Methionine, cysteine, homocysteine, and taurine are the 4 common sulfur-containing amino acids, but only the first 2 are incorporated into proteins.

Serine has hydroxyl methyl group as its R group.

Glycine (Gly/G) is the amino acid with the shortest side chain, having an R-group consistent only of a single hydrogen. As a result, glycine is the only amino acid that is not chiral. Its small side chain allows it to readily fit into both hydrophobic and hydrophilic environments.

Alanine, Leucine, Valine, Isoleucine, Threonine and Methionine are the six natural amino acids containing methyl groups and labeling protocols have been developed for high yield production of deuterated proteins with 1H-13C methyl labeled amino acids with minimum scrambling.

Every amino acid also has another atom or group of atoms bonded to the central atom known as the R group. This R group, or side chain, gives each amino acid proteins specific characteristics, including size, polarity, and pH.

General structure. In the structure shown at the top of the page R represents a side chain specific to each amino acid. The carbon atom next to the carboxyl group is called the α–carbon. Amino acids containing an amino group bonded directly to the α-carbon are referred to as α-amino acids.

radical
R group: An abbreviation for any group in which a carbon or hydrogen atom is attached to the rest of the molecule. R is an abbreviation for radical, when the term radical applied to a portion of a complete molecule (not necessarily a free radical), such as a methyl group.

-CH2 -OH
The R group or side chain of the amino acid serine is -CH2 -OH.

For example, the codon CAG represents the amino acid glutamine, and TAA is a stop codon.

The chemical structure of glycine is. protein: Structures of common amino acids. The simplest amino acid is glycine, in which R is a hydrogen atom. In a number of amino acids, R represents straight or branched carbon chains. One of these amino acids is alanine, in which R is the methyl group (−CH3).

What is the R group on glycine and alanine? Aliphatic R groups are nonpolar and hydrophobic. Hydrophobicity increases with increasing number of C atoms in the hydrocarbon chain. Although these amino acids prefer to remain inside protein molecules, alanine and glycine are ambivalent, meaning that they can be inside or outside the protein molecule.

Pharmacology. Glycine is a non-essential, non-polar, non-optical, glucogenic amino acid. Glycine, an inhibitory neurotransmitter in the CNS, triggers chloride ion influx via ionotropic receptors, thereby creating an inhibitory post-synaptic potential. In contrast, this agent also acts as a co-agonist, along with glutamate,…

Each amino acid has at least one amine and one acid functional group as the name implies. The different properties result from variations in the structures of different R groups. The R group is often referred to as the amino acid side chain.