Peptide Glossary: 50+ Research Terms Defined
Your complete A-Z reference for research peptide terminology, compounds, and laboratory concepts. Clear, accurate definitions for scientists, researchers, and informed buyers.
Welcome to the PS Peptides peptide glossary — a curated A-to-Z dictionary of more than 50 essential terms in the world of research peptides. Whether you are decoding a Certificate of Analysis, comparing a GHRH analog to a secretagogue, or simply trying to understand what lyophilized means, this resource is designed to make peptide terminology accessible.
All definitions are written for educational purposes. Every compound mentioned is sold strictly for in vitro laboratory research and is not intended for human or veterinary use.
A
Adipotide (FTPP)
Adipotide is an experimental peptidomimetic compound studied in laboratory research for its targeted action on blood vessels that supply adipose tissue. The molecule combines a homing sequence with a pro-apoptotic domain, and has been evaluated in preclinical models investigating adipose vasculature. It is supplied exclusively as a research chemical for in vitro scientific investigation.
Amino Acid
Amino acids are organic molecules containing an amine group, a carboxylic acid group, and a variable side chain that defines each one’s properties. They are the fundamental building blocks of peptides and proteins. Twenty standard amino acids are encoded by the genetic code and combine through peptide bonds to form the sequences that define each peptide’s structure, function, and biological behavior in laboratory models.
Angiogenesis
Angiogenesis is the biological process by which new blood vessels form from pre-existing vasculature. It is essential for tissue growth, wound repair, and development. In peptide research, several compounds — including BPC-157, TB-500, and GHK-Cu — are studied for their potential influence on angiogenic pathways. Understanding angiogenesis is central to regenerative research, oncology models, and cardiovascular investigations.
AOD-9604
AOD-9604 is a modified fragment of the human growth hormone molecule, representing amino acids 176-191 of the parent sequence with an additional tyrosine residue. Researchers study this peptide for its effects on lipid metabolism in laboratory models without the growth-promoting effects of full-length growth hormone. AOD-9604 is provided strictly as a research compound for controlled in vitro studies.
B
Bacteriostatic Water
Bacteriostatic water is sterile water containing 0.9% benzyl alcohol as a preservative, which inhibits the growth of most common bacteria. In a research laboratory, it is commonly used as a diluent to reconstitute lyophilized peptides, allowing solutions to be stored and drawn from multiple times without microbial contamination. It should always be handled using proper aseptic technique and stored under refrigeration after opening.
Bioavailability
Bioavailability refers to the fraction of an administered substance that reaches systemic circulation in an active, unchanged form. Peptides often have low oral bioavailability because they are rapidly degraded by digestive enzymes, which is why many research peptides are delivered via subcutaneous, intranasal, or intravenous routes in laboratory studies. Bioavailability is a critical variable in pharmacokinetic research and dose-response modeling.
BPC-157
BPC-157 (Body Protection Compound-157) is a synthetic pentadecapeptide composed of 15 amino acids, originally derived from a protective protein sequence found in human gastric juice. In research settings, it is investigated for its potential role in tissue repair, angiogenesis, and gastrointestinal protection in laboratory models. BPC-157 is sold strictly as a research chemical and is not approved for human consumption or therapeutic use.
Bremelanotide (PT-141)
Bremelanotide, also known as PT-141, is a synthetic cyclic melanocortin peptide studied as an agonist at the melanocortin receptors, particularly MC4R. It is a research analog derived from Melanotan II and is examined in laboratory investigations of central nervous system signaling pathways related to sexual arousal. Bremelanotide is sold solely for in vitro scientific research purposes.
C
CagriSema
CagriSema is a research combination of two peptides — cagrilintide, a long-acting amylin analog, and semaglutide, a GLP-1 receptor agonist. The pairing is studied in laboratory metabolic research to investigate complementary signaling pathways associated with appetite regulation and glucose homeostasis. CagriSema is provided as a reference research compound for in vitro scientific work and is not intended for human use.
Certificate of Analysis (COA)
A Certificate of Analysis (COA) is a quality-control document issued by an analytical laboratory that verifies a compound’s identity, purity, and key physical characteristics. For research peptides, a COA typically includes HPLC purity percentages, mass spectrometry confirmation of molecular weight, appearance, and lot number. A reputable peptide supplier provides a COA for every product batch so researchers can verify quality before use.
CJC-1295
CJC-1295 is a synthetic analog of growth hormone-releasing hormone (GHRH) engineered with amino acid substitutions that extend its half-life in laboratory settings. Researchers study it for its ability to stimulate pulsatile growth hormone release in model systems. It is available with or without DAC (Drug Affinity Complex), which further prolongs activity by binding to serum albumin. Supplied strictly for research use.
