The generic structure of an alpha amino acid in its unionized form

Amino acids (,, or ) are biologically important molecules made from amine (- NH < sub > 2 </ sub >) and carboxylic acid (- COOH ) functional groups, along with a side-chain specific to each amino acid.

The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen.

Structurally they can be classified according to the functional groups ' locations as alpha-( α -), beta-( β -), gamma-( γ -) or delta-( δ -) amino acids ; other categories relate to polarity, acid / base / neutral, and side chain group type ( including: aliphatic, acyclic, hydroxyl or sulphur-containing, aromatic ).

It lacks the NH < sub > 2 </ sub > group because of the cyclization of the side-chain and is known as an imino acid ; it falls under the category of special structured amino acids .</ ref > where R is an organic substituent known as a " side-chain "); often the term " amino acid " is used to refer specifically to these.

For example the standard glutamic acid ( glutamate ) and the non-standard gamma-amino acid gamma-amino-butyric acid ( GABA ) are respectively the brain's main excitatory and inhibitory neurotransmitters, hydroxyproline-a major component of the connective tissue collagen-is synthesised from proline, the standard amino acid glycine is used to synthesise porphyrins used in red blood cells, and the non-standard carnitine is used in lipid transport.

In 1806, the French chemists Louis-Nicolas Vauquelin and Pierre Jean Robiquet isolated a compound in asparagus that was subsequently named asparagine, the first amino acid to be discovered.

Another amino acid that was discovered in the early 19th century was cystine, in 1810, although its monomer, cysteine, was discovered much later, in 1884.

The side-chain can make an amino acid a weak acid or a weak base, and a hydrophile if the side-chain is polar or a hydrophobe if it is nonpolar.

Proline is the only proteinogenic amino acid whose side-group links to the α-amino group and, thus, is also the only proteinogenic amino acid containing a secondary amine at this position.

In chemical terms, proline is, therefore, an imino acid, since it lacks a primary amino group, although it is still classed as an amino acid in the current biochemical nomenclature, and may also be called an " N-alkylated alpha-amino acid ".

Subsequently, various modes of Chou's pseudo amino acid composition were developed for improving the quality of predicting subcellular localization of apoptosis proteins based on their sequence information alone.

The primary structure of a protein simply consists of its linear sequence of amino acids ; for instance, " alanine-glycine-tryptophan-serine-glutamate-asparagine-glycine-lysine -…".

This shape is determined by the sequence of amino acids.

A sequence of codons results in a corresponding sequence of amino acids that form a protein.

The most common motifs in the amino acid sequence of collagen are Glycine-Proline-X and Glycine-X-Hydroxyproline, where X is any amino acid other than glycine, proline or hydroxyproline.

Calreticulin binds to the synthetic peptide KLGFFKR, which is almost identical to an amino acid sequence in the DNA-binding domain of the superfamily of nuclear receptors.

The mRNA code is then translated into an amino acid chain ( sequence ) that comprises the newly made protein.

It consists of a triple helix made of the repetitious amino acid sequence glycine-X-Y, where X and Y are frequently proline or hydroxyproline.

This information is read using the genetic code, which specifies the sequence of the amino acids within proteins.

* Primary structure, such as the sequence of amino acids held together by covalent peptide bonds, is not disrupted by denaturation.

" Molecular biologists, using phylogenetics, can compare protein amino acid or nucleotide sequence homology ( i. e., similarity ) to infer taxonomy and evolutionary distances among organisms, but with limited statistical confidence.

The sequence of nucleotides in a gene is translated by cells to produce a chain of amino acids, creating proteins — the order of amino acids in a protein corresponds to the order of nucleotides in the gene.

This relationship between nucleotide sequence and amino acid sequence is known as the genetic code.

With some exceptions, a three-nucleotide codon in a nucleic acid sequence specifies a single amino acid.

They used a cell-free system to translate a poly-uracil RNA sequence ( i. e., UUUUU ...) and discovered that the polypeptide that they had synthesized consisted of only the amino acid phenylalanine.

