Peptide Glossary
Key terms and definitions used in peptide research. Tap a letter to jump to that section.
A
Ac-SDKP
N-acetyl-seryl-aspartyl-lysyl-proline, a naturally occurring tetrapeptide fragment of Thymosin Beta-4 with anti-inflammatory and anti-fibrotic properties studied for cardiac and pulmonary research.
Agonist
A substance that binds to a receptor and activates it, triggering a biological response similar to the receptor's natural ligand.
Amino Acid
An organic molecule that serves as a building block of peptides and proteins. There are 20 standard amino acids encoded by the genetic code.
AMPK
AMP-activated protein kinase, a cellular energy sensor that regulates metabolism. Activation of AMPK promotes glucose uptake, fatty acid oxidation, and mitochondrial biogenesis.
Anabolic
Relating to metabolic processes that build complex molecules from simpler ones, promoting tissue growth and repair. Anabolic processes include muscle protein synthesis and bone formation. The opposite of catabolic.
Angiogenesis
The formation of new blood vessels from pre-existing vasculature. Certain peptides like TB-500 (Thymosin Beta-4) are studied for their role in promoting angiogenesis during tissue repair.
Antagonist
A substance that binds to a receptor and blocks or dampens its biological response, preventing the natural ligand from activating it.
Apoptosis
Programmed cell death, a tightly regulated process by which the body eliminates damaged, aged, or unwanted cells. Unlike necrosis, apoptosis is orderly and does not trigger inflammation. Many peptides modulate apoptosis pathways for therapeutic research.
B
Bacteriostatic Water
Sterile water containing 0.9% benzyl alcohol as a preservative. Used to reconstitute lyophilized peptides while inhibiting bacterial growth, allowing multi-dose use.
BDNF
Brain-derived neurotrophic factor, a protein that supports neuron survival, growth, and synaptic plasticity. Several peptides are researched for their ability to upregulate BDNF expression.
Bioavailability
The proportion of a substance that enters systemic circulation and is available to exert its biological effect. Route of administration significantly affects peptide bioavailability.
Biomarker
A measurable biological indicator (like a blood test value, hormone level, or genetic marker) used to assess a biological state, disease, or response to treatment. Biomarkers are essential for tracking how peptides affect the body in research studies.
Bioregulator
Short peptides (typically 2-4 amino acids) theorized to interact with DNA to regulate gene expression. Also known as Khavinson peptides after the researcher who pioneered the field.
BPC-157
Body Protection Compound-157, a synthetic pentadecapeptide derived from a protein found in human gastric juice. One of the most widely researched peptides, studied for its effects on wound healing, tendon repair, gut protection, and inflammation in preclinical models.
C
Cardiolipin
A phospholipid found almost exclusively in the inner mitochondrial membrane, critical for mitochondrial energy production. Peptides like SS-31 (elamipretide) target cardiolipin to restore mitochondrial function.
Catabolic
Relating to metabolic processes that break down complex molecules into simpler ones, releasing energy. Prolonged stress, illness, or caloric deficit can shift the body into a catabolic state, leading to muscle loss. The opposite of anabolic.
Cathelicidin
A family of antimicrobial peptides found in mammals that play a key role in innate immune defense. LL-37 is the only human cathelicidin.
Certificate of Analysis
A document from an analytical laboratory verifying a peptide's identity, purity, and quality. A legitimate COA includes HPLC purity data, mass spectrometry confirmation, and endotoxin testing.
Collagen
The most abundant structural protein in the human body, providing strength and elasticity to skin, tendons, ligaments, bones, and blood vessels. Many repair-oriented peptides (BPC-157, GHK-Cu, TB-500) stimulate collagen synthesis.
Compounding Pharmacy
A licensed pharmacy that prepares customized medications tailored to individual needs, often combining or altering ingredients not available in standard commercial drugs. Many peptides are obtained through compounding pharmacies under a prescription.
Cytokine
Small signaling proteins (like interleukins, interferons, and TNF) released by cells to regulate immune response, inflammation, and cell communication. Many peptides modulate cytokine production to achieve anti-inflammatory effects.
D
Deamidation
A common degradation reaction where asparagine or glutamine residues lose their amide group, altering peptide structure and potentially reducing biological activity. Deamidation is a key concern during peptide storage and reconstitution.
