Essential Peptide Terminology

Peptide Basics

Amino Acid

The building blocks of peptides and proteins. There are 20 standard amino acids that combine in different sequences to form peptides. Each amino acid has unique properties that affect the peptide's function.

Peptide Bond

The chemical bond that links amino acids together. Formed through a condensation reaction between the carboxyl group of one amino acid and the amino group of another.

Sequence

The specific order of amino acids in a peptide chain. Even a single amino acid change can dramatically alter a peptide's properties and effects.

Molecular Weight (MW)

The mass of a peptide molecule, measured in Daltons (Da). Most research peptides range from 500-5000 Da. Important for identifying peptides in mass spectrometry testing.

Quality & Testing Terms

HPLC (High-Performance Liquid Chromatography)

The gold standard method for measuring peptide purity. Separates compounds based on their chemical properties. Results show purity percentage - look for >98% for research-grade peptides.

Mass Spectrometry (MS)

Analytical technique that identifies compounds by their molecular weight. Confirms the peptide is actually what it claims to be. Essential for verifying identity alongside HPLC purity testing.

COA (Certificate of Analysis)

Document provided by vendors showing test results for a specific batch. Should include HPLC purity, mass spec confirmation, batch number, and testing date. Learn how to read COAs →

Third-Party Testing

Independent laboratory verification not performed by the vendor. More reliable than in-house testing as it eliminates conflict of interest.

Purity

The percentage of the sample that is the actual target peptide vs. impurities. Research-grade peptides should be >98% pure. Pharmaceutical grade is typically >99%.

Preparation Terms

Lyophilized (Freeze-Dried)

Peptides with water removed through freeze-drying. This powder form is more stable for storage than reconstituted peptides. Most peptides ship in lyophilized form.

Reconstitution

The process of adding liquid (usually bacteriostatic water) to lyophilized peptide powder to create an injectable solution. See our reconstitution guide →

Bacteriostatic Water (BAC Water)

Sterile water containing 0.9% benzyl alcohol as a preservative. Preferred for reconstitution because it inhibits bacterial growth, extending the usable life of reconstituted peptides.

Sterile Water

Water that has been sterilized but contains no preservatives. Reconstituted peptides using sterile water must be used quickly or refrigerated and used within days.

Concentration

The amount of peptide per unit of liquid, typically expressed as mg/mL or mcg/unit. Calculated by dividing peptide amount by water volume used. Learn dosing calculations →

Pharmacology Terms

Half-Life

The time it takes for half of the peptide to be eliminated from the body. Short half-life peptides (minutes to hours) may require multiple daily doses. Long half-life peptides may be dosed weekly.

Bioavailability

The percentage of administered peptide that reaches systemic circulation. Subcutaneous injection typically provides high bioavailability for peptides, while oral bioavailability is usually very low.

Route of Administration

How the peptide is delivered to the body:

• Subcutaneous (SubQ): Injection under the skin - most common for peptides
• Intramuscular (IM): Injection into muscle tissue
• Intravenous (IV): Direct injection into bloodstream
• Oral: Taken by mouth - poor bioavailability for most peptides
• Transdermal: Applied to skin
• Intranasal: Sprayed into nasal passages

Agonist

A compound that binds to a receptor and activates it, producing a biological response. Many peptides act as agonists for specific receptors (e.g., GLP-1 agonists).

Receptor

Protein on cell surfaces that peptides bind to in order to produce effects. Different peptides target different receptor types.

Storage Terms

Stability

How well a peptide maintains its structure and potency over time. Affected by temperature, light, moisture, and whether reconstituted. Read about peptide stability →

Degradation

The breakdown of peptide structure over time, reducing potency. Signs include color changes, cloudiness, or precipitation in reconstituted solutions.

Cold Chain

Maintaining appropriate temperature during shipping and storage. Most peptides require refrigeration or freezing to maintain stability.

Measurement Terms

mcg (Microgram)

One millionth of a gram (0.000001g). Most peptide doses are measured in micrograms. 1000 mcg = 1 mg.

mg (Milligram)

One thousandth of a gram (0.001g). Peptide vials are typically labeled in milligrams (e.g., 5mg vial).

mL (Milliliter)

One thousandth of a liter. Used to measure liquid volume for reconstitution and dosing.

IU (International Unit)

A standardized measurement unit used for some hormones and peptides. The actual weight per IU varies by compound.

Peptide Categories

GHRP (Growth Hormone Releasing Peptide)

Peptides that stimulate growth hormone release by activating ghrelin receptors. Examples: Ipamorelin, GHRP-2, GHRP-6.

GHRH (Growth Hormone Releasing Hormone)

Peptides that trigger growth hormone release through a different pathway than GHRPs. Examples: CJC-1295, Mod GRF 1-29, Sermorelin.

GLP-1 (Glucagon-Like Peptide-1)

Peptides that mimic GLP-1 hormone effects, primarily affecting appetite and glucose metabolism. Examples: Semaglutide, Tirzepatide.

BPC (Body Protection Compound)

Peptides derived from gastric juice proteins, researched for tissue healing properties. Example: BPC-157.

Research Terms

In Vitro

Research conducted in test tubes or cell cultures outside of living organisms. "In vitro" is Latin for "in glass."

In Vivo

Research conducted in living organisms. Provides more relevant data for biological effects.

Protocol

A standardized procedure for conducting research, including dosing schedule, timing, and measurement methods.

Anecdotal

Evidence based on personal accounts rather than controlled research. Important to distinguish from peer-reviewed scientific evidence.