Collagen Peptide
Collagen peptides are short chains of amino acids produced by enzymatic hydrolysis of collagen, the most abundant structural protein in connective tissues. In research, collagen peptides are studied for their bioactive fragments, which may influence cell signaling pathways involved in skin, bone, and joint tissue biology. They are commonly referenced in dermatological and regenerative science investigations.
Copper Peptide
A copper peptide is any short peptide that binds copper ions, the best-known example being GHK-Cu. The copper-peptide complex is studied for its influence on wound healing pathways, collagen synthesis, and antioxidant activity in cellular research models. Copper peptides are frequently referenced in dermatological, hair follicle, and regenerative research literature, and are distributed strictly for in vitro investigation.
D
Diluent
A diluent is any sterile liquid used to dissolve or dilute a lyophilized peptide into a working solution. Common diluents in peptide research include bacteriostatic water, sterile water for injection, and 0.9% sodium chloride. The choice of diluent depends on the peptide’s solubility profile, intended storage duration, and the experimental protocol being followed in the laboratory.
DSIP (Delta Sleep-Inducing Peptide)
DSIP, or Delta Sleep-Inducing Peptide, is a naturally occurring neuropeptide composed of nine amino acids. It was first isolated from the cerebral venous blood of rabbits in slow-wave sleep. In research, DSIP is studied for its modulatory effects on sleep architecture, stress response pathways, and neuroendocrine regulation in laboratory models. It is supplied exclusively as a research chemical.
E
Endogenous
Endogenous refers to any substance that is produced naturally within an organism. Many research peptides are synthetic analogs of endogenous hormones or signaling molecules — for example, GLP-1, GHRH, and oxytocin all occur endogenously in the human body. Understanding whether a peptide is endogenous or exogenous helps researchers frame its biological role and experimental context.
Epitalon
Epitalon is a synthetic tetrapeptide (Ala-Glu-Asp-Gly) developed based on studies of the pineal gland peptide epithalamin. In laboratory research, it is examined for its potential effects on telomerase activity, circadian rhythm signaling, and cellular aging pathways. Epitalon is provided strictly as a research compound for in vitro experimentation and is not intended for human consumption.
Exogenous
Exogenous refers to any substance introduced into an organism from outside its own biological systems. In peptide research, administering a synthetic analog of an endogenous hormone is considered an exogenous intervention. The distinction matters because exogenous compounds may activate feedback loops, alter receptor sensitivity, or produce effects that differ from naturally released molecules in laboratory models.
F
Follistatin
Follistatin is an endogenous protein that binds and neutralizes members of the TGF-beta superfamily, most notably myostatin and activin. In peptide research, follistatin and its derivatives are studied for their influence on muscle tissue development, reproductive signaling, and cellular differentiation. Research-grade follistatin peptides are used as reference materials in laboratory investigations of growth regulation pathways.
Fragment 176-191
Fragment 176-191 refers to a modified segment of the human growth hormone molecule, specifically amino acids 176 through 191 of the parent sequence. This fragment is studied in laboratory research for its potential effects on lipid metabolism without the broader activity of full-length growth hormone. It is closely related to AOD-9604 and is supplied only for in vitro research.
G
Ghrelin
Ghrelin is an endogenous peptide hormone primarily produced in the stomach that signals hunger and stimulates growth hormone release through the growth hormone secretagogue receptor (GHSR). Several research peptides, including Ipamorelin and Hexarelin, are synthetic ghrelin mimetics. Studying ghrelin and its analogs provides insight into appetite regulation, energy balance, and neuroendocrine signaling in laboratory research.
GHK-Cu
GHK-Cu is a naturally occurring tripeptide (glycyl-L-histidyl-L-lysine) that binds copper ions with high affinity, forming a biologically active complex. It is studied in research settings for its role in wound healing pathways, collagen synthesis, and antioxidant activity. GHK-Cu is frequently referenced in dermatological and regenerative research literature. Our supply is intended strictly for laboratory investigation.
GHRH (Growth Hormone Releasing Hormone)
GHRH is an endogenous hypothalamic peptide that stimulates the anterior pituitary to synthesize and release growth hormone. In research, synthetic GHRH analogs such as CJC-1295 and Sermorelin are used to study growth hormone pulsatility, the somatotropic axis, and downstream metabolic endpoints in laboratory models. Understanding GHRH biology is foundational to much of growth hormone-related peptide research.
