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For amino acids with charged side chains, the pK a of the side chain is involved. Thus for aspartate or glutamate with negative side chains, the terminal amino group is essentially entirely in the charged form −NH + 3 , but this positive charge needs to be balanced by the state with just one C-terminal carboxylate group is negatively charged.
The "side chain" from the α carbon connects to the nitrogen forming a pyrrolidine loop, classifying it as a aliphatic amino acid. It is non-essential in humans, meaning the body can synthesize it from the non-essential amino acid L-glutamate. It is encoded by all the codons starting with CC (CCU, CCC, CCA, and CCG).
Also, amino acid side chain affinity for water was measured using vapor phases. [14] Vapor phases represent the simplest non polar phases, because it has no interaction with the solute. [18] The hydration potential and its correlation to the appearance of amino acids on the surface of proteins was studied by Wolfenden.
Similar functionality is also presented in serine and threonine, whose side chains have a hydroxy group, but are alcohols. Phosphorylation of these three amino acids' moieties (including tyrosine) creates a negative charge on their ends, that is greater than the negative charge of the only negatively charged aspartic and glutamic acids ...
The side chain connected to the alpha-carbon is specific for each amino acid and is responsible for determining charge and polarity of the amino acid. The amino acid side chains are also responsible for many of the interactions that lead to proper protein folding and function. [ 5 ]
Lysine. Technically, any organic compound with an amine (–NH 2) and a carboxylic acid (–COOH) functional group is an amino acid. The proteinogenic amino acids are a small subset of this group that possess a central carbon atom (α- or 2-) bearing an amino group, a carboxyl group, a side chain and an α-hydrogen levo conformation, with the exception of glycine, which is achiral, and proline ...
Since most enzymes have an optimum pH of 6 to 7, the amino acids in the side chain usually have a pK a of 4~10. Candidate include aspartate , glutamate , histidine , cysteine . These acids and bases can stabilise the nucleophile or electrophile formed during the catalysis by providing positive and negative charges.
The amino-acid side-chains are on the outside of the helix, and point roughly "downward" (i.e., toward the N-terminus), like the branches of an evergreen tree (Christmas tree effect). This directionality is sometimes used in preliminary, low-resolution electron-density maps to determine the direction of the protein backbone.