Precision Tools for Peptide Research

Semaglutide is a synthetic analogue of Glucagon-Like Peptide-1 (GLP-1), a 30-amino-acid incretin hormone naturally produced by L-cells in the distal small intestine and colon in response to food ingestion. Endogenous GLP-1 has a plasma half-life of only 1–2 minutes due to rapid degradation by the enzyme dipeptidyl peptidase-4 (DPP-4). Semaglutide was engineered by Novo Nordisk to share ~94% sequence homology with native GLP-1 while incorporating a C-18 fatty diacid chain at position 34 via a linker, enabling albumin binding and dramatically extending its half-life to approximately 165–184 hours.

Tirzepatide is a first-in-class dual incretin receptor agonist, designed to simultaneously activate both GLP-1 and Glucose-Dependent Insulinotropic Polypeptide (GIP) receptors. GIP is a 42-amino-acid incretin secreted by K-cells in the duodenum and jejunum, historically considered a less potent target. Tirzepatide is a 39-residue synthetic peptide based on the GIP sequence with modifications enabling GLP-1R co-agonism, with a C20 fatty diacid moiety for albumin binding and a ~5-day half-life.

Retatrutide represents the next frontier in incretin-based therapy — a triple receptor agonist simultaneously engaging GLP-1R, GIPR, and the Glucagon Receptor (GCGR). Glucagon, a 29-amino-acid peptide secreted by pancreatic α-cells, is best known for raising blood glucose, but GCGR signaling in adipose tissue, liver, and brown adipose tissue (BAT) drives potent energy expenditure and lipolysis. Retatrutide's co-engagement of GCGR adds thermogenic energy expenditure on top of the appetite suppression of GLP-1 and metabolic sensitization of GIP.

BPC-157 is a 15-amino-acid peptide fragment derived from the sequence of Body Protection Compound (BPC), a protein naturally present in human gastric juice at trace concentrations. It was first isolated and characterized by Dr. Predrag Sikiric and colleagues at the University of Zagreb in the early 1990s. Unlike many synthetic peptides, BPC-157 appears to represent a naturally occurring cytoprotective sequence that the gastric mucosa utilizes as part of its intrinsic repair and defense mechanisms. Its sequence (Gly-Glu-Pro-Pro-Pro-Gly-Lys-Pro-Ala-Asp-Asp-Ala-Gly-Leu-Val) has no known endocrine gland of origin but is constitutively present in stomach secretions.

Thymosin Beta-4 (Tβ4) is a naturally occurring 43-amino-acid peptide found in virtually every nucleated cell of the human body, with particularly high concentrations in platelets, white blood cells, and wound fluids. It was first isolated from thymic tissue by Low and colleagues in 1981 after the broader thymosin fraction was identified in the 1960s. Tβ4 is among the most abundant intracellular peptides in mammals, estimated at 0.5% of total cellular protein in some tissues. It is constitutively expressed but significantly upregulated following injury. TB-500 refers to a synthetic version of the active fragment of Tβ4, specifically the actin-binding domain (amino acids 17–23: LKKTETQ).

GHK-Cu (Glycyl-L-histidyl-L-lysine complexed with copper²⁺) is a naturally occurring tripeptide found in human plasma, saliva, and urine. It was first identified by Loren Pickart in 1973 when he observed that plasma from young subjects rejuvenated aged liver tissue function. Plasma concentrations of GHK are approximately 200 ng/mL in young adults, declining significantly with age to ~80 ng/mL by age 60 — a pattern consistent with its proposed role as an endogenous age-modulating signal. GHK is naturally released during tissue breakdown (proteolysis), suggesting it functions as a damage-sensing signal that recruits repair machinery.

Epitalon (Ala-Glu-Asp-Gly) is a synthetic tetrapeptide analogue of Epithalamin, a natural polypeptide extract derived from the pineal gland. It was developed and extensively studied by Professor Vladimir Khavinson at the St. Petersburg Institute of Bioregulation and Gerontology. Epithalamin (the endogenous precursor) is secreted by pinealocytes and plays a central role in circadian rhythm regulation, neuroendocrine signaling, and the aging process. Epitalon represents the minimal bioactive sequence responsible for Epithalamin's bioregulatory effects.