GHRP (Growth Hormone Releasing Peptide)
GHRP refers to a class of synthetic peptides that stimulate growth hormone release by acting on the ghrelin receptor rather than the GHRH receptor. Examples include GHRP-2, GHRP-6, and Hexarelin. In research, GHRPs are often paired with GHRH analogs for synergistic studies of growth hormone pulsatility. They are supplied exclusively as research compounds for in vitro investigation.
GLP-1 (Glucagon-Like Peptide-1)
GLP-1 is an endogenous incretin hormone secreted by intestinal L-cells in response to nutrient intake. It plays a central role in glucose-dependent insulin secretion, glucagon suppression, and gastric emptying. GLP-1 is the parent molecule behind a major class of research peptides, including Semaglutide and Liraglutide, which are studied as long-acting GLP-1 receptor agonists in metabolic research.
H
Half-Life
Half-life is the time required for the concentration of a substance in a biological system to decrease by half. In peptide research, half-life is a key pharmacokinetic parameter that informs dosing intervals in experiments and helps predict steady-state concentrations. Modifications such as pegylation, lipidation, or DAC technology are often used to extend the half-life of naturally short-lived peptides.
Hexarelin
Hexarelin is a synthetic hexapeptide that belongs to the growth hormone releasing peptide (GHRP) family. It acts on the ghrelin receptor to stimulate growth hormone release in laboratory models. Researchers study Hexarelin for its effects on the somatotropic axis, comparative potency versus other GHRPs, and cardiovascular signaling pathways. It is supplied strictly as a research chemical for in vitro work.
HPLC (High-Performance Liquid Chromatography)
HPLC is an analytical technique used to separate, identify, and quantify components in a complex mixture. For peptides, HPLC is the standard method of measuring purity, typically reported as a percentage on a Certificate of Analysis. A purity level of 98% or higher is generally considered research grade. HPLC data gives researchers confidence in the identity and quality of their compounds.
I
IGF-1 LR3
IGF-1 LR3 (Long R3 Insulin-like Growth Factor 1) is a synthetic analog of IGF-1 engineered with substitutions that reduce its binding affinity for IGF-binding proteins, thereby extending its biological activity. In cell culture and laboratory research, IGF-1 LR3 is used to study growth signaling, cell proliferation, and differentiation pathways. It is supplied strictly as a research reference compound.
Insulin-Like Growth Factor (IGF)
Insulin-like growth factors are endogenous polypeptides structurally similar to insulin that mediate many of the effects of growth hormone. IGF-1 is the most studied member and plays a central role in cellular growth, development, and metabolic regulation. In peptide research, IGF-1 and its analogs are examined for their signaling roles in cell culture and preclinical model systems.
Ipamorelin
Ipamorelin is a selective growth hormone secretagogue peptide that targets the ghrelin receptor. In research, it is studied for its ability to promote growth hormone release without significantly affecting cortisol or prolactin levels in laboratory models. Ipamorelin is frequently paired with GHRH analogs like CJC-1295 in comparative studies of growth hormone pulsatility and is distributed strictly for in vitro research.
K
Kisspeptin
Kisspeptin is an endogenous peptide encoded by the KISS1 gene that plays a central role in regulating the hypothalamic-pituitary-gonadal axis. It acts on the GPR54 receptor and is studied in reproductive research for its role in puberty onset, gonadotropin-releasing hormone signaling, and fertility pathways. Research-grade kisspeptin is supplied exclusively for in vitro scientific investigation.
KPV
KPV is a tripeptide composed of lysine, proline, and valine, corresponding to the C-terminal region of alpha-melanocyte-stimulating hormone (alpha-MSH). In laboratory research, KPV is studied for its potential modulatory effects on inflammatory signaling pathways and its interactions with cellular immune responses in model systems. It is supplied strictly as a research reference compound for in vitro experimentation only.
L
Liraglutide
Liraglutide is a GLP-1 receptor agonist peptide that shares extensive structural homology with native human GLP-1, modified by the addition of a fatty acid chain that extends its half-life through albumin binding. In research, it is studied for its effects on glucose metabolism, insulin secretion, and appetite signaling pathways in laboratory models. It is provided strictly for in vitro research.
Lyophilized
Lyophilized refers to a freeze-drying process in which water is removed from a peptide solution under low temperature and vacuum, yielding a stable dry powder. Lyophilization extends shelf life, simplifies shipping, and preserves peptide integrity. Before use, a lyophilized peptide must be reconstituted with an appropriate diluent such as bacteriostatic or sterile water in a controlled laboratory environment.
