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The iron sulfur proteins contain iron–sulfur clusters, some with elaborate structures, that feature iron and sulfide centers. One broad biosynthetic task is producing sulfide (S 2-), which requires various families of enzymes. Another broad task is affixing the sulfide to iron, which is achieved on scaffolds, which are nonfunctional.
Iron sulfides occur widely in nature in the form of iron–sulfur proteins. As organic matter decays under low-oxygen (or hypoxic) conditions such as in swamps or dead zones of lakes and oceans, sulfate-reducing bacteria reduce various sulfates present in the water, producing hydrogen sulfide. Some of the hydrogen sulfide will react with metal ...
Three sulfide ions bridge two iron ions each, while the fourth sulfide bridges three iron ions. Their formal oxidation states may vary from [Fe 3 S 4] + (all-Fe 3+ form) to [Fe 3 S 4] 2− (all-Fe 2+ form). In a number of iron–sulfur proteins, the [Fe 4 S 4] cluster can be reversibly converted by oxidation and loss of one iron ion to a [Fe 3 ...
These organisms can use iron as either an electron donor, Fe(II) → Fe(III), or as an electron acceptor, Fe (III) → Fe(II). [30] Another example is the cycling of nitrogen. Many lithotrophic bacteria play a role in reducing inorganic nitrogen (nitrogen gas) to organic nitrogen in a process called nitrogen fixation. [28]
The important sulfur cycle is a biogeochemical cycle in which the sulfur moves between rocks, waterways and living systems. It is important in geology as it affects many minerals and in life because sulfur is an essential element (), being a constituent of many proteins and cofactors, and sulfur compounds can be used as oxidants or reductants in microbial respiration. [1]
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. [ 2 ] Many Fe–S clusters are known in the area of organometallic chemistry and as precursors to synthetic analogues of the biological clusters.
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 to the "iron protein" first purified in 1962 by Mortenson, Valentine, and Carnahan from the anaerobic bacterium Clostridium pasteurianum.
Absorption of dietary iron in iron salt form (as in most supplements) varies somewhat according to the body's need for iron, and is usually between 10% and 20% of iron intake. Absorption of iron from animal products, and some plant products, is in the form of heme iron, and is more efficient, allowing absorption of from 15% to 35% of intake.