Reference

Peptide Research Glossary

Reference definitions of terminology used throughout peptide research, chemistry, and the Australian regulatory landscape. Each term links to relevant deeper guides and product pages.

A

AEEA: 8-amino-3,6-dioxaoctanoic acid spacer used in fatty-acid linkers.; AEEA is a polyethylene-glycol-based spacer commonly used in conjugating fatty acids to peptides. Tirzepatide uses a γGlu-2xAEEA spacer to attach its C20 fatty acid moiety, contributing to extended half-life through albumin binding.
Aib (α-aminoisobutyric acid): Non-canonical amino acid that confers DPP-4 resistance.; α-Aminoisobutyric acid is a synthetic amino acid frequently inserted at position 2 of GLP-1 receptor agonists to confer resistance to DPP-4 enzymatic cleavage. Used in Tirzepatide, Retatrutide, and many other engineered incretin peptides.
Albumin binding: Strategy for extending peptide half-life via plasma protein attachment.; Modern peptide therapeutics often carry fatty acid moieties that bind reversibly to circulating albumin (the most abundant plasma protein). This raises the effective hydrodynamic size of the peptide above renal filtration thresholds, extending circulating half-life from hours to days.; See also: Peptide Stability and Half-Life
ARTG (Australian Register of Therapeutic Goods): TGA registry of approved therapeutic goods in Australia.; The ARTG is the official register maintained by the Therapeutic Goods Administration of products approved as therapeutic goods in Australia. Research peptides supplied under the RUO framework are not listed on the ARTG and are not therapeutic goods.; See also: Are Research Peptides Legal in Australia?

C

CAS number: Chemical Abstracts Service registry number — unique compound identifier.; A CAS number is a unique numerical identifier assigned to every chemical compound by the Chemical Abstracts Service. CAS numbers appear on every legitimate research peptide COA. BPC-157 is CAS 137525-51-0; Retatrutide is CAS 2381089-83-2.
Certificate of Analysis (COA): Batch-specific document confirming peptide purity, identity, and endotoxin level.; A Certificate of Analysis is a third-party laboratory document accompanying every batch of research peptide. It documents purity (by HPLC), identity (by mass spectrometry), and endotoxin level (by LAL assay), along with batch number, manufacturing date, and testing laboratory.; See also: How to Read a Peptide COA
Cyclisation: Constraining a linear peptide into a ring structure.; Cyclisation locks a peptide into a bioactive conformation and confers resistance to enzymatic degradation. Achieved via disulphide bridges, head-to-tail amide bonds, or lactam bridges between side chains. Melanotan II is a cyclic lactam analogue of α-MSH.

D

DAC (Drug Affinity Complex): Maleimidopropionic acid linker for covalent albumin binding.; A DAC linker uses a maleimidopropionic acid (MPA) group that forms a covalent bond with the free Cys34 residue on albumin. Once attached, the peptide is irreversibly tethered to albumin until the albumin itself is degraded (~20 day half-life). Used in CJC-1295 with DAC.; See also: CJC-1295 with DAC
DPP-4 (dipeptidyl peptidase-4): Plasma serine protease that cleaves peptides at position 2 (Pro/Ala).; DPP-4 is a ubiquitous serine protease responsible for the rapid degradation of native GLP-1, GIP, and many other peptides. Engineered peptide analogues substitute the position 2 alanine with Aib or D-alanine to resist cleavage and dramatically extend half-life.

E

Endotoxin (LAL assay): Bacterial lipopolysaccharide contamination, measured in EU/mg.; Endotoxin contamination is measured by the Limulus Amoebocyte Lysate (LAL) chromogenic assay and reported in endotoxin units per milligram (EU/mg). Sub-1 EU/mg is generally considered low-endotoxin grade for cell culture and in vitro work.

F

Fatty acid conjugation: Covalent attachment of long-chain fatty acids to a peptide.; Fatty acids (typically C16, C18, or C20) are conjugated to peptide side chains via spacer linkers. The fatty acid promotes albumin binding, extending circulating half-life. Semaglutide (C18), Tirzepatide (C20), and Retatrutide (C20 diacid) all use this strategy.

