Peptide glossary

A

Agonist

A molecule that attaches to a receptor and switches it on, causing a biological effect. Peptides PT-141 are labeled as receptor agonists.

Amino Acid

Amino acid is a basic building block of peptides and proteins. It is made of an amino group, a carboxyl group, and a side chain that changes from one amino acid to another.

AOD-9604

AOD-9604 is a modified fragment of human growth hormone (residues 177–191 plus an N-terminal tyrosine), studied in fat-metabolism research.

Antagonist

Antagonist is a functional opposite of agonist. It is a compound that attaches to a receptor but blocks or weakens its activity.

Assay

Assay is a lab test or procedure used to measure the presence, concentration, or biological activity of a substance such as a peptide.

B

Bacteriostatic Water

Bacteriostatic Water (BAC) is a sterile liquid containing a small amount of benzyl alcohol, used to mix freeze-dried peptides back into liquid form.

Bioactive Peptide

Bioactive peptide is a peptide sequence that has a measurable effect on living tissue or cell cultures.

Bioavailability

Bioavailability is actually the portion of a compound that enters the bloodstream and becomes able to act biologically.

BPC-157

BPC-157 is a man-made peptide made of 15 amino acids, studied for tissue-repair research.

Buffer

Buffer is a solution that keeps pH levels stable. It is used to help mix (reconstitute) and store peptides safely.

C

Certificate of Analysis (COA)

COA is a lab document that confirms a peptide batch's purity, identity, and quality, usually produced using HPLC and mass spectrometry.

CJC-1295

CJC-1295 is a man-made version of growth hormone-releasing hormone (GHRH).

Cold Chain

Cold Chain: An uninterrupted, temperature-controlled process used to keep peptides stable from the time they're prepared through to storage.

Cytokine

Cytokine is a small signaling protein released by cells, used in cell-to-cell communication and immune research.

Chromatography

Chromatography is a lab technique used to separate the different parts of a mixture, often used to check a peptide's purity.

D

DAC (Drug Affinity Complex)

DAC is a chemical modification that extends a peptide's active life by allowing it to bind directly to albumin in the bloodstream.

Denaturation

Denaturation is when a peptide's structure comes undone, usually caused by heat, extreme pH, or shaking, making it lose its biological activity.

Diluent

Diluent is a liquid (e.g. BAC) used to turn a freeze-dried peptide back into a solution.

Dipeptide

Dipeptide is a term used for a peptide made of exactly two amino acids joined by a single peptide bond.

E

Elamipretide (SS-31)

A man-made (synthetic) peptide made of four amino acids that targets mitochondria, studied in cell-energy research.

Enzyme

Enzyme is a protein that speeds up chemical reactions, often building or breaking down peptides in biological systems.

Excipient

Excipient is an inactive ingredient added to a peptide (for example mannitol) to help keep it stable during freeze-drying.

F

FOXO4-DRI

A peptide made to interfere with the interaction between the FOXO4 and p53 proteins, studied in research on cell ageing.

Fragment

Term fragment used for a shorter piece of a larger peptide, such as HGH Fragment 176-191 , that keeps a specific part of biological interest.

Freeze-Drying (Lyophilisation)

Freeze-Drying is a process that removes water from a frozen peptide solution using a vacuum, producing a stable powder for storage.

G

GHK-Cu

A naturally occurring tripeptide that binds copper, studied for tissue and skin research.

GHRH

GHRH is an endogenous hormone that stimulates growth hormone release; serves as the basis for synthetic analogs like Tesamorelin and CJC-1295.

GHRP

A group of synthetic (man-made) peptides studied for how they interact with growth hormone secretagogue receptors to stimulate growth hormone release.

GLOW Blend

A mix of BPC-157, GHK-Cu and TB-500, studied together in tissue-repair and skin research.

Growth Hormone Secretagogue Receptor (GHS-R)

A receptor that, when activated, triggers the release of growth hormone. GHRP-type peptides are studied for how they act on this receptor.

H

HGH Fragment 176-191

A truncated segment of human growth hormone, studied in metabolism and fat-loss research.

HPLC

High-Performance Liquid Chromatography, the standard method for checking a peptide's purity and identity.

Hydrophilic / Hydrophobic

Hydrophilic/ Hydrophobic are terms describing whether a molecule attracts water/is water-soluble (hydrophilic) or repels water/is water-insoluble (hydrophobic), which dictates how it dissolves and is formulated.

Half-Life

The time required for half of a substance to break down or clear from a system, used to measure how long a peptide remains active in biological research.

I

IGF-1 LR3

IGF-1 LR3 is a longer-lasting version of insulin-like growth factor 1, changed so it resists breaking down.

In-Vitro

In-vitro means when research is done outside a living organism, for example, in a test tube or cell culture. All products here are for in-vitro research only; see our note for UK researchers .

Ipamorelin

A specific GHRP studied for triggering growth hormone release with little effect on other hormones.

Isoelectric Point

Isoelectric point is the pH level at which a peptide carries no overall electrical charge, relevant to how it dissolves and behaves in solution.

J

JAK-STAT Pathway

A cell-signalling pathway often mentioned in research on cytokines and peptide receptors, linking receptor activity to gene activity.

K

Kilodalton (kDa)

Kilodalton (kDa) is a unit equal to 1,000 daltons, used to measure the size of peptides and proteins.

KPV

A short three-amino-acid piece of alpha-MSH, studied for its possible anti-inflammatory properties.

