A dipeptide is an organic compound derived from two amino acids . The constituent amino acids may be the same or different. Depending on the sequence, two isomers of the dipeptide are possible, when separated. Many dipeptides are physiologically important, and some are physiologically and commercially important. One well-known dipeptide is aspartame , an artificial sweetener .
Dipeptides are white solids. Many parent amino acids are far more soluble in water than they are.  For example, the dipeptide Ala-Gln has a solubility of 586 g/L that is 10-fold higher than the solubility of Gln (35 g/L). Dipeptides can also exhibit different stability, for example with respect to hydrolysis. Gln does not withstand sterilization processes, whereas this dipeptide does. Because dipeptides are prone to hydrolysis, high solubility is used in infusion, that is, to provide nutrition.
About six dipeptides are of commercial interest.
- Aspartame ( N – L -α-aspartyl- L – phenylalanine 1-methyl ester) is an artificial sweetener .
- Carnosine ( beta -alanyl- L -histidine) and fool ( beta -alanyl- N -methyl histidine) are highly concentrated in muscle and brain tissue . They are used in sports medicine.
- acetylcarnosine , cataract prevention
- Ala-gln and gly-tire , infusion 
- Val-Tire, Antihypertensive
- Homoanserine ( N- (4-aminobutyryl) -L – histidine) is another dipeptide identified in the brain and muscle of mammals.
- Diphenylalanine is the most studied building block in peptide nanotechnology
- Kyotorphin ( L -tyrosyl- L -arginine) is a neuroactive dipeptide that plays a role in pain regulation in the brain.
- Balanine [JA] (or ophidin) ( beta- alnyl – N tau -methyl histidine) has been identified in the muscles of several species of mammal (including humans) and chicken .
- Glorin ( N -propionyl-γ- L -glutamyl- L -ornithine-δ-lac ethyl ester) is a chemotactic dipeptide for the slime mold Polysphondylium violaceum .
- Barytin ( cyclo -[(6-bromo-8-N-tryptophan)-arginine]) is a cyclic dipeptide from the marine sponge Geodia barytii .
- Dylanine is commonly used as a model in molecular dynamics .
Dipeptides are formed by the coupling of amino acids. The amino group on one amino acid is rendered non-nucleophilic (P in EQ) and the inactive carboxylic acid group on the other amino acid as its methyl ester. The two modified amino acids are linked in the presence of a coupling agent, which facilitates the formation of an amide bond:
RCH (NHP) CO 2 H + R’CH (NH 2 ) CO 2 CH 3 → RCH (NHP) C (O) NH (CHR’) CO 2 CH 3 + H 2 O
Following this coupling reaction, the amine protecting group P and the ester are converted to free amines and carboxylic acids, respectively. 
For many amino acids, auxiliary functional groups are conserved . The condensation of amines and carboxylic acids to form peptide bonds usually employs coupling agents to activate the carboxylic acid. 
Bergmann azlactone peptide synthesis is a classic organic synthesis for the preparation of dipeptides.
Dipeptides are generated from polypeptides by the action of the hydrolase enzyme dipeptidyl peptidase .  Dietary proteins are digested into dipeptides and amino acids, and dipeptides are absorbed more rapidly than amino acids, as a different mechanism is involved in their absorption. Dipeptides activate G-cells in the stomach to secrete gastrin .
Diketopiperazines (Cyclic Dipeptides)
Diketopiperazines are a special class of dipeptides, which are cyclic. They are formed as side products in peptide synthesis. Many have been produced from non-canonical amino acids.
Nomenclature of peptido :
The peptido has a free -NH 2 group at one end and a free COOH group at the other end, the first end is called the N-terminal and the other end is called the C-terminal.
In the structure of a peptide, the N-terminal is always written on the left side and the C-terminal is always written on the right side. In the nomenclature of the peptide, the names of amino acids other than the C-terminal amino acids are removed and written by adding Il (-yl) in sequence from left to right.
Determination of Peptide Structure: The structure of a peptide is determined on the basis of the number of amino acids present in it and the sequence of their addition.
