A Research Peptide Glossary: Terms, Abbreviations and Units
A reference glossary of the terms, abbreviations and units used on peptide product pages and certificates of analysis, written for laboratory contexts.
Peptide documentation carries a dense vocabulary. A single product page can reference a sequence in three-letter code, a molecular formula, a CAS registry number, a purity figure and a storage temperature, and a certificate of analysis adds another layer on top. We have assembled this glossary as a standing reference for anyone reading our catalogue or our batch documentation.
Definitions here describe chemistry, analysis and laboratory handling. Nothing in this glossary is a use instruction. All compounds we supply are certified reference material samples sold and distributed for laboratory research only.
Structure and identity
Peptide. A chain of amino acids joined by peptide bonds. The boundary with a protein is conventional rather than absolute, but chains of roughly fifty residues or fewer are generally described as peptides.
**Residue.** A single amino acid unit within a chain. A pentadecapeptide such as BPC-157 has fifteen residues.
Sequence. The order of residues from the N-terminus to the C-terminus, written in either three-letter code (Gly-Glu-Pro) or one-letter code (GEP). Sequence is the primary identity claim for a synthetic peptide, and it is what mass spectrometry is used to corroborate.
N-terminus and C-terminus. The two ends of the chain. The N-terminus carries a free amino group, the C-terminus a free carboxyl group. Modifications at either end, such as acetylation or amidation, change the molecular weight and are part of the compound's identity.
Analogue. A compound whose structure is deliberately modified relative to a reference sequence. Tesamorelin, for example, is described in the literature as an analogue of growth-hormone-releasing hormone carrying an N-terminal modification.
Fragment. A defined sub-sequence of a larger parent molecule. HGH-Fragment 176-191 corresponds to residues 176 to 191 of the human growth hormone sequence.
Cyclic peptide. A peptide in which the chain is closed into a ring, commonly through a disulfide bridge or a bond between side chains. Ring closure constrains the molecule's shape and is frequently reported in the literature as altering receptor selectivity relative to the linear form.
D-retro-inverso. A design in which the sequence is reversed and every residue is switched to its D-amino acid form. The resulting molecule presents a comparable side-chain arrangement while being substantially more resistant to proteolytic degradation in vitro.
Numbers on a product page
Molecular formula. The atom count of the molecule, for example the formula given for BPC-157. Formulas are quoted for the free base unless a salt form is stated.
Molecular weight. The mass of one mole of the compound, in grams per mole. Reported figures differ between suppliers when one quotes the free base and another quotes a salt form, which is why the formula matters alongside the number.
CAS number. A unique registry identifier assigned by the Chemical Abstracts Service. It is the most reliable way to confirm that two listings refer to the same chemical entity, since common names and abbreviations vary widely.
Half-life. The time taken for a measured concentration to fall by half under stated conditions. Where we quote a half-life it comes from published animal pharmacokinetic data and describes those experimental conditions, not any other context.
Solubility. The solvent and concentration at which a compound has been observed to dissolve, for example water at 1 mg/mL. Solubility governs which reconstitution solvent is appropriate for a given assay.
Storage. The temperature and light conditions under which the lyophilised material is documented as stable, commonly minus 20 degrees Celsius and protected from light.
Physical form and handling
Lyophilised. Freeze-dried. The compound is frozen and the solvent removed by sublimation under vacuum, leaving a dry cake or powder. Peptides are supplied in this form because dry material is markedly more stable in storage and transit than material held in solution.
**Reconstitution.** Returning a lyophilised powder to solution by adding a defined volume of solvent. The chosen solvent and volume together determine the working concentration, which our peptide calculator exists to compute.
**Bacteriostatic water.** Water containing a small proportion of benzyl alcohol, which inhibits bacterial proliferation in a multi-use container. See our bacteriostatic water page for the specification we supply.
Aliquot. A measured sub-portion of a reconstituted stock, separated into its own vessel so that the main stock is not repeatedly warmed and refrozen.
Freeze-thaw cycle. One round of freezing and thawing. Repeated cycles are widely reported as a source of peptide degradation and of variability between assay runs.
Adsorption. The tendency of peptides in dilute solution to bind to container surfaces, particularly untreated plastic. It reduces the concentration actually present in solution and is a recognised source of discrepancy between nominal and measured values.
Analysis and documentation
HPLC. High-performance liquid chromatography. The sample is carried through a packed column and its components separate according to how strongly they interact with the column material. It is the standard method for measuring purity.
Retention time. How long a component takes to pass through the column. Under fixed conditions it is characteristic of a given compound, so a batch's retention time is compared against the reference value as an identity check.
Purity (percentage area). The proportion of the total detected signal attributable to the main peak. A purity figure is a statement about what fraction of the detected material is the target compound, not a statement about the whole contents of the vial.
Net peptide content. The proportion of the vial's mass that is peptide, as distinct from counter-ions, residual solvent and water. Purity and net peptide content answer different questions, and both are needed to know what a vial actually contains.
Mass spectrometry. Measurement of the mass-to-charge ratio of ionised molecules. The observed mass is compared against the mass calculated from the sequence, which confirms identity in a way a purity figure alone cannot.
Counter-ion. An ion paired with the peptide to form a stable salt, most often acetate or trifluoroacetate. The counter-ion contributes to the vial mass and therefore to the difference between gross mass and net peptide content.
Truncated and deletion sequences. Synthesis by-products in which a residue is missing or a chain terminated early. They are the principal impurities that preparative purification is designed to remove, and they appear as minor peaks on a chromatogram.
**Certificate of analysis.** The batch document reporting identity and purity results, with the batch number and the issuing laboratory named. Ours are issued by an independent analytical laboratory and published on our lab reports page.
Batch number. The identifier tying a specific production run to its analytical results. Recording it alongside experimental data is what makes a result traceable back to the material used.
Reading the abbreviations
Several compound names in the catalogue are abbreviations whose expansion is not obvious.
- GHK-Cu is glycyl-L-histidyl-L-lysine complexed with a copper ion, described in the literature as a copper tripeptide.
- KPV denotes its three residues, lysine-proline-valine, a fragment of the alpha-MSH C-terminal sequence.
- DSIP stands for delta sleep-inducing peptide, a name given at the time of its isolation and retained as a chemical identifier.
- GHRP-6 is growth hormone releasing peptide 6, a first-generation compound of that class.
- CJC-1295 without DAC refers to the absence of the drug affinity complex linker present in the other form.
- MOTS-C is mitochondrial open reading frame of the twelve S ribosomal RNA type-C.
Research status language
Our product pages annotate each documented research area with one of three labels. They describe how much published literature exists, and nothing more.
- Extensive research indicates a substantial published body across multiple independent groups.
- Moderate research indicates a smaller but established set of published reports.
- Preliminary research indicates early or limited published work.
These labels are a guide to the depth of the literature. They are not a ranking of compounds and they carry no implication about outcomes in any setting.
Where this sits in our documentation
Every compound in our catalogue carries its formula, molecular weight, CAS number and, where defined, its sequence on the product page, alongside the documented storage and solubility conditions. Batch analytical results are published separately on our lab reports page, each carrying a verification key that can be checked directly with the issuing laboratory.
We maintain this glossary because precise vocabulary is part of reliable documentation. If a term you need is missing, our team is glad to add it.
All Zenterex products are certified reference material samples sold and distributed for laboratory research only. They are not for human or veterinary consumption, nor for any diagnostic use.
