Peptide Glossary
Plain-English definitions of common terms you'll encounter in peptide research.
Terms
15Amino Acid
The building blocks of peptides and proteins. There are 20 standard amino acids that combine in different sequences to form peptides. Essential amino acids must be obtained from diet, while non-essential ones are produced by the body.
Bacteriostatic Water
Sterile water containing 0.9% benzyl alcohol as a preservative that prevents bacterial growth. Used to reconstitute lyophilized peptides. Unlike sterile water, it can be punctured multiple times safely. Must be discarded 28 days after first use.
Bioavailability
The percentage of an administered compound that reaches the bloodstream in active form. Intravenous injection has 100% bioavailability. Subcutaneous injection is typically 60-80%. Oral bioavailability for most peptides is very low because digestive enzymes break them down.
Half-Life
The time it takes for the concentration of a substance in the body to decrease by half. A short half-life (minutes) means frequent dosing is needed. A long half-life (days) allows less frequent administration. Half-life determines dosing frequency and duration of effects.
Intramuscular (IM)
An injection delivered deep into a large muscle such as the deltoid (shoulder), vastus lateralis (thigh), or gluteus (buttock). IM injections use a longer needle than subcutaneous injections and absorb faster due to higher blood flow in muscle tissue.
Intranasal
Administration through the nasal passages using a specialized spray bottle. Allows certain peptides to bypass the blood-brain barrier for more direct neurological effects. Non-invasive and easy to self-administer.
Intravenous (IV)
An injection or infusion delivered directly into a vein, usually by a healthcare professional. Provides 100% bioavailability and the fastest onset since the compound enters the bloodstream immediately.
Lyophilized
Freeze-dried. Most research peptides are sold as a lyophilized powder that must be reconstituted with bacteriostatic water before use. Lyophilization preserves the peptide's structure and extends shelf life significantly compared to liquid form.
Mechanism of Action
How a compound produces its biological effects at the molecular level. This includes which receptors it binds to, what signaling pathways it activates or inhibits, and the downstream cellular responses that lead to observable effects.
PEGylation
The attachment of polyethylene glycol (PEG) chains to a peptide molecule. PEGylation increases the half-life by shielding the peptide from enzymatic breakdown, reducing kidney clearance, and decreasing immune recognition. Common in modified peptides like PEG-MGF.
Peptide
A short chain of amino acids, typically between 2 and 50 amino acids long. Peptides act as signaling molecules in the body, influencing processes like growth, recovery, immune function, and metabolism. Smaller and more targeted than proteins.
Potency
A measure of how strongly a compound produces its effect at a given dose. High-potency peptides require smaller doses to achieve the same effect as low-potency alternatives. Not to be confused with efficacy, which is the maximum effect achievable.
Reconstitution
The process of adding bacteriostatic water to a lyophilized (freeze-dried) peptide to create an injectable solution. Water should be added slowly against the vial wall to avoid damaging the peptide. The resulting solution must be refrigerated.
Subcutaneous (SubQ)
An injection delivered just under the skin into the fatty tissue layer, typically around the abdomen, thigh, or upper arm. Uses a short needle (usually an insulin syringe). This is the most common route for peptide administration.
Topical
Applied directly to the skin as a cream, serum, or gel. Used when the target is the skin itself, such as for wound healing or anti-aging. Absorption is limited to the local area, which can be an advantage for targeted effects.
This glossary is for informational purposes only. Not medical advice.