L

Ligand

Any molecule that attaches to a specific spot on a receptor or protein, causing or blocking a biological response.

LR3

Short for "Long Arg3", the change used in IGF-1 LR3 that helps it stay stable in solution.

Lyophilisation

Lyophilisation (or lyophilization) is the formal technical term for freeze-drying, a dehydration process typically used to preserve biological material or peptides for storage.

M

Melanocortin

Melanocortin is a part of a group of peptide hormones, including some studied for libido and skin-colour research, such as PT-141 .

Mitochondrial Peptide

Accurately identifies peptides like SS-31 that target cellular energy and mitochondrial function.

Molecular Weight

Molecular Weight is the mass of a peptide molecule, usually given in daltons or kilodaltons, which affects how it dissolves and behaves.

Mass Spectrometry

Mass Spectrometry is a lab technique that measures the mass of molecules, used to confirm a peptide's identity alongside HPLC.

Molarity

A way of measuring how concentrated a solution is, based on the amount of a substance dissolved in a set volume of liquid.

N

NAD+ (Nicotinamide Adenine Dinucleotide)

A critical coenzyme found in all living cells involved in redox reactions and cellular energy production, widely studied in longevity and metabolic research.

Neuropeptide

A small, protein-like messenger molecule (short amino acid chain) produced and released by neurons to communicate and modulate signals in the nervous system.

Nomenclature

The systematic naming conventions used for peptides, typically based on their amino acid sequence, physiological origin, or structural modifications (e.g., "LR3", "DAC", "BPC-157").

O

Oligopeptide

A peptide chain made of a small number of amino acids, usually between two and twenty.

Osmolarity

The total concentration of solute particles in a solution, which is essential to match when preparing peptide solutions to prevent cellular stress or tissue damage.

P

Peptide Bond

Peptide bond accurately describes the condensation reaction (releasing water) that links amino acids together via carboxyl and amino groups.

Peptidomimetic

A man-made compound designed to copy a natural peptide's activity while being more stable or better absorbed.

PT-141 (Bremelanotide)

A man-made peptide similar to alpha-MSH, studied for how it interacts with melanocortin receptors.

Purity

The percentage of a sample made up of the intended compound, usually checked by HPLC (e.g. "≥98% purity").

pH

A scale used to measure how acidic or alkaline a solution is, which affects a peptide's stability and structure.

Q

Quality Control (QC)

The testing steps, including HPLC and mass spectrometry, used to confirm a batch matches its stated purity and identity before it's sold.

Quaternary Structure

Correctly defines the assembly of multiple distinct polypeptide subunits into a multi-subunit protein complex, contrasting it with smaller, single-chain peptides.

R

Receptor

A protein, usually on the outside of a cell on its surface, that attaches to specific molecules (ligands) and causes a biological response.

Reconstitution

Adding a liquid, such as bacteriostatic water, to a freeze-dried peptide to turn it back into a solution. Read our reconstitution guide or BPC-157 mixing guide .

Research Use Only (RUO)

A label showing that a product is meant only for lab research, not for use in humans or animals.

S

Somatostatin

Somatostatin is a peptide hormone that slows the release of growth hormone and insulin, helping regulate the endocrine system.

Storage & Stability

Accurately outlines the temperature, light, and moisture parameters needed to prevent peptide degradation (e.g., hydrolysis, oxidation).

Synthetic Peptide

A peptide made artificially, usually through solid-phase peptide synthesis, rather than taken from a natural source.

Secretagogue

A substance that causes another substance, such as a hormone, to be released. GHRPs are studied as growth hormone secretagogues.

Shelf Life

The length of time a peptide stays stable and usable when stored correctly, before it starts to break down.

Solid-Phase Peptide Synthesis (SPPS)

The most common lab method for building peptides, where amino acids are added one at a time to a chain attached to a solid support.

T

TB-500

A man-made piece of Thymosin Beta-4, widely studied in tissue-repair and recovery research.

Tesamorelin

Tesamorelin is a man-made version of GHRH, studied for growth hormone research.

Tripeptide

Tripeptide is a peptide made of exactly three amino acids joined by two peptide bonds, such as GHK-Cu .

U

Uptake

Uptake is the process by which a cell takes in a peptide or other molecule through its outer membrane.

USP Grade

A purity standard (United States Pharmacopeia) sometimes used for water and other ingredients in peptide preparation.

V

Vasopressin

A peptide hormone involved in water balance and blood pressure control, often mentioned in comparisons of peptide hormones.

Vial

The sealed, sterile container used to store peptides.

Vial Adapter

A small fitting attached to a vial that pierces the stopper once, allowing syringes to connect without using needles each time.

W

Wolverine Stack

A well-known (Popular) research combination of BPC-157 and TB-500. Read the Wolverine Stack guide or shop the 5mg blend .

X

X-Ray Crystallography

A technique used to work out the 3D atomic shape of a peptide by studying its crystal form.

Y

Yield

The amount of purified peptide obtained at the end of a synthesis, shown as a percentage of the highest possible amount.

Z

Zwitterion

A zwitterion is a molecule carrying both a positive and a negative charge at normal body pH — common in free amino acids and some peptides.

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All products referenced on this page are sold for in-vitro laboratory research use only. They are not medicines and are not intended for human or veterinary use, or for any therapeutic, diagnostic or clinical application. Definitions are provided for general educational reference only.