Dosage
The specific amount of a substance administered at one time or over a period. Peptide dosages are typically measured in micrograms (mcg) or milligrams (mg) and vary based on the compound, route of administration, and research protocol.
E
Electron Transport Chain
A series of protein complexes in the inner mitochondrial membrane that transfer electrons to produce ATP, the cell's main energy currency. Dysfunction in the electron transport chain is linked to aging and many diseases.
Endogenous
Produced naturally within the body. For example, BPC-157 is a fragment of a protein naturally found in human gastric juice.
Endotoxin
Lipopolysaccharides released from the outer membrane of gram-negative bacteria. Endotoxin testing (LAL test) is critical for injectable peptide quality assurance.
Exogenous
Originating outside the body. Exogenous peptides are synthesized externally and introduced into the body for research or therapeutic purposes.
F
FDA
The U.S. Food and Drug Administration, responsible for regulating drugs, biologics, and medical devices. Peptide therapeutics must undergo FDA approval through clinical trials before they can be marketed as drugs.
Fibroblast
The most common cell type in connective tissue, responsible for producing collagen and other extracellular matrix components. Fibroblast activity is central to wound healing, and many repair peptides stimulate fibroblast proliferation.
Follistatin
A glycoprotein that binds and inhibits activin and myostatin, both of which limit muscle growth. Follistatin is studied for its potential role in increasing muscle mass and strength.
G
GHK-Cu
Glycyl-L-histidyl-L-lysine copper complex, a naturally occurring tripeptide-copper complex found in human plasma. Studied for its roles in wound healing, collagen synthesis, skin remodeling, and hair follicle stimulation.
GHRH
Growth hormone-releasing hormone, a hypothalamic peptide that stimulates the pituitary gland to produce and release growth hormone. Synthetic analogs like CJC-1295 and Sermorelin mimic GHRH activity.
GHRP
Growth hormone-releasing peptides, a class of synthetic peptides that stimulate growth hormone secretion through the ghrelin receptor. Examples include GHRP-2, GHRP-6, Ipamorelin, and Hexarelin.
GLP-1
Glucagon-like peptide-1, an incretin hormone that stimulates insulin secretion, inhibits glucagon release, and slows gastric emptying. GLP-1 receptor agonists (e.g., semaglutide) are used in metabolic research.
GPCR
G-protein-coupled receptors, the largest and most diverse family of membrane receptors in eukaryotes. GPCRs detect hormones, neurotransmitters, and peptides outside the cell and trigger internal signaling cascades. Most peptide drugs work through GPCRs.
Growth Hormone
A peptide hormone produced by the anterior pituitary gland that stimulates growth, cell reproduction, and regeneration. Many peptides (secretagogues like CJC-1295, Ipamorelin, and GHRP-6) work by stimulating the body's own growth hormone release rather than replacing it directly.
H
Half-Life
The time required for the concentration of a substance in the body to decrease by half. Peptide half-lives vary widely and influence dosing frequency.
HPLC
High-performance liquid chromatography, an analytical technique used to separate, identify, and quantify components in a mixture. HPLC is the standard method for determining peptide purity.
Hypertrophy
An increase in the size of an organ or tissue caused by enlargement of its existing cells (as opposed to hyperplasia, which is increased cell number). Skeletal muscle hypertrophy is the primary mechanism of muscle growth from resistance training.
I
IGF-1
Insulin-like growth factor 1, a hormone structurally similar to insulin that mediates many of growth hormone's anabolic effects. IGF-1 plays roles in cell growth, proliferation, and survival.
In Vitro
Latin for 'in glass.' Refers to experiments performed outside a living organism, typically in test tubes, petri dishes, or cell cultures.
In Vivo
Latin for 'in the living.' Refers to experiments conducted within a living organism, such as animal or human studies.
Intramuscular
An injection route delivering a substance directly into muscle tissue. Some peptides are administered intramuscularly for slower, sustained absorption.
Ipamorelin
A synthetic pentapeptide that selectively stimulates growth hormone release from the pituitary gland via the ghrelin receptor. Known for its specificity — it increases GH without significantly affecting cortisol, prolactin, or appetite, making it one of the most studied GH secretagogues.
