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Your search keyword '"Rigby, Stephen E. J."' showing total 18 results
Start Over Author "Rigby, Stephen E. J." Journal biochemistry
18 results on '"Rigby, Stephen E. J."'

1. Site-directed mutagenesis of PsaA residue W693 affects phylloquinone binding and function in the photosystem I reaction center of Chlamydomonas reinhardti

Author

Purton, Saul, Stevens, David R., Muhiuddin, Irine P., Evans, Michael C. W., Carter, Susan, Rigby, Stephen E. J., and Heathcote, Peter

Subjects
Biochemistry -- Research, Mutagenesis -- Physiological aspects, Chlamydomonas -- Physiological aspects, Tryptophan -- Research, Histidine -- Physiological aspects, Leucine -- Physiological aspects, Biological sciences, Chemistry
Abstract

Research has been conducted on the phylloquinone secondary electron acceptor A (sub)1. The environment of this acceptor within the photosystem I reaction center has been investigated via site-directed mutagenesis of tryptophan residues in the Chlamydomonas reinhardtii PsaA sumunit.

Published
2001

17. Amyloid β-Cu[sup2+] Complexes in both Monomeric and Fibrillar Forms Do Not Generate H[sub2]O[sub2] Catalytically but Quench Hydroxyl Radicals.

Author

Nadal, Rebecca C., Rigby, Stephen E. J., and Vi!es, John H.

Subjects
*AMYLOID beta-protein, *ALZHEIMER'S disease, *OXIDATIVE stress, *CEREBROSPINAL fluid, *HYDROXYL group, *PEPTIDE synthesis, *SOLUBILIZATION, *NUCLEAR magnetic resonance
Abstract

Oxidative stress plays a key role in Alzheimer's disease (AD). In addition, the abnormally high Cu[sup2+] ion concentrations present in senile plaques has provoked a substantial interest in the relationship between the amyloid β peptide (Aβ) found within plaques and redox-active copper ions. There have been a number of studies monitoring reactive oxygen species (ROS) generation by copper and ascorbate that suggest that Aβ acts as a prooxidant producing H[sub2[O[sub2]. However, others have indicated Aβ acts as an antioxidant, but to date most cell-free studies directly monitoring ROS have not supported this hypothesis. We therefore chose to look again at ROS generation by both monomeric and fibrillar forms of Aβ under aerobic conditions in the presence of Cu[sup2+] with/Without the biological reductant ascorbate in a cell-free system. We used a variety of fluorescence and absorption based assays to monitor the production of ROS, as well as Cu[sup2+] reduction. In contrast to previous studies, we show here that Aβ does not generate any more ROS than controls of Cu[sup2+] and ascorbate. Aβ does not silence the redox activity of Cu[sup2+] via chelation, but rather hydroxyl radicals produced as a result of Fenton-Haber Weiss reactions of ascorbate and Cu[sup2+] rapidly react with Aβ; thus the potentially harmful radicals are quenched. In support of this, chemical modification of the Aβ peptide was examined using [sup1]H NMR, and specific oxidation sites within the peptide were identified at the histidine and methionine residues. Our studies add significant weight to a modified amyloid cascade hypothesis in which sporadic AD is the result of Aβ being upregulated as a response to oxidative stress. However, our results do not preclude the possibility that Aβ in an oligomeric form may concentrate the redox-active copper at neuronal membranes and so cause lipid peroxidation. [ABSTRACT FROM AUTHOR]

Published
2008
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