Peptide research has a vocabulary problem: most explanations assume you already know the words being used to explain things. This glossary fixes that. Every term below is defined in plain English, grouped by where you will run into it.
The basics
| Term | Plain English |
|---|---|
| Amino acid | The building block. Think of one bead on a string. |
| Peptide | A short chain of amino acids — a few beads linked together. |
| Protein | A long chain of the same building blocks. A peptide is essentially a short protein. |
| Dipeptide | Two amino acids. About as small as a peptide gets. |
| Tripeptide | Three amino acids. GHK-Cu and glutathione are examples. |
| Tetrapeptide | Four amino acids. Epithalon is one. |
| Sequence | The specific order of amino acids. Change the order and you have a different molecule. |
| Alpha helix | The spiral shape most peptides fold into — roughly 3.6 building blocks per turn. |
How things work in the body
| Term | Plain English |
|---|---|
| Receptor | A lock on the surface of a cell. The right molecule is the key. |
| Agonist | Something that switches a signal on. A dual agonist flips two switches at once. |
| Antagonist | The opposite — something that blocks a signal. |
| Secretagogue | A nudge that tells the body to release more of its own hormone, rather than adding hormone directly. |
| Analog | A lab-made near-copy of a natural molecule, tweaked to last longer or work better. |
| Fragment | A piece of a larger molecule. AOD-9604 is a fragment of growth hormone. |
| Half-life | How long it takes for half of a substance to clear the body. Longer half-life means longer-lasting. |
| Bioavailability | How much of something actually makes it into the bloodstream and can be used. |
| Mitochondria | The tiny batteries inside cells that produce energy. |
| Enzyme | A biological tool that speeds up a reaction — often by cutting things into smaller pieces. |
Delivery and formulation
| Term | Plain English |
|---|---|
| Sublingual | Under the tongue. (sub = under, lingual = tongue) |
| Buccal | Inside the cheek. |
| Mucosa | The soft, moist tissue inside the mouth — thin and rich in small blood vessels. |
| Subcutaneous | Under the skin. The most common injection route for peptides. |
| Lyophilized | Freeze-dried. The white powder form most research peptides ship in. |
| Excipient | Helper ingredients that aren't the active compound — like flour and eggs in a cake. |
| Formulation | The recipe science: what goes in, in what proportions, and how it's made. |
| Dissolution | How fast something dissolves. |
| First-pass metabolism | When a swallowed substance gets broken down by the gut and liver before reaching circulation. The reason most peptides can't be swallowed. |
Testing and documentation
| Term | Plain English |
|---|---|
| COA | Certificate of Analysis — the lab report for a specific batch. |
| Lot / batch number | The fingerprint of one production run. Must match between your vial and your COA. |
| HPLC | High-performance liquid chromatography. Separates a sample into its parts to measure purity. |
| Chromatogram | The graph HPLC produces. One tall peak is good; several peaks means several substances. |
| Mass spectrometry | Measures molecular weight to confirm identity — that the compound is what the label says. |
| Release threshold | The minimum standard a batch must clear to be sold. |
| Residual solvent | Manufacturing leftovers. Small amounts are normal and expected. |
| Third-party tested | Analyzed by an independent lab rather than by the seller. |
Regulatory terms
| Term | Plain English |
|---|---|
| Research Use Only (RUO) | Supplied for laboratory research. Not a medicine, not a supplement, not for human or veterinary consumption. |
| Investigational | Still in clinical trials. Not approved as a medicine. |
| Preclinical | Research done before human trials — lab and animal work. |
| In vitro | In glass. Cell or test-tube studies. |
| In vivo | In a living organism — animal or human studies. |
| Clinical trial | A controlled study in humans, run in phases. |
Compound categories
| Term | Plain English |
|---|---|
| GLP-1 | A natural gut hormone that signals fullness. The backbone of the weight-research category. |
| GIP | A second gut hormone involved in blood sugar and fat storage. |
| Glucagon | A signal associated with the body using stored fuel. |
| Amylin | Another fullness signal that also slows stomach emptying. |
| Bioregulator | Very short peptides (2–4 amino acids) studied as tissue-specific signals, mostly in Russian research. |
| Senolytic | Something studied for clearing out worn-out "zombie" cells that build up with age. |
| Nootropic | Studied for cognition — focus, memory, mental clarity. |
| Copper peptide | A peptide bound to a copper ion, such as GHK-Cu. Common in skin research. |
Frequently asked questions
What is the difference between a peptide and a protein?
Length. Both are chains of amino acids; peptides are short and proteins are long. There is no universally fixed cutoff, but chains under roughly 50 amino acids are typically called peptides.
What does "agonist" mean in peptide research?
An agonist activates a receptor — it switches a body signal on. A dual agonist activates two receptor types; a triple agonist activates three.
What does lyophilized mean?
Freeze-dried. Water is removed under vacuum at low temperature, leaving a stable white powder that survives shipping and storage far better than a liquid.
What is the difference between in vitro and in vivo?
In vitro means in a dish or test tube. In vivo means in a living organism. In vitro results are a starting point, not a conclusion about what happens in a body.
Keep reading
- The Peptide Directory — every compound in plain English
- Research & Education — the science, simplified
- How to read a Certificate of Analysis
Dissolv products are supplied for laboratory research and are not for human or veterinary consumption. This glossary is educational and is not medical advice.
