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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 ...
A polyhistidine-tag, best known by the trademarked name His-tag, is an amino acid motif in proteins that typically consists of at least six histidine (His) residues, often at the N- or C-terminus of the protein. It is also known as a hexa histidine-tag, 6xHis-tag, or His6 tag.
In this case, one can use various free energy calculation methods to obtain the protonation free energy [15] such as biased Metropolis MC, [24] free-energy perturbation, [25] [26] thermodynamic integration, [27] [28] [29] the non-equilibrium work method [30] or the Bennett acceptance ratio method. [31] Note that the pK HH
These opposing protonation and deprotonation reactions occur in equilibrium resulting in little overall change in blood pH. The Bohr effect enables the body to adapt to changing conditions and makes it possible to supply extra oxygen to tissues that need it the most.
In orthodox two-component signaling, a histidine kinase protein autophosphorylates on a histidine residue in response to an extracellular signal, and the phosphoryl group is subsequently transferred to an aspartate residue on the receiver domain of a response regulator. In phosphorelays, the "hybrid" histidine kinase contains an internal ...
The endothelial protease vasohibin [f] uses a cysteine as the nucleophile, but a serine to coordinate the histidine base. [43] [44] Despite the serine being a poor acid, it is still effective in orienting the histidine in the catalytic triad. [43] Some homologues alternatively have a threonine instead of serine at the acid location. [43]
The protonation of isobutene in the formation of a carbocation: (CH 3) 2 C=CH 2 + HBF 4 ⇌ (CH 3) 3 C + + BF − 4; The protonation of ammonia in the formation of ammonium chloride from ammonia and hydrogen chloride: NH 3 + HCl → NH 4 Cl; Protonation is a fundamental chemical reaction and is a step in many stoichiometric and catalytic processes.
Most organic bases are considered to be weak.Many factors can affect the strength of the compounds. One such factor is the inductive effect.A simple explanation of the term would state that electropositive atoms (such as carbon groups) attached in close proximity to the potential proton acceptor have an "electron-releasing" effect, such that the positive charge acquired by the proton acceptor ...