CJC-1295 is a 29-amino-acid synthetic analogue of Growth Hormone-Releasing Hormone (GHRH), the endogenous hypothalamic peptide responsible for stimulating pituitary GH secretion. Endogenous GHRH has a plasma half-life of only ~7 minutes due to DPP-4 cleavage. CJC-1295 incorporates four amino acid substitutions to resist proteolytic degradation and, in its DAC (Drug Affinity Complex) form, includes a maleimidoproprionic acid (MPA) moiety that enables covalent albumin binding, extending the half-life to 6–8 days while preserving GHRH receptor specificity.

Ipamorelin is a pentapeptide (Aib-His-D-2-Nal-D-Phe-Lys-NH₂) belonging to the Growth Hormone Releasing Peptide (GHRP) class. It mimics ghrelin, the 28-amino-acid "hunger hormone" produced by gastric X/A-like cells, which serves as the endogenous ligand for the Growth Hormone Secretagogue Receptor (GHSR-1a). Ipamorelin was specifically engineered for its high selectivity — it stimulates GH release without the ACTH/cortisol or prolactin spikes seen with earlier GHRPs like GHRP-6, making it the cleanest GH secretagogue in its class.

Sermorelin is a 29-amino-acid synthetic peptide corresponding to the first 29 residues of endogenous GHRH(1-44), the full-length hypothalamic growth hormone-releasing hormone. GHRH was isolated by Roger Guillemin in 1982 (Nobel Prize 1977 for related hypothalamic hormone work). Sermorelin retains full biological activity as the 1-29 fragment contains the complete receptor-binding domain of GHRH. It was FDA-approved as Geref for pediatric GH deficiency before being discontinued for commercial reasons unrelated to safety.

Tesamorelin is a synthetic analogue of the full-length 44-amino-acid GHRH(1-44), with the addition of a trans-3-hexenoic acid group at the N-terminus, which confers resistance to DPP-4 cleavage and extends the half-life from minutes to ~38 minutes. It is the only FDA-approved GHRH analogue, indicated for reducing excess visceral adipose tissue (VAT) in HIV-infected adults with lipodystrophy. Its clinical approval provides the strongest regulatory validation of GHRH analogue safety and efficacy in adults.

NAD⁺ (Nicotinamide Adenine Dinucleotide) is a universal cellular coenzyme present in every living cell. It is synthesized endogenously via three main pathways: the de novo pathway from tryptophan (via the kynurenine pathway), the Preiss-Handler pathway from dietary nicotinic acid, and the salvage pathway from nicotinamide (the most predominant route in mammals). NAD⁺ levels decline significantly with age — by approximately 50% between age 40 and 60 in most tissues — a finding directly correlated with mitochondrial dysfunction, metabolic decline, and age-related disease onset.

MOTS-c is a 16-amino-acid peptide encoded within the mitochondrial genome (12S rRNA region) — a remarkable discovery by Pinchas Cohen's group in 2015 that revealed mitochondria can produce bioactive peptides with systemic hormonal functions. This class of peptides, termed mitochondrial-derived peptides (MDPs), challenges the long-held view of mitochondria as purely metabolic organelles. MOTS-c circulates in human plasma, with levels declining with age and correlating with metabolic health. Physical exercise significantly increases MOTS-c plasma concentrations, suggesting it may mediate some of exercise's systemic metabolic benefits.

SS-31 (D-Arg-2'6'-Dmt-Lys-Phe-NH₂) is a synthetic tetrapeptide developed by Drs. Hazel Szeto and Peter Schiller, designed specifically to target the inner mitochondrial membrane (IMM). Its alternating aromatic-cationic residue pattern enables spontaneous concentration within the IMM — achieving mitochondrial levels 1,000-fold higher than cytoplasmic concentrations without requiring any active transport mechanism. SS-31 selectively binds cardiolipin, a unique phospholipid exclusive to the IMM that is essential for the structural integrity and electron transport function of the respiratory chain.

Thymosin Alpha-1 (Tα1) is a 28-amino-acid peptide naturally produced and secreted by thymic epithelial cells. It represents the N-terminal fragment of a larger precursor protein, Prothymosin Alpha. The thymus gland — the primary organ of T-cell maturation — secretes Tα1 as a key hormonal signal coordinating adaptive immunity. Thymic output and Tα1 levels decline sharply after puberty as the thymus involutes, contributing to the age-related deterioration of T-cell-mediated immune function. Tα1 is FDA-approved in over 35 countries (as Zadaxin) for hepatitis B, hepatitis C, and as an adjuvant in cancer immunotherapy.