Every sequence can, thus, be read in three reading frames, each of which will produce a different amino acid sequence ( in the given example, Gly-Lys-Pro, Gly-Asn, or Glu-Thr, respectively ).

Some web-servers and bioinformatics prediction methods have been used for predicting the classification of GPCRs according to their amino acid sequence alone, by means of the pseudo amino acid composition approach.

In all proteins, it is the amino acid sequence, which determines the protein's chemical properties and function.

Proteins with the same three-dimensional structure need not have identical amino acid sequences ; any irrelevant similarity between the sequences is evidence for common descent.

Polypeptide can refer to any single linear chain of amino acids, usually regardless of length, but often implies an absence of a defined conformation.

Peroxisome targeting signal 2 ( PTS2 ): a nonapeptide located near the N-terminus with a consensus sequence ( R / K )-( L / V / I )- XXXXX -( H / Q )-( L / A / F ) ( where X can be any amino acid ).

A specialized enzyme, sortase, cleaves the target protein at a characteristic recognition site near the protein C-terminus, such as an LPXTG motif ( where X can be any amino acid ), then transfers the protein onto the cell wall.

No currently existing algorithm is yet able to consistently predict a proteins ' tertiary or quaternary structure given only its primary structure ; learning how to accurately predict the tertiary and quaternary structure of any protein given only its amino acid sequence and the pertinent cellular conditions would be a monumental achievement.

By contrast, the cis and trans isomers of the X-Pro peptide bond ( where X represents any amino acid ) both experience steric clashes with the neighboring substitution and are nearly equal energetically.

Dopamine is synthesized in the body from within cells ( mainly by neurons and cells in the medulla of the adrenal glands ) and can be created from any one of the following three amino acids:

Deficiency in any required amino acid or cofactor will result in subsequent dopamine, norepinephrine, and epinephrine biosynthesis impairment and deficiency as well.

A protease ( also termed peptidase or proteinase ) is any enzyme that conducts proteolysis, that is, begins protein catabolism by hydrolysis of the peptide bonds that link amino acids together in the polypeptide chain forming the protein.

* Protein synthesis, as any other amino acid.

However the specific system proposed by Gamow ( known as " Gamow's diamonds ") was incorrect, as the triplets were supposed to be overlapping ( so that in the sequence GGAC ( for example ), GGA could produce one amino acid and GAC another ) and non-degenerate ( meaning that each amino acid would correspond to one combination of three bases-in any order ).

Instead, manufacturers and distributors who wish to market dietary supplements that contain a " new dietary ingredient " ( defined as " a vitamin ; a mineral ; a herb or other botanical ; an amino acid ; a dietary substance for use by man to supplement the diet by increasing total dietary intake ; or a concentrate, metabolite, constituent, extract, or combination of any of the above dietary ingredients " not marketed before October 15, 1994 ) must notify the FDA beforehand.

A non-regulatory allosteric site refers to any non-regulatory component of an enzyme ( or any protein ) that is not itself an amino acid.

Proteins produced in the symplast included RXLR proteins, which contain an arginine-X-leucine-arginine ( where X can be any amino acid ) sequence at the amino terminus of the protein.

It may also be, based on general observations of development and songbird results, that any difference between humans and non-humans would be due to regulatory sequence divergence ( affecting where and when FOXP2 is expressed ) rather than the two amino acid differences mentioned above.

In any case, vegetarian cultures often serve legumes along with grains, which are low in the essential amino acid lysine, creating a more complete protein than either the beans or the grains on their own.

The cis isomer is mainly observed in Xaa-Pro peptide bonds ( where Xaa is any amino acid ).

In molecular biology a selenoprotein is any protein that includes a selenocysteine ( Se-Cys ) amino acid residue.

The natural occurrence of such alkaloids then gives us a poser in any attempts to propose a definition of polyphenols strickly based on biosynthetic origin ( s ) grounds, for these amino acids themselves are primary metabolites of the shikimate / phenylpropanoid pathway.