The vocabulary of research peptides is small, precise and worth learning. Most of the terms you meet on a product page or a Certificate of Analysis describe how a peptide is made, tested, stored and handled. This glossary defines them in plain English. Definitions are kept to the chemistry and quality control; nothing here describes a use in or on the body.
A short orientation
A peptide is a chain of amino acids joined by peptide bonds. Research peptides are built by chemical synthesis, purified, freeze-dried into a powder, and tested by an independent laboratory before release. Two questions run through everything below: what is the molecule (identity), and how pure and clean is it (purity and safety).
Glossary
Bacteriostatic water
Sterile water containing a small percentage of benzyl alcohol as a preservative, which inhibits bacterial growth. It is a common diluent for redissolving a lyophilised peptide for laboratory handling. Adding it is a solution-preparation step, not a dose.
Certificate of Analysis (CoA)
The test report for a specific production batch. A serious CoA states identity (by mass spectrometry), purity (by HPLC with a chromatogram), the salt form, and a safety panel, all tied to a lot number.
Endotoxin (LAL)
Endotoxins are components of the outer membrane of certain bacteria that can contaminate a material. The Limulus Amebocyte Lysate (LAL) test measures bacterial endotoxin against a stated limit, and appears on the CoA as part of the safety panel.
Heavy metals (ICP-MS)
A screen for metallic contaminants such as lead, arsenic, cadmium and mercury. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) measures these elements at trace levels and reports them against limits on the CoA.
HPLC
High-Performance Liquid Chromatography, the standard method for measuring purity. The peptide mixture is separated on a column and the target peak is integrated to give a purity percentage, supplied with the printed chromatogram behind it.
Lyophilisation
Freeze-drying: water is removed from a frozen peptide solution by sublimation under vacuum, leaving a dry solid “cake”. Because most peptide degradation needs water, the lyophilised powder is the stable storage and shipping form.
Mass spectrometry
The method that establishes identity by measuring the molecule’s mass. The CoA reports expected mass against observed mass; a match confirms the vial holds the molecule on the label.
Molecular weight (MW)
The mass of the molecule, usually quoted for the free base in grams per mole (also written as daltons, Da). Because a salt form adds counterion mass, a molecular weight only makes sense once the salt form is stated.
Net peptide content
The percentage of the gross vial mass that is actually peptide, the rest being counterion, residual water and any bulking agent. It is why two vials of the same stated milligrams can hold different amounts of peptide if supplied in different salt forms.
Reconstitution
Redissolving a lyophilised peptide powder in a suitable sterile diluent, such as bacteriostatic water, for laboratory handling. The concentration obtained is the peptide mass divided by the volume of diluent added. This is a solubility and handling calculation, not a dosing instruction.
Research use only (RUO)
A material supplied strictly for laboratory research. It is not a medicine, supplement, cosmetic or food, is not for human or animal consumption, and carries no therapeutic claim.
Salt form / counterion
Peptides carry charged groups and in the solid state are paired with a balancing ion, the counterion, forming a salt. Common forms are trifluoroacetate (TFA), acetate and arginate. See the salt forms guide.
Solid-phase peptide synthesis (SPPS)
The standard way research peptides are made. The chain is built one amino acid at a time on an insoluble resin bead, then cleaved from the resin and purified. The method was introduced by Bruce Merrifield in 1963.
Where to look next
- Lab results: certificates by lot number.
- Reading a CoA: how to read a certificate line by line.
- Shop: browse the catalogue by molecule.
For research use only. Not for human consumption. Not a medicine, supplement or cosmetic. No therapeutic use is stated or implied.