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New Method for the Spin Quantitation of [4Fe?4S] + Clusters with S = 3 / 2 . Application to the FS0 Center of the NarGHI Nitrate Reductase from Escherichia coli

Abstract : In conventional analyses of g ≈ 5 signals given by [4Fe−4S]+ clusters with S = 3/2, the effective g values that cannot be measured in the electron paramagnetic resonance (EPR) spectrum are deduced from rhombograms calculated by assuming that the g̃ matrix is isotropic with gx = gy = gz = 2.00. We have shown that when the two low-field peaks corresponding to the Kramers doublets are visible in the spectrum, a new, independent piece of information about the system can be obtained by studying the temperature dependence of the ratio of the area under these peaks. By applying this method to the g ≈ 5 signals displayed by NarGHI nitrate reductase, we were able to determine all the parameters of the spin Hamiltonian of FS0 centers with S = 3/2 and to measure accurately their number. Our results indicate that simple analyses based on the assumption of an isotropic g̃ matrix can give rise to very large errors.
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https://hal.archives-ouvertes.fr/hal-00336023
Contributor : Laure Azzopardi <>
Submitted on : Friday, October 31, 2008 - 3:59:18 PM
Last modification on : Thursday, January 25, 2018 - 6:26:02 PM

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Lanciano Pascal, Savoyant Adrien, Grimaldi Stéphane, Magalon Axel, Guigliarelli Bruno, et al.. New Method for the Spin Quantitation of [4Fe?4S] + Clusters with S = 3 / 2 . Application to the FS0 Center of the NarGHI Nitrate Reductase from Escherichia coli. Journal of Physical Chemistry B, American Chemical Society, 2007, 111 (48), pp.13632 - 13637. ⟨10.1021/jp075243t⟩. ⟨hal-00336023⟩

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