ChemInform Abstract: Temperature Dependence of and Ligation Effects on Long‐Range Electron Transfer in Complementary [Zn,Fe(III)]Hemoglobin Hybrids.

Peterson-Kennedy, Sydney E.; McGourty, Jacqueline L.; Kalweit, Juliette A.; Hoffman, Brian M.

doi:10.1002/chin.198632261

Cited by 4 publications

(5 citation statements)

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“…The possibility of electron transfer is supported by the efficient quenching of porphyrin phosphorescence by this mechanism (Zemel and Hoffman, 1981;McLendon et al, 1985;Peterson-Kennedy et al, 1986;Koloczek et al, 1987). If quenching by electron transfer does occur, it cannot involve transfer of an electron to or from the iron ion because, as is seen in Table 1, k, is about the same for both reduced and oxidized forms of cytochrome c. However, because the quenching of BNS phosphorescence has been shown to occur only at short distance, the nature of the mechanism is of no consequence in the use and interpretation of results involving the quenching of BNS phosphorescnce as a probe of heme accessibility.…”

Section: Discussionmentioning

confidence: 99%

Demonstration That Phosphorescent 6‐bromo‐2‐naphthyl Sulfate Can Be Used to Probe Heme Accessibility in Heme Proteins

Bayles

Beckham

Leidig

et al. 1991

Photochem & Photobiology

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The phosphorescence properties of 6-bromo-2-naphthyl sulfate (BNS) in aqueous solution were studied. The phosphorescence lifetime is several hundred microseconds and is self-quenched. Although a fluorescent photoproduct is formed from BNS, it does not interfere with the decay properties of triplet-state BNS and its utility as a probe of the accessibility of the heme group in heme proteins. Quenching of BNS phosphorescence does not occur for the non-heme protein lysozyme and apomyoglobin but occurs by a dynamic mechanism with a quenching constant of 1-2 x 10(9) M-1 s-1 for cytochrome c and myoglobin and with a quenching constant of 6.2 x 10(9) M-1 s-1 for protoporphyrin IX. The phosphorescence of an inclusion complex of 1-bromonaphthalene and beta-cyclodextrin is not quenched by heme-containing proteins. The temperature and viscosity dependencies of the rate with which BNS phosphorescence is quenched by microperoxidase-11 are consistent with unit quenching efficiency. These results indicate that quenching of BNS phosphorescence occurs only upon contact with the quencher, and the quenching constant can be used to assess the degree of accessibility of the heme group.

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Section: Discussionmentioning

confidence: 99%

Demonstration That Phosphorescent 6‐bromo‐2‐naphthyl Sulfate Can Be Used to Probe Heme Accessibility in Heme Proteins

Bayles

Beckham

Leidig

et al. 1991

Photochem & Photobiology

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“…The time constant for ET from a triplet excited ZnPor in the b-subunit to an Fe(III) center in the a-subunit is about 16 ms (McGourty et al 1983). Extensive studies of temperature dependences of hybrid Hb ET rates led to the conclusion that the reorganization energy for these reactions (ly1 eV) is dominated by outer-sphere contributions (Peterson-Kennedy et al 1986 ;Dick et al 1998). Measurements of ET rates in cryogenic glasses suggest that the polypeptide is the primary outer-sphere medium for the reaction and that bulk solvent reorganization does not play an important role in the reaction (Kuila et al 1991).…”

Section: Hemoglobin (Hb) Hybridsmentioning

confidence: 99%

Electron tunneling through proteins

Gray

2003

Quart. Rev. Biophys.

612

795

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Electron transfer processes are vital elements of energy transduction pathways in living cells. More than a half century of research has produced a remarkably detailed understanding of the factors that regulate these 'currents of life'. We review investigations of Ru-modified proteins that have delineated the distance- and driving-force dependences of intra-protein electron-transfer rates. We also discuss electron transfer across protein-protein interfaces that has been probed both in solution and in structurally characterized crystals. It is now clear that electrons tunnel between sites in biological redox chains, and that protein structures tune thermodynamic properties and electronic coupling interactions to facilitate these reactions. Our work has produced an experimentally validated timetable for electron tunneling across specified distances in proteins. Many electron tunneling rates in cytochrome c oxidase and photosynthetic reaction centers agree well with timetable predictions, indicating that the natural reactions are highly optimized, both in terms of thermodynamics and electronic coupling. The rates of some reactions, however, significantly exceed timetable predictions: it is likely that multistep tunneling is responsible for these anomalously rapid charge transfer events.

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“…Such an alternative seems implausable because of the results showing nuclear tunneling in analogous synthetically modified systems. The possibility of having multiple donors in modified hemoglobins (Peterson-Kennedy et al 1986) which indeed show 'nuclear tunneling' does not exist.) These nuclear modes undergo reorganizations which are coupled to removal/introduction of charge at the two localization sites in the protein.…”

Section: Electron Transfer and Bridge Protein Tunnelingmentioning

confidence: 99%

Electron tunneling pathways in proteins: influences on the transfer rate

Beratan

Onuchic

1989

Photosynth Res

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A strategy for calculating the tunneling matrix element dependence on the medium intervening between donor and acceptor in specific proteins is described. The scheme is based on prior studies of small molecules and is general enough to allow inclusion of through bond and through space contributions to the electronic tunneling interaction. This strategy should allow the prediction of relative electron transfer rates in a number of proteins. It will therefore serve as a design tool and will be explicitly testable, in contrast with calculations on single molecules. As an example, the method is applied to ruthenated myoglobin and the tunneling matrix elements are estimated. Quantitative improvements of the model are described and effects due to motion of the bridging protein are discussed. The method should be of use for designing target proteins having tailored electron transfer rates for production with site directed mutagenesis. The relevance of the technique to understanding certain photosynthetic reaction center electron transfer rates is discussed.

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ChemInform Abstract: Temperature Dependence of and Ligation Effects on Long‐Range Electron Transfer in Complementary [Zn,Fe(III)]Hemoglobin Hybrids.

Cited by 4 publications

References 1 publication

Demonstration That Phosphorescent 6‐bromo‐2‐naphthyl Sulfate Can Be Used to Probe Heme Accessibility in Heme Proteins

Demonstration That Phosphorescent 6‐bromo‐2‐naphthyl Sulfate Can Be Used to Probe Heme Accessibility in Heme Proteins

Electron tunneling through proteins

Electron tunneling pathways in proteins: influences on the transfer rate

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