Iron–sulfur clusters are molecular ensembles of
iron
Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...
and
sulfide
Sulfide (also sulphide in British English) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to large families o ...
. They are most often discussed in the context of the biological role for
iron–sulfur proteins, which are pervasive. Many Fe–S clusters are known in the area of
organometallic chemistry
Organometallic chemistry is the study of organometallic compounds, chemical compounds containing at least one chemical bond between a carbon atom of an organic molecule and a metal, including alkali, alkaline earth, and transition metals, and so ...
and as precursors to synthetic analogues of the biological clusters. It is supposed that the
last universal common ancestor
The last universal common ancestor (LUCA) is the hypothesized common ancestral cell from which the three domains of life, the Bacteria, the Archaea, and the Eukarya originated. The cell had a lipid bilayer; it possessed the genetic code a ...
had many iron-sulfur clusters.
In biology
Iron–sulfur clusters occur in many biological systems, often as components of
electron transfer
Electron transfer (ET) occurs when an electron relocates from an atom, ion, or molecule, to another such chemical entity. ET describes the mechanism by which electrons are transferred in redox reactions.
Electrochemical processes are ET reactio ...
proteins. The
ferredoxin
Ferredoxins (from Latin ''ferrum'': iron + redox, often abbreviated "fd") are iron–sulfur proteins that mediate electron transfer in a range of metabolic reactions. The term "ferredoxin" was coined by D.C. Wharton of the DuPont Co. and applied t ...
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.
Fe–S clusters can be classified according to their Fe:S stoichiometry
Fe–2S Fe–3S Fe–4S and
Fe–4S The
Fe–4Sclusters occur in two forms: normal ferredoxins and
high potential iron proteins (HiPIP). Both adopt
cuboidal structures, but they utilize different
oxidation state
In chemistry, the oxidation state, or oxidation number, is the hypothetical Electrical charge, charge of an atom if all of its Chemical bond, bonds to other atoms are fully Ionic bond, ionic. It describes the degree of oxidation (loss of electrons ...
s. They are found in all forms of life.
The relevant
redox couple in all
Fe–S proteins is Fe(II)/Fe(III).
Many clusters have been synthesized in the laboratory with the formula
e4S4(SR)4sup>2−, which are known for many R substituents, and with many
cations
An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...
. Variations have been prepared including the incomplete
cubanes e3S4(SR)3sup>3−.
Synthetic Fe–S clusters
Organometallic clusters
Organometallic Fe–S clusters include the sulfido carbonyls with the formula Fe
2S
2(CO)
6, H
2Fe
3S(CO)
9, and Fe
3S
2(CO)
9. Compounds are also known that incorporate
cyclopentadienyl Cyclopentadienyl can refer to
* Cyclopentadienyl anion, or cyclopentadienide,
** Cyclopentadienyl ligand
* Cyclopentadienyl radical, •
* Cyclopentadienyl cation,
See also
* Pentadienyl
{{Chemistry index ...
ligands
In coordination chemistry, a ligand is an ion or molecule with a functional group that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's ...
, such as (C
5H
5)
4Fe
4S
4.
Inorganic materials
center, Structure of potassium dithioferrate, which features infinite chains of Fe(III) centers.
See also
*
Bioinorganic chemistry
*
Ligand (biochemistry)
In biochemistry and pharmacology, a ligand is a substance that forms a complex with a biomolecule to serve a biological purpose. The etymology stems from Latin ''ligare'', which means 'to bind'. In protein-ligand binding, the ligand is usually ...
*
Iron-binding proteins
*
Biometal (biology)
Biometals (also called biocompatible metals, bioactive metals, metallic biomaterials) are metals normally present, in small but important and measurable amounts, in biology, biochemistry, and medicine. The metals copper, zinc, iron, and manganes ...
References
External links
{{DEFAULTSORT:Iron-sulfur cluster
Cluster chemistry
Iron compounds
Sulfur compounds