approximately 7 nm TiO2 nanocrystals that are modified with a phosphonated bipyridine Ru(II) dye (RuP). The step-by-step construction of the MtrC/TiO2 system is monitored with (photo)electrochemistry, quartz-crystal microbalance with dissipation (QCM-D), and atomic force microscopy (AFM). Photocurrents are dependent on the redox state of the MtrC, confirming that electrons are transferred from the TiO2 nanocrystals to the surface via the MtrC conduit. In other words, in these TiO2/MtrC hybrid photodiodes, MtrC traps the conduction-band electrons from TiO2 before transferring them to the electrode, creating a photobioelectrochemical system in which a redox protein is used to mimic the efficient charge separation found in biological photosystems.

No MeSH data available.


Related in: MedlinePlus