Peptide Bond
Definition
The amide link between two amino acids, formed when the carboxyl group of one condenses with the amino group of the next and a molecule of water is lost. A run of these bonds is the backbone that makes a molecule a peptide.
In more detail
The peptide bond is the amide link between the carboxyl group of one amino acid and the amino group of the next, formed with the loss of a molecule of water. A chain is a series of these, and the repeating backbone they create is what every peptide has in common.
The bond has partial double-bond character, so the six atoms around it sit in a plane and rotation about it is restricted. That rigidity is why a chain folds into a limited set of shapes rather than behaving like a free string, and it is the basis of secondary structure.
It also absorbs ultraviolet light near 214 nm, which is the practical reason purity methods read at that wavelength: the detector responds to the backbone itself rather than to a feature only some sequences have.
Where this term comes up
Entries whose definition mentions Peptide Bond.
What this means for research sourcing
Foundational terminology for researchers new to peptide science. Volta's introductory resources connect these fundamentals to the compounds available for study.
Related Terms in Basics
Sequence
The order of the amino acids along a chain, written N-terminus first in one-letter or three-letter codes. The sequence is the compound's identity: two materials with different sequences are different substances whatever name is printed on the vial.
Analogue
A known peptide altered on purpose, by substituting a residue, shortening the chain or attaching something to it, so that it resists degradation or binds differently while still acting at the same target. GLP-1 SM is an analogue of GLP-1.
Endogenous and Exogenous
Endogenous describes a molecule the organism makes itself, such as native GLP-1 or growth hormone. Exogenous describes one introduced from outside. The distinction matters in assay work, because an exogenous analogue and the endogenous hormone it mimics can both be present in a sample.
Recombinant
Produced by an engineered organism rather than by chemical synthesis. A gene is expressed in bacterial or mammalian cells and the product is purified from the culture. Longer chains such as somatropin are made this way; short peptides are usually synthesised instead.
Bioregulator
A very short peptide, typically two to four residues, from a line of work begun in Russia by Khavinson and colleagues and based on fragments reported in specific tissues. The published evidence is largely Russian-language and the group has little independent replication.
Neuropeptide
A peptide that neurons release to signal to one another, acting as a transmitter or as a modulator of other transmitters. Semax and Selank are the examples most often cited in this class, both registered in Russia.
Signaling Peptide
A peptide whose function is to carry a message, binding a receptor to change what a cell does. Appetite, fluid balance and pituitary output are all regulated this way, by GLP-1, oxytocin and kisspeptin respectively.
D-Retro-Inverso
A design in which the sequence is read backwards and every L-amino acid is swapped for its D isomer. Side-chain geometry comes out close to the original while proteases, which recognise L-residues, no longer cut it. FOXO4-DRI is built this way.