M
Mass Spectrometry (MS)
Mass spectrometry is an analytical technique that measures the mass-to-charge ratio of ions to determine molecular weight and structure. In peptide research, mass spectrometry is used alongside HPLC to confirm the identity of a synthesized peptide by matching its observed mass to the theoretical mass of the target sequence. MS data is a standard component of a peptide Certificate of Analysis.
MCG (Microgram)
MCG is the abbreviation for microgram, a unit of mass equal to one millionth of a gram (0.000001 g) or one thousandth of a milligram. Research peptides are frequently dosed and reported in microgram quantities because they are biologically active at very small concentrations. Accurate MCG measurements are essential for reproducible results in any peptide research protocol.
Melanotan II
Melanotan II is a synthetic cyclic analog of alpha-melanocyte-stimulating hormone (alpha-MSH) that binds to several melanocortin receptors. In laboratory research, it is studied for its effects on melanocortin signaling pathways, which are involved in pigmentation biology and central nervous system regulation. Melanotan II is sold strictly as a research chemical for in vitro scientific investigation only.
MOTS-c
MOTS-c is a mitochondrial-derived peptide of 16 amino acids encoded within the mitochondrial genome itself. In research, it is studied for its role in metabolic homeostasis, insulin sensitivity pathways, and mitochondrial-nuclear communication. MOTS-c is considered a member of an emerging class of mitochondrially encoded peptides with regulatory functions and is supplied strictly for in vitro laboratory research.
N
N-Acetyl (Modification)
N-Acetyl refers to the addition of an acetyl group to the N-terminus (amino end) of a peptide. This chemical modification can improve stability, resist enzymatic degradation, and alter pharmacokinetic properties. Several research peptides exist in N-acetylated forms, and the modification is a common strategy used by chemists when designing analogs for laboratory investigation and structure-activity studies.
Nootropic
A nootropic is a compound studied for its potential to influence cognitive functions such as memory, attention, or learning in research models. Several peptides, including certain fragments of ACTH and cerebrolysin-related molecules, are examined as nootropic research candidates. The term is broad and scientifically contested, so nootropic peptides should always be evaluated within the specific context of their published research literature.
O
Oxytocin
Oxytocin is an endogenous nine-amino-acid peptide hormone produced in the hypothalamus and released by the posterior pituitary gland. In research, it is studied for its roles in social bonding behavior, reproductive physiology, and smooth-muscle contraction pathways. Synthetic research-grade oxytocin is used as a reference compound in cell culture and preclinical experiments and is not intended for human use.
P
PEG (Pegylation)
Pegylation is the process of covalently attaching one or more polyethylene glycol (PEG) chains to a peptide. This modification typically increases molecular size, reduces renal clearance, and extends plasma half-life, making short-lived peptides more practical for extended research protocols. Pegylation is one of several strategies — along with lipidation and DAC — used to improve peptide pharmacokinetic properties in laboratory studies.
Peptide
A peptide is a short chain of amino acids linked by peptide bonds, typically containing fewer than about 50 residues. Longer chains are generally classified as proteins. Peptides occupy a unique space between small molecules and proteins and serve as hormones, neurotransmitters, and signaling molecules. Peptide research explores their therapeutic potential, receptor interactions, and structural-functional relationships in laboratory settings.
Peptide Bond
A peptide bond is a covalent amide linkage formed between the carboxyl group of one amino acid and the amino group of another, releasing a molecule of water in the process. Peptide bonds form the backbone of all peptides and proteins, and their sequence, length, and folding together determine a molecule’s three-dimensional structure, biological activity, and stability.
Purity
Purity is the percentage of a peptide sample consisting of the intended target molecule versus impurities, synthesis byproducts, or residual solvents. It is typically measured by HPLC and reported on a Certificate of Analysis. Research-grade peptides are generally 98% pure or higher. High purity is essential for reliable, reproducible results in any scientific experimentation involving peptide compounds.
R
Reconstitution
Reconstitution is the process of dissolving a lyophilized (freeze-dried) peptide in a sterile liquid diluent to prepare a working solution. Researchers typically use sterile or bacteriostatic water, adding it slowly down the inside wall of the vial to avoid foaming and denaturation. Proper reconstitution preserves peptide integrity, enables accurate concentration calculations, and is essential before any laboratory experimentation.
Retatrutide
Retatrutide is a next-generation triple-receptor agonist peptide under research investigation for its simultaneous activity at the GLP-1, GIP, and glucagon receptors. Its multi-target design is studied in laboratory models for metabolic research endpoints, including energy expenditure, glucose regulation, and lipid modulation. Retatrutide is offered strictly for in vitro scientific research and is not approved for human administration.
