The following glossary covers the most common terms encountered when reading about research peptides, COAs, and analytical testing. Definitions are framed for research contexts only.
Core Chemistry Terms
Amino acid The monomer unit from which peptides and proteins are built. Twenty standard amino acids are used by biology; each has an amino group (-NH₂), a carboxyl group (-COOH), and a unique side chain (R group) that determines its chemical properties. Peptide sequences are written as ordered lists of amino acids, abbreviated by single letters (e.g., G = glycine, E = glutamic acid).
Peptide bond The covalent bond that links one amino acid to the next in a peptide chain. It forms between the carboxyl group of one amino acid and the amino group of the next, releasing a water molecule (condensation reaction). Also called an amide bond. The repeating backbone of amino acids connected by peptide bonds is the defining structural feature of every peptide.
Sequence The ordered arrangement of amino acids in a peptide chain, read from the amino terminus (N-terminus) to the carboxyl terminus (C-terminus). Sequence is the molecular fingerprint of a peptide. Two peptides with different sequences are different compounds. For example, BPC-157 has the sequence GEPPPGKPADDAGLV (15 amino acids).
Molecular weight (MW) The mass of one molecule of a compound, expressed in daltons (Da) or grams per mole (g/mol). Molecular weight is a calculated property based on the molecular formula. It is confirmed experimentally by mass spectrometry. On a COA, molecular weight confirmation validates compound identity: if the measured mass matches the theoretical, the correct compound is present.
VerificationAnalytical Testing Terms
Purity The percentage of the total sample that is the target compound. Expressed as a percentage (e.g., “≥98% purity”). Determined by HPLC analysis. Impurities are typically synthesis byproducts or related compounds. Research-grade peptides are generally characterized at ≥95% purity; many suppliers aim for ≥98%.
HPLC (High-Performance Liquid Chromatography) The standard analytical method for measuring peptide purity. A sample dissolved in solvent is pushed through a column packed with stationary-phase material. Different compounds move through the column at different rates (based on polarity and affinity) and exit at different times. A detector measures the signal as each compound elutes, producing a chromatogram. The area under each peak is proportional to the amount of that compound. The target compound’s peak area expressed as a percentage of the total is the purity figure.
Mass spectrometry (MS) An analytical method that measures the molecular weight of compounds by ionizing the sample and measuring the mass-to-charge ratio (m/z) of the resulting ions. Used alongside HPLC to confirm compound identity: HPLC says “the sample is pure,” MS says “the compound in the sample is the one we expected.” Together they constitute the minimum verification standard for research-grade peptides.
Certificate of Analysis (COA) Documentation issued by a testing laboratory for a specific production lot. A COA for a research peptide typically reports: (1) lot number, (2) compound name, (3) purity by HPLC, (4) molecular weight confirmation by MS, (5) physical appearance, and (6) the test date and issuing laboratory. The lot number links the COA to a specific production batch, allowing quality to be traced back to manufacturing.
Physical Form Terms
Lyophilization (freeze-drying) The process of removing water from a peptide solution by freezing it and then sublimating the ice under vacuum. The result is a dry powder that is stable for storage at low temperatures. Lyophilized peptides are the standard shipping form for research compounds: the powder form reduces degradation during transport and storage relative to liquid form.
Reconstitution Dissolving lyophilized peptide powder in a suitable sterile solvent prior to use in research. The solvent choice depends on the peptide’s solubility characteristics. Reconstituted solutions should be used promptly or stored appropriately according to the compound’s stability profile.
ComplianceRegulatory and Sourcing Terms
RUO (Research Use Only) A regulatory designation indicating that a substance is supplied for in vitro and laboratory research purposes and is not approved by the FDA for human or veterinary use. RUO labeling signals that the compound has not been evaluated in the clinical trial framework required for pharmaceutical approval and is not intended for administration to humans or animals. Research peptides sold in the United States operate under RUO designation.
In vitro Latin for “in glass.” Research conducted in a controlled laboratory environment (in cell cultures, test tubes, or similar apparatus) outside a living organism. Distinguished from in vivo (within a living organism) and ex vivo (tissue removed from an organism and studied outside of it). Most mechanistic research on peptides is conducted in vitro or in animal models; results in these systems do not establish effects in humans.
COA-on-request A supplier practice of providing a Certificate of Analysis for a specific lot upon customer request. When evaluating a research supplier, confirm that the certificate reflects (a) the actual lot shipped, (b) HPLC purity testing, and (c) MS molecular-weight confirmation. Read who commissioned the analysis, since a certificate states on its face whether the testing was arranged by the manufacturer, by the seller, or by an independent party.
ReferencesFurther Reference
- What Is a Peptide? Structure and Types Explained
- HPLC and Mass-Spectrometry Peptide Testing
- How to Read a Certificate of Analysis (COA)
- What “Research Use Only” Means
- A Short History of Peptide Science
- Compound Reference Index
For research use only. Not for human or veterinary use. Not approved by the FDA. 21+
- HPLC + MS tested, every batch
- U.S. synthesized
- Batch COA on the product page