What Are Peptides?
A peptide is a chain of amino-acid residues joined by peptide bonds. The residue order gives its sequence. To identify a particular research peptide, you may also need its terminal groups, chemical modifications and supplied form. The label KPV is a useful starting example. [1] [2]
From amino acid to residue
A peptide bond is an amide link between a carboxyl group of one amino acid and an amino group of another. Once incorporated, each amino-acid unit is called a residue. Forming the bond changes the formula relative to the two free amino acids. Some peptides use a side-chain group at the linkage. [1]
Sequence gives the order
Read an ordinary peptide sequence from its amino end (N-terminus) to its carboxyl end (C-terminus). KPV reads lysine, proline, valine. Reversing those letters would describe another sequence with the same residue count. The KPV profile shows how to check the terminal form as well. [2]
When matching a paper with a specification, write the sequence on one line and the explicit modifications, terminal groups and salt form on the next. This makes a difference such as a free acid versus a C-terminal amide visible before you compare quantities.
Examples across the reference library
| Example | What it helps explain |
|---|---|
| KPV | A three-residue sequence and the need to state terminal chemistry |
| Glutathione | A tripeptide with a gamma-glutamyl linkage and a redox distinction |
| MOTS-c | A 16-residue reference peptide associated with mitochondrial-derived peptide research |
| NAD+ | A related research compound that belongs to a different chemical class |
Glutathione illustrates a less familiar bond. Its glutamate side chain links to cysteinylglycine. MOTS-c illustrates a longer peptide, with 16 residues in the original report. NAD+ belongs to another class, an oxidised dinucleotide coenzyme, even though it appears in the same research catalogue. [3] [4]
Why the distinction matters when reading a product page
Open the research materials catalogue to see the stated presentation. A named peptide there may be a single material or one component of a blend. For a laboratory decision, match the product, quantity basis and lot code to the product specification and applicable report.
Use peptides, proteins and amino acids for chemical terminology, compound names and identifiers for a conflicting record, or the compound index for an individual molecule.
The mass and molarity guide shows how the defined entity and its molecular weight affect the interpretation of a concentration.
Explore the related evidence
| Resource | Why open it |
|---|---|
| Solid-Phase Peptide Synthesis and Where Impurities Originate | Understand synthesis-related impurity questions. |
| BPC-157 | Resolve the BPC-157 reference sequence and supplied-form questions. |
| Guides & Resources | Choose another scientific, analytical or procurement guide. |
Sources and scope
- IUPAC–IUB: Amino-acid and peptide nomenclature, 3AA-11 to 3AA-13 Definitions of a peptide, residues and terminal groups in sections 3AA-11 and 3AA-12.
- IUPAC–IUB: One-letter sequence notation, 3AA-20 to 3AA-21 Section 3AA-21 gives the direction of the one-letter sequence notation and the residue symbols.
- ChEBI. Glutathione, CHEBI:16856. Reference structure for reduced glutathione and its glutamyl side-chain linkage.
- Lee et al. (2015). MOTS-c and metabolic homeostasis. Cell Metabolism. The original study identifies a 16-residue peptide associated with the mitochondrial 12S rRNA region.