A plain-language reference for the terms that come up when reading peptide research papers, product pages and certificates of analysis. Each entry is a short definition; where Rogue has a deeper research overview, the term links to it.
All compounds mentioned are sold for laboratory research use only. This glossary explains terminology and is not guidance for human or veterinary use.
Jump to: Testing & quality · Peptide chemistry · Research & biology · Compound classes · Regulatory
Testing & quality terms
- Acetate salt
- A peptide supplied with acetate as its counter-ion instead of TFA. Many labs prefer acetate forms because acetate is gentler in cell-based experiments. See also TFA salt.
- Batch number
- An identifier for one production run of a compound. A batch number ties a physical vial to the specific test results for that run, which is why it should match the number on the certificate of analysis.
- Certificate of Analysis (COA)
- A document from a testing lab reporting the results for one batch, typically purity by HPLC and identity by mass spectrometry. A COA is only meaningful if its batch number matches the vial. See how to read a peptide COA and the COA Library.
- Chromatogram
- The graph produced by an HPLC run. Each peak represents a substance passing the detector; the main peak is the target peptide and smaller peaks are impurities. Purity is calculated from the area of the main peak relative to all peaks.
- Endotoxin testing
- Testing for bacterial endotoxins (lipopolysaccharides), usually by the LAL method. Endotoxins can interfere with cell and animal experiments even at very low levels.
- HPLC (high-performance liquid chromatography)
- An analytical method that separates the components of a sample so each can be measured. In peptide testing, HPLC is the standard way to report purity as a percentage.
- Identity testing
- Confirming that a sample is the compound it claims to be, most often by matching its measured mass to the expected molecular weight using mass spectrometry. Purity and identity are separate questions: a sample can be pure but the wrong compound.
- ISO/IEC 17025
- The international standard for the competence of testing and calibration laboratories. Accreditation means an outside body has audited the lab’s methods, equipment and quality system.
- Lyophilized
- Freeze-dried. Peptides are commonly supplied as a lyophilized powder or “cake” because removing water improves stability during storage and shipping. Lyophilized research peptides are typically stored refrigerated.
- Mass spectrometry (MS)
- A technique that measures the mass of molecules. For peptides it confirms identity: the observed mass should match the calculated molecular weight of the sequence. LC-MS combines liquid chromatography with mass spectrometry.
- Molecular weight
- The mass of one molecule, usually given in g/mol or daltons (Da). It is calculated from the amino acid sequence and is the value mass spectrometry checks against.
- Net peptide content
- The percentage of a powder’s total weight that is actually peptide, as opposed to counter-ions (such as TFA or acetate) and residual water. It is different from purity: a sample can be 99% pure by HPLC and still have a net peptide content well below 100%.
- Purity
- The proportion of the target peptide among all peptide-related substances in a sample, usually measured by HPLC and reported as a percentage. Purity does not by itself confirm identity.
- Retention time
- How long a substance takes to pass through the HPLC column to the detector. Under the same method, a given peptide elutes at a consistent retention time, which helps tell it apart from impurities.
- TFA salt (trifluoroacetate)
- Trifluoroacetic acid is used during peptide synthesis and purification, so many peptides are supplied as TFA salts. Residual TFA counts toward the powder’s weight and can matter in sensitive cell assays.
- Third-party testing
- Testing performed by a lab independent of the seller or manufacturer. Every Rogue batch is tested by an independent, ISO 17025 accredited U.S. lab, and the QR code on each vial links to that batch’s report on the lab’s own website.
Peptide chemistry terms
- Amino acid
- The building blocks of peptides and proteins. There are 20 standard amino acids, each usually written as a three-letter (Lys) or one-letter (K) code.
- Analog
- A molecule modeled on a natural peptide but changed in some way, for example a substituted amino acid or an added chemical group, often to change stability or how long it lasts in experiments. IGF-1 LR3 and CJC-1295 are analogs.
- C-terminal amidation
- A modification where the peptide’s final carboxyl group is replaced with an amide. Many natural and synthetic peptides are amidated, which can affect stability and receptor activity.
- Cyclic peptide
- A peptide whose chain is joined into a ring. Cyclization generally makes peptides more resistant to breakdown. PT-141 is an example of a cyclic peptide.
- D-amino acid
- The mirror-image form of an amino acid. Natural proteins use L-amino acids; peptides built from D-amino acids resist breakdown by enzymes. See retro-inverso peptide.
- DAC (Drug Affinity Complex)
- A chemical linker added to a peptide so it binds to albumin in the blood, greatly extending its half-life in animal studies. It is the difference between CJC-1295 with and without DAC. See CJC-1295 DAC vs No DAC.
- Fragment peptide
- A short peptide that corresponds to part of a larger protein or hormone. AOD-9604 is based on a fragment of the growth hormone C-terminus, and KPV is the final three residues of alpha-MSH.
- Half-life
- The time it takes for half of a compound to be cleared or broken down in a given system. Many natural peptides have half-lives of minutes, which is why analogs are often designed to last longer.
- Peptide
- A short chain of amino acids joined by peptide bonds. There is no strict cutoff, but chains under roughly 50 amino acids are usually called peptides and longer ones proteins.