The number of amino acids is determined by the decomposition of the polypeptide.
1. Decomposition of Poly Peptide :
On acidic hydrolysis of polypeptide, all the peptide bonds present in it are broken and a mixture of amino acids is obtained, analysis of amino acids by chromatography, ion exchange and electrophoresis etc. The concentration is known.
2. To find the sequence of amino acids in a peptide :
A peptide is a bifunctional group, with free NH 2 at one end and a free COOH group at the other.
Their sequence is known as follows –
(i) Method of determination of N-terminal amino acid : The following two methods are used in this series
(a) Sanger method / DNP method : In this method the Sanger reagent 1-fluoro 2,4-di nitro benzene (FDNB) is reacted with the peptide in the presence of sodium bicarbonate solution at room temperature, then 2 of the peptide, 4-Die nitrophenyl derivative (DNP) is formed.
Whose hydrolysis in acidic medium gives a mixture of independent amino acids with N-terminal amino acids bonded with dinitrophenyl group, amino acid containing dinitrophenyl group is yellow in color, so it can be easily identified and separated. is taken.
(b) Edmon Method :
In this method, the peptide is reacted with phenyl isothio cyanate in the presence of dilute base, then phenyl isothio cyanate reacts with the Fe NH 2 group of the peptide, after which acidic hydrolysis of the identified peptide forms phenyl thio high dentide. which is a cyclic amide, it can be identified by comparing it with a hydantoide obtained from a standard amino acid.
(ii) C-terminal amino acid determination method : The following two methods are used in this series
(a) Hydrazino lysis method : In this method the peptide is heated with dry hydrazine which converts all amino acids except c-terminal amino acids into hydrazide, this mixture is called colum chromate containing strong cation exchange resin adsorbent. separated by graphene method. Due to the strong alkaline nature, hydrazides are adsorbed in the column and the C terminal amino acids are separated from the mixture by passing through the column and are easily identifiable.
synthesis of peptido
In peptide synthesis, it is necessary to preserve the independent NH 2 or -COOH group, otherwise both functional groups present in the amino acid condense with another molecule of the same amino acid.
The synthesis of peptide takes place in three steps –
(1) Protection of NH 2 or -COOH group : (protection)
(2) condensation of amino acids
(3) Removal of the protected group i.e. (deprotection)
Solid Phase Peptide Synthesis Method:
RB Mary Field developed this method of peptide synthesis.
This method is mainly used in the formation of large peptide chains like insulin etc.
In this method the amino acid at the C-terminal of the peptide is joined by an ester bond with a solid polymer such as polystyrene resin. This provides a solid base and eventually the peptide chain is separated from the polymer.
In this method the NH 2 group of an amino acid is protected by a tertiary butyloxycarbonyl group.
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Frequently Asked Question
Where are dipeptides found?
Dipeptides are usually derived from polypeptides cleaved by a specialized peptidase (ie dipeptidyl peptidase, a hydrolase enzyme). Dipeptides are found to stimulate the release of gastrin from G-cells in the stomach.
What are dipeptides used for?
Peptides composed of two amino acid units. Used as a dietary supplement and sugar substitute. A prodrug of an ACE inhibitor is used to treat high blood pressure and congestive heart failure.
What does a dipeptide look like?
Dipeptides are white solids. Many parent amino acids are far more soluble in water than they are. For example, the solubility of 586 g/L in the dipeptide Ala-Gln is 10x greater than that of Gln (35 g/L). Dipeptides can also exhibit different stability, for example with respect to hydrolysis.
Can a dipeptide be a protein?
A dipeptide is a small protein consisting of only two amino acids linked together by a peptide bond. Many different dipeptides can be made using dehydration synthesis, which removes a molecule of water, resulting in the formation of a peptide bond.
What is a peptide, classify them?
Molecules of amino acids have both acidic -COOH group and basic -NH2 group, so COOH group of one amino acid reacts with -NH2 of other amino acid to form amide or salt, it is called peptide. The amino acids in a peptide are linked together by a peptide bond.