The Research Peptide Glossary: 40 Terms Every Researcher Should Know

Research peptide literature is dense with vocabulary that is assumed rather than explained. Most of it is straightforward once you know what the words mean. The problem is that nobody teaches it in one place. Papers define a term if they have space. Vendors define a term if it sells something. Forums assume you already know.

This glossary is the missing one-stop definition set. Forty terms, each one defined in plain language, organized by what you actually need them for. Every definition is written to be extractable on its own, so you can jump in, find what you need, and move on.

Peptide fundamentals

Peptide

A short chain of amino acids linked by peptide bonds. The boundary between "peptide" and "protein" is not strict, but peptides are generally under 50 amino acids long and proteins are longer. Research peptides discussed in this catalog range from 4 amino acids (Epitalon) to 191 amino acids (HGH).

Amino acid

The building block of peptides and proteins. There are 20 standard amino acids, each with a characteristic side chain that determines its chemistry. Peptide sequences are written using three-letter abbreviations (for example, Ala-Glu-Asp-Gly) or single-letter codes (AEDG).

Peptide bond

The chemical bond that links amino acids in a chain. Formed by a condensation reaction between the carboxyl group of one amino acid and the amino group of the next, releasing water. The sequence of peptide bonds defines the primary structure of the peptide.

Sequence

The order of amino acids in a peptide chain, read from the N-terminus (free amino group) to the C-terminus (free carboxyl group). Two peptides with the same amino acid composition but different sequences are different molecules with different activity.

Molecular weight (Da, kDa)

The mass of one molecule of the peptide, measured in daltons (Da) or kilodaltons (kDa). A dalton is approximately the mass of one hydrogen atom. Research peptide molecular weights range from a few hundred Da for small peptides to tens of thousands for large proteins. A real Certificate of Analysis shows the measured molecular weight alongside the theoretical value.

Lyophilized

Freeze-dried. A lyophilized peptide is a peptide that has been frozen and then had the water removed under vacuum, leaving a dry powder or cake. Lyophilization is how research peptides are made stable for shipping and storage. See the reconstitution guide for what happens next.

Reconstitution

The process of adding a liquid (almost always bacteriostatic water) to a lyophilized peptide to dissolve it into a working solution at a known concentration. Covered step by step in how to reconstitute research peptides.

Bacteriostatic water

Sterile water with 0.9 percent benzyl alcohol added as a preservative. The preservative prevents bacterial growth after the vial stopper is punctured, making bacteriostatic water suitable for multi-dose reconstitution. The standard reconstitution solvent for most research peptides.

Purity and analytical chemistry

HPLC (High Performance Liquid Chromatography)

The standard analytical method for measuring peptide purity. An HPLC run separates the components of a sample by their interaction with a stationary phase, producing a chromatogram where each peak represents a distinct component. The area under the main peak divided by the total area of all peaks gives the purity percentage.

Chromatogram

The graph output of an HPLC run. A real peptide COA includes a chromatogram image showing a dominant peak (the target peptide) and smaller peaks representing impurities. Covered in detail in the COA verification guide.

Mass spectrometry (MS)

An analytical method that measures the mass-to-charge ratio of molecules, confirming identity. A real peptide COA includes a mass spec spectrum showing a peak within tolerance of the theoretical molecular weight. Without mass spec confirmation, a purity number is a quantity claim with no identity check behind it.

COA (Certificate of Analysis)

The lab report that documents purity, identity, and other analytical parameters for a specific batch of a peptide. A proper COA answers four questions: what is the compound, how pure is it, what else is in it, and which batch is this. Covered in full in how to read a peptide COA.

Batch (lot)

A defined quantity of peptide produced in a single synthesis run. Each batch has a unique identifier (batch number or lot number) that ties it to a specific COA. Reputable vendors publish a batch-specific COA for every shipment. Recycled COAs across multiple batches are a red flag.

TFA (Trifluoroacetic Acid)

A counterion commonly paired with synthetic peptides during purification. Peptides with charged residues carry a counterion to balance the charges, and TFA is the most common in research peptide synthesis. TFA content is reported separately on a COA because it contributes to the total vial mass without being active peptide.

Counterion

A small molecule ion paired with a charged peptide to balance its overall charge. Common counterions for research peptides are TFA and acetate. Different counterions can be important for specific research protocols because they affect solubility and certain downstream chemistry.

Net peptide content

The mass of actual peptide in a vial, excluding water, counterion, and any other non-peptide residues. A 10 mg vial of a peptide supplied at 85 percent net peptide content contains 8.5 mg of actual peptide. Accurate dosing requires knowing this number, which a real COA reports.

