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  2. Histidine - Wikipedia

    en.wikipedia.org/wiki/Histidine

    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 protonated), classifying it as a ...

  3. Catalytic triad - Wikipedia

    en.wikipedia.org/wiki/Catalytic_triad

    The positive charge on the basic residue is simultaneously stabilised, leading to its polarisation. [3] Two amino acids have acidic side chains at physiological pH (aspartate or glutamate) and so are the most common members of the acidic triad residue. [3]

  4. 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 ]

  5. Salt bridge (protein and supramolecular) - Wikipedia

    en.wikipedia.org/wiki/Salt_bridge_(protein_and...

    The midpoint of the titration curve corresponds to the pK a, or the pH where the ratio of protonated: deprotonated molecules is 1:1. Continuing with the T4 lysozyme example, a titration curve is obtained through observation of a shift in the C2 proton of histidine 31 (Figure 5).

  6. Acid–base homeostasis - Wikipedia

    en.wikipedia.org/wiki/Acid–base_homeostasis

    Acid–base homeostasis is the homeostatic regulation of the pH of the body's extracellular fluid (ECF). [1] The proper balance between the acids and bases (i.e. the pH) in the ECF is crucial for the normal physiology of the body—and for cellular metabolism. [1]

  7. Protein phosphorylation - Wikipedia

    en.wikipedia.org/wiki/Protein_phosphorylation

    Thus, below pH 5.5, phosphates add a single negative charge; near pH 6.5, they add 1.5 negative charges; above pH 7.5, they add 2 negative charges. The relative amount of each isoform can also easily and rapidly be determined from staining intensity on 2D gels.

  8. Gibbs–Donnan effect - Wikipedia

    en.wikipedia.org/wiki/Gibbs–Donnan_effect

    Donnan equilibrium across a cell membrane (schematic). The Gibbs–Donnan effect (also known as the Donnan's effect, Donnan law, Donnan equilibrium, or Gibbs–Donnan equilibrium) is a name for the behaviour of charged particles near a semi-permeable membrane that sometimes fail to distribute evenly across the two sides of the membrane. [1]

  9. His-tag - Wikipedia

    en.wikipedia.org/wiki/His-tag

    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.