How to use this glossary
Peptide research has a vocabulary of its own, and the same handful of terms show up again and again — in mechanism explainers, on certificates of analysis, and across every compound guide in the Research Hub. This glossary collects the ones you are most likely to meet and defines each in plain language, grouped into molecule and structure terms, mechanism and receptor terms, and quality and handling terms.
Every entry is a factual, educational definition of how a term is used in the scientific literature. Where a term maps to a compound Peptora covers, the definition links out to the relevant guide — for example GLP-3 RT, NAD+, or GHK-Cu — so you can see the word in context.
New to research peptides?
Start with the guides that put every term in context — mechanisms, compound profiles, and laboratory standards, all written for research use only.
Explore the research guidesMolecule & structure terms
Start here: the words that describe what a peptide actually is and how it is built. These terms recur in every other section, so they are the natural foundation for the rest of the glossary.
| Term | Definition |
|---|---|
| Peptide | A short chain of amino acids linked by peptide bonds. Peptides are generally defined as chains shorter than roughly 50 amino acids; longer chains are classed as proteins. |
| Amino acid | The building block of peptides and proteins. Twenty standard amino acids combine in different orders to define each molecule's identity. |
| Peptide bond | The covalent amide bond that joins one amino acid to the next along the chain. |
| Residue | A single amino acid unit within a chain — what remains of each amino acid once the peptide bonds have formed. |
| Amino acid sequence | The specific order of amino acids in a peptide. This primary structure determines how the molecule folds and behaves. |
| Peptide vs. protein | A size convention rather than a hard rule: short chains (roughly under 50 residues) are peptides, while longer folded chains are proteins. |
| Analog (analogue) | A peptide whose sequence is modified from a natural template to alter properties such as stability or receptor selectivity — for example, engineered incretin analogs. |
| Molecular weight (Da / kDa) | The mass of the molecule, reported in daltons (Da) or kilodaltons (kDa). Larger peptides carry higher molecular weights. |
Mechanism & receptor terms
This is the pharmacology vocabulary — the terms that describe how a peptide interacts with the body's signaling machinery in a research setting. Four of them unlock most of the rest:
Four terms that unlock the rest
Receptor
The protein a peptide binds to. Binding is what triggers a downstream signal.
Agonist
A molecule that binds a receptor and activates it, producing a response.
Antagonist
A molecule that binds a receptor and blocks or dampens it without activating it.
Secretagogue
A substance that prompts the release of another substance — such as a hormone.
| Term | Definition |
|---|---|
| Receptor | A protein, often on a cell surface, that a peptide or other molecule binds to, triggering a downstream response. Many research peptides are studied for the receptors they engage. |
| Ligand | Any molecule that binds a receptor. A peptide acting on a receptor is one kind of ligand. |
| Agonist | A ligand that binds a receptor and activates it. A triple-receptor agonist such as GLP-3 RT is studied for engaging three receptors at once. |
| Antagonist | A ligand that binds a receptor and blocks or reduces its activity without activating it — the functional opposite of an agonist. |
| GLP-1 receptor | The glucagon-like peptide-1 receptor, studied in metabolic research for its associations with insulin secretion and satiety signaling. |
| GIP receptor | The glucose-dependent insulinotropic polypeptide receptor — the other major incretin receptor studied in metabolism and lipid handling. |
| Glucagon receptor | A receptor associated in research with energy expenditure and hepatic glucose and lipid metabolism. |
| Incretin | A class of gut hormones (principally GLP-1 and GIP) released after nutrient intake and studied for their role in insulin signaling. |
| Secretagogue | A substance that prompts another substance to be released. Growth-hormone secretagogues, for instance, are studied for their effect on GH release. |
| GHRH | Growth-hormone-releasing hormone — the peptide that signals the pituitary to release growth hormone, and the template behind analogs such as Tesamorelin and Sermorelin. |
| Half-life | The time for half of a peptide to be cleared or degraded — a key property in how long a molecule persists in a research model. |
| Sirtuin | A family of enzymes involved in cellular metabolism and studied in longevity research; their activity is linked to NAD+. |
| Bioavailability | The proportion of a substance that reaches its target in active form. Peptides often have low oral bioavailability, which shapes how they are studied. |
Peptide families you'll see referenced
Research peptides are often grouped into families defined by what they act on or how they are built. These labels are shorthand you will see across the compound guides:
| Term | Definition |
|---|---|
| Incretin mimetic | A peptide that mimics incretin hormones by activating the GLP-1 receptor (and sometimes the GIP and glucagon receptors), such as GLP-3 RT. |
| Copper peptide | A peptide complexed with a copper ion, such as GHK-Cu, studied in skin- and tissue-research contexts. |
| Mitochondrial peptide | A peptide encoded by or acting on the mitochondria (for example MOTS-c or SS-31), studied in metabolism and cellular-energy research. |
| Growth-hormone secretagogue | A peptide studied for prompting growth-hormone release, such as Sermorelin and CJC-1295 / Ipamorelin. |
| Peptide blend | A formulated combination of two or more peptides supplied together for research convenience. |
Quality, testing & handling terms
Finally, the vocabulary of the vial itself — how a research peptide is supplied, prepared, and verified. These are the terms that appear on a certificate of analysis and in the handling guides:
How a peptide's quality is verified
HPLC
The standard analytical method for measuring how pure a peptide is.
