Amino Acid
The fundamental building blocks of peptides and proteins. Each amino acid contains an amino group, a carboxyl group, and a variable side chain that determines its chemical properties. Twenty standard amino acids encode the vast majority of biological peptides.
Angiogenesis
The formation of new blood vessels from pre-existing vasculature. Several research peptides (BPC-157, GHK-Cu, TB-500) promote angiogenesis in injured tissue, which may accelerate healing by improving blood and nutrient supply.
Autocrine Signaling
A form of cell signaling where a cell produces a chemical messenger that binds to receptors on the same cell. Many peptide growth factors use autocrine signaling to regulate their own production.
Bacteriostatic Water
Sterile water containing 0.9% benzyl alcohol, used to reconstitute lyophilized peptides. The benzyl alcohol inhibits bacterial growth, extending the shelf life of reconstituted solutions to approximately 28–30 days when refrigerated.
BDNF (Brain-Derived Neurotrophic Factor)
A neurotrophin that supports neuron survival, synaptic plasticity, and neurogenesis. Low BDNF is associated with depression and cognitive decline. Peptides like Semax and Selank have demonstrated BDNF upregulation in preclinical models.
Bioavailability
The fraction of an administered dose that reaches systemic circulation in an active form. Subcutaneous injection of peptides achieves ~100% bioavailability; oral bioavailability is typically near zero for most peptides due to enzymatic degradation in the GI tract.
Certificate of Analysis (COA)
A document from a testing laboratory confirming the identity, purity, and other quality attributes of a compound. A legitimate peptide COA should include mass spectrometry identity confirmation, HPLC purity, and ideally endotoxin testing for injectable compounds.
Counterion
An ion that balances the charge of an oppositely charged ion. In peptide synthesis, trifluoroacetate (TFA) is a common counterion that may constitute 20–40% of vial weight. High-quality suppliers exchange TFA for a more benign counterion like acetate.
Coupling Efficiency
In solid-phase peptide synthesis, the percentage of successful amino acid couplings per synthesis step. High coupling efficiency (>99%) is essential for long peptides — each fractionally incomplete step compounds error accumulation across the full sequence.
DAC (Drug Affinity Complex)
A peptide modification technology that enables binding to serum albumin, dramatically extending circulating half-life. CJC-1295 with DAC achieves a half-life of 6–8 days through this mechanism, enabling weekly dosing.
Delta Wave Sleep
Slow-wave sleep characterized by high-amplitude, low-frequency EEG activity (0.5–4 Hz). The most restorative sleep stage, associated with tissue repair, growth hormone pulsation, and memory consolidation. DSIP was named for its ability to induce this sleep stage.
Dose-Response Relationship
The quantitative relationship between the dose of a compound and the magnitude of its effect. A key feature distinguishing pharmacologically active substances from inert ones — and a fundamental element of any credible clinical study.
Endocrine System
The system of glands and organs that produce, store, and secrete hormones directly into the bloodstream. The hypothalamic-pituitary axis is the central regulatory hub that many peptide secretagogues target.
Endotoxin
Lipopolysaccharides (LPS) derived from the outer membrane of gram-negative bacteria — common contaminants in chemically synthesized peptides. Endotoxin injection can cause fever, chills, and systemic inflammatory response. LAL testing is the standard detection method.
Evidence Level (EL)
A hierarchical system for classifying the quality of scientific evidence. Peptidely uses EL1 (RCT/FDA approved), EL2 (human Phase I/II), EL3 (animal/limited human), and EL4 (anecdotal/theoretical) to communicate confidence in research.
Fibroblast
The primary cell type responsible for producing collagen, elastin, and other extracellular matrix components in connective tissue. Fibroblast recruitment and activation is a key mechanism for tendons, ligaments, and wound healing — a common target of repair peptides like BPC-157 and GHK-Cu.
