Peptides are chemical compounds that comprise of two or more amino acids or amino acid polymers joined together by peptide bonds. The bonds happen to be exceptional linkages within which one amino acid’s nitrogen atom binds to another’s carboxyl carbon atom. Molecules that have molecular weights, which range between thousands to millions of Daltons, are referred to as polypeptides. A polypeptide is a term interchangeably used with protein in most cases. Dipeptides are the shortest peptides and they comprise of two amino acids that are joined together by one peptide bond. Tripeptides are the second shortest peptides followed by tetrapeptides etc. A long continuous unbranched peptide chain is called a polypeptide. Peptides are categorized under the wide biological oligomers and polymers classes, together with oligosaccharides, polysaccharides, and nucleic acids.

Short History

The 1st synthetic peptide glycyl-glycine was discovered in the year 1901 by Emil Fischer and Ernest Fourneau. It was in the year 1953 that Vincent du Vigneaud synthesized the 1st polypeptide (oxytocin – 9 amino acid sequence). It is on size basis that peptides are distinguished from proteins, as well as a random standard can be assumed to contain roughly fifty or less amino acids. Proteins comprise of 1 or more polypeptides that are arranged in some biologically functional manner, frequently bound to ligands like cofactors and coenzymes, or even another protein or further macromolecule (RNA, DNA, etc.) or to multifaceted macromolecular assemblies. Size boundaries differentiating proteins and polypeptides from peptides are not absolute (Small proteins like insulin have been regarded as peptides while long peptides like amyloid beta have been regarded to as proteins). More about peptide history can be found at



Amino acids, which have been combined into peptides, are called residues because of either the amine and hydrogen ion release or the carboxyl end hydroxyl release or even both, as the release of a water molecule takes place during each amide bond’s formation. Every peptide excluding cyclic peptides has a C-terminal and an N-terminal residue at the peptides end. It is in accordance with the quantity of amino acid residues that peptides are frequently classified.


Classification of Peptides

There exists various categories that peptides are divided into, founded on their manner of production.  Ribosomal peptides- These are synthesized through mRNA translation. They are frequently exposed to proteolysis for a mature form generation. They typically function within higher organisms as signaling molecules and hormones. More or fewer organisms produce peptides as antibiotics like microcins. Due to the fact that they are translated, the amino acid residues that are involved are limited to the ones used by the ribosome. Peptide fragments- these are protein fragments, which are utilized in quantifying or identifying the source protein. these are frequently the enzymatic degradation (carried out within the lab in some controlled sample, however, may as will be forensic or paleontological samples, which get degraded due to natural effects) products. Milk peptides- 2 milk peptides occurring naturally are made from the milk protein casein after this is broken down by digestive enzymes. They may as well be formed from the proteinases that are formed by lactobacilli in the course of milk fomentation. Other classes of peptides include peptones and nonribosomal peptides.

Molecular Biology

It is due to a number of reasons that peptides received importance in molecular biology. One of such reasons is that they permit peptide antibodies creation within animals in the absence of the need to purify the protein of interest. This includes creating antigenic peptides for sections of the interest protein. They are then utilized to make antibodies within a mouse or a rabbit against the protein. Another thing is that peptides are becoming instrumental within mass spectrometry, making it possible for the interest protein identification on the basis of peptide sequence and masses. Here, the peptides are frequently created by in-gel digestion after the protein’s’ electrophoretic separation.

Recently, peptides have been utilized in the study of protein function as well as structure. A good example is that synthetic peptides may be utilized as inquiries to see where the interactions of peptide and proteins occur. Inhibition peptides are utilized in clinical research in examining peptides’ effects on cancer protein and other diseases’ inhibition. For instance, among the highly promising application is by means of peptides, which target LHRH. Such peptides behave as an agonist, which means that they bind to a cell in LHRH receptors regulatory manner. The cell receptors inhibiting process proposes that peptides may be quite significant in prostate cancer treatment, but more research is needed.