Iron recognition element

Two well characterized internal loops that serve as protein recognition elements in an RNA mediated regulation are the Iron Responsive Element, IRE, found in the 5 -untranslated region (UTR) of ferritin mRNA and the 3 UTR of transferrin receptor mRNA and the Rev Response Element, RRE, found in the env gene of the HIV-1 retrovirus. These RNA elements are the binding sites of the IRP and Rev proteins respectively. 

The first transition element compound containing only carbocyclic rings as ligands was bis(ri5-cyclopentadienyl)iron, [Fe(r 5-C5H5)2], which has a sandwich structure with two parallel p5- or Ji-bonded rings. The recognition that this compound was amenable to electrophilic substitution, similar to the aromatic behaviour of benzene, led to the suggestion of the non-systematic name ferrocene and to similar names for other metallocenes . 

The recognition of metals as integral parts of enzyme systems has led to investigations aimed at elucidating their functional role in the catalytic process. Of the transition metals, iron has been best studied in this regard. This stems from several circumstances first, the characteristic color of the heme pigments early called attention to this element second, the concentration of iron in liver, muscle, and red cells is high, relative to the other transition elements third, the functional heme unit can be isolated with... 

Fourcroy and Hatiy suggested chromium as a suitable name for the element in recognition of the various colours shown by its derivatives, Greek khroma colour. The same year Vauquelin detected chromium in the spinel ruby while Taessert showed it to be an essential constituent of chrome iron ore or chromite, FeO.Cr2Os — now the main source of chromium compounds. The colour of the ruby is now usually attributed to its chromium content and artificial rubies are manufactured by fusing pure alumina with a little oxide of chromium, to colour it, in an... 

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