Third-party lab

A laboratory independent of the vendor that tests peptide samples and issues a Certificate of Analysis. In research peptides, Janoshik Analytical is the most widely recognized third-party lab. Third-party testing is the gold standard for purity verification because the lab has no incentive to overstate quality.

Pharmacology and receptors

Agonist

A compound that binds to a receptor and activates it, triggering a biological response. Semaglutide, for example, is a GLP-1 receptor agonist: it binds the GLP-1 receptor and activates the downstream insulinotropic signaling. See Semaglutide research guide for the full mechanism.

Antagonist

A compound that binds to a receptor but does not activate it, and in doing so blocks the natural ligand from binding. Antagonists are used to probe the consequences of receptor blockade. Most of the peptides in the LyzeLabs catalog are agonists, not antagonists.

Dual agonist

A compound that activates two receptors simultaneously. Tirzepatide is a dual agonist of the GLP-1 and GIP receptors. Dual agonists are used to probe synergistic effects that single agonists cannot produce.

Triple agonist

A compound that activates three receptors simultaneously. Retatrutide is a triple agonist of the GLP-1, GIP, and glucagon receptors. Detailed in Retatrutide vs Tirzepatide vs Semaglutide.

Selectivity

The extent to which a compound binds one target receptor more strongly than other related receptors. Selective compounds have fewer off-target effects. Ipamorelin, for example, is a selective ghrelin receptor agonist, minimizing the cortisol and prolactin off-target effects seen with less selective compounds like GHRP-2 and GHRP-6.

Half-life

The time it takes for the concentration of a compound in a research model to decrease by half through clearance mechanisms. Short half-lives produce sharp pulsatile effects. Long half-lives produce sustained effects. CJC-1295 without DAC has a short half-life (minutes to hours). CJC-1295 with DAC has a long half-life (days).

Pharmacokinetics (PK)

The study of how a compound is absorbed, distributed, metabolized, and excreted over time. The PK profile of a peptide determines its dosing schedule, onset, duration of action, and clearance. A research protocol design should match the PK of the compound.

Pharmacodynamics (PD)

The study of what a compound does to a research model (its biological effects) and how those effects relate to concentration. Where PK is about what the body does to the compound, PD is about what the compound does to the body.

Dose-response curve

A graph showing how a biological effect changes as the dose of a compound increases. A flat curve means the effect does not change much with dose. A steep curve means small dose changes produce large effect changes. Understanding the dose-response curve is essential for designing a research protocol.

Specific peptide classes

GLP-1 (Glucagon-Like Peptide-1)

A gut hormone secreted after a meal that triggers insulin release, suppresses glucagon, slows gastric emptying, and reduces appetite. GLP-1 receptor agonists like Semaglutide are based on this hormone. GLP-1 is the foundational mechanism of the entire incretin-class metabolic peptides.

GIP (Glucose-dependent Insulinotropic Polypeptide)

A gut hormone that amplifies insulin release and contributes to lipid handling. GIP was long thought to be unimportant for metabolic interventions until research demonstrated that combining GIP receptor activation with GLP-1 activation produces synergistic effects. The basis for dual agonists like Tirzepatide.

Glucagon

A hormone secreted by pancreatic alpha cells that raises blood glucose by stimulating hepatic glucose release. Glucagon also increases resting energy expenditure and promotes fat oxidation. Triple agonists like Retatrutide include glucagon receptor activation to drive the "energy out" side of metabolism.

GHRH (Growth Hormone Releasing Hormone)

A hypothalamic hormone that triggers growth hormone release from the anterior pituitary via the GHRH receptor. CJC-1295 is a synthetic GHRH analog. The target of one arm of the CJC + Ipamorelin stack.

Ghrelin

A stomach-derived hormone that binds the growth hormone secretagogue receptor (GHSR) and triggers growth hormone release through a different pathway than GHRH. Ghrelin is also involved in appetite regulation. Ipamorelin is a selective synthetic ghrelin receptor agonist.

Secretagogue

A compound that causes another compound to be secreted. Growth hormone secretagogues are compounds that cause growth hormone release from the pituitary. CJC-1295, Ipamorelin, GHRP-2, GHRP-6, and Sermorelin are all growth hormone secretagogues.

Incretin

A class of gut hormones (GLP-1 and GIP being the two main ones) that are released after eating and stimulate insulin release in a glucose-dependent manner. "Incretin-class peptides" refers to synthetic compounds that act on incretin receptors, including Semaglutide, Tirzepatide, and Retatrutide.

