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Zinc fingers help read DNA sequences.. Zinc is an essential trace element for humans [1] [2] [3] and other animals, [4] for plants [5] and for microorganisms. [6] Zinc is required for the function of over 300 enzymes and 1000 transcription factors, [3] and is stored and transferred in metallothioneins.
A zinc finger is a small protein structural motif that is characterized by the coordination of one or more zinc ions (Zn 2+) which stabilizes the fold. The term zinc finger was originally coined to describe the finger-like appearance of a hypothesized structure from the African clawed frog ( Xenopus laevis ) transcription factor IIIA .
Naturally occurring zinc (30 Zn) is composed of the 5 stable isotopes 64 Zn, 66 Zn, 67 Zn, 68 Zn, and 70 Zn with 64 Zn being the most abundant (48.6% natural abundance).Twenty-eight radioisotopes have been characterised with the most stable being 65 Zn with a half-life of 244.26 days, and then 72 Zn with a half-life of 46.5 hours.
The formal oxidation state of the oxygen atoms is − 1 ⁄ 2. In solutions at neutral pH, the superoxide ion disproportionates to molecular oxygen and hydrogen peroxide. 2 O − 2 + 2 H + → O 2 + H 2 O 2. In biology this type of reaction is called a dismutation reaction. It involves both oxidation and reduction of superoxide ions.
For example, terpyridine, which is a tridentate ligand forms the complex [Zn(terpy)Cl 2]. Another example would involve a tripodal ligand such as Tris(2-aminoethyl)amine. Square pyramidal 5-coordinate Zinc is found in Tetra(4-pyridyl)porphinatomonopyridinezinc(II) [ 19 ] Solution studies of other 5-coordinate Zinc porphyrins have been reported.
Metallothioneins are rich in thiols, causing them to bind a number of trace metals. Metallothionein is one of the few eukaryotic proteins playing a substantial role in metal detoxification. Zinc and Cadmium are tetrahedrally coordinated to cysteine residues, and each metallothionein protein molecule may bind up to 7 atoms of Zn or Cd. [5]
Zinc is a chemical element with the symbol Zn and atomic number 30. It is a slightly brittle metal at room temperature and has a shiny-greyish appearance when oxidation is removed. It is the first element in group 12 (IIB) of the periodic table .
This dualism is an example of polymorphism. In each form, the coordination geometry at Zn and S is tetrahedral. The more stable cubic form is known also as zinc blende or sphalerite. The hexagonal form is known as the mineral wurtzite, although it also can be produced synthetically. [2]