Iron–sulfur cluster
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Iron–sulfur clusters are molecular ensembles of iron and sulfide. They are most often discussed in the context of the biological role for iron–sulfur proteins, which are pervasive.<ref>Lippard, S. J. and Berg, J. M. (1994). "Principles of Bioinorganic Chemistry". University Science Books: Mill Valley, CA. Template:ISBN.</ref> Many Fe–S clusters are known in the area of organometallic chemistry and as precursors to synthetic analogues of the biological clusters. It is supposed that the last universal common ancestor had many iron-sulfur clusters.<ref>Weiss, Madeline C., et al. (2016). "The physiology and habitat of the last universal common ancestor." Nature Microbiology 1 (9): 1–8.</ref>
In biologyEdit
{{#invoke:Labelled list hatnote|labelledList|Main article|Main articles|Main page|Main pages}} Iron–sulfur clusters occur in many biological systems, often as components of electron transfer proteins. The ferredoxin proteins are the most common Fe–S proteins in nature. They feature either 2Fe–2S or 4Fe–4S centers. They occur in all branches of life.<ref name=":0">Template:Cite journal</ref>
Fe–S clusters can be classified according to their Fe:S stoichiometry [2Fe–2S], [4Fe–3S], [3Fe–4S], and [4Fe–4S].<ref>Template:Cite journal</ref> The [4Fe–4S] clusters occur in two forms: normal ferredoxins and high potential iron proteins (HiPIP). Both adopt cuboidal structures, but they utilize different oxidation states. They are found in all forms of life.<ref name="ReferenceA">Template:Cite journal</ref>
The relevant redox couple in all Fe–S proteins is Fe(II)/Fe(III).<ref name="ReferenceA"/>
Many clusters have been synthesized in the laboratory with the formula [Fe4S4(SR)4]2−, which are known for many R substituents, and with many cations. Variations have been prepared including the incomplete cubanes [Fe3S4(SR)3]3−.<ref>Template:Cite journal</ref>
Synthetic Fe–S clustersEdit
Organometallic clustersEdit
Organometallic Fe–S clusters include the sulfido carbonyls with the formula Fe2S2(CO)6, H2Fe3S(CO)9, and Fe3S2(CO)9. Compounds are also known that incorporate cyclopentadienyl ligands, such as (C5H5)4Fe4S4.<ref>Template:Cite journal</ref>
