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Imidazole is incorporated into many important biological compounds. The most pervasive is the amino acid histidine, which has an imidazole side-chain. Histidine is present in many proteins and enzymes, e.g. by binding metal cofactors, as seen in hemoglobin. Imidazole-based histidine compounds play an important role in intracellular buffering. [17]
Histidine ball and stick model spinning. Histidine (symbol His or H) [2] is an essential amino acid that is used in the biosynthesis of proteins.It contains an α-amino group (which is in the protonated –NH 3 + form under biological conditions), a carboxylic acid group (which is in the deprotonated –COO − form under biological conditions), and an imidazole side chain (which is partially ...
Structure of the histidine complex [Ni(κ 3-histidinate) 2] 2-. [1] A transition metal imidazole complex is a coordination complex that has one or more imidazole ligands. Complexes of imidazole itself are of little practical importance. In contrast, imidazole derivatives, especially histidine, are pervasive ligands in biology where they bind ...
English: Top row: L-Histidine, D-Histidine and DL (or RS)-Histidine. Bottom row: same but with the alternative 3H tautomer in the imidazole ring. Bottom row: same but with the alternative 3H tautomer in the imidazole ring.
Imidazole is the side chain of histidine and is typically used at a concentration of 150 - 500 mM for elution. Histidine or histamine can also be used. Decrease in pH; When the pH decreases, the histidine residue is protonated and can no longer coordinate the metal tag, allowing the protein to be eluted.
Ergothioneine is a thiourea derivative of the betaine of histidine and contains a sulfur atom bonded to the 2-position of the imidazole ring. [19] Typical of thioureas, ergothioneine is less reactive than typical thiols such as glutathione towards alkylating agents like maleimides. It also resists oxidation by air. [9]
In nature, imidazole alkaloids are found both as secondary plant compounds and as byproducts of histidine metabolism in marine organisms. One well-known imidazole alkaloid is pilocarpine , which is present in the leaves of Paraguay jaborandi .
The bottom row shows the same three compounds with the imidazole ring drawn in its alternative tautomer form. For histidine, it has been experimentally determined by 15 N NMR spectroscopy that the 1-H tautomer is preferred over the 3-H form in samples. [11] Choice of representation for storage in a database can influence substucture searches.