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Structure of a typical L-alpha-amino acid in the "neutral" form. Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. [1] Although over 500 amino acids exist in nature, by far the most important are the 22 α-amino acids incorporated into proteins. [2] Only these 22 appear in the genetic code of life ...
The second table, appropriately called the inverse, does the opposite: it can be used to deduce a possible triplet code if the amino acid is known. As multiple codons can code for the same amino acid, the International Union of Pure and Applied Chemistry's (IUPAC) nucleic acid notation is given in some instances.
A rule of thumb for determining the D/L isomeric form of an amino acid is the "CORN" rule. The groups COOH, R, NH 2 and H (where R is the side-chain) are arranged around the chiral center carbon atom. With the hydrogen atom away from the viewer, if the arrangement of the CO→R→N groups around the carbon atom as center is counter-clockwise ...
If the pH drops, some amino acids in the polypeptide chain can become protonated if the pka of their R groups is higher than the new pH. Protonation can change the charge these R groups have. If the pH raises, some amino acids in the chain can become deprotonated (if the pka of the R group is lower than the new pH). This also changes the R ...
The migration occurs with full retention of configuration at the R-group. The migratory aptitude of the R-group is roughly tertiary > secondary ~ aryl > primary. The isocyanate formed can then be hydrolyzed to give a primary amine, or undergo nucleophilic attack with alcohols and amines to form carbamates and urea derivatives respectively.
The alpha helix is also commonly called a: Pauling–Corey–Branson α-helix (from the names of three scientists who described its structure); 3.6 13-helix because there are 3.6 amino acids in one ring, with 13 atoms being involved in the ring formed by the hydrogen bond (starting with amidic hydrogen and ending with carbonyl oxygen)
The sequence of nucleobases on a nucleic acid strand is translated by cell machinery into a sequence of amino acids making up a protein strand. Each group of three bases, called a codon, corresponds to a single amino acid, and there is a specific genetic code by which each possible combination of three bases corresponds to a specific amino acid.
A phosphate group can be attached to the sidechain hydroxyl group of serine, threonine and tyrosine residues, adding a negative charge at that site and producing an unnatural amino acid. Such reactions are catalyzed by kinases and the reverse reaction is catalyzed by phosphatases.