A Glossary of Common Peptide Research Terms

Peptide research comes with its own vocabulary, scattered across labels, certificates of analysis, and protocols. This glossary collects the terms that come up most often, defined in plain language, so the documentation that accompanies research compounds is easier to read.

Peptide

A short chain of amino acids linked by peptide bonds. Peptides are smaller than proteins and are defined by their specific amino acid sequence, which determines their properties.

Lyophilization (freeze-drying)

The process of removing water from a frozen sample under vacuum, leaving a dry, stable powder. Peptides are commonly supplied lyophilized because the dry form degrades far more slowly than solution.

Reconstitution

Dissolving a lyophilized powder back into liquid with an appropriate solvent to make a stock solution of known concentration.

HPLC (High-Performance Liquid Chromatography)

An analytical technique that separates the components of a sample so their relative proportions can be measured. On a peptide COA, HPLC provides the purity percentage.

Mass spectrometry (MS)

A technique that measures molecular weight, used to confirm a peptide’s identity by checking the observed mass against the mass predicted from its sequence.

Purity

The proportion of a sample that is the target peptide rather than impurities, usually expressed as a percentage from HPLC. Purity describes how clean a sample is, not whether it is the correct molecule.

Net peptide content

An estimate of how much of a vial’s mass is actually peptide, accounting for residual water, salts, and counter-ions that make up the rest of the lyophilized material.

Certificate of Analysis (COA)

The batch-specific lab report documenting the tests run on a compound — typically HPLC purity and MS identity — and tying those results to a specific lot number.

Bacteriostatic water

Sterile water containing a small amount of benzyl alcohol as a preservative, which inhibits bacterial growth and allows a sealed container to be accessed more than once.

Research Use Only (RUO)

A designation indicating a compound is intended for laboratory and in-vitro research, not for human or animal use, diagnostic, or therapeutic applications.

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