Amino Acid
A small building block used to make peptides and proteins. Amino acids connect in a specific order to form a sequence.
Definitions
Peptide Definitions & Glossary
Plain-English explanations for common peptide, research, preparation, and source-literacy terms.
- By
- PD Team
- Published
- May 23, 2026
- Last updated
- May 23, 2026
- Definitions
- 41 terms
- Read time
- 4 min read
- Review
- Editorially reviewed by PD Team
Basics
Analog
A modified version of a natural molecule. Analogs are often designed to change stability, receptor activity, or duration.
Molecular Weight
The mass of a molecule, commonly expressed in daltons or g/mol. It depends on the peptide sequence and modifications.
Peptide
A short chain of amino acids linked by peptide bonds. Peptides are smaller than most proteins but can still have highly specific biological roles.
Sequence
The exact order of amino acids in a peptide. Sequence changes can affect structure, receptor activity, and stability.
Mechanism
Agonist
A molecule that activates a receptor and produces a biological signal, either fully or partially.
Antagonist
A molecule that blocks or reduces receptor activation by another molecule.
GIP
Glucose-dependent insulinotropic polypeptide, an incretin hormone involved in metabolic signaling.
GLP-1
Glucagon-like peptide-1, an incretin hormone involved in insulin secretion, appetite signaling, and glucose regulation.
Glucagon
A hormone that helps regulate blood glucose and energy availability, often discussed alongside insulin and incretin pathways.
Incretin
A gut-derived hormone signal that helps coordinate insulin release and metabolic responses after eating.
Receptor
A biological target, often a protein, that receives a signal from a molecule and triggers downstream activity.
Pharmacology
Bioavailability
The fraction of an administered amount that reaches systemic circulation in an active form.
Half-life
The time it takes for the measured amount or concentration of a substance to decrease by half in a given context.
Pharmacodynamics
What a substance does to the body or biological system, including receptor effects, downstream signaling, and measured response.
Pharmacokinetics
What the body does to a substance over time, including absorption, distribution, metabolism, and elimination.
Preparation Terms
Bacteriostatic Water
Sterile water that contains a preservative intended to inhibit bacterial growth. Product labeling and professional guidance determine appropriate use.
Concentration
The amount of material in a given volume, commonly written as mg/mL or mcg/mL.
Diluent
A liquid used to dissolve or dilute a material. The correct diluent depends on the product and context.
Lyophilized
Freeze-dried. Many peptides are supplied as a dry powder or cake to improve stability before reconstitution.
Reconstitution
The process of adding a liquid to a dry material to create a solution at a calculable concentration.
Sterile Water
Water processed to meet sterility standards. Suitability depends on labeling, context, and professional guidance.
Research Literacy
Adverse Event
An unwanted health occurrence observed during a study or treatment period. It does not always mean the peptide or drug caused the event.
Clinical Trial
A structured human research study designed to answer specific questions about safety, dosing, effectiveness, or comparison with another intervention.
Endpoint
A specific outcome a study measures, such as a lab value, symptom score, body weight change, event rate, or safety result.
Placebo-controlled
A study design that compares an intervention against an inactive comparator to help separate treatment effects from expectation or background changes.
Route Terms
Subcutaneous
Located under the skin. The word describes an anatomical route or tissue space, not whether a product should be used that way.
Source Literacy
COA
Certificate of Analysis. A lab document that reports test results such as identity, purity, quantity, or contaminant screening for a sample.
Purity
A measure of how much of a sample is the intended compound compared with related impurities or other material.
Research Use Only
A label used for materials intended for laboratory research rather than human or veterinary use. It is not a quality guarantee by itself.
Units
Microgram (mcg, ug)
A mass unit equal to one one-thousandth of a milligram. Common shorthand: mcg or ug.
Microgram per Milliliter (mcg/mL, ug/mL)
A concentration unit written as mcg/mL or ug/mL. It means micrograms of material per milliliter of liquid.
Microliter (uL)
A volume unit equal to one one-thousandth of a milliliter. Common shorthand: uL.
Micromolar (uM)
A molar concentration unit equal to one one-millionth of a mole per liter. Common shorthand: uM.
Milligram (mg)
A mass unit equal to one one-thousandth of a gram. Peptide vial quantities are often listed in mg.
Milliliter (mL)
A volume unit equal to one one-thousandth of a liter. Liquid volumes are often written as mL.
Milligram per Milliliter (mg/mL)
A concentration unit written as mg/mL. It means milligrams of material per milliliter of liquid.
Millimolar (mM)
A molar concentration unit equal to one one-thousandth of a mole per liter. Common shorthand: mM.
Molar (M)
A concentration unit for amount of substance per liter. Common shorthand: M, with smaller forms such as mM, uM, and nM.
Nanogram (ng)
A mass unit equal to one one-thousandth of a microgram. Common shorthand: ng.
Nanomolar (nM)
A molar concentration unit equal to one one-billionth of a mole per liter. Common shorthand: nM.