Glossary

Terminology, defined.

Collagen (Extracellular Matrix Protein): Collagen is the most abundant structural protein in the human body, comprising approximately 30% of total protein mass and forming the primary scaffold of skin, tendon, ligament, bone, and blood vessel walls. Over 28 collagen types exist; Types I, III, and VI are the primary dermal collagens relevant to skin aging research. Collagen production by dermal fibroblasts declines approximately 1% per year after age 25, contributing to skin thinning, wrinkle formation, and reduced wound healing capacity. GHK-Cu is the most studied peptide for collagen synthesis stimulation, upregulating collagen I, III, and VI gene expression in fibroblast cultures at nanomolar concentrations (Pickart & Margolina, 2018, PMID: 29987172). **Related peptides:** [GHK-Cu](/peptides/ghk-cu) *Part of the [Aevitas Peptide Glossary](/glossary).*
GHRH (Growth Hormone-Releasing Hormone): GHRH (Growth Hormone-Releasing Hormone) is a 44-amino-acid neuropeptide produced in the hypothalamus that is the primary positive stimulator of GH secretion from the anterior pituitary. It binds the GHRH receptor (GHRHR) on somatotroph cells, activating adenylate cyclase and cAMP-mediated GH gene transcription and pulsatile release. Endogenous GHRH has a plasma half-life of approximately 2 minutes due to rapid DPP-IV cleavage. Sermorelin is the full 44-AA synthetic analog of GHRH; CJC-1295 (Modified GRF 1-29) is a 29-AA modified version with 4 amino acid substitutions that extend its half-life to ~30 minutes by resisting DPP-IV cleavage. Both act as full GHRHR agonists. **Related peptides:** [Sermorelin](/peptides/sermorelin) · [CJC-1295](/peptides/cjc-1295) *Part of the [Aevitas Peptide Glossary](/glossary).*
Growth Hormone Secretagogue (GHS): A growth hormone secretagogue (GHS) is a compound that stimulates the release of growth hormone (GH) from the anterior pituitary gland, typically by acting as an agonist at the ghrelin receptor (GHSR-1a) or the GHRH receptor (GHRHR). Unlike exogenous recombinant GH, secretagogues stimulate endogenous GH release and preserve the physiological feedback loop — high GH and IGF-1 suppress further secretagogue-stimulated release, preventing supraphysiological GH exposure. The most studied GH secretagogues are: **Ipamorelin** (selective GHSR-1a agonist, minimal cortisol/ACTH elevation); **GHRP-2** and **GHRP-6** (GHSR-1a agonists; more cortisol elevation); **Sermorelin** and **CJC-1295** (GHRHR agonists, acting on the GHRH rather than ghrelin pathway). **Related peptides:** [Ipamorelin](/peptides/ipamorelin) · [CJC-1295](/peptides/cjc-1295) · [Sermorelin](/peptides/sermorelin) *Part of the [Aevitas Peptide Glossary](/glossary).*
Half-Life (Biological): Biological half-life is the time required for the concentration of a peptide (or other compound) in a biological system — typically plasma or tissue — to fall to half its initial value. For peptides, half-life is primarily determined by enzymatic degradation (by serum proteases, dipeptidylpeptidase IV, etc.) rather than renal or hepatic clearance alone. Short-half-life peptides like Sermorelin (~15 minutes) require more frequent dosing in research to maintain receptor exposure; longer half-life compounds like TB-500 (~4 hours) provide extended receptor stimulation per administration. Half-life values listed in Aevitas monographs reflect figures reported in pharmacokinetic studies. **Examples:** Epitalon ~45 min · Ipamorelin ~2 hrs · BPC-157 ~4 hrs · TB-500 ~4 hrs · CJC-1295 no DAC ~30 min *Part of the [Aevitas Peptide Glossary](/glossary).*
HPLC (High-Performance Liquid Chromatography): HPLC (High-Performance Liquid Chromatography) is the gold standard analytical technique for measuring peptide purity. It works by passing a dissolved sample through a column packed with stationary-phase particles; different compounds travel at different speeds based on their chemical interactions with the stationary phase and are detected by UV absorbance (typically at 214 nm for peptide bonds) as they elute. The resulting chromatogram shows distinct peaks; purity is calculated as the target compound''s peak area as a percentage of total peak area. For research-grade peptides, ≥98% HPLC purity is the accepted minimum threshold, meaning ≤2% of the detected material is impurities, degradation products, or residual synthesis byproducts. **Related peptides:** All Aevitas peptides are ≥98% HPLC verified. *Part of the [Aevitas Peptide Glossary](/glossary).*
