Peptide Glossary: The Terms You Will Meet
Plain-English definitions for RUO, DAC, U-100, bacteriostatic water, GHK-Cu, BPC-157 and the rest of the vocabulary that vendor copy assumes you know.
The short version
Peptide talk mixes science words, brand names and legal labels in one sentence. This glossary defines the common terms so you can tell a supplement claim from a research chemical, and a trial design from a sales pitch.
- Same word can mean different things in marketing vs papers.
- Bucket (clean / rx / research) changes what “legal to buy” means.
- Use definitions to check claims - not as medical advice.
A working glossary for the words that make peptide pages hard to read, and for the ones vendors lean on.
Core chemistry
Peptide - Short chain of amino acids joined by peptide bonds. A structural term, not a product category. See what are peptides?.
Protein - Longer amino-acid chain. The cutoff is conventional, not a hard law of nature.
Amino acid - Building block of peptides and proteins.
Sequence - The ordered list of amino acids (often written as one-letter codes).
Legal / marketing
RUO / research use only - Lab-sales framing. Not a purity certificate. FDA judges intended use from the whole marketing picture. See research peptides and the law.
Dietary supplement - In US law, must be intended for ingestion. Injectables are not supplements.
Cosmetic - Appearance claims. Structure/function claims can pull a product into drug territory.
Compounding (503A / 503B) - Legal pharmacy pathways with rules. It does not cover “any peptide, any time.”
Buckets (this site)
Clean - Off-the-shelf supplements/cosmetics (e.g. collagen, many topical peptides).
Prescription - FDA-approved medicines (e.g. certain GLP-1s).
Research - Unapproved compounds sold as research chemicals (e.g. BPC-157, TB-500).
Reconstitution maths
Lyophilized - Freeze-dried powder form common for research peptides.
Reconstitution - Dissolving powder into a liquid so a volume can be measured. Maths guide: how to reconstitute.
Bacteriostatic water - Sterile water with benzyl alcohol preservative, used for multi-dose vials per its label. See bacteriostatic water.
U-100 - 100 units per mL syringe scale. Units = mL × 100.
Barrel size - 0.3 / 0.5 / 1.0 mL capacity. Not the same as a U-number. “U-50” is usually a 0.5 mL U-100 syringe, not 50 units/mL.
Concentration - Mass per volume after mixing (I usually talk mcg/mL).
Calculators: dosage tool · reconstitution calculator
Compounds you’ll see
BPC-157 - Short for body protection compound 157, the name used in the research literature. The number is a serial designation, not a dose, and the name records what researchers called it, not a demonstrated effect. Synthetic 15-aa research peptide; rodent-heavy literature; not approved. Gwyer 2019 - Gwyer D, Wragg NM, Wilson SL. Gastric pentadecapeptide body protection compound BPC 157 and its role in accelerating musculoskeletal soft tissue healing. Cell Tissue Res. 2019;377(2):153-159., in the references below Guide: BPC-157.
TB-500 - 7-aa fragment (not full thymosin beta-4). Guide: TB-500.
CJC-1295 - GHRH analogue; with DAC vs without DAC are different. Guide: CJC-1295.
Ipamorelin - GH secretagogue; never approved; Phase 2 stopped for efficacy. Raun 1998 - Raun K, Hansen BS, Johansen NL et al. Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol. 1998;139(5):552-61., in the references below Guide: ipamorelin.
GHK-Cu / copper peptide - Cosmetic copper tripeptide (Copper Tripeptide-1). Guide: copper peptides.
Matrixyl - Trade name for certain palmitoyl signal peptides. Guide: Matrixyl.
Argireline - Trade association with acetyl hexapeptide-8. Guide: argireline.
Skin science shorthand
500 Dalton rule - Rule of thumb that many compounds above ~500 Da struggle to pass the stratum corneum passively. Bos 2000 - Bos JD, Meinardi MM. The 500 Dalton rule for the skin penetration of chemical compounds and drugs. Exp Dermatol. 2000;9(3):165-9., in the references below It does not prove your serum penetrates.
INCI - International Nomenclature of Cosmetic Ingredients: the standard ingredient name on the back of the bottle.
Anti-doping
WADA Prohibited List - Many research peptides are banned in sport (e.g. BPC-157 S0; CJC/ipamorelin S2.2.4; TB-500 under S2.3 as Tβ4 derivative). Check the current list.
Related
Common questions
What is a peptide?
A peptide is a short chain of amino acids linked by peptide bonds. The word describes chemical structure, not safety, legality or effectiveness.
What does RUO mean?
Research use only. It is a sales and labelling position for products not marketed as approved medicines. It is not a government safety rating and does not prove purity.
What is DAC in CJC-1295?
Drug Affinity Complex: an albumin-binding linker used on some CJC-1295 products. It keeps the peptide in circulation much longer than the version without the linker.
References (5 sources)
Bibliographic detail is fetched from PubMed, not written by me - so a citation here cannot drift from the paper it names. Study design comes from PubMed's own tags rather than my judgement.
- 1.Bos JD, Meinardi MM. The 500 Dalton rule for the skin penetration of chemical compounds and drugs. Exp Dermatol. 2000;9(3):165-9.ReviewPMID 10839713
- 2.Raun K, Hansen BS, Johansen NL et al. Ipamorelin, the first selective growth hormone secretagogue. Eur J Endocrinol. 1998;139(5):552-61.StudyPMID 9849822
- 3.Gwyer D, Wragg NM, Wilson SL. Gastric pentadecapeptide body protection compound BPC 157 and its role in accelerating musculoskeletal soft tissue healing. Cell Tissue Res. 2019;377(2):153-159.ReviewPMID 30915550
- 4.WADA 2026 Prohibited List (PDF mirror) - used for anti-doping term references on this site.- World Anti-Doping Agency (mirrored by the Jamaica Anti-Doping Commission)regulatory
- 5.21 U.S.C. §321 - drug, cosmetic, dietary supplement definitions.- Cornell Legal Information Institutestatute