Peptide specifications and certificates of analysis use a lot of technical shorthand. This glossary explains the most common terms in plain language.
A–C
- Acetate salt
- A form in which the peptide is paired with acetate counter-ions. Often preferred in research over TFA salts.
- Acetylation (Ac-)
- A chemical cap on the N-terminus of a peptide. Shown as “Ac-” at the start of a sequence, as in thymosin beta-4.
- Amidation (-NH2)
- A modification of the C-terminus. Shown as “-NH2” at the end of a sequence.
- Amino acid
- The building blocks of peptides and proteins. Twenty standard amino acids are written with one-letter or three-letter codes.
- Batch / lot number
- The identifier for a single production run. Test results apply only to the batch tested.
- CAS number
- A unique registry number assigned to a chemical substance by the Chemical Abstracts Service.
- Certificate of analysis (COA)
- A batch-specific report of the tests run and their results. See how to read a COA.
- Chromatogram
- The graph produced by HPLC, showing each detected component as a peak.
- Counter-ion
- An ion paired with the charged peptide in its salt form, such as acetate or trifluoroacetate.
- Cyclic peptide
- A peptide whose chain is joined into a ring, which can increase stability.
D–L
- Daltons (Da)
- The unit of molecular mass; numerically equal to g/mol.
- Deamidation
- A degradation reaction affecting asparagine or glutamine residues.
- Deletion sequence
- An impurity missing one or more amino acids, formed during synthesis.
- Desiccator
- A sealed container that keeps samples dry.
- Endotoxin
- Bacterial cell-wall material. Endotoxin testing (for example the LAL assay) is a separate test not included in a standard COA unless stated.
- HPLC
- High-performance liquid chromatography, the standard method for measuring peptide purity. See what HPLC purity means.
- In vitro
- Experiments performed outside a living organism, such as in cell culture.
- In vivo
- Experiments performed in a living organism, such as an animal model.
- LC-MS
- Liquid chromatography combined with mass spectrometry, used to separate and identify components.
- Lyophilization
- Freeze-drying. See what lyophilization is.
M–R
- Mass spectrometry (MS)
- A technique that measures molecular mass, used to confirm a peptide’s identity.
- Molar concentration (mM, µM)
- Concentration expressed as moles per litre. Our concentration calculator converts between mg/mL and mM.
- Molecular weight (MW)
- The mass of one molecule, calculated from its formula, in g/mol.
- Net peptide content
- The share of a powder’s weight that is peptide, excluding counter-ions and water. Different from purity.
- Oxidation
- A degradation reaction that particularly affects methionine, cysteine and tryptophan.
- Purity
- Usually HPLC area percent: the share of detected material that is the target peptide.
- Research use only (RUO)
- Materials supplied for laboratory research, not for human or animal use.
- Residue
- A single amino acid within a peptide chain.
S–Z
- Sequence
- The order of amino acids in a peptide, written from N-terminus to C-terminus.
- Solid-phase peptide synthesis (SPPS)
- The standard way peptides are built, one amino acid at a time on a resin. See understanding research peptides.
- TFA salt
- A form containing trifluoroacetate counter-ions, which often remain after HPLC purification.
- Third-party testing
- Analysis by an independent laboratory. See how third-party testing works.
- Truncated sequence
- An impurity in which the chain stopped growing early during synthesis.
Research use only. OxygenLab products are supplied for in-vitro laboratory research and analytical use only. They are not for human or animal use and are not intended to diagnose, treat, cure or prevent any disease. See our Legal & Compliance policy.