Lyophilized (Freeze-Dried): Lyophilized (freeze-dried) is the preferred storage form for research-grade peptides. The lyophilization process removes water from the peptide solution under vacuum at low temperature, leaving a dry, stable powder that can be stored at −20°C for 24+ months without significant degradation. Liquid reconstituted peptides degrade much faster due to hydrolysis and enzymatic activity. Before use in research, lyophilized peptides are typically reconstituted with bacteriostatic water or sterile water. All Aevitas peptides are supplied in lyophilized powder form. *Part of the [Aevitas Peptide Glossary](/glossary).*
Peptide: A peptide is a short chain of amino acids linked by peptide bonds (amide bonds between the carboxyl group of one amino acid and the amino group of the next). Peptides are distinguished from proteins primarily by length: peptides typically contain 2–50 amino acids, while proteins contain 50+. In biological systems, peptides function as hormones (e.g., GHRH, ghrelin), signalling molecules, enzyme cofactors, and structural components. Research-grade peptides like those in the Aevitas catalog are synthesised chemically using solid-phase peptide synthesis (SPPS) and verified by HPLC for purity and mass spectrometry for identity. The specificity of peptide-receptor interactions — and the short biological half-lives that limit systemic exposure — make peptides attractive tools for targeted research. *Part of the [Aevitas Peptide Glossary](/glossary).*
Research Use Only (RUO): Research Use Only (RUO) is a regulatory designation indicating that a compound is intended exclusively for scientific research — laboratory studies, preclinical investigations, in vitro experiments — and has not been evaluated for safety or efficacy in humans or animals as a treatment. RUO compounds are not approved by the FDA, EMA, or other regulatory authorities for therapeutic, diagnostic, or preventive use. They must be handled by qualified researchers in appropriate facilities. Aevitas supplies all peptides under RUO designation in compliance with this classification. RUO is not a temporary regulatory status; it is a classification reflecting the intended use of the compound at the time of sale. *Part of the [Aevitas Peptide Glossary](/glossary).*
Telomerase: Telomerase is a ribonucleoprotein enzyme (RNA-protein complex) that adds TTAGGG hexanucleotide repeat sequences to the ends of linear chromosomes (telomeres), counteracting the telomere shortening that occurs with each cell division. In most somatic cells, telomerase is inactive or expressed at very low levels, causing progressive telomere shortening and eventually replicative senescence. In germline cells, stem cells, and most cancer cells, telomerase is active, maintaining telomere length and enabling continued proliferation. Epitalon is the most studied peptide for telomerase activation in normal somatic cells — Khavinson et al. (2003) demonstrated Epitalon-induced telomerase activation in human fetal fibroblasts and lymphocytes via a p53-independent mechanism (PMID: 12665553). **Related peptides:** [Epitalon](/peptides/epitalon) **Related research:** [Khavinson 2003 — Epitalon Telomerase Study](/research/khavinson-2002-epitalon-telomerase) *Part of the [Aevitas Peptide Glossary](/glossary).*
VEGF (Vascular Endothelial Growth Factor): VEGF (Vascular Endothelial Growth Factor) is a family of signalling proteins that stimulate angiogenesis — the formation of new blood vessels from existing vasculature. VEGF-A, the primary isoform studied in tissue repair, binds VEGFR-2 (KDR) on endothelial cells, triggering proliferation, migration, and tube formation — the three processes that produce new capillaries in healing tissue. In peptide research, VEGF upregulation is a key mechanism for both BPC-157 (which robustly induces VEGF-A in tendon and GI repair models) and GHK-Cu (which upregulates VEGF-A gene expression in wound healing models). Angiogenesis is essential for tissue repair because new capillaries deliver oxygen and nutrients and remove inflammatory debris from injury sites. **Related peptides:** [BPC-157](/peptides/bpc-157) · [GHK-Cu](/peptides/ghk-cu) *Part of the [Aevitas Peptide Glossary](/glossary).*