- Peptide bond
- The amide bond that links one amino acid to the next in a chain.
- PEGylation
- Attaching polyethylene glycol (PEG) chains to a molecule to slow its breakdown and clearance. PEG-MGF is a PEGylated form of mechano growth factor. See PEG-MGF research.
- Pentadecapeptide
- A peptide made of 15 amino acids. BPC-157 is the best-known example in research. See the BPC-157 research overview.
- Retro-inverso peptide
- A peptide built from D-amino acids in reversed order, designed to mimic the shape of the original while resisting enzymes. FOXO4-DRI is a retro-inverso peptide. See FOXO4-DRI research.
- Sequence
- The order of amino acids in a peptide, written from the N-terminus to the C-terminus. The sequence defines the compound and determines its molecular weight.
- Tripeptide
- A peptide of three amino acids. KPV (Lys-Pro-Val) and GHK (Gly-His-Lys) are tripeptides studied in research. See KPV and GHK-Cu.
Research & biology terms
- Agonist
- A molecule that binds a receptor and activates it. An antagonist binds without activating, blocking the receptor instead.
- Animal model
- An animal, often a mouse or rat, used to study a biological process or condition. Results in animal models frequently do not carry over to humans.
- In vitro
- Experiments done outside a living organism, such as in cultured cells or test tubes.
- In vivo
- Experiments done in a living organism, such as an animal model.
- Mechanism of action
- The specific biological process through which a compound produces its effect, for example binding a particular receptor. For many research peptides the mechanism is still only partly understood.
- Preclinical
- Research done before any human trials, in cells and animals. Most of the published literature on research peptides is preclinical.
- Receptor
- A protein, usually on a cell surface, that a molecule binds to in order to trigger a response. Many peptides act by binding specific receptors.
- Secretagogue
- A substance that causes a gland to release (secrete) something. Growth hormone secretagogues are compounds studied for stimulating growth hormone release. See growth hormone research peptides.
- Systematic review
- A paper that gathers and evaluates all published studies on a question using a defined method. Reviews are useful for seeing how strong, or how thin, the evidence on a compound is.
Compound classes
- Bioregulator peptides
- Very short peptides, often two to four amino acids, developed largely through the work of Vladimir Khavinson’s group in Russia. Epithalon (Ala-Glu-Asp-Gly) and Pinealon (Glu-Asp-Arg) are examples. See Epithalon vs Pinealon.
- Blend
- A vial containing more than one compound in fixed amounts. Researchers often test each compound on its own before testing a blend. See GLOW vs KLOW.
- Copper peptide
- A peptide bound to a copper ion. GHK-Cu, the copper complex of the tripeptide GHK, is the most studied example. See GHK-Cu research.
- GHRH analogs
- Compounds based on growth hormone–releasing hormone, which signals the pituitary to release growth hormone. Sermorelin (the first 29 amino acids of GHRH), CJC-1295 and Tesamorelin belong to this group. See Sermorelin vs CJC-1295 vs Tesamorelin.
- GHRPs (growth hormone–releasing peptides)
- Peptides that act on the ghrelin receptor to stimulate growth hormone release, a different pathway from GHRH. Ipamorelin is a selective example. See Sermorelin vs Ipamorelin.
- IGF-1 variants
- Forms of insulin-like growth factor 1 modified for research, such as IGF-1 LR3 (an 83–amino acid analog with reduced binding to IGF binding proteins) and IGF-1 DES (a shortened form). See IGF-1 LR3 vs IGF-1 DES.
- Melanocortin peptides
- Peptides related to alpha-MSH that act on melanocortin receptors, which are involved in pigmentation, inflammation and other signaling. MT-1, MT-2, PT-141 and KPV are studied in this family. See MT-1 vs MT-2.
- Mitochondrial-derived peptides
- Peptides encoded within mitochondrial DNA. MOTS-c, a 16–amino acid peptide, is the best-known example in metabolic research. See MOTS-c research.
- Mitochondria-targeted peptides
- Peptides designed to concentrate in mitochondria. SS-31 is studied for binding cardiolipin, a lipid in the inner mitochondrial membrane. See MOTS-c vs SS-31.
- Neuropeptide research compounds
- Peptides studied in nervous system and behavior research, such as Semax, Selank and DSIP. See Semax vs Selank.
- Thymosins
- A family of peptides first isolated from the thymus. Thymosin alpha-1 is studied in immune research, while TB-500 is based on a region of thymosin beta-4 studied in tissue repair models. See Thymosin Alpha-1 vs TB-500.
Regulatory terms
- FDA approval
- Authorization by the U.S. Food and Drug Administration to market a drug for a specific use after clinical trials. Research peptides sold for laboratory use are not FDA approved for human use.
- Research use only (RUO)
- A label meaning a product is intended for laboratory research, not for human or veterinary use, diagnosis or treatment.
- WADA Prohibited List
- The World Anti-Doping Agency’s list of substances banned in sport. Several research peptides appear on it, including BPC-157 (added in 2022) and growth hormone secretagogues.
Keep reading
- How to read a peptide COA
- COA Library: every released batch’s test results
- Research overviews for every compound Rogue carries