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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 ...
The triad of cytomegalovirus protease [b] uses histidine as both the acid and base triad members. Removing the acid histidine results in only a 10-fold activity loss (compared to >10,000-fold when aspartate is removed from chymotrypsin). This triad has been interpreted as a possible way of generating a less active enzyme to control cleavage ...
Chemical formula: C 6 H 9 N 3 O 2 ... (L-histidine) This page was last edited on 12 April 2023, at 11:40 (UTC). Text is available under the Creative Commons ...
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).
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 ]
pH Small Tiny Aromatic or Aliphatic van der Waals volume (Å 3) Alanine: A Ala -CH 3 - - Aliphatic 67 Cysteine: C Cys -CH 2 SH: 8.55 acidic - 86 Aspartic acid: D Asp -CH 2 COOH 3.67 acidic - 91 Glutamic acid: E Glu -CH 2 CH 2 COOH 4.25 acidic - 109 Phenylalanine: F Phe -CH 2 C 6 H 5 - - Aromatic 135 Glycine: G Gly -H - - - 48 Histidine: H His ...
[13] [16] [17] [18] [1] The normal pH in the fetus differs from that in the adult. In the fetus, the pH in the umbilical vein pH is normally 7.25 to 7.45 and that in the umbilical artery is normally 7.18 to 7.38. [19] Aqueous buffer solutions will react with strong acids or strong bases by absorbing excess H + ions, or OH −
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.