ORCID Profile
0000-0002-9549-4220
Current Organisation
University of Oxford
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Publisher: Royal Society of Chemistry (RSC)
Date: 2017
DOI: 10.1039/C7CC02591B
Abstract: We manipulate and verify the redox state of single metalloprotein crystals by combining electrochemical control with synchrotron infrared microspectroscopy.
Publisher: American Chemical Society (ACS)
Date: 02-08-2018
DOI: 10.1021/JACS.8B04798
Abstract: Catalytic long-range proton transfer in [NiFe]-hydrogenases has long been associated with a highly conserved glutamate (E) situated within 4 Å of the active site. Substituting for glutamine (Q) in the O
Publisher: Royal Society of Chemistry (RSC)
Date: 2023
DOI: 10.1039/D2SC05641K
Abstract: Changing the conserved active-site arginine of [NiFe]-hydrogenases into a lysine greatly lowers the rates of catalytic H 2 activation in each direction and results in the extremely tight binding of a diatomic ligand.
Publisher: Royal Society of Chemistry (RSC)
Date: 2021
DOI: 10.1039/D1SC01734A
Abstract: Electrochemically-coupled IR microspectroscopy of single crystals provides insight into proton-coupled electron transfer in [NiFe] hydrogenase.
Publisher: Wiley
Date: 21-09-2009
Abstract: We report the crystal structure of dihydrofolate reductase (DHFR) from the psychropiezophilic bacterium Moritella profunda, which was isolated from the deep ocean at 2 degrees C and 280 bar. The structure is typical of a chromosomal DHFR and we were unable to identify any obvious structural features that would suggest pressure adaptation. In particular, the core regions of the enzyme are virtually identical to those of the DHFR from the mesophile Escherichia coli. The steady-state rate at pH 9, which is limited by hydride transfer at atmospheric pressure, is roughly constant between 1 and 750 bar, falling at higher pressures. However, the value of K(M) increases with increasing pressure, and as a result k(cat)/K(M) decreases over the entire pressure range studied. Isotope effect studies showed that increasing the pressure causes a change in the rate-limiting step of the reaction. We therefore see no evidence of pressure adaptation in either the structure or the activity of this enzyme.
Publisher: American Chemical Society (ACS)
Date: 04-09-2012
DOI: 10.1021/JA307117Y
Abstract: The unusual [4Fe-3S] cluster proximal to the active site plays a crucial role in allowing a class of [NiFe]-hydrogenases to function in the presence of O(2) through its unique ability to undergo two rapid, consecutive one-electron transfers. This property helps to neutralize reactive oxygen species. Mechanistic details and the role of the medial and distal clusters remain unresolved. To probe the Fe-S relay, continuous wave and pulse electron paramagnetic resonance (EPR) studies were conducted on the O(2)-tolerant hydrogenase from Escherichia coli (Hyd-1) and three variants with point mutations at the proximal and/or medial clusters. Reduction potentials of the proximal ([4Fe-3S](5+/4+/3+)) and medial ([3Fe-4S](+/0)) clusters were determined by potentiometry. The medial [3Fe-4S](+/0) reduction potential is exceptionally high, implicating a mechanistic role in O(2)-tolerance. Numerous experiments establish that the distal cluster has a ground state S > 1/2 in all three variants and indicate that this is also the case for native Hyd-1. Concurrent with the Hyd-1 crystal structure, EPR data for the 'superoxidized' P242C variant, in which the medial cluster is 'magnetically silenced', reveal two conformations of the proximal [4Fe-3S](5+) cluster, and X-band HYSCORE spectroscopy shows two (14)N hyperfine couplings attributed to one conformer. The largest, A((14)N) = [11.5,11.5,16.0] ± 1.5 MHz, characterizes the unusual bond between one Fe (Fe(4)) and the backbone amide-N of cysteine-20. The second, A((14)N) = [2.8,4.6,3.5] ± 0.3 MHz, is assigned to N(C19). The (14)N hyperfine couplings are conclusive evidence that Fe(4) is a valence-localized Fe(3+) in the superoxidized state, whose formation permits an additional electron to be transferred rapidly back to the active site during O(2) attack.
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Rhiannon Evans.