Distance Dependence of Electron Transfer Across Peptides with Different Secondary Structures:  The Role of Peptide Energetics and Electronic Coupling

Shin, Yeung-gyo K.; Newton, Marshall D.; Isied, Stephan S.

doi:10.1021/ja020358q

Cited by 151 publications

(205 citation statements)

References 72 publications

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“…A value of β = 1.4 Å −1 was originally suggested for proteins, while more accurate estimates also take the protein secondary structure into account. 36 88 which has consistently been used in several studies. 89−93 Determining Marcus Parameters.…”

Section: ■ Models and Methodsmentioning

confidence: 99%

Charge Transfer in Model Peptides: Obtaining Marcus Parameters from Molecular Simulation

et al. 2012

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Charge transfer within and between biomolecules remains a highly active field of biophysics. Due to the complexities of real systems, model compounds are a useful alternative to study the mechanistic fundamentals of charge transfer. In recent years, such model experiments have been underpinned by molecular simulation methods as well. In this work, we study electron hole transfer in helical model peptides by means of molecular dynamics simulations. A theoretical framework to extract Marcus parameters of charge transfer from simulations is presented. We find that the peptides form stable helical structures with sequence dependent small deviations from ideal PPII helices. We identify direct exposure of charged side chains to solvent as a cause of high reorganization energies, significantly larger than typical for electron transfer in proteins. This, together with small direct couplings, makes long-range superexchange electron transport in this system very slow. In good agreement with experiment, direct transfer between the terminal amino acid side chains can be dicounted in favor of a two-step hopping process if appropriate bridging groups exist. ■ INTRODUCTIONCharge transfer is a fundamental phenomenon in physical chemistry, enjoying strong and consistent scientific interest for more than fifty years. 1 Understanding charge transfer in complex and flexible biomolecules is crucial for a huge variety of processes, from cellular respiration and photosynthesis to DNA damage and repair. 2−4 Describing it accurately has turned out to be particularly challenging, both to experimentalists and theoreticians. Biochemical charge transfer involves the directed movement of electrons over large distances (multiple nanometers) through macromolecules, typically proteins or large heterogeneous multiprotein assemblies. These processes involve dynamical changes that occur on a time scale spanning multiple orders of magnitude, from subpicosecond changes in electronic structure to microsecond or even slower conformational changes. Only recently has the complicated interplay between atomic structural fluctuations and electron dynamics become a focus for charge transfer studies in biochemical systems, 5−9 building onto earlier work on model systems. 10−15 This fact, combined with the large system dimensions and difficult experimental conditions, explains why many open questions on electron transfer (ET) in biomolecules remain. Therefore, simpler model systems to study some aspects of ET have gained popularity, and theoretical models based on computer simulations have become important tools to help interpret experiments and gain a better understanding of the structure and function of the involved molecules. 16−22 An important model system in the study of charge transfer processes has always been peptide systems. Extensive experimental work was done by Isied et al., who have studied ET over distances of 8−32 Å via spectroscopical techniques and determined the properties of polyproline II helices as ET bridges. 27−34 This wo...

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Section: ■ Models and Methodsmentioning

confidence: 99%

Charge Transfer in Model Peptides: Obtaining Marcus Parameters from Molecular Simulation

et al. 2012

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“…Electron transfer though peptide secondary structures has been of great interest for clarifying efficient electron-transfer reactions occurring in protein assemblies in nature [1][2][3][4][5]. Especially, electron transfer through helices has attracted much attention because it is believed that α-helical segments play an essential role in mediating an electron and determining its direction in biological systems [6].…”

Section: Introductionmentioning

confidence: 99%

Distance dependence of long‐range electron transfer through helical peptides

Kai

Takeda

Morita

et al. 2007

Journal of Peptide Science

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Helical peptides of 8mer, 16mer, and 24mer carrying a disulfide group at the N -terminal and a ferrocene moiety at the C-terminal were synthesized, and they were self-assembled on gold by a sulfur-gold linkage. Infrared reflection-absorption spectroscopy and ellipsometry confirmed that they formed a monolayer with upright orientation. Cyclic voltammetry showed that the electron transfer from the ferrocene moiety to gold occurred even with the longest 24mer peptide. Chronoamperometry and electrochemical impedance spectroscopy were carried out to determine the standard electron transfer rate constants. It was found that the dependence of the electron-transfer rates on the distance was significantly weak with the extension of the chain from 16mer to 24mer (decay constant β = 0.02-0.04). This dependence on distance cannot be explained by an electron tunneling mechanism even if increased hydrogen-bonding cooperativity or molecular dynamics is considered. It is thus concluded that this long-range electron transfer is operated by an electron hopping mechanism.

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“…As a result, the GS pilin has a strong electrostatic field along the helix axis that is predicted to accelerate the rates of electron transfer through the helical peptide (Feliciano et al ., 2012). Furthermore, the GS pilin lacks the more insulating β‐strand conformations (Shin et al ., 2003), a structural property that contributes to creating a peptide environment optimal for charge transport (Feliciano et al ., 2012). Consistent with these predictions, the GS pilin assembly is conductive whereas PAK pilins form insulating T4P (Lampa‐Pastirk et al ., 2016).…”

Section: Geobacter T4p: a Paradigm In Structure And Functionmentioning

confidence: 99%

Harnessing the power of microbial nanowires

Reguera

2018

Microbial Biotechnology

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SummaryThe reduction of iron oxide minerals and uranium in model metal reducers in the genus Geobacter is mediated by conductive pili composed primarily of a structurally divergent pilin peptide that is otherwise recognized, processed and assembled in the inner membrane by a conserved Type IVa pilus apparatus. Electronic coupling among the peptides is promoted upon assembly, allowing the discharge of respiratory electrons at rates that greatly exceed the rates of cellular respiration. Harnessing the unique properties of these conductive appendages and their peptide building blocks in metal bioremediation will require understanding of how the pilins assemble to form a protein nanowire with specialized sites for metal immobilization. Also important are insights into how cells assemble the pili to make an electroactive matrix and grow on electrodes as biofilms that harvest electrical currents from the oxidation of waste organic substrates. Genetic engineering shows promise to modulate the properties of the peptide building blocks, protein nanowires and current‐harvesting biofilms for various applications. This minireview discusses what is known about the pilus material properties and reactions they catalyse and how this information can be harnessed in nanotechnology, bioremediation and bioenergy applications.

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Distance Dependence of Electron Transfer Across Peptides with Different Secondary Structures: The Role of Peptide Energetics and Electronic Coupling

Cited by 151 publications

References 72 publications

Charge Transfer in Model Peptides: Obtaining Marcus Parameters from Molecular Simulation

Charge Transfer in Model Peptides: Obtaining Marcus Parameters from Molecular Simulation

Distance dependence of long‐range electron transfer through helical peptides

Harnessing the power of microbial nanowires

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