S
SARMs (Selective Androgen Receptor Modulators)
SARMs are a class of small-molecule research compounds — notably not peptides — that bind selectively to androgen receptors in specific tissues. They are often listed alongside peptides in research catalogs because of overlapping interest in anabolic research pathways. It is important to distinguish SARMs from true peptides: they differ fundamentally in chemistry, mechanism, and analytical characterization methods used in the laboratory.
Secretagogue
A secretagogue is any substance that causes another substance to be secreted from a cell or gland. In peptide research, the term most often refers to growth hormone secretagogues — compounds such as Ipamorelin and GHRP-6 that stimulate the pituitary gland to release growth hormone. Secretagogues are valuable tools for studying endocrine pulsatility and receptor signaling in laboratory models.
Semaglutide
Semaglutide is a GLP-1 (glucagon-like peptide-1) receptor agonist studied for its effects on glucose regulation and metabolic pathways. Structurally, it is an analog of native GLP-1 with amino acid substitutions and a fatty-acid side chain that extend its half-life. In research, it is examined for insulin secretion, appetite signaling, and metabolic endpoints. Any reference on this page is for scientific purposes only.
Sermorelin
Sermorelin is a synthetic peptide consisting of the first 29 amino acids of human growth hormone-releasing hormone (GHRH), making it the shortest fully bioactive fragment of GHRH. In research, it is studied for its ability to stimulate growth hormone release from the pituitary in laboratory models. Sermorelin is provided strictly as a research reference compound for in vitro investigation.
Somatropin
Somatropin is the generic name for recombinant human growth hormone (rhGH), a 191-amino-acid polypeptide produced using recombinant DNA technology. While technically a protein rather than a short peptide, it is frequently referenced in peptide research contexts because many research peptides are studied specifically for their effects on the endogenous growth hormone axis that somatropin directly supplements.
Subcutaneous
Subcutaneous refers to the layer of tissue directly beneath the skin. In research laboratories, subcutaneous administration is a common route for delivering peptides to animal models because it allows for steady absorption into the bloodstream. This route is frequently chosen when oral delivery is impractical due to enzymatic degradation of the peptide in the gastrointestinal tract during standard research protocols.
T
TB-500
TB-500 is a synthetic fragment derived from Thymosin Beta-4, a naturally occurring regulatory peptide involved in actin binding and cell migration. In research, TB-500 is studied for its potential role in cellular motility, angiogenesis, and tissue repair pathways in laboratory models. It is supplied as a lyophilized research chemical for controlled laboratory experimentation only, not for clinical or veterinary application.
Thymalin
Thymalin is a complex of polypeptides extracted from the thymus gland and studied in research for its potential immunomodulatory properties. It is closely related to other thymic peptide preparations and is examined in laboratory investigations of immune signaling and cellular aging pathways. Thymalin is offered strictly as a research compound for in vitro scientific work.
Thymosin Alpha-1
Thymosin Alpha-1 is a 28-amino-acid peptide originally isolated from the thymus gland. It plays a role in immune system regulation and is studied in research for its effects on T-cell maturation, cytokine signaling, and innate immune responses in laboratory models. Thymosin Alpha-1 is supplied as a research-grade reference compound for in vitro experimentation only.
Tirzepatide
Tirzepatide is a synthetic dual agonist peptide that binds to both the GLP-1 and GIP (glucose-dependent insulinotropic polypeptide) receptors. Researchers study its dual mechanism of action for insights into glucose homeostasis, lipid metabolism, and body-weight related endpoints in laboratory models. Tirzepatide is sold here solely as a reference compound for in vitro research and is not intended for human use.
V
Vasopressin
Vasopressin, also called antidiuretic hormone (ADH), is an endogenous nine-amino-acid peptide hormone produced in the hypothalamus and released from the posterior pituitary. It regulates water retention by the kidneys and plays roles in blood pressure regulation and certain behavioral pathways. In research, vasopressin and its analogs are used as reference compounds for studying receptor signaling and fluid homeostasis.
Research-Use Disclaimer: All peptides and compounds discussed in this glossary are sold strictly for in vitro laboratory research and scientific investigation. None of the products referenced are intended for human or veterinary consumption, diagnostic use, or therapeutic application. The information in this peptide glossary is provided for educational and informational purposes only and should not be interpreted as medical advice. Always consult a qualified healthcare professional before making any decisions regarding personal health.