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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 CID 71083 from PubChem (D-histidine) ^a CID 6274 from PubChem (L-histidine) This page was last edited on 12 April 2023, at 11:40 (UTC). Text is ...
The enzyme histidine decarboxylase (EC 4.1.1.22, HDC) is transcribed on chromosome 15, region q21.1-21.2, and catalyzes the decarboxylation of histidine to form histamine. In mammals, histamine is an important biogenic amine with regulatory roles in neurotransmission , gastric acid secretion and immune response .
where c = composition, p = polarity, and v = molecular volume; and are constants of squares of the inverses of the mean distance for each property, respectively equal to 1.833, 0.1018, 0.000399. According to Grantham's distance, most similar amino acids are leucine and isoleucine and the most distant are cysteine and tryptophan.
Deamidation reactions have been conjectured to be one of the factors that limit the useful lifetime of proteins. [1]Deamidation proceeds much more quickly if the susceptible amino acid is followed by a small, flexible residue such as glycine whose low steric hindrance leaves the peptide group open for attack.
Free base (freebase, free-base) is a descriptor for the neutral form of an amine commonly used in reference to illicit drugs. The amine is often an alkaloid , such as nicotine , cocaine , morphine , and ephedrine , or derivatives thereof.
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.
A conservative replacement (also called a conservative mutation or a conservative substitution or a homologous replacement) is an amino acid replacement in a protein that changes a given amino acid to a different amino acid with similar biochemical properties (e.g. charge, hydrophobicity and size).