Special Amino Acids and Protecting Groups
In contrast to the 20 natural amino acids (or proteinogenic), these amino acids are not encoded by the Universal Genetic Code – usually they can be found in nature as metabolic products, especially in plants and bacteria.
Biopeptek’s range of special amino acids comprises the following molecules. Please inquire if you do not find your desired amino acid listed:
-Alanine (3-amino-propionic acid)
-Alanine is the only natural occurring -amino acid, present e.g in panthothenic acid.
6-Aminocaproic acid (Aca, 6-Aminohexanoic acid)
This amino acid is often used as a linker to increase the distance between the peptide and an additional modification, e.g. a fluorescent dye.
?-Aminobutyric acid (Abu)
?-aminobutyric acid (or GABA) is an inhibitory transmitter of the central nerval system. It enhances permeability of postsynaptic membranes for chloride ions, thus leading to hyperpolarisation and consequently to an increase of the membrane’s activation potential.
Citrulline is a metabolic reagent in the urea metabolism pathway of many terrestric vertebrates. In this pathway, unwanted ammonia is being detoxified and eliminated.
Cysteine, Acm (Acetamidomethyl) protected
This specially protected Cys is used to selectively form disulfide bridges.
Hydroxy-proline is present almost exclusively in structural proteins (e.g. collagens or connective tissues in plant cell walls or mammals). It is formed during a posttranslational modification of proline in cells.
Norleucine (Nle = 2-amino hexanoic acid)
pyro-Glutamic acid (Pyr)
Special protecting group for N-terminus.
Amino acids carrying four different groups on their a-C atom (i.e. asymmetric C atom, or C*) are chiral substances. These a-amino acids can be found in respective L- and D-forms (enantiomers):
The predominant form in natural proteins is the L-form.
As some enzyme classes are enantioselective, i.e. they can distinguish between L- and D-forms and specifically accept only one of the two forms as substrate, this enantioselectivity makes D-amino acids a valuable tool in medicine (e.g. in peptide antibiotics) and enzyme assays.
Heavy Amino Acids
In contrast to special amino acids composed of 12C and 14N atoms, heavy amino acids can be substituted with 13C and/or 15N atoms. These heavy amino acids are non-radioactive, but 1 Da heavier than the standard amino acids. This molecular weight difference makes them useful tools for quantitative analysis of peptides by Mass Spectrometry (MS) and Nucleic Magnetic Resonance Spectroscopy (NMR) e.g. for determination of protein structure and dynamics. The standard heavy amino acids you can find: