Peptide Glossary: Amino Acid, Peptide Bond, Half-Life, Reconstitution and More
A plain-English peptide glossary covering amino acids, peptide bonds, residues, molecular weight, half-life, reconstitution, BAC water, GLP-1 and research terms.
Peptide research gets confusing fast because chemistry terms, clinical terms, product labels and forum slang all get mixed together. This glossary keeps the definitions practical and links out to the relevant PeptideStat tools.
Start with what are peptides if you want the foundation first, or use the peptide chemistry calculator when you have a sequence to analyze. For practical handling terms, pair this with the peptide storage guide and peptide half-life guide.
Core Chemistry Terms
| Term | Meaning | Related tool or guide |
|---|---|---|
| Amino acid | The building block of peptides and proteins. Standard sequences use 20 common amino acids. | Peptide chemistry calculator |
| Peptide | A chain of amino acids linked by peptide bonds. Usually shorter than a protein, though cutoffs vary. | What are peptides? |
| Peptide bond | The amide linkage connecting one amino acid residue to the next in a chain. | Peptide basics |
| Residue | An amino acid after it has been incorporated into a peptide or protein chain. | Composition calculator |
| N-terminus | The amino end of a peptide sequence. Sequences are conventionally written from N-terminus to C-terminus. | Sequence basics |
| C-terminus | The carboxyl end of a peptide sequence. | Sequence basics |
| Molecular weight | The mass of the peptide molecule, usually shown in daltons or kilodaltons. | Molecular weight calculator |
| Monoisotopic mass | The mass calculated using the most abundant isotope of each element. | Sequence calculator |
| Average mass | The mass calculated from natural isotope abundance averages. | Sequence calculator |
| GRAVY | Grand average of hydropathy. A rough score for how hydrophobic or hydrophilic a sequence is. | Hydropathy calculator |
| Extinction coefficient | An estimate of absorbance at 280 nm, mainly driven by tryptophan and tyrosine. | Chemistry calculator |
Handling and Calculator Terms
| Term | Meaning | Related tool or guide |
|---|---|---|
| Reconstitution | Adding a diluent to a dry or concentrated vial so a measured volume can be drawn. | Reconstitution guide |
| BAC water | Bacteriostatic water, a sterile water product containing preservative. Use depends on product instructions. | Bacteriostatic water guide |
| Concentration | Amount of peptide per volume, commonly mg/mL after reconstitution. | Concentration calculator |
| Units | Syringe scale markings. On a U-100 syringe, 100 units equals 1 mL. | Unit converter |
| mcg | Microgram. 1 mg equals 1000 mcg. | mg to mcg converter |
| Half-life | The time it takes for the amount of a compound in the body or model to fall by half. | Half-life guide |
| Steady state | A repeated-dose pattern where peaks and troughs become more consistent over time. | Half-life calculator |
| Beyond-use date | The date after which a punctured, mixed or pharmacy-prepared product should not be used. | Storage guide |
| Room-temperature excursion | Time a product spends outside its labeled storage range. | Storage and travel guide |
| Subcutaneous | Injected under the skin into subcutaneous tissue. | Injection safety guide |
GLP-1 and Drug-Class Terms
| Term | Meaning | Related guide |
|---|---|---|
| GLP-1 | Glucagon-like peptide-1, an incretin hormone pathway involved in satiety and glucose regulation. | What is GLP-1? |
| GLP-1 receptor agonist | A drug that activates GLP-1 receptors, such as semaglutide or liraglutide. | GLP-1 receptor agonists |
| Dual agonist | A compound that activates two receptor pathways. Tirzepatide targets GIP and GLP-1 receptors. | Tirzepatide database |
| Triple agonist | A compound that activates three receptor pathways. Retatrutide targets GLP-1, GIP and glucagon receptors. | Retatrutide guide |
| Amylin analog | A compound designed around the amylin satiety pathway, such as cagrilintide. | Cagrilintide database |
| Investigational | Studied in clinical research but not approved for a specific consumer indication. | Peptides for weight loss |
| Research-only | Not approved as a medicine for the claimed consumer use. | Peptide database |
Quick Conversions
| Conversion | Value | Tool |
|---|---|---|
| 1 mg to mcg | 1 mg = 1000 mcg | Unit converter |
| U-100 syringe | 100 units = 1 mL | Reconstitution calculator |
| Dalton | Mass unit commonly used for molecules and peptides | Molecular weight calculator |
References
IUPAC Gold Book. Peptide definition.
NCBI Bookshelf. Biochemistry, Peptide.
ExPASy. ProtParam sequence parameter tool.
Kyte J, Doolittle RF. A simple method for displaying the hydropathic character of a protein.
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