A practical reference on MC1R: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2025-11-11. Anything still debated is marked as such rather than presented as settled.
Identity testing for a cyclic peptide of this size usually relies on reversed-phase high-performance liquid chromatography coupled to mass spectrometry. The mass spectrum confirms molecular weight, while the chromatographic trace indicates the proportion of related impurities. Tandem mass spectrometry can provide sequence-level information when fragmentation data are compared against a reference standard. Nuclear magnetic resonance is sometimes used to confirm the lactam bridge, although it requires more material and greater operator expertise than routine chromatographic methods.
Lyophilised peptide powder is comparatively stable when kept dry, cold and protected from light. Once dissolved, the molecule is exposed to hydrolysis, oxidation and microbial growth, and degradation accelerates at higher temperatures and in alkaline solution. Repeated freeze-thaw cycles concentrate solutes and promote aggregation. Handling guidance for research peptides commonly clusters around freezer temperatures for powder and short refrigerated use for reconstituted solutions, with pH control and sterile technique applied throughout.
Verification of a purchased sample requires documentation linking a batch to a certificate of analysis, and that document should be read for the methods used rather than the headline purity figure. A single chromatographic percentage does not establish identity. Independent laboratories can perform identity and content assays, but no such test establishes that a product is suitable for human use. Claims about efficacy rest largely on small, early studies rather than on replicated controlled trials, and that gap remains open.
Activity is attributed to agonism at melanocortin receptors, particularly MC1R and MC4R. Activation of MC1R on melanocytes increases melanin synthesis, which underlies the reported tanning effect. MC4R engagement in the central nervous system is linked to appetite suppression and to effects on sexual arousal reported in early clinical studies. Those studies were small and were not designed to establish efficacy or long-term safety. Receptor selectivity among the melanocortin subtypes is not absolute, which complicates attribution of any effect to a single pathway.
Regulatory treatment varies between countries. Several national medicines agencies have classified the peptide as unapproved, and customs authorities in some jurisdictions seize shipments on that basis. A few jurisdictions channel supply through prescription-only frameworks that do not list the substance by name. Because the material circulates mainly through online vendors, composition and purity are rarely verified before sale. Surveys of unapproved peptide products have reported labels that did not match measured content in a substantial fraction of samples.
Melanotan II is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone, a naturally occurring peptide involved in pigmentation signalling. Its structure substitutes a lactam bridge between side chains to increase stability relative to the native hormone. The compound is also known by the shorthand MT-II and by several non-proprietary synonyms used in research catalogues. It is not an approved therapeutic product in any major jurisdiction; material sold under this name is typically offered as a laboratory reagent rather than as a medicine.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white solid | Lyophilised cake or flake |
| Solubility class | Soluble in water and aqueous buffer | Also soluble in some polar organic solvents |
| Typical storage temperature | Minus 20 degrees Celsius or below | Desiccated and protected from light |
| Typical analytical method | LC-MS/MS | Reversed-phase separation with mass detection |
| Molecular formula | C50H69N15O9 | Free base; salt forms differ |
Solid peptide material is generally stable when kept cold and dry. Common practice is storage at -20 degrees Celsius or lower, with desiccant and protection from light. Repeated freeze-thaw cycles and exposure to moisture are associated with degradation, aggregation, or loss of material. Once dissolved, stability depends on solvent, concentration, and temperature, and solutions are usually treated as short-lived unless stability data support longer periods. Handling notes typically emphasise minimising time at ambient temperature.
Identity and purity are assessed with chromatographic and mass spectrometric techniques. Reversed-phase high-performance liquid chromatography separates the target peptide from related impurities and degradation products, and the resulting retention time is compared against a reference standard. Mass spectrometry, often coupled to liquid chromatography, confirms molecular mass. Amino acid analysis or peptide mapping can provide additional sequence-level confirmation when required. Results are only as reliable as the reference materials used alongside them.
Regulatory treatment varies by country. In the United States, melanotan-2 is not approved for any indication, and products marketed for human use fall outside the approved drug framework. Some other jurisdictions have placed it under prescription controls or listed it as a prohibited or restricted substance. Online listings frequently describe the material as a research chemical, a category that does not carry the same manufacturing and labelling requirements as approved medicines.
The compound emerged from research programs in the 1980s that examined analogues of alpha-melanocyte-stimulating hormone for pigmentation and photoprotection. Investigators modified the native sequence to extend activity duration and potency. A related analogue, afamelanotide, was developed within the same broad line of inquiry and eventually gained approval in certain jurisdictions for a rare light-sensitivity condition. Melanotan-2 itself did not progress through the same regulatory route and has no approved therapeutic indication.
Melanocortin receptors comprise five subtypes with distinct tissue distributions and functions. Melanotan-2 is described in the literature as a non-selective agonist that engages several of these subtypes, including MC1R, MC3R, MC4R, and MC5R. MC1R is the subtype most directly linked to melanin production in skin cells. Because the compound is not subtype-selective, its observed effects in experimental settings are generally attributed to activity across multiple receptor pathways rather than to a single target.
Melanotan-2 is a synthetic linear peptide built from seven amino acids arranged in a short chain. Its sequence is commonly written as Ac-Nle-Asp-His-D-Phe-Arg-Trp-Lys-NH2, which includes a modified N-terminus and an amidated C-terminus. The molecule belongs to the melanocortin family and acts as a receptor agonist. Structural features such as the D-phenylalanine residue and the Nle substitution are associated with increased stability against enzymatic degradation relative to the natural parent peptide.
