Protein
Definition
A long amino acid chain, usually above the 50-residue convention, that folds into a defined three-dimensional structure. Collagen, insulin and antibodies are proteins; the shorter chains studied as research peptides are not, although the chemistry of the backbone is identical.
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Where this term comes up
Entries whose definition mentions Protein.
What this means for research sourcing
Foundational terminology for researchers new to peptide science. Volta's beginner resources connect these fundamentals to the compounds available for study.
Related Terms in Basics
Peptide Bond
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.
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. Semaglutide 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.