3Fe4S

3Fe4S most commonly denotes the [3Fe-4S] iron–sulfur cluster, a redox-active assembly found in a variety of metalloproteins. The cluster contains three iron atoms bridged by four sulfide ligands, forming an Fe3S4 core. In proteins, the cluster is coordinated to the protein framework by cysteine or other ligating residues that anchor the irons. The [3Fe-4S] cluster participates in electron transfer and catalysis and can interconvert between oxidation states, typically existing as [3Fe-4S]2+ or [3Fe-4S]1+ depending on the redox environment. It is often more sensitive to oxidative damage than some other iron–sulfur clusters and can undergo rearrangements under oxidative stress.

Biological role: [3Fe-4S] clusters are found in various ferredoxins and other enzymes that shuttle electrons in anaerobic metabolism and photosynthesis. They act as redox centers, coupling electron transfer with substrate activation in certain metabolic pathways and enzymatic reactions.

Other meaning: 3Fe4S can also be written as Fe3S4, the chemical formula for greigite, a naturally occurring iron sulfide mineral with an inverse spinel structure. Greigite forms in sedimentary and hydrothermal environments and is studied for its magnetic properties and potential spintronic applications.

Context matters: To avoid ambiguity, researchers usually specify [3Fe-4S] for the iron–sulfur cluster, or Fe3S4 for the mineral greigite, with the context indicating whether the discussion is biological/inorganic clusters or mineralogy.