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  2. Histidine - Wikipedia

    en.wikipedia.org/wiki/Histidine

    [5] [6] [7] The imidazole/imidazolium ring of histidine is aromatic at all pH values. [8] Under certain conditions, all three ion-forming groups of histidine can be charged forming the histidinium cation. [9] The acid-base properties of the imidazole side chain are relevant to the catalytic mechanism of many enzymes. [10]

  3. His-tag - Wikipedia

    en.wikipedia.org/wiki/His-tag

    The compound added at high concentration replaces virtually all carrier-bound protein which is thus eluted from the carrier. 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

  4. Amino acid - Wikipedia

    en.wikipedia.org/wiki/Amino_acid

    Arginine has a charged guanidino group and lysine a charged alkyl amino group, and are fully protonated at pH 7. Histidine's imidazole group has a pK a of 6.0, and is only around 10% protonated at neutral pH. Because histidine is easily found in its basic and conjugate acid forms it often participates in catalytic proton transfers in enzyme ...

  5. Imidazole - Wikipedia

    en.wikipedia.org/wiki/Imidazole

    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]

  6. Histidine (data page) - Wikipedia

    en.wikipedia.org/wiki/Histidine_(data_page)

    Chemical formula: C 6 H 9 N 3 O 2 Molar mass: 155.16 g·mol −1 Systematic name: 2-amino-3-(3H-imidazol-4-yl)propanoic acid Abbreviations: H, His Synonyms: Imidazole alanine ({S/D})-α-amino-1H-imidazole-4-propanoic acid

  7. Isoelectric point - Wikipedia

    en.wikipedia.org/wiki/Isoelectric_point

    The isoelectric point (pI, pH(I), IEP), is the pH at which a molecule carries no net electrical charge or is electrically neutral in the statistical mean. The standard nomenclature to represent the isoelectric point is pH(I). [ 1 ]

  8. Transition metal imidazole complex - Wikipedia

    en.wikipedia.org/wiki/Transition_metal_imidazole...

    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 ...

  9. Histamine - Wikipedia

    en.wikipedia.org/wiki/Histamine

    Histamine is an organic nitrogenous compound involved ... (with a normal pH range of 7. ... Histamine is derived from the decarboxylation of the amino acid histidine, ...