Electron transfer across polypeptides. 6. Long-range electron transfer in osmium-ruthenium binuclear complexes bridged with oligoproline peptides

Vassilian, Asbed; Wishart, James F.; Hemelryck, Bruno Van; Schwarz, Harold A.; Isied, Stephan S.

doi:10.1021/ja00176a030

Cited by 71 publications

(59 citation statements)

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“…In a natural protein, a proline-rich proline-IT helix serves as a spacer between other secondary structures or as an interdomain linker (13). Synthetic redox assemblies containing oligoproline spacers as long as Pros have been used to study distance effects in intramolecular electron transfer (14)(15)(16)(17).…”

Section: Resultsmentioning

confidence: 99%

Photochemical energy conversion in a helical oligoproline assembly.

McCafferty

Friesen

Danielson

et al. 1996

Proc. Natl. Acad. Sci. U.S.A.

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A biological photosynthetic reaction center contains a spatially ordered array of chromophores, electron donors, and electron acceptors that efficiently separate reductive and oxidative equivalents upon irradiation with visible light. This fundamental process of redox separation has been modeled in redox assemblies based on metal-bipyridyl complexes (1) or porphyrin-quinone systems (2-5). We have described the synthesis and photophysical characterization of lysine-based donorchromophore-acceptor triads that undergo light-induced redox separation (6-9). We describe here a general method for designing and constructing a helical oligoproline assembly having a spatially ordered array of redox or other functional groups protruding from a proline-II helical rod. Solid-phase peptide synthesis (10) is an efficient method for assembling a modular chain containing functional sites at specific positions. An a-helical peptide chain can serve as a molecular framework to display functional sites in a spatially ordered array (9). Alternatively, a chain of nine or more proline residues folds into a stable proline-II helix even when several of the proline residues have large functional sites on their side chains (11). The distance between two functional sites is determined by their helical location and orientation. The position of a modified proline residue in the proline chain determines its location on the helical surface. The configuration and conformation of the modified proline residue determine its orientation on the helical surface. To illustrate this general method, we have assembled an oligoproline assembly (triad 1) bearing three different redox sites (Fig. 1). Folding of the peptide triad 1 into a proline-II helix places the donor, chromophore, and acceptor sites in a linear array on one side of the helical rod.

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Section: Resultsmentioning

confidence: 99%

Photochemical energy conversion in a helical oligoproline assembly.

McCafferty

Friesen

Danielson

et al. 1996

Proc. Natl. Acad. Sci. U.S.A.

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“…The matrix should show defined structural properties. We therefore chose prolines as spacers since proline oligomers are known to form stable helices starting already from 3 units, [34] and decided to set the distances to one repeat unit of the helix, that is, 3 proline monomers between acceptor or, respectively, donor and relay amino acid (Scheme 7). Intramolecular H-bonding does not occur in our model.…”

Section: Peptidesmentioning

confidence: 99%

Development of a Model System for the Study of Long Distance Electron Transfer in Peptides

et al. 2008

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Abstract:We have designed and synthesized a peptide model in which stepwise electron transfer (ET) through amino acid side chains could be observed. An injection system, which generates an electron hole upon laser irradiation, was connected directly to the aromatic side chain of a modified C-terminal amino acid. This electron acceptor could be observed by transient absorption spectroscopy. The N-terminal amino acid tyrosine acts as an electron donor, giving a different signal in the transient absorption spectrum. Additional non-natural oxidizable aromatic amino acids were synthesized as spectroscopic sensors to detect oxidized amino acid side chains as chemical intermediates in long range ET.

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“…This pathway is characterized by a low value of the descriptor of the exponential distance dependence of the electron transfer rate, β ΤΒ = 2.5 ± 0.1 nm -1 , suggesting that helical segments in proteins can function as efficient channels of long-distance electron transfer. Long-range electron transfer (LRET) between various oligoproline-bridged redox pairs has been studied over the past 10 years in several laboratories (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18) with the aim of elucidating the parameters of LRET across a single peptide pathway. The choice of oligoprolines for such a study was dictated by the known ability of short H-(Pro)n-OH peptides to attain, in aqueous solution, a stable helical conformation similar to that of the 3X left-handed helix of alltrans poly-L-proline II (19)(20)(21)(22).…”

Section: Risø National Laboratory Dk-4000 Roskilde Denmarkmentioning

confidence: 99%

Long-Range Electron Transfer Between Proline-Bridged Aromatic Amino Acids

Bobrowski

Poznański

Holcman

et al. 1998

Photochemistry and Radiation Chemistry

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Interpretation of the kinetic pulse radiolysis data for intramolecular Trp --> Tyr radical transformation in aqueous solutions of linear H-Trp-(Pro)n-Tyr-OH, n = 0-5, is presented in terms of the Marcus electron transfer theory, taking into account conformational dynamics of the molecules. For this purpose, for each peptide, representative sets of low-energy conformers were selected with the help of experimental methods ( 1 H and 13 C NMR, and circular dichroism) and modeling meth ods (molecular mechanics and dynamics ); and relative electron transfer rates averaged over all the conformers were calculated for two assumed competitive electron transfer pathways: through space (TS) and through the peptide backbone (TB). The TS rates were obtained by taking into account the overlap integrals of aromatic ring orbitals calu lated quantum mechanically. By fitting the calculated rates to the experi mental data for the rate constants for electron transfer, ket, with an exponential function appropriate for the two-pathway model, we have demonstrated that in linear short-bridged peptides (n = 0-2), electron transfer predominantly takes the TS pathway, which consists of van der Waals contacts between the aromatic rings, whereas in longer peptides (n = 3-5), it occurs exclusively by the TB pathway, which is made of a -(Pro)n-bridge in a helical conformation similar to that of all-trans poly-L-proline II. This pathway is characterized by a low value of the descriptor of the exponential distance dependence of the electron transfer rate, β ΤΒ = 2.5 ± 0.1 nm -1 , suggesting that helical segments in proteins can function as efficient channels of long-distance electron transfer.

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Electron transfer across polypeptides. 6. Long-range electron transfer in osmium-ruthenium binuclear complexes bridged with oligoproline peptides

Cited by 71 publications

References 0 publications

Photochemical energy conversion in a helical oligoproline assembly.

Photochemical energy conversion in a helical oligoproline assembly.

Development of a Model System for the Study of Long Distance Electron Transfer in Peptides

Long-Range Electron Transfer Between Proline-Bridged Aromatic Amino Acids

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