Editing Iron–sulfur cluster (section)

==Biological Fe–S clusters==
{{main|iron–sulfur protein}}
Iron–sulfur clusters occur in many biological systems, often as components of [[electron transfer]] proteins.  The [[ferredoxin]] proteins are the most common Fe–S clusters in nature.  They feature either 2Fe–2S or 4Fe–4S centers. They occur in all branches of life.<ref name=":0">{{cite journal|author=Johnson, D. C. |author2=Dean, D. R. |author3=Smith, A. D. |author4=Johnson, M. K. |year=2005|title=Structure, function, and formation of biological iron-sulfur clusters|journal=Annual Review of Biochemistry|volume=74|issue=1 |pages=247–281|doi=10.1146/annurev.biochem.74.082803.133518|pmid=15952888}}</ref>

Fe–S clusters can be classified according to their Fe:S stoichiometry [2Fe–2S], [4Fe–3S], [3Fe–4S], and [4Fe–4S].<ref>{{cite journal |last1=Lill |first1=Roland |title=Issue of iron-sulfur protein |journal=Biochimica et Biophysica Acta (BBA) - Molecular Cell Research |volume=1853 |issue=6 |pages=1251–1252 |pmc=5501863 |year=2015 |pmid=25746719 |doi=10.1016/j.bbamcr.2015.03.001 }}</ref> The [4Fe–4S] clusters occur in two forms: normal ferredoxins and [[High potential iron–sulfur protein|high potential iron proteins]] (HiPIP). Both adopt [[Cube|cuboidal]] structures, but they utilize different [[oxidation state]]s.  They are found in all forms of life.<ref name="ReferenceA">{{cite journal |last1=Fisher |first1=N |title=Intramolecular electron transfer in [4Fe–4S)] |journal=The EMBO Journal |date=1998 |pages=849–858}}</ref>

The relevant [[Redox|redox couple]] in all [[Iron–sulfur protein|Fe–S proteins]] is Fe(II)/Fe(III).<ref name="ReferenceA"/>

Many clusters have been synthesized in the laboratory with the formula [Fe<sub>4</sub>S<sub>4</sub>(SR)<sub>4</sub>]<sup>2−</sup>, which are known for many R substituents, and with many cations.  Variations have been prepared including the incomplete [[Cubane-type cluster|cubanes]] [Fe<sub>3</sub>S<sub>4</sub>(SR)<sub>3</sub>]<sup>3−</sup>.<ref>{{cite journal|author1=Rao, P. V. |author2=Holm, R. H. |title=Synthetic Analogues of the Active Sites of Iron-Sulfur Proteins|journal=Chem. Rev.|year=2004|volume=104|issue=2|pages=527─559|doi=10.1021/Cr020615+|pmid=14871134}}</ref>