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 - Archive ouverte HAL Access content directly
Journal Articles Journal of Physical Chemistry B Year : 2007

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.

Dates and versions

hal-00336023 , version 1 (31-10-2008)

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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, 2007, 111 (48), pp.13632 - 13637. ⟨10.1021/jp075243t⟩. ⟨hal-00336023⟩

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