G

GHK-Cu (Gly-His-Lys-Cu): Copper tripeptide complex with gene-expression and ECM activity.; GHK-Cu is a naturally occurring tripeptide-copper coordination complex. The copper coordination is functionally essential to its activity in extracellular matrix remodelling and gene-expression modulation research.; See also: GHK-Cu
GHRH (growth hormone-releasing hormone): Hypothalamic peptide that stimulates pituitary GH release.; GHRH is a 44-amino-acid hypothalamic hormone that binds the GHRH receptor on pituitary somatotrophs to stimulate growth hormone release. CJC-1295 is a synthetic GHRH(1-29) analogue with extended half-life.
GHRP (growth hormone-releasing peptide): Synthetic peptide class that activates the ghrelin receptor (GHS-R1a).; GHRPs are synthetic peptides that act on the ghrelin receptor to stimulate growth hormone release. Ipamorelin is a selective GHRP characterised in published literature by a non-stimulatory profile in ACTH and cortisol assays.; See also: Ipamorelin
GIP (glucose-dependent insulinotropic polypeptide): Incretin hormone that stimulates insulin secretion.; GIP is a 42-amino-acid intestinal incretin hormone that potentiates glucose-dependent insulin secretion from pancreatic beta cells. Tirzepatide and Retatrutide both activate the GIP receptor, with Tirzepatide showing greater potency at GIPR than native GIP.; See also: GLP-1, GIP, Glucagon Receptor Biology
GLP-1 (glucagon-like peptide-1): Incretin hormone with appetite, gastric, and pancreatic effects.; GLP-1 is a 30-amino-acid intestinal incretin hormone. Native half-life is under two minutes due to DPP-4 cleavage. Engineered analogues (Semaglutide, Tirzepatide, Retatrutide) achieve weekly dosing through Aib substitution and fatty acid conjugation.

H

HPLC (high-performance liquid chromatography): Chromatography technique used for peptide purity analysis.; HPLC separates compounds in a mixture by their interaction with a stationary phase under high pressure. Reversed-phase HPLC with C18 columns and acetonitrile gradients is the standard method for peptide purity analysis. Purity is reported as percent area under the main peak.; See also: HPLC Purity Standards

L

Lyophilisation: Freeze-drying — removes water under vacuum to produce stable powder.; Lyophilisation freezes a peptide solution and removes water by sublimation under vacuum, producing a dry powder cake. Lyophilised peptides are stable for 24+ months at 2–8 °C and require reconstitution before use.

M

Mass spectrometry: Analytical technique that confirms peptide identity by mass.; Mass spectrometry ionises and measures the mass-to-charge ratio of molecules. ESI-MS (electrospray ionisation) is the standard for peptides under ~5 kDa. Identity is confirmed when the observed mass matches the theoretical mass calculated from the amino acid sequence.
Melanocortin receptors (MC1R-MC5R): Five G-protein coupled receptors targeted by α-MSH and analogues.; The melanocortin receptor family comprises five subtypes (MC1R through MC5R) with distinct tissue distributions and physiological functions. Melanotan II is a non-selective cyclic agonist used as a tool compound in receptor binding research.; See also: Melanotan II

P

Pentadecapeptide: Peptide of 15 amino acids.; A pentadecapeptide contains 15 amino acid residues. BPC-157 is the most widely studied pentadecapeptide research compound, derived from a fragment of human gastric protective protein.; See also: BPC-157
Pentapeptide: Peptide of 5 amino acids.; A pentapeptide contains 5 amino acid residues. Ipamorelin (Aib-His-D-2-Nal-D-Phe-Lys-NH₂) is a research-grade pentapeptide growth hormone secretagogue.
PubChem: NIH-maintained chemical database.; PubChem is a free chemistry database maintained by the National Center for Biotechnology Information (NCBI). PubChem Compound IDs (CIDs) provide a unique identifier for each substance and are commonly cited on COAs alongside CAS numbers.

R

RUO (Research Use Only): Regulatory category restricting compounds to in vitro laboratory research.; Research Use Only is a regulatory category specifying that a compound is supplied for in vitro laboratory and educational research only. It is not approved, intended, or marketed for human or animal therapeutic use, self-administration, or any clinical application.; See also: Are Research Peptides Legal in Australia?

S

Schedule 4: Prescription-only classification under the Australian Poisons Standard.; Schedule 4 of the Standard for the Uniform Scheduling of Medicines and Poisons (SUSMP) classifies prescription-only substances. Most research peptides are Schedule 4 in Australia. Lawful supply for research purposes is permitted under the RUO framework with appropriate controls.
SPPS (solid-phase peptide synthesis): Stepwise peptide manufacturing method on a solid resin.; SPPS, developed by Bruce Merrifield (Nobel Prize in Chemistry, 1984), anchors the C-terminal amino acid to a polymer resin and adds residues stepwise toward the N-terminus. The dominant method for research peptides under approximately 50 amino acids.; See also: Peptide Synthesis Methods

T

Thymosin Beta-4 (Tβ4): 43-amino-acid actin-binding protein found in nearly all human cells.; Thymosin Beta-4 is a 43-amino-acid actin-binding protein originally isolated from the thymus gland. TB-500 is a synthetic peptide derived from Tβ4 that retains the actin-sequestering activity and is investigated in tissue research.; See also: TB-500
TGA (Therapeutic Goods Administration): Australian government regulator of therapeutic goods.; The TGA is the Australian Government agency responsible for regulating therapeutic goods, including prescription medicines, medical devices, and complementary medicines. It maintains the Poisons Standard and the Australian Register of Therapeutic Goods (ARTG).
Tripeptide: Peptide of 3 amino acids.; A tripeptide contains 3 amino acid residues. GHK (Gly-His-Lys) is a classic example, particularly when complexed with copper(II) as GHK-Cu.