Peptide Glossary
Plain-English definitions for the terms used across the manual — from pharmacology to preparation and administration.
Basics
Peptide
A short chain of amino acids (typically 2–50) linked by peptide bonds. Peptides act as signaling molecules in the body and are the focus of this manual.
Protein
A longer chain of amino acids folded into a three-dimensional structure. Peptides and proteins differ mainly in length and folding.
Amino Acid
The building block of peptides and proteins. Twenty standard amino acids combine in different sequences to form peptides.
Peptide Bond
The chemical bond formed between the carboxyl group of one amino acid and the amino group of another, linking them into a peptide chain.
Pharmacology
Agonist
A molecule that binds a receptor and activates it, producing a biological response. Many therapeutic peptides are receptor agonists.
Antagonist
A molecule that binds a receptor without activating it, blocking the action of agonists.
Receptor
A protein on or in a cell that binds specific molecules (like peptides) and triggers a cellular response.
Half-life
The time it takes for half of a substance to be cleared from the body. Half-life influences dosing frequency for peptides.
Bioavailability
The fraction of an administered dose that reaches the systemic circulation unchanged. Routes like subcutaneous injection generally improve peptide bioavailability over oral dosing.
Secretagogue
A substance that stimulates the secretion of another substance. Growth-hormone secretagogues, for example, stimulate growth-hormone release.
Metabolism
Incretin
A gut-derived hormone that stimulates insulin release after eating. GLP-1 and GIP are incretins targeted by several weight-management peptides.
AMPK
AMP-activated protein kinase — a cellular energy sensor. Activating AMPK is one mechanism studied in metabolism and longevity peptide research.
mTOR
A central regulator of cell growth and metabolism. Modulating mTOR signaling is a focus of longevity research.
Preparation
Lyophilization
Freeze-drying. Peptides are often supplied lyophilized (as a powder) and must be reconstituted with a sterile solvent before use.
Reconstitution
Mixing a lyophilized peptide powder with a sterile solvent (commonly bacteriostatic water) to dissolve it for administration.
Bacteriostatic Water
Sterile water containing a small amount of benzyl alcohol to inhibit bacterial growth, commonly used to reconstitute peptides for research.
Administration
Subcutaneous
An injection into the fatty tissue just beneath the skin. A common administration route for peptides in research contexts.
Intramuscular
An injection directly into a muscle, used for some peptides where deeper tissue delivery is studied.
Intranasal
Delivery through the nasal mucosa, a route studied for several brain-active peptides to improve access to the nervous system.