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Peptide glossary

Written by The Peptide Record editorialClinical review not yet completedLast reviewed 11 September 2026

The terms this Library uses most often, defined plainly and linked to the page that goes deeper.

On this page
  1. A–D
  2. E–M
  3. N–S
  4. T–Z

In brief

Should you care? Bookmark it rather than read it top to bottom — this page exists to be looked something up in, not read straight through.

A–D

Amino acid — the individual building block peptides and proteins are made from. Full comparison.

Carrier peptide — a peptide that delivers a trace element (usually copper) to support a biological process, rather than signalling a cell directly. Full breakdown.

COA (Certificate of Analysis) — lab documentation showing what a specific batch actually contains. How to read one.

Compounding pharmacy — a pharmacy licensed to prepare customised medicines, including some peptides, on a valid prescription under specific FDA categories.

E–M

Enzyme-inhibitor peptide — a peptide that slows enzymes which break down existing collagen, rather than stimulating new production. Full breakdown.

Hydrolysed collagen — collagen protein broken into short peptide fragments so it can be absorbed when eaten. Full explanation.

HPLC — a lab method that measures how pure a sample is. Doesn’t confirm identity on its own. HPLC vs mass spec.

INCI name — the standardised ingredient name used on cosmetic labels, e.g. "copper tripeptide-1."

Mass spectrometry (MS) — a lab method that confirms a sample’s molecular identity, distinct from purity. Full explanation.

N–S

Neurotransmitter-inhibitor peptide — a peptide that dampens the nerve signal behind muscle contraction, the mechanism behind Argireline. Full breakdown.

Peptide bond — the chemical bond linking amino acids into a chain.

RUO (Research Use Only) — a labelling disclaimer used by grey-market sellers. The FDA has stated this label does not exempt a product sold for human use from drug regulation. Full explanation.

Signal peptide — a peptide that instructs cells (usually fibroblasts) to produce more of something, such as collagen. Full breakdown.

T–Z

Category 1 / Category 2 (FDA) — a classification governing whether a substance is eligible for pharmacy compounding. Frequently confused; explained in full here.

Warning letter — a formal FDA notice alleging a company is violating drug or cosmetic law. Publicly searchable, and one of the checks in the Register.

References