Mössbauer spectroscopy is pivotal for characterizing Fe/S clusters.
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Nuclearity and redox states of Fe/S cofactors can be uniquely addressed.
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Geometric and electronic properties of Fe metallocofactors can be established.
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Unparallel insight into novel ‘non-traditional’ polynuclear Fe/S cluster forms.
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Mössbauer studies on Fe/S centers can be carried out both in-vivo and in-vitro.
Abstract
Iron-sulfur (Fe/S) clusters are structurally and functionally diverse cofactors that are found in all domains of life. 57Fe Mössbauer spectroscopy is a technique that provides information about the chemical nature of all chemically distinct Fe species contained in a sample, such as Fe oxidation and spin state, nuclearity of a cluster with more than one metal ion, electron spin ground state of the cluster, and delocalization properties in mixed-valent clusters. Moreover, the technique allows for quantitation of all Fe species, when it is used in conjunction with electron paramagnetic resonance (EPR) spectroscopy and analytical methods. 57Fe-Mössbauer spectroscopy played a pivotal role in unraveling the electronic structures of the “well-established” [2Fe-2S]2+/+, [3Fe-4S]1+/0, and [4Fe-4S]3+/2+/1+/0 clusters and -more-recently- was used to characterize novel Fe/S clustsers, including the [4Fe-3S] cluster of the O2-tolerant hydrogenase from Aquifex aeolicus and the 3Fe-cluster intermediate observed during the reaction of lipoyl synthase, a member of the radical SAM enzyme superfamily.
This work was supported by NIH Grants GM-63847 and GM-103268 (S.J.B.), the Dreyfus Foundation (Teacher Scholar Award to C.K.), and the Beckman Foundation (Young Investigator Award to C.K.).