L
Ligand
A molecule that binds to a specific receptor to produce a signal or trigger a biological response. Peptides themselves often act as ligands, binding to receptors on cell surfaces to initiate their effects.
Lyophilized
Freeze-dried. Peptides are commonly supplied in lyophilized (powdered) form to preserve stability during storage. They must be reconstituted with bacteriostatic water or sterile water before use.
M
Mass Spectrometry
An analytical technique that measures the mass-to-charge ratio of ions to identify and characterize molecules. Used alongside HPLC to confirm peptide identity and molecular weight.
Mechanism of Action
The specific biochemical interaction through which a drug or peptide produces its pharmacological effect. Understanding a peptide's mechanism of action is essential for predicting its benefits, side effects, and interactions.
Melanocortin
A group of peptide hormones that act on melanocortin receptors (MC1R-MC5R). They regulate pigmentation, energy balance, inflammation, and sexual function. Melanotan II is a synthetic melanocortin analog.
Melanotan II
A synthetic analog of alpha-melanocyte-stimulating hormone (α-MSH) that activates melanocortin receptors to stimulate melanin production, resulting in skin darkening. Also researched for effects on libido and appetite.
Mitochondria
Membrane-bound organelles inside cells that generate ATP, the primary energy currency of life. Often called 'the powerhouse of the cell.' Mitochondrial dysfunction is linked to aging, metabolic disease, and neurodegeneration.
Mitochondrial DNA
A small, circular DNA molecule located inside mitochondria, separate from the main genome in the cell nucleus. Damage to mitochondrial DNA is strongly linked to aging and age-related diseases.
Myostatin
A protein (also known as GDF-8) that acts as a negative regulator of muscle growth. Inhibiting myostatin is a research target for increasing muscle mass and treating muscle-wasting conditions.
N
Neuropeptide
A small protein-like molecule produced and released by neurons to communicate with other cells. Examples include oxytocin, substance P, and neuropeptide Y.
NF-κB
Nuclear factor kappa-light-chain-enhancer of activated B cells, a protein complex that controls transcription of DNA, cytokine production, and cell survival. Many peptides modulate NF-κB signaling to exert anti-inflammatory effects.
O
Oral Peptide
A peptide formulated for oral administration rather than injection. Oral peptides face challenges with stomach acid degradation and low bioavailability, so many use protective coatings or modifications. BPC-157 is one of the most commonly studied oral peptides.
P
PEGylation
The process of attaching polyethylene glycol (PEG) chains to a peptide or protein. PEGylation extends a peptide's half-life by slowing kidney clearance and reducing immune recognition. PEG-MGF is an example of a PEGylated peptide.
Pentadecapeptide
A peptide composed of exactly 15 amino acids linked by peptide bonds. BPC-157 is the best-known research pentadecapeptide.
Peptide
A short chain of amino acids linked by peptide bonds, typically containing 2–50 amino acids. Peptides are smaller than proteins and play diverse roles in the body as hormones, neurotransmitters, and signaling molecules. Many are being researched for therapeutic applications.
Peptide Bond
A covalent chemical bond formed between the carboxyl group of one amino acid and the amino group of another, releasing a molecule of water. Peptide bonds link amino acids into chains.
Phase 1 Clinical Trial
The first stage of testing a new treatment in humans. Phase 1 trials focus on safety, dosage, and side effects, typically involving a small number of healthy volunteers.
Phase 2 Clinical Trial
The second stage of human testing that evaluates efficacy and further assesses safety. Phase 2 trials involve a larger group of participants who have the condition being studied.
Phase 3 Clinical Trial
Large-scale studies comparing the new treatment to existing standard treatments. Phase 3 trials confirm efficacy, monitor side effects, and collect data for regulatory approval.
Preclinical
Research conducted before clinical (human) trials, including in vitro studies and animal models. Preclinical data is required to support an Investigational New Drug (IND) application.
PubMed
A free search engine maintained by the National Library of Medicine that provides access to the MEDLINE database of biomedical and life sciences literature. The primary source for peer-reviewed peptide research.
Purity
The percentage of the target peptide relative to total content in a sample, typically measured by HPLC. Research-grade peptides generally require 98%+ purity.