Oxaloacetic acid (also known as oxalacetic acid or OAA) is a crystalline organic compound with the chemical formula HO2CC(O)CH2CO2H. Oxaloacetic acid, in the form of its conjugate base oxaloacetate, is a metabolic intermediate in many processes that occur in animals. It takes part in gluconeogenesis, the urea cycle, the glyoxylate cycle, amino acid synthesis, fatty acid synthesis and the citric acid cycle.
Since Bryant Park itself was located several feet above the surrounding streets, an iron fence, hedge, and embankment wall were built on the north, west, and south borders to separate the park from the bordering sidewalks. Benches were also installed along the retaining walls. Bryant Park's interior was split into three lawns, divided by a pair of west–east gravel paths that aligned roughly with the sidewalks of 41st Street on the west end of the park. Four stone stairways were built: one each from Sixth Avenue's intersections with 40th and 42nd Streets, and one each from 40th and 42nd Streets between Fifth and Sixth Avenues. In addition, 42nd Street was widened in 1910, necessitating the relocation of the fence on Bryant Park's northern border and the removal of plants there. The NYPL's Main Branch was opened on May 23, 1911.
=== Da === Valerie Daggett (BS 1993). American protein chemist at the University of Washington, known for molecular dynamics simulations of proteins and other biomolecules. John Call Dalton (1825–1889). American physiologist at the New York Metropolitan Board of Health, known for detailed and precise sketches of the brain. John W. Daly (1933–2008). American biochemist at the NIH, working primarily on alkaloids. Member Natl. Acad. Sci. USA. Marie Maynard Daly (1921–2003). American biochemist at the Albert Einstein College of Medicine, who studied the chemistry of histones, protein synthesis, the relationships between cholesterol and hypertension, and uptake of creatine by muscle cells. Keith Dalziel FRS (1921–1994). British biochemist at Oxford University, pioneer in analysis of the kinetics of two-substrate enzyme-catalysed reactions. Carl Peter Henrik Dam (1895–1976). Danish biochemist and physiologist at Copenhagen University who discovered vitamin K and its role in human physiology. Nobel Prize in Physiology or Medicine (1943). Marguerite Davis (1887–1967). American biochemist at the University of Wisconsin, co-discoverer of vitamins A and B Ronald W. Davis (b. 1941). American biochemist and geneticist at Stanford, known for developing new technologies in genomics. Member Natl. Acad. Sci. USA. Jean Dausset (1916–2009). French immunologist at INSERM who worked on the major histocompatibility complex. Nobel Prize in Physiology and Medicine (1980). Member Natl. Acad. Sci. USA. Member of the French Academy of Science Margaret Oakley Dayhoff (1925–1983).
==== Thermal stress ==== Thermal (heat) stress is defined as temperatures lethal or inhibitory towards growth. MAA concentrations have been shown to be up-regulated when an organism is under thermal stress. Multipurpose MAAs could also be compatible solutes under freezing conditions, because a high incidence of MAA producing organisms have been reported in cold aquatic environments.
Sources: en.wikipedia.org
Gingras research focuses on the development of experimental and bioinformatics approaches for functional proteomics, with a focus on protein-protein and proximity interactions. She applies these tools to the study of signaling pathways in health and disease and in mapping the physical organization of the dynamic proteome. Some of her work focuses on the consequence of disease-associated mutations on the interactions established by proteins. In addition to proteomics, Gingras laboratory has interest in studying human protein phosphatase and their systematic interactions and has now expanded into the field of systems biology.
Soy-based food products, such as soybeans, miso, tempeh, tofu, meatless soy burgers, and soy protein infant foods contain the highest amounts of isoflavones. According to a 2006 study of nine common phytoestrogens in Canadian foods, the highest relative phytoestrogen content were nuts and oilseeds, followed by soy products, cereals and breads, legumes, meat products, and other processed foods that may contain soy, vegetables, fruits, alcoholic, and nonalcoholic beverages. The highest concentrations of isoflavones are found in soybeans and soybean products followed by legumes, whereas lignans are the primary source of phytoestrogens found in nuts and oilseeds (e.g. flax) and also found in cereals, legumes, fruits and vegetables. Phytoestrogen content varies in different foods, and may vary significantly within the same group of foods (e.g. soy beverages, tofu) depending on processing mechanisms and type of soybean used. Legumes (in particular soybeans), whole grain cereals, and some seeds are high in phytoestrogens. Food content of phytoestrogens is highly variable, and accurate estimates of intake are therefore difficult and depends on the databases used. Data from the European Prospective Investigation into Cancer and Nutrition found intakes between 1 mg/d in Mediterranean Countries and more than 20 mg/d in the United Kingdom.
‰ Peedee Belemnite ("PDB"), a fossil belemnite from the eponym Late Cretaceous geological formation in North and South Carolina (USA), was the original reference standard used for standardizing carbon isotope ratio values. Due to the depletion of the original PDB, an artificial "Vienna PDB" standard, or "VPDB", is generally used today.
Sources: en.wikipedia.org
Mass spectrometry combined with liquid chromatography provides both molecular weight confirmation and a measure of related impurities. Tandem mass spectrometry adds sequence information. A purity percentage reported without a mass measurement does not confirm what the material is.
No. Lyophilisation slows degradation rather than stopping it, and the rate depends on residual moisture, temperature and light exposure. Freezer storage extends useful life but does not make the material permanent.
A certificate is only as good as its traceability to a specific batch and a named laboratory. Documents lacking batch numbers, method descriptions or laboratory identifiers carry little weight. Confirming what was actually received generally requires a separate test of the material in hand.
No. No major regulatory agency has granted a marketing authorisation for melanotan II as a medicine. Products sold under this name are generally presented as laboratory reagents and are not subject to the batch-release testing applied to approved drugs.