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Chemistry of the nitrogenase active site

Reference	BBS/E/J/0000A007
Principal Investigator / Supervisor	Professor Barry Smith
Co-Investigators / Co-Supervisors
Institution	John Innes Centre
Department	John Innes Centre Department
Funding type	Research
Value (£)	36,895
Status	Completed
Type	Institute Project
Start date	01/10/2001
End date	30/09/2003
Duration	24 months

Abstract

The overall aim of this project is to understand the requirements for N2 activation by nitrogenase and thus to provide a sound chemical basis for the development of new catalysts. A major experimental tool will be electrochemistry, in collaboration with Prof. C.J.Pickett, continuing our recent successful research. Additional tools will be stopped-flow spectrometry and Infra-red, EPR and ENDOR spectroscopies to characterise complexes . All of these are readily available to me at JIC. We have shown that, with appropriate acids, FeMoco can evolve H2 electrochemically at relatively high potentials. Most importantly, FeMoco can be further reduced, by up to 3 electrons whilst binding the inhibitor CO, to form complexes with IR spectra similar to those detected during enzyme turnover. However these lower redox states were unstable and decayed to the semi-reduced form of FeMoco, presumably through re-oxidation by H+ in the solvent and so spectroscopic characterisation of the complexes has not been possible except in a thin-layer cell under high CO pressures. It is known that nitrogenase substrates and inhibitors bind to lower redox states of FeMoco in the enzyme but again these have previously only been accessed transiently during turnover. Therefore a key objective of my research will be to find conditions where these lower redox states of isolated FeMoco are stabilised I plan to use alternative solvents for FeMoco electrochemistry in order to be able to control the availability of protons. The normal FeMoco solvent NMF has a potentially dissociable proton and FeMoco preparations typically are made anoxic by adding Na2S2O4 in aqueous phosphate buffer. It is known that FeMoco can be extracted into other organic solvents provided a suitable cation is present although there have been very few investigations of FeMoco reactivity in these solvents.

Summary

unavailable

Committee	Closed Committee - Biomolecular Sciences (BMS)
Research Topics	X – not assigned to a current Research Topic
Research Priority	X – Research Priority information not available
Research Initiative	X - not in an Initiative
Funding Scheme	X – not Funded via a specific Funding Scheme

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