Electron Transfer through H-bonded Peptide Assemblies

Kraatz, Heinz‐Bernhard; Bediako-Amoa, Irene; Gyepi-Garbrah, Samuel H.; Sutherland, Todd C.

doi:10.1021/jp047900c

Cited by 61 publications

(96 citation statements)

References 92 publications

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“…Hydrogen bonding could induce stable secondary structures which might assist electron transfer reactions. [37,38] Hole hopping along amide groups [39,40] in a-helices composed of Ala and a-aminoisobutyric acid (Aib) has been shown to be efficient over long distances. [41] Attempts to understand and exploit conformations and electronic interactions in oligoamides composed of ferrocenes are subjects of the following report.…”

Section: Introductionmentioning

confidence: 99%

Oligonuclear Ferrocene Amides: Mixed‐Valent Peptides and Potential Redox‐Switchable Foldamers

Siebler

Linseis

Gasi

et al. 2011

Chemistry A European J

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Trinuclear ferrocene tris-amides were synthesized from an Fmoc- or Boc-protected ferrocene amino acid, and hydrogen-bonded zigzag conformations were determined by NMR spectroscopy, molecular modelling, and X-ray diffraction. In these ordered secondary structures orientation of the individual amide dipole moments approximately in the same direction results in a macrodipole moment similar to that of α-helices composed of α-amino acids. Unlike ordinary α-amino acids, the building blocks in these ferrocene amides with defined secondary structure can be sequentially oxidized to mono-, di-, and trications. Singly and doubly charged mixed-valent cations were probed experimentally by Vis/NIR, paramagnetic ¹H NMR and Mössbauer spectroscopy and investigated theoretically by DFT calculations. According to the appearance of intervalence charge transfer (IVCT) bands in solution, the ferrocene/ferrocenium amides are described as Robin-Day class II mixed-valent systems. Mössbauer spectroscopy indicates trapped valences in the solid state. The secondary structure of trinuclear ferrocene tris-amides remains intact (coiled form) upon oxidation to mono- and dications according to DFT calculations, while oxidation to the trication should break the intramolecular hydrogen bonding and unfold the ferrocene peptide (uncoiled form).

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Section: Introductionmentioning

confidence: 99%

Oligonuclear Ferrocene Amides: Mixed‐Valent Peptides and Potential Redox‐Switchable Foldamers

Siebler

Linseis

Gasi

et al. 2011

Chemistry A European J

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“…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]. To study the nature of electron transfer, radiolysis [7,8] and photoinduced electron-transfer [9] studies in solution (donor-peptide-acceptor), electrochemical studies on self-assembled monolayer (SAM) systems (donor-peptide-metal) [10][11][12][13][14][15], and recently, single molecule measurements by scanning probe microscopy (metal-peptide-metal) [16][17][18], have been conducted intensively. Most of the researchers agree that a helical peptide is a good electron mediator and enables electron transfer over a long distance.…”

Section: Introductionmentioning

confidence: 99%

“…We thus suggested that a hopping mechanism with amide groups as hopping sites was responsible for this long-range electron transfer. Kraatz and co-workers studied a similar monolayer system with Pro-based peptides carrying a ferrocene moiety at the terminal, and they observed a very weak distance dependence that could be attributed to hopping [12,13]. Recently, however, they have emphasized the importance of molecular dynamics whether the electron transfer is governed by tunneling or hopping [14].…”

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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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“…Our electrochemical measurements by CV and CA in H 2 O and D 2 O, allowed us to evaluate the ET kinetics (see Figure 8). [21] A linear and shallow distance dependence of k ET on film thickness was found. Furthermore, our ET studies in D 2 O show that the ET rates are slower and a kinetic isotope effect (KIE) of 1.2 to 1.6 was observed.…”

Section: Electron Transfer Studies Of Peptides On Surfacesmentioning

confidence: 87%

Peptide Electron Transfer: More Questions than Answers

Long

Abu-Irhayem

Kraatz

2005

Chemistry A European J

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Nature has specifically designed proteins, as opposed to DNA, for electron transfer. There is no doubt about the electron transfer within proteins compared with the uncertain and continuing debate about charge transfer through DNA. However, the exact mechanism of electron transfer within peptide systems has been a source of controversy. Two different mechanisms for electron transfer between a donor and an acceptor, electron hopping and bridge-assisted superexchange, have been proposed, and are supported by experimental evidence and theoretical calculations. Several factors were found to affect the kinetics of this process, including peptide chain length, secondary structure and hydrogen bonding. Electrochemical measurements of surface-supported peptides have contributed significantly to the debate. Here we summarize the current approaches to the study of electron transfer in peptides with a focus on surface measurements and comment on these results in light of the current and often controversial debate on electron transfer mechanisms in peptides.

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Electron Transfer through H-bonded Peptide Assemblies

Cited by 61 publications

References 92 publications

Oligonuclear Ferrocene Amides: Mixed‐Valent Peptides and Potential Redox‐Switchable Foldamers

Oligonuclear Ferrocene Amides: Mixed‐Valent Peptides and Potential Redox‐Switchable Foldamers

Distance dependence of long‐range electron transfer through helical peptides

Peptide Electron Transfer: More Questions than Answers

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