GABA (Gamma-Aminobutyric Acid)
The primary inhibitory neurotransmitter in the mammalian central nervous system. GABAergic modulation underlies the mechanism of action of several anxiolytic compounds, including Selank, which modulates GABA-A receptors without causing dependence.
GABA-A Receptor
An ionotropic receptor for GABA that, when activated, increases chloride conductance and inhibits neuronal firing. Benzodiazepines work at the benzodiazepine binding site on GABA-A receptors; Selank modulates the receptor through a distinct mechanism without causing tolerance.
GHK-Cu (Copper Tripeptide-1)
A naturally occurring tripeptide (glycyl-histidyl-lysine) complexed with copper. First identified in human plasma by Loren Pickart in 1973, GHK-Cu has documented effects on over 4,000 genes related to tissue repair, inflammation, and antioxidant defense.
Ghrelin
An endogenous peptide hormone produced primarily in the stomach, acting as the natural ligand for the growth hormone secretagogue receptor (GHSR-1a). Ghrelin stimulates GH release and appetite. Ipamorelin, GHRP-2, and MK-677 are synthetic GHSR agonists that mimic ghrelin.
GHRH (Growth Hormone-Releasing Hormone)
A 44-amino-acid hypothalamic peptide that stimulates the anterior pituitary to release growth hormone. CJC-1295 and Sermorelin are synthetic GHRH analogs designed to mimic and extend the action of endogenous GHRH.
GHSR (Growth Hormone Secretagogue Receptor)
Also called the ghrelin receptor, GHSR-1a is a G protein-coupled receptor expressed on pituitary somatotrophs. Activation by ghrelin or synthetic agonists (Ipamorelin, GHRP-2, MK-677) triggers GH release through a calcium-mediated signaling cascade.
GLP-1 (Glucagon-Like Peptide-1)
An incretin hormone secreted by intestinal L-cells in response to food intake. GLP-1 stimulates insulin secretion, suppresses glucagon, slows gastric emptying, and reduces appetite. GLP-1 receptor agonists (semaglutide, liraglutide, tirzepatide) are FDA-approved for T2D and obesity.
GMP (Good Manufacturing Practice)
A regulatory system ensuring pharmaceutical products are consistently produced and controlled according to quality standards. FDA requires GMP compliance for approved drugs; research peptide suppliers are not required to meet GMP standards unless they are 503B outsourcing facilities.
Growth Hormone (GH)
A 191-amino-acid protein hormone secreted by the anterior pituitary in pulsatile fashion. GH promotes muscle protein synthesis, lipolysis, bone density, and tissue repair primarily through IGF-1 production in the liver. GH secretion declines with age (somatopause).
Half-Life
The time required for the plasma concentration of a drug to reduce by 50%. Longer half-life allows less frequent dosing. CJC-1295 with DAC has a half-life of 6–8 days; ipamorelin ~2 hours; native GHRH ~7 minutes. Half-life determines dosing frequency.
HPA Axis (Hypothalamic-Pituitary-Adrenal)
The neuroendocrine axis regulating stress response, cortisol production, and immune function. GHRP-2 causes cortisol spillover via HPA axis activation — a disadvantage vs. Ipamorelin, which has minimal HPA axis effects.
HPG Axis (Hypothalamic-Pituitary-Gonadal)
The regulatory axis controlling sex hormone production. GnRH from the hypothalamus triggers LH and FSH from the pituitary, which stimulate gonadal testosterone/estrogen production. Exogenous testosterone suppresses this axis; secretagogue peptides do not directly suppress it.
HPLC (High-Performance Liquid Chromatography)
A chromatographic technique for separating, identifying, and quantifying components of a mixture. HPLC is the standard method for measuring peptide purity on a COA — a result of ≥98% indicates a high-purity product with minimal impurities.
IGF-1 (Insulin-Like Growth Factor 1)
A peptide hormone produced primarily in the liver in response to growth hormone stimulation. IGF-1 mediates most of GH's anabolic effects — muscle protein synthesis, lipolysis, bone density, and tissue repair. IGF-1 levels are used as a proxy biomarker for GH axis activity.
