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135 results on '"Rigby, Stephen E.J."'

8. Heterologous production, reconstitution and EPR spectroscopic analysis of prFMN dependent enzymes

Author

Marshall, Stephen A., primary, Payne, Karl A.P., additional, Fisher, Karl, additional, Gahloth, Deepankar, additional, Bailey, Samuel S., additional, Balaikaite, Arune, additional, Saaret, Annica, additional, Gostimskaya, Irina, additional, Aleku, Godwin, additional, Huang, Huanming, additional, Rigby, Stephen E.J., additional, Procter, David, additional, and Leys, David, additional

Published
2019
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19. Reductive dehalogenase structure suggests a mechanism for B12-dependent dehalogenation

Author

Payne, Karl A.P., Quezada, Carolina P., Fisher, Karl, Dunstan, Mark S., Collins, Fraser A., Sjuts, Hanno, Levy, Colin, Hay, Sam, Rigby, Stephen E.J., and Leys, David

Subjects
Structure, Analysis, Physiological aspects, Halogen elements -- Structure, Polychlorinated biphenyls -- Structure, Catalysis -- Analysis, Enzymes -- Structure -- Physiological aspects, Halogens -- Structure
Abstract

Cobalamin consists of a cobalt ion coordinated by a tetrapyrrole-derived macrocycle and readily forms a weak organometallic C-Co(III) bond (14). This bond can be homolytically or heterolytically cleaved and the [...], Organohalide chemistry underpins many industrial and agricultural processes, and a large proportion of environmental pollutants are organohalides (1). Nevertheless, organohalide chemistry is not exclusively of anthropogenic origin, with natural abiotic and biological processes contributing to the global halide cycle (2, 3). Reductive dehalogenases are responsible for biological dehalogenation in organohalide respiring bacteria (4, 5), with substrates including polychlorinated biphenyls or dioxins (6, 7). Reductive dehalogenases form a distinct subfamily of cobalamin (B12)-dependent enzymes that are usually membrane associated and oxygen sensitive, hindering detailed studies (8, 12). Here we report the characterization of a soluble, oxygen-tolerant reductive dehalogenase and, by combining structure determination with EPR (electron paramagnetic resonance) spectroscopy and simulation, show that a direct interaction between the cobalamin cobalt and the substrate halogen underpins catalysis. In contrast to the carbon-cobalt bond chemistry catalysed by the other cobalamin-dependent subfamilies (13), we propose that reductive dehalogenases achieve reduction of the organohalide substrate via halogen-cobalt bond formation. This presents a new model in both organohalide and cobalamin (bio)chemistry that will guide future exploitation of these enzymes in bioremediation or biocatalysis.

Published
2015

28. Thermodynamic basis of electron transfer in dihydroorotate dehydrogenase B from lactococcus lactis: analysis by potentiometry, EPR spectroscopy, and ENDOR spectroscopy

Author

Mohsen, Al-Walid A., Rigby, Stephen E.J., Jensen, Kaj Frank, You Qun He, and Halpert, James R.

Subjects
Sulfur compounds -- Research, Sulfur compounds -- Chemical properties, Sulfur compounds -- Magnetic properties, Iron compounds -- Research, Iron compounds -- Magnetic properties, Iron compounds -- Electric properties, Electron transport -- Observations, Biological sciences, Chemistry
Abstract

The study provides a detailed thermodynamic framework for electron transfer in this complex iron-sulphur flavoprotein. Their potentiometric analysis indicates that all of the redox centers in dihydroorotate dehydrogenase B (DHODB) titrate in the range of -200 to -320 mV. The detailed thermodynamic basis for electron transfer in DHODB provides a framework for transient kinetic studies of electron transfer.

Published
2004

32. Reaction of bovine cytochrome c oxidase with hydrogen prtoxide produces a tryptophan cation radical and a porphyrin cation radical

Author

Rigby, Stephen E.J., Junemann, Susanne, Rich, Peter R., and Heathcote, Peter

Subjects
Biochemistry -- Research, Cytochrome c -- Research, Oxidases -- Research, Hydrogen peroxide -- Research, Tryptophan -- Research, Cations -- Research, Porphyrins -- Analysis, Biological sciences, Chemistry
Abstract

Research has been conducted on the oxidized bovine cytochrome c oxidase. The reaction of this oxidase with hydrogen peroxide has been examined.

Published
2000

33. ENDOR and special TRIPLE resonance spectroscopy of photoaccumulated semiquinone electron acceptors in the reaction centers of green sulfur bacteria and heliobacteria

Author

Muhiuddin, Irine P., Rigby, Stephen E.J., Evans, Michael C.W., Amesz, Jan, and Heathcote, Peter

Subjects
Anaerobic bacteria -- Research, Bacteria, Photosynthetic -- Research, Electron transport -- Research, Quinone -- Research, Biological sciences, Chemistry
Abstract

A study of the oxygen-sensitive reaction centers of anaerobic, photosynthetic organisms, namely, green sulfur bacteria and heliobacteria, was conducted to determine whether EPR signals in these organisms originate from a semiquinone electron acceptor in bacterial type I reaction centers. Magnetic resonance techniques were used to conclusively assign observed asymmetric EPR signals in anaerobically prepared membranes of Chlorobium limicola and Heliobacterium chlorum following photoaccumulation at low temperatures under reducing conditions. Results are discussed.