R
Reactive Oxygen Species
Highly reactive molecules containing oxygen (like free radicals and peroxides) generated as byproducts of normal metabolism. Excess ROS cause oxidative stress, damaging DNA, proteins, and lipids. This is central to aging and many diseases.
Receptor
A protein molecule on a cell surface or inside a cell that binds specific substances (ligands) and triggers a cellular response. Peptides exert their effects by binding to specific receptors.
Reconstitution
The process of dissolving a lyophilized (freeze-dried) peptide in a sterile diluent such as bacteriostatic water. Proper reconstitution technique preserves peptide integrity.
S
Satellite Cells
Muscle-specific stem cells that sit dormant beside muscle fibers. When muscle is damaged or stressed, satellite cells activate to repair and grow new muscle tissue. They're essential for muscle hypertrophy.
Secretagogue
A substance that promotes the secretion of another substance. Growth hormone secretagogues (GHS) stimulate the pituitary gland to release growth hormone.
Semaglutide
A GLP-1 receptor agonist originally developed for type 2 diabetes (brand name Ozempic) and later approved for chronic weight management (brand name Wegovy). It works by mimicking the GLP-1 hormone to regulate insulin, suppress appetite, and slow gastric emptying.
Senolytic
A class of compounds that selectively clear senescent (aged, non-dividing) cells from tissues. Some peptides are being researched for senolytic properties in the context of aging.
Sermorelin
A synthetic analog of growth hormone-releasing hormone (GHRH) containing the first 29 amino acids of the natural 44-amino-acid hormone. Sermorelin stimulates the pituitary gland to produce and release growth hormone naturally, rather than introducing external GH directly.
SNARE Complex
Soluble N-ethylmaleimide-sensitive factor attachment protein receptor complex, a group of proteins that mediate the fusion of vesicles with target membranes. Critical for neurotransmitter release and cellular secretion.
Splice Variant
Different protein products generated from a single gene through alternative RNA splicing. MGF (Mechano Growth Factor), for example, is a splice variant of IGF-1 that activates in response to muscle damage.
Sterility
The absence of viable microorganisms. Injectable peptide solutions must be sterile to prevent infection. Sterility is confirmed through testing per pharmacopeial standards.
Subcutaneous
An injection route delivering a substance into the layer of fat and connective tissue just beneath the skin. The most common administration route for research peptides.
T
TB-500
A synthetic version of a region of Thymosin Beta-4, a naturally occurring 43-amino-acid peptide involved in tissue repair, cell migration, and blood vessel formation. TB-500 is one of the most commonly researched peptides for wound healing and recovery.
Telomerase
An enzyme that adds DNA sequence repeats to the ends of chromosomes (telomeres), counteracting the shortening that occurs during cell division. Telomerase activation is a research focus in longevity science.
Tirzepatide
A dual glucose-dependent insulinotropic polypeptide (GIP) and GLP-1 receptor agonist. Approved as Mounjaro for type 2 diabetes and Zepbound for chronic weight management. It activates two incretin pathways simultaneously, which may produce stronger metabolic effects than GLP-1-only drugs.
Tyrosine Kinase
An enzyme that transfers a phosphate group to the tyrosine residues of target proteins, activating or deactivating signaling pathways. Many growth factor receptors (including the insulin and IGF-1 receptors) are tyrosine kinases.
V
Vasodilation
The widening of blood vessels due to relaxation of smooth muscle in vessel walls. Vasodilation increases blood flow and lowers blood pressure. Nitric oxide is the body's primary vasodilator.
VEGF
Vascular Endothelial Growth Factor, a signaling protein that stimulates the formation of new blood vessels (angiogenesis). Peptides like BPC-157 upregulate VEGF as part of their tissue-repair mechanisms.
W
WADA
The World Anti-Doping Agency, an international organization that maintains the Prohibited List of substances banned in competitive sports. Many peptides, including GH secretagogues, are on the WADA Prohibited List.
This glossary is for educational and informational purposes only. It does not constitute medical advice, diagnosis, or treatment recommendations. Definitions are simplified for accessibility and may not capture the full complexity of each term. Always consult peer-reviewed literature and qualified professionals for research and clinical decisions.