IGF-1 LR3
A recombinant analog of IGF-1 with an extended half-life (~20 hours vs. ~15 minutes for native IGF-1) due to reduced binding affinity for IGF-binding proteins. Used in research settings for its longer duration of IGF-1 receptor activation.
Incretin
A group of gastrointestinal hormones (GLP-1 and GIP) that stimulate insulin secretion in response to food intake. GLP-1 receptor agonists are the dominant drug class in metabolic medicine because they leverage this mechanism to treat both diabetes and obesity.
Injection Site Reaction
Local adverse effects at the site of subcutaneous or intramuscular injection, including redness, swelling, bruising, or nodule formation. Common with any injectable; minimized by rotating injection sites, using small gauge needles, and proper technique.
Intramuscular (IM) Administration
Injection of a substance directly into muscle tissue, typically the deltoid, vastus lateralis, or gluteus medius. IM injection generally provides faster absorption than subcutaneous but requires longer needles and carries slightly higher risk of hitting blood vessels.
LAL Test (Limulus Amebocyte Lysate)
The gold standard assay for detecting bacterial endotoxins (lipopolysaccharides). Uses blood cells from the horseshoe crab (Limulus polyphemus) that react strongly to endotoxin. Pharmaceutical-grade injectables must pass LAL testing; research peptide suppliers are not required but reputable ones perform it.
Lyophilization (Freeze-Drying)
A dehydration process that removes water from a peptide by freezing it and then sublimating the ice under vacuum. Produces a stable powder or cake that can be stored at room temperature (weeks) or refrigerated/frozen (months to years) and reconstituted with bacteriostatic water before use.
MACE (Major Adverse Cardiovascular Events)
A composite clinical endpoint used in cardiovascular outcomes trials, typically comprising cardiovascular death, non-fatal myocardial infarction, and non-fatal stroke. GLP-1 agonists (semaglutide, liraglutide) have demonstrated MACE reduction in landmark trials.
Mass Spectrometry (MS)
An analytical technique that measures the mass-to-charge ratio of ions, used to confirm the molecular weight and identity of a peptide. A COA without mass spectrometry cannot confirm that the compound is what it claims to be — only that something with a certain HPLC retention time is present.
Mechanism of Action (MOA)
The specific biochemical or physiological process through which a drug or therapeutic compound produces its effect. Understanding MOA is essential for predicting adverse effects, drug interactions, and optimizing use.
Melanocortin System
A family of receptors (MC1R–MC5R) and their peptide ligands (alpha-MSH, ACTH fragments) that regulate pigmentation, inflammation, energy balance, sexual function, and other processes. PT-141 (bremelanotide) acts at MC3R and MC4R in the hypothalamus to enhance sexual desire.
NGF (Nerve Growth Factor)
A neurotrophic factor essential for the survival, development, and maintenance of sympathetic and sensory neurons. Like BDNF, NGF is upregulated by Semax in animal models, suggesting neuroprotective and neuroregenerative potential.
Off-Label Use
Prescribing an FDA-approved drug for an indication, patient population, or route of administration not included in the FDA-approved label. Common in medicine; carries different risk profile than approved use since evidence for the specific off-label indication may be limited.
Paracrine Signaling
Cell signaling where a molecule produced by one cell acts on neighboring cells in the local tissue environment. Many tissue repair peptides work through paracrine mechanisms — stimulating adjacent fibroblasts, endothelial cells, or immune cells.
Peptide
A molecule consisting of two or more amino acids linked by peptide bonds. Generally defined as chains of 2–50 amino acids (longer chains are proteins). Peptides serve diverse biological roles as hormones, neurotransmitters, growth factors, and antimicrobial agents.
Peptide Purity
The proportion of a peptide sample that consists of the target molecule, measured by HPLC as an area percentage. ≥98% purity is the standard benchmark for research-grade quality; lower purity means a higher proportion of uncharacterized impurities, which may have unknown biological effects.