Published
1999

40. ENDOR and special triple resonance spectroscopy of A(super .-)(sub 1) of photosystem 1

Author

Rigby, Stephen E.J., Evans, Michael C.W., and Heathcote, Peter

Subjects
Nuclear spectroscopy -- Observations, Radicals (Chemistry) -- Spectra, Cyanobacteria -- Research, Spinach -- Research, Biological sciences, Chemistry
Abstract

The electron nuclear double resonance and electron-nuclear-nuclear special triple resonance spectra of the Anabaena variabilis and spinach photosystem I secondary electron acceptor A(super .-)(sub 1) are similar. The spectra show that A(super .-)(sub 1) is a phylloquinone anion radical (PhQ(super .-)). The electron spin density of the radical is distorted. There are hyperfine couplings to the methyl group, protons bound to the quinone oxygen and methylene proton of the quinone phytyl side chain. However, the hyperfine coupling constants of A(super .-)(sub 1) and PhQ(super .-) are different.

Published
1996

41. Photoaccumulation in photosystem I does produce a phylloquinone (A(super .-)(sub 1)) radical

Author

Heathcote, Peter, Moenne-Loccoz, Pierre, Rigby, Stephen E.J., and Evans, M.C.W.

Subjects
Cyanobacteria -- Research, Electron paramagnetic resonance spectroscopy -- Observations, Quinone -- Research, Radicals (Chemistry) -- Spectra, Biological sciences, Chemistry
Abstract

The biosynthetic deuteration of phylloquinone confirms that the photoaccumulated electron paramagnetic resonance (EPR) signal arises from the phylloquinone electron acceptor (A(super .-)(sub 1)). The deuteration causes a narrowing of the EPR and electron spin polarized spectra in the cyanobacterium Anabaena variabilis. The narrowing of the signal shows that the (A(super .-)(sub 1)) radical produces the EPR signal. The replacement of the protonated phylloquinone by a deuterated phylloquinone causes a broadening of the EPR signal.

Published
1996

42. ENDOR and special TRIPLE resonance spectroscopy of Q(super .-)(sub A) of photosystem 2

Author

Rigby, Stephen E.J., Heathcote, Peter, Evans, Michael C.W., and Nugent, Jonathan H.A.

Subjects
Photosynthesis research -- Observations, Quinone -- Analysis, Spectrum analysis -- Observations, Biological sciences, Chemistry
Abstract

The electron spin density distribution and hydrogen bonding of the anionic plastosemiquinone radical Q(super .-)(sub A) of photosystem 2 of oxygenic photosynthesis are analyzed by electron nuclear double-resonance and special TRIPLE spectroscopies. One of the hydrogen bond in Q(super .-)(sub A) si parallel and the other perpendicular to the quinone ring plane.

Published
1995

43. ENDOR and special triple resonance studies of chlorophyll cation radicals in photosystem 2

Author

Rigby, Stephen E.J., Nugent, Jonathan H.A., and O'Malley, Patrick J.

Subjects
Photosynthesis -- Analysis, Chlorophyll -- Analysis, Cations -- Analysis, Biological sciences, Chemistry
Abstract

Electron nuclear double resonance (ENDOR) and special triple (ST) resonance spectroscopic studies of photosystem (PS) 2 identify one primary donor cation radical, P680 and two secondary donor chlorophylls. A comparative study with ENDOR spectra of the primary donor cation radical of PS1, P700(.+) helps assign the methyl groups' hyperfine splittings, and the measured hyperfine coupling constants enable determination of electron spin densities. The weakly coupled chlorophyll pair P680(.+) has 82% of electron density on one chlorophyll of the pair.

Published
1994

44. The dark stable tyrosine radical of photosystem 2 studied in three species using ENDOR and EPR spectroscopies

Author

Rigby, Stephen E.J., Nugent, Jonathan H.A., and O'Malley, Patrick J.

Subjects
Tyrosine -- Research, Electron paramagnetic resonance -- Analysis, Protons -- Analysis, Biological sciences, Chemistry
Abstract

Electron paramagnetic resonance and electron nuclear double-resonance spectroscopies yield the properties of dark, stable, neutral tyrosine radical Y(D) of photosystem 2. The photosystem in cyanobacterium Phormidium laminosum, alga Chlamydomonas reinhardtii and spinach are investigated to determine the proton hyperfine coupling constants of the four ring protons. The ring proton coupling constants are independent of the species while the beta proton coupling constants vary from species to species.

Published
1994

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