Pinealon is a synthetic tripeptide (Glu-Asp-Arg) derived from the research of Prof. Khavinson's group, representing a bioregulatory peptide with affinity for brain and pineal gland tissue. It belongs to the class of short peptide bioregulators (cytomedines) developed from organ-specific polypeptide extracts, where tissue-specific short peptides were identified as carrying tissue-targeting biological information. Pinealon exhibits particular affinity for neuronal cells and has demonstrated neuroprotective and neurorestorative properties in multiple in vitro and in vivo models.

Selank (Thr-Lys-Pro-Arg-Pro-Gly-Pro) is a synthetic heptapeptide analogue of Tuftsin, a naturally occurring tetrapeptide (Thr-Lys-Pro-Arg) derived from the Fc region of IgG immunoglobulin through enzymatic cleavage. Tuftsin is produced in the spleen and is a key endogenous immunomodulator. Selank extends the Tuftsin sequence with an additional Pro-Gly-Pro fragment from the ECM protein proline-rich peptides, dramatically increasing metabolic stability. It has undergone clinical trials in Russia and received approval there as an anxiolytic drug.

Semax is a synthetic heptapeptide (Met-Glu-His-Phe-Pro-Gly-Pro) based on the 4th to 7th amino acid sequence of Adrenocorticotropic Hormone (ACTH), the pituitary peptide that regulates cortisol synthesis. The ACTH(4-7) core (Met-Glu-His-Phe) is the primary neuroactive fragment of ACTH, and Semax extends this with a C-terminal PGP sequence to prevent rapid degradation. Unlike full ACTH, Semax has no steroidogenic activity — it lacks the receptor domains required to stimulate cortisol production — but retains the neurotrophin-stimulating and cognitive properties of the ACTH molecule.

Endogenous IGF-1 (Insulin-like Growth Factor-1) is a 70-amino-acid single-chain polypeptide primarily synthesized in the liver in response to growth hormone (GH) receptor activation via JAK2/STAT5b signaling. It is also produced locally in virtually every tissue (autocrine/paracrine IGF-1) where it mediates GH's tissue-building effects. Plasma IGF-1 is bound to IGF binding proteins (IGFBPs 1-6), which regulate its bioavailability — only ~1% of circulating IGF-1 is free and active. IGF-1 LR3 is an 83-amino-acid synthetic analogue containing an N-terminal 13-amino-acid extension and a glutamate → arginine substitution at position 3, which drastically reduces IGFBP binding affinity, extending its half-life from ~12 hours to ~20–30 hours and greatly increasing systemic bioavailability.

Kisspeptin is a family of neuropeptides derived from the KISS1 gene, produced primarily by hypothalamic KNDy neurons (neurons co-expressing Kisspeptin, Neurokinin B, and Dynorphin) in the arcuate nucleus and anteroventral periventricular nucleus. The KISS1 precursor protein is cleaved into bioactive fragments including KP-54, KP-14, KP-13, and KP-10 — all of which bind the same receptor. Kisspeptin was originally discovered as a metastasis suppressor gene product ("metastin") before its central role in controlling the reproductive axis was revealed. It serves as the master regulator of the hypothalamic-pituitary-gonadal (HPG) axis.

Melanotan II is a synthetic cyclic 7-amino-acid analogue of α-Melanocyte Stimulating Hormone (α-MSH), itself a 13-amino-acid peptide cleaved from the precursor protein Pro-opiomelanocortin (POMC) in the pituitary intermediate lobe and hypothalamic POMC neurons. The melanocortin system — comprising α-MSH, β-MSH, γ-MSH, and ACTH (all POMC-derived) and their five receptors (MC1R–MC5R) — serves as a master regulator of pigmentation, energy balance, inflammation, sexual function, and immune modulation. Melanotan II was designed as a metabolically stable, more potent α-MSH analogue for research into melanocortin physiology.

PT-141 (Bremelanotide) emerged directly from research on Melanotan II — when clinical volunteers studying its tanning effects unexpectedly reported spontaneous sexual arousal, investigators recognized the profound MC4R-mediated sexual function pathway. PT-141 is a cyclic heptapeptide metabolite of Melanotan II, formed by removal of the C-terminal amide group, and became the focus of sexual dysfunction research. It was FDA-approved in 2019 as Vyleesi for hypoactive sexual desire disorder (HSDD) in premenopausal women — the first centrally-acting treatment for female sexual dysfunction, representing a fundamentally different mechanism from PDE5 inhibitors which act peripherally.