Mass spectrometry
Confirms a peptide's identity by measuring its precise molecular mass.
Certificate of analysis
The batch-specific report of a peptide's measured purity and identity.
Purity
The share of a sample that is the target peptide — Peptora verifies to 99%+.
| Term | Definition |
|---|---|
| Lyophilization | Freeze-drying: removing water from a peptide solution to yield a stable dry powder for storage and shipping. |
| Lyophilized powder | The freeze-dried form in which research peptides are typically supplied. |
| Reconstitution | Dissolving a lyophilized peptide in a suitable solvent to form a solution before research use. Full handling is covered in the reconstitution guide. |
| Bacteriostatic water | Water containing a small amount of preservative, commonly referenced as a solvent for reconstitution in laboratory handling. |
| HPLC | High-performance liquid chromatography — the standard analytical method for measuring a peptide's purity. |
| Mass spectrometry (LC-MS) | An analytical method that confirms a peptide's identity by measuring its molecular mass. |
| Certificate of analysis (COA) | The batch-specific document reporting a peptide's measured purity and confirmed identity. Every Peptora order ships with one. |
| Purity | The percentage of a sample that is the target peptide. Peptora verifies its peptides to 99%+ purity by HPLC. |
| Subcutaneous (research context) | Beneath the skin — a route described in the scientific literature for how peptides are administered in research models. This describes how studies are conducted, not a use instruction; Peptora's materials are for laboratory research only and not for human or animal use. |
| Research use only (RUO) | A designation meaning the material is supplied strictly for laboratory research and is not intended for human or veterinary use. |
Further reading
For readers who want the primary science behind this vocabulary, the foundational reviews below — indexed on PubMed — cover peptide drug discovery, therapeutic-peptide development, and the receptor pharmacology of the incretin system. They describe peptide science broadly and are provided for educational context only.
- 1Muttenthaler M, King GF, Adams DJ, Alewood PF. Trends in peptide drug discovery. Nat Rev Drug Discov. 2021;20(4):309-325. doi:10.1038/s41573-020-00135-8 (PMID: 33536635).
- 2Lau JL, Dunn MK. Therapeutic peptides: historical perspectives, current development trends, and future directions. Bioorg Med Chem. 2018;26(10):2700-2707. doi:10.1016/j.bmc.2017.06.052 (PMID: 28720325).
- 3Drucker DJ. Mechanisms of action and therapeutic application of glucagon-like peptide-1. Cell Metab. 2018;27(4):740-756. doi:10.1016/j.cmet.2018.03.001 (PMID: 29617641).
- 4Campbell JE, Drucker DJ. Pharmacology, physiology, and mechanisms of incretin hormone action. Cell Metab. 2013;17(6):819-837. doi:10.1016/j.cmet.2013.04.008 (PMID: 23684623).
Put these terms to work
See the whole vocabulary come together around one molecule in the flagship compound guide — for laboratory research use only.
Read the GLP-3 RT guideKey takeaways
- A peptide is a short chain of amino acids joined by peptide bonds; chains longer than roughly 50 residues are classed as proteins.
- A receptor is the protein a peptide binds; an agonist activates it, while an antagonist occupies it without activating it.
- Incretins (GLP-1, GIP) and secretagogues are defined by what they prompt the body to release — the vocabulary behind many metabolic and growth-hormone research peptides.
- Lyophilization (freeze-drying) and reconstitution describe how research peptides are shipped and prepared; HPLC and mass spectrometry verify their purity and identity.
- A certificate of analysis (COA) reports a batch's measured purity and identity, and "research use only" means the material is for laboratory research, not human or veterinary use.
- Every Peptora peptide is HPLC-verified to 99%+ purity with a lot-specific certificate of analysis.
Frequently asked questions
This article is intended solely as an educational summary of publicly available scientific literature. Products offered by Peptora are supplied exclusively for laboratory research purposes and are not approved for human or veterinary use. The information presented should not be interpreted as medical advice, treatment recommendations, or clinical guidance.
