Research Library›Glossary

Peptide Research Glossary

The vocabulary used across this library, in plain English. 34 terms — what they mean and, where relevant, where to read more.

The basics

Amino acid: The basic building block of peptides and proteins. There are 20 standard amino acids; each shares a common backbone and differs only in its side chain. Read more →
Peptide: A short chain of amino acids, typically 2 to around 50, joined by peptide bonds. Peptides act as signalling molecules, carrying instructions between and within cells. Read more →
Polypeptide: A single unbroken chain of amino acids longer than a peptide, generally 50 or more residues.
Protein: One or more polypeptide chains folded into a specific three-dimensional shape that gives the molecule its function. Insulin and haemoglobin are proteins.
Sequence: The order of amino acids in a peptide, usually written as letter codes. The sequence determines the molecule’s shape and what it interacts with.
Tripeptide / Tetrapeptide: A peptide made of exactly three (tri-) or four (tetra-) amino acids. GHK-Cu is a tripeptide; Epitalon is a tetrapeptide.

How compounds act

Receptor: A protein, usually on a cell surface, that a signalling molecule binds to in order to trigger a response inside the cell.
Agonist: A compound that binds a receptor and activates it, producing a response. A dual or triple agonist activates two or three receptor types at once.
Antagonist: A compound that binds a receptor and blocks it, preventing the normal signalling molecule from producing its effect.
Secretagogue: A compound that prompts a gland to secrete a substance. Growth hormone secretagogues stimulate the pituitary to release growth hormone rather than supplying the hormone itself.
GHRH analogue: A synthetic version of growth hormone-releasing hormone, the body’s own signal telling the pituitary to release growth hormone. CJC-1295 and Tesamorelin are GHRH analogues.
Bioregulator: An ultra-short peptide, usually 2 to 4 amino acids, studied for acting at the level of gene expression within a specific tissue rather than at cell-surface receptors. Associated with the research of Vladimir Khavinson. Read more →
Gene expression: The process by which the instructions in a gene are read and acted upon. Influencing gene expression changes which instructions a cell follows, without altering the DNA sequence itself.
Epigenetic: Relating to changes in how genes are read rather than changes to the genetic code itself.
Half-life: The time taken for the amount of a compound in the body to fall by half. Half-life governs dosing frequency but says nothing about which class a compound belongs to.

Form, handling and storage

Lyophilised: Freeze-dried. Water is removed under vacuum, leaving a stable dry powder. Because water drives most peptide degradation, lyophilised peptides are far more stable than those in solution. Read more →
Reconstitution: The process of returning a lyophilised powder to liquid form by adding a solvent such as bacteriostatic water.
Bacteriostatic water: Sterile water containing a small amount of benzyl alcohol, which inhibits bacterial growth and so allows a vial to be accessed more than once.
Vial: The sealed glass container a research compound is supplied in, typically closed with a rubber stopper and an aluminium flip-top cap.
Cold chain: Temperature-controlled handling through storage and transport. Lyophilised peptides are stable enough in dry form that a short period outside refrigeration does not degrade them meaningfully. Read more →
Degradation: The breakdown of a peptide over time through processes such as oxidation, hydrolysis, aggregation or deamidation, reducing the proportion of intact compound present.

Testing and documentation

Certificate of Analysis (COA): A document reporting the analytical test results for a specific batch, typically including identity confirmation and a purity figure, tied to a batch number. Read more →
HPLC: High-performance liquid chromatography. An analytical method that separates the components of a sample so the proportion of the intended compound can be measured. The standard basis for a stated purity percentage. Read more →
Mass spectrometry: An analytical method that measures a molecule’s mass, used to confirm that the compound present is the one intended. HPLC answers "how much is the target compound"; mass spectrometry answers "is it the right molecule".
Purity: The proportion of a sample that is the intended compound, expressed as a percentage and normally determined by HPLC. The remainder consists of related substances such as synthesis by-products and residual solvents.
Batch number: The identifier tying a specific production run to its test results, allowing a vial in hand to be matched against its certificate of analysis. Read more →
Third-party testing: Analysis carried out by an independent laboratory with no commercial interest in the result, as distinct from testing performed by the manufacturer.

Research and regulatory terms

Research use only (RUO): A designation meaning a compound is supplied strictly for laboratory and scientific research. RUO compounds are not approved for human or veterinary use and carry no therapeutic claims.
In vitro: Research conducted outside a living organism, such as in cell culture. Latin for "in glass".
In vivo: Research conducted within a living organism, such as an animal model.
Preclinical: Research conducted before human trials begin, typically in cell and animal models. Much peptide research remains at this stage.
TGA: The Therapeutic Goods Administration, Australia’s regulator of therapeutic goods. Research peptides are not TGA-approved for therapeutic use.
Analogue: A compound structurally modified from a parent molecule, altered to change properties such as stability or selectivity while retaining the core activity.
Selectivity: How narrowly a compound acts on its intended target. A highly selective compound produces fewer unrelated effects; Ipamorelin is described as selective because it triggers growth hormone release without also raising cortisol or prolactin.

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