Peptide research glossary.

A document issued by a testing laboratory for one specific production lot, reporting what was measured and the result — for a peptide, typically identity (does the measured mass match the expected molecule?) and purity (what percentage of the material is the target peptide?). A COA is lot-specific: a certificate for lot A says nothing about lot B. APX Labs ships the batch-specific COA with every order. How to read one →

An analytical technique that pushes a dissolved sample through a packed column under pressure; different molecules travel at different speeds and emerge as separate peaks. For peptides, the area of the main peak relative to all peaks gives purity as a percentage. It is the standard purity method on peptide COAs.

An analytical technique that measures the mass-to-charge ratio of ionised molecules. On a peptide COA it confirms identity: the measured molecular weight is compared with the theoretical value for the expected sequence. Often paired with HPLC as 'HPLC/MS' or 'LC-MS'.

The proportion of a sample that is the intended compound, usually reported as an HPLC peak-area percentage (e.g. 99.2%). It does not by itself prove identity — a sample can be 99% pure and be the wrong molecule — which is why COAs report both HPLC and MS. What HPLC/MS purity testing is →

Freeze-dried. The peptide is frozen and the water removed under vacuum, leaving a dry powder or cake in the vial that is far more stable in storage than a solution. Lyophilized peptides are reconstituted with a suitable solvent before laboratory use.

Dissolving a lyophilized peptide in a solvent — commonly bacteriostatic water for research use — to produce a solution of known concentration. Step-by-step guide →

Sterile water containing 0.9% benzyl alcohol as a preservative, which inhibits bacterial growth in a multi-use vial. It is the most common reconstitution solvent for research peptides. Not the same as sterile water for injection (no preservative) or saline.

An identifier assigned to one production batch. Everything with the same lot number was made and tested together; the COA is issued per lot. APX Labs prints the lot on the vial or pen and on the accompanying COA so the two can be matched.

A short chain of amino acids linked by peptide bonds. Conventionally 'peptide' is used for chains up to about 50 residues and 'protein' for longer chains, though the boundary is loose — IGF-1 LR3 at 83 residues is often called a peptide in this field.

The order of amino acids in a peptide, written N-terminus to C-terminus using three-letter (Gly-His-Lys) or one-letter (GHK) codes. The sequence defines the molecule; the molecular formula and weight follow from it.

The mass of one molecule, expressed in g/mol (or daltons, Da). On a COA, the mass measured by MS is compared to the theoretical MW calculated from the sequence — agreement within instrument tolerance confirms identity.

A synthetic variant of a natural peptide with one or more changes — substituted residues, added groups, altered length — usually made to resist enzymatic breakdown or change receptor behaviour. CJC-1295 and tesamorelin are GHRH analogs; GLP1-R is a GLP-1 analog.

A shorter piece of a longer peptide or protein that retains a specific activity of the parent in research models. TB-500 is a fragment of thymosin β4; KPV is a fragment of α-MSH; Semax derives from an ACTH fragment.

A regulatory and labelling category for materials sold strictly for laboratory and in-vitro research. RUO products are not drugs, supplements, cosmetics or foods; they are not manufactured, labelled or approved for administration to humans or animals. What RUO means in practice →

Keeping a temperature-sensitive product within a controlled temperature range from dispatch to receipt. APX Labs ships in temperature-aware packaging and recommends refrigerated storage on arrival.

Growth-hormone-releasing hormone, a 44-amino-acid hypothalamic peptide that stimulates growth-hormone release from the pituitary. Several catalog compounds are GHRH analogs studied for this pathway.

A gut hormone released after eating that amplifies insulin secretion. The two incretins are GLP-1 and GIP; single- and dual-receptor incretin agonists are a major research class. GLP-1 vs dual agonist →

A format in which the compound is supplied already in solution in a sealed, refrigerated pen device, removing the reconstitution step and holding a fixed concentration — or, for blends, a fixed ratio — across a series. Vial vs pen →