Telomerase

An enzyme that adds repetitive sequences to the ends of chromosomes (telomeres), counteracting the natural shortening that occurs with each cell division. Telomerase activity is central to some models of cellular aging. Epitalon is one of the few peptides associated with reported telomerase activity effects in research. See Epitalon research guide.

Angiogenesis

The formation of new blood vessels from pre-existing ones. Central to tissue repair because new blood supply is required to deliver nutrients and oxygen to damaged areas. BPC-157 has documented effects on angiogenesis, one of the reasons it is a staple in recovery research.

Actin sequestration

The process of binding free G-actin monomers to prevent them from polymerizing into filaments. Actin sequestration regulates cell migration and tissue remodeling. TB-500 (Thymosin Beta-4 fragment) works through actin sequestration, which is why it is paired with BPC-157 in many healing research protocols.

Research and sourcing

Research use only

A designation indicating that a compound is intended strictly for laboratory research and is not approved for human consumption or therapeutic use. All LyzeLabs products are supplied under research-use-only terms.

Lot number

A unique identifier assigned to a specific batch of a peptide. Used to match a physical vial to its COA. A real vendor COA includes the lot number of the batch in question. A vendor who cannot match a COA to your vial's lot number is not providing real analytical verification.

Sterile

Free of viable microorganisms. A sterile vial has been manufactured and sealed under conditions that prevent microbial contamination. Sterility is maintained as long as the vial seal is intact. Once a needle has been inserted through the rubber stopper, sterility depends on the handling protocol and, in the case of bacteriostatic water, on the preservative.

SPPS (Solid-Phase Peptide Synthesis)

The standard method for synthesizing peptides. Amino acids are added one at a time to a growing chain anchored to a solid resin, with protecting groups preventing unwanted side reactions at each step. SPPS is how the peptides in the research supply chain are made.

Peptide bond hydrolysis

The breakdown of a peptide bond through reaction with water, splitting the chain. Hydrolysis is accelerated by heat and by extreme pH, which is why refrigerated and pH-neutral storage extends peptide stability. Covered in detail in the peptide storage guide.

Want a specific term added to the glossary

We keep this glossary updated. If there is a term you wish was here and is not, note it and reach out via Contact so we can add it in a future revision. The goal is to make this the single best reference for research peptide terminology on the open internet.

Frequently asked questions

Why do peptide names sometimes have numbers (like BPC-157, CJC-1295, LY3437943)

Numbers after a compound name typically refer to the position of a fragment in a larger parent protein (BPC-157), the developer's internal compound identifier (LY3437943 is Eli Lilly's identifier for Retatrutide), or a sequence variant. They are not dose numbers or potency rankings. They are reference IDs.

What is the difference between a peptide and a protein

The distinction is a matter of length rather than chemistry. Peptides are short chains (typically under 50 amino acids) and proteins are longer. Both are made of amino acids linked by peptide bonds. Some research compounds are peptides by length (BPC-157 at 15 amino acids) and some are proteins (HGH at 191 amino acids) but both are sometimes loosely called "peptides" in informal usage.

What is a "research grade" peptide

A peptide that has been synthesized, purified, and analytically verified to meet research-grade purity standards, typically 98 percent or higher HPLC purity with mass spec confirmation and a third-party COA. Research grade is the working standard for laboratory research. Not all vendors meet this standard, which is why reading the COA and screening for red flags matter.

What is SAR in peptide research

SAR stands for Structure-Activity Relationship. It refers to the study of how changes in a peptide's chemical structure affect its biological activity. SAR research is how new analog peptides (like CJC-1295's modifications of native GHRH) are designed to improve stability, receptor selectivity, or half-life.

What is lyophilization

Lyophilization is freeze-drying, the process used to produce dry peptide from a synthesized solution. The solution is frozen and then exposed to vacuum, causing the water to sublimate directly from ice to vapor. The result is a stable dry powder or cake that can be shipped and stored, then reconstituted when needed.

The takeaway

Research peptides have their own vocabulary and most of it is simpler than it looks once you have the definitions in front of you. This glossary gives you the forty terms that cover 95 percent of what you will encounter reading a product page, a research paper, or a Certificate of Analysis. Bookmark it, reference it, and come back when a new term surfaces.

For the practical side of research peptide work, pair this glossary with the COA verification guide, the reconstitution how-to, and the storage guide. Together they are the full working reference for handling research peptides properly.

This article is for research and educational purposes. All products sold by LyzeLabs are strictly for laboratory research and not intended for human consumption or therapeutic use.