Pharmacodynamics
The study of how a drug affects the body — including mechanism of action, receptor binding, dose-response relationships, and downstream biochemical effects. Distinct from pharmacokinetics (what the body does to the drug).
Pharmacokinetics (PK)
The study of how the body processes a drug over time — absorption, distribution, metabolism, and excretion (ADME). Key PK parameters for peptides include half-life, bioavailability by route, and volume of distribution.
Phase Clinical Trials
The sequential stages of clinical drug development: Phase I (safety/PK in small groups), Phase II (preliminary efficacy and dosing), Phase III (definitive efficacy in large RCTs), Phase IV (post-marketing surveillance). Most research peptides have not progressed beyond Phase I or II.
Pituitary Gland
A pea-sized endocrine gland at the base of the brain that produces and secretes multiple hormones including GH, LH, FSH, TSH, and ACTH. The anterior pituitary is the target of GHRH analogs (CJC-1295) and GHSR agonists (Ipamorelin) that stimulate GH release.
Proteolysis
The enzymatic degradation of proteins and peptides by proteases. Most peptides administered orally are rapidly degraded by GI proteases before reaching systemic circulation — the primary reason subcutaneous injection is the preferred route for most research peptides.
Randomized Controlled Trial (RCT)
The gold standard design for evaluating drug efficacy. Participants are randomly assigned to receive the treatment or placebo/control; neither participants nor researchers know who received which (double-blind). The highest-quality evidence for therapeutic interventions.
Receptor
A protein molecule that receives chemical signals and initiates a cellular response. Peptides and hormones typically act by binding to specific receptors on cell surfaces (like GHSR-1a, GLP-1R, or MC4R) or inside cells (steroid hormone receptors). Receptor specificity determines which cells a peptide affects.
Reconstitution
The process of dissolving a lyophilized (freeze-dried) peptide powder in bacteriostatic water or another diluent to create an injectable solution. Proper technique involves swirling (not shaking) to avoid foaming, and storing the solution refrigerated for up to 28–30 days.
Route of Administration
The pathway by which a drug is introduced into the body. For peptides, the primary routes are subcutaneous injection (~100% bioavailability), intramuscular, intranasal, sublingual, and oral (typically near-zero bioavailability unless specially formulated).
Secretagogue
A substance that stimulates the secretion of another substance. GH secretagogues (CJC-1295, Ipamorelin, Sermorelin, MK-677) stimulate the pituitary to release growth hormone — as opposed to exogenous GH, which replaces the hormone directly.
Somatopause
The age-related decline in growth hormone secretion and IGF-1 levels, beginning in the third decade of life and progressing at approximately 14% per decade. A key rationale for GH secretagogue use in anti-aging medicine, though clinical benefit in non-deficient adults is debated.
SPPS (Solid-Phase Peptide Synthesis)
The dominant method for producing synthetic peptides, developed by Robert Bruce Merrifield (Nobel Prize, 1984). Amino acids are sequentially added to a solid resin support, then cleaved and purified. Enables production of peptides from milligrams to kilograms.
Subcutaneous (SubQ) Injection
Injection into the fatty tissue beneath the skin, typically in the abdomen, thigh, or upper arm. The preferred route for most research peptides — provides reliable absorption (~100% bioavailability), is less painful than intramuscular, and can be self-administered with short (6–8mm) needles.
TFA (Trifluoroacetate)
A counterion commonly used in solid-phase peptide synthesis that can constitute 20–40% of a peptide vial's measured weight. TFA has been shown to be potentially toxic in cellular models. High-quality suppliers perform counterion exchange to replace TFA with acetate before packaging.
VEGF (Vascular Endothelial Growth Factor)
A signal protein that promotes the growth of blood vessels (angiogenesis). BPC-157 has been shown to upregulate VEGF and its receptor VEGFR2 in animal studies, providing a mechanism for its observed effects on wound healing and tissue repair.
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