Sulfur hexafluoride (SF 6) or sulphur hexafluoride (British spelling) is an extremely potent and persistent greenhouse gas that is primarily utilized as an electrical insulator and arc suppressant. It is inorganic, colorless, odorless, non-flammable, and non-toxic. SF 6 has an octahedral geometry, consisting of six fluorine atoms attached to a central sulfur atom.

Iron–sulfur proteins (or iron–sulphur proteins in British spelling) are proteins characterized by the presence of iron–sulfur clusters containing sulfide-linked di-, tri-, and tetrairon centers in variable oxidation states.Iron–sulfur clusters are found in a variety of metalloproteins, such as the ferredoxins, as well as NADH dehydrogenase, hydrogenases, coenzyme Q – cytochrome c ...