The short version of melanocortin receptor fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-08-01. Anything still debated is marked as such rather than presented as settled.
Lyophilized peptide powder is generally stored frozen, protected from light and moisture. Tryptophan residues are susceptible to oxidation, and the lactam bridge can hydrolyze under strongly acidic or basic conditions. Solutions prepared for laboratory work degrade faster than dry powder, and repeated freeze-thaw cycles accelerate loss. Common practice is to aliquot solutions before freezing and to avoid alkaline buffers. Reported stability windows vary with concentration, buffer, and temperature, so exact shelf lives are method-specific rather than universal.
Regulatory status differs by country, and in many places supplying the compound for human consumption is unlawful. Vendors frequently label material as intended for research use only, a designation that shifts stated purpose but does not create a legal pathway for personal use. Certificates of analysis accompanying such products vary widely in detail and provenance. Third-party testing exists but is voluntary, and results are rarely linked to a specific lot in a publicly verifiable way.
Identity testing for a synthetic peptide relies on several complementary methods. Reversed-phase high-performance liquid chromatography separates the target from related impurities and reports purity as a percentage of total peak area. Mass spectrometry confirms molecular mass and can reveal deletions or truncations. Amino acid analysis and peptide mapping provide sequence-level confirmation, while counter-ion content and residual solvents are measured separately. A purity figure alone does not establish identity, so a complete dataset combines chromatographic and spectrometric evidence.
Melanotan-2, also written Melanotan II, is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone. Its sequence is Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, and the lactam bridge between the aspartate and lysine side chains constrains the peptide into a ring. This structural change increases receptor affinity and metabolic stability relative to the native hormone. The compound was created in the 1980s as a research tool for studying pigmentation biology.
Melanocytes are the pigment-producing cells of the skin, and they carry melanocortin-1 receptors on their surface. When the receptor is activated, cyclic adenosine monophosphate rises inside the cell and raises the activity of enzymes such as tyrosinase, which increases melanin output. Melanotan-2 binds melanocortin-1 receptors in vitro and in animal models, and this binding is generally described as the basis for the tanning effect. Other receptors account for different effects: melanocortin-4 receptors contribute to appetite and erectile signalling, while melanocortin-3 and melanocortin-5 receptors contribute to energy balance and exocrine function.
Early published reports described melanotan-2 as a tanning agent without sun protection, which means darkening is not the same as protection against ultraviolet radiation. Later studies explored the peptide in erectile dysfunction, hemorrhagic shock, and some skin conditions. No regulator in the United States or Europe has approved it for clinical use. Many products labelled melanotan-2 are sold without approval and their identity and purity are unverified. Its long-term safety in humans remains an open question.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C50H69N15O9 | Free base; salt forms differ |
| Molecular mass | About 1024.2 g/mol | Monoisotopic value for the free base |
| Appearance | White to off-white lyophilized powder | Visual inspection is not an identity test |
| Solubility | Soluble in water and polar organic solvents | Dissolution depends on salt form and pH |
| Typical storage | -20 °C, dry, protected from light | Powder is more stable than prepared solutions |
Reversed-phase high-performance liquid chromatography is the routine method for purity assessment. Peptides absorb near 214 nm because of the peptide bond, and a gradient of acetonitrile in water separates the intact peptide from deletion sequences, oxidised products, and earlier-eluting fragments at neutral pH. Electrospray ionisation mass spectrometry provides an orthogonal check: the measured mass must agree with the theoretical value. Amino acid analysis and peptide mapping confirm structure but are used less often. Reference standards remain scarce because the peptide is not described in any pharmacopoeia.
Regulatory treatment varies by country. In the United States the peptide is not approved as a medicine, and products offered for human use may be treated as unapproved new drugs; some states also restrict sale. Australia, the United Kingdom, and European Union member states apply comparable restrictions to unapproved peptide products. Border agencies have seized shipments labelled as research chemicals. Classification may change over time, and the legal position for personal importation is not clearly settled in most published guidance.
Lyophilised melanotan-2 is supplied as a solid, which is more stable than a solution. The material is hygroscopic, so weighing is done quickly, in low humidity, with the container kept sealed. Reconstitution usually uses water for injection or bacteriostatic water, added down the wall of the vial to limit foaming. A reconstituted solution is held at 2 to 8 °C and kept away from light. Repeated freezing and thawing of the same vial is avoided because ice crystal formation and concentration effects degrade the peptide.
Melanotan II is a synthetic cyclic heptapeptide that acts as an agonist at melanocortin receptors. It was designed as a structural analogue of alpha-melanocyte-stimulating hormone, the endogenous peptide involved in pigment production. The analogue carries a lactam bridge that constrains the ring and slows enzymatic breakdown relative to the native hormone. In research literature it appears under several abbreviations, and naming conventions are not fully standardized. Published descriptions usually place it within the broader melanocortin agonist family.
Receptor binding at MC1R on melanocytes raises intracellular cyclic AMP and increases expression of tyrosinase and related enzymes. The downstream result is greater synthesis of eumelanin, the dark pigment, without ultraviolet exposure acting as the trigger. The compound is not selective, however, and also engages MC3R, MC4R and MC5R, which are expressed in the central nervous system and elsewhere. That lack of selectivity is the explanation usually offered for effects reported outside pigmentation, including appetite suppression and nausea. Selectivity remains a central theme in comparative studies of related peptides.
Human data remain limited and mostly short-term. Reports describe small trials and observational accounts rather than large controlled studies, so questions about dose-response relationships and long-term effects on melanocytes stay open. Whether repeated exposure alters naevus behaviour is not settled in the published record. Researchers also note that self-administered use outside clinical settings makes actual exposure difficult to quantify. Statements about efficacy and safety should therefore be read as preliminary rather than established.
The material is commonly handled as a lyophilized powder in sealed vials. The solid dissolves readily in water and in polar organic solvents, producing a clear solution after reconstitution. Light, heat and repeated freeze-thaw cycles are the concerns most often raised in handling guidance, because peptide bonds and the constrained ring can degrade. Working solutions are generally prepared fresh, and material left in solution is treated as less stable than the dry form. These properties shape how laboratories store and aliquot reference material.
Identity and purity are assessed mainly by reversed-phase high-performance liquid chromatography with ultraviolet detection, often paired with mass spectrometry. Retention time supports identity, while the mass spectrum confirms the molecular weight of the intact peptide. Purity is frequently reported as a percentage of total peak area, a figure that depends on the wavelength, column and gradient used. Impurity profiling may also look for truncated sequences, oxidised forms and residual counterions. Amino acid analysis and peptide mapping provide orthogonal confirmation when required.
Regulatory status varies by jurisdiction, and the substance is frequently described as unapproved for therapeutic use. Some authorities classify it alongside prescription-only medicines or controlled categories, while others address it through general consumer protection rules. Analytical surveys have reported mismatches between label claims and measured content in products sold online, although the scope of such testing is limited. Whether these discrepancies are widespread remains an open question. Discussion in the literature therefore tends to combine chemistry, supply-chain observation and policy analysis.
HbA1c of less than 7.0% if they are achievable without significant hypoglycemia Preprandial (before eating) blood glucose: 70 to 130 mg/dL (3.9 to 7.2 mmol/L) 2-hour postprandial (after eating) blood glucose: Less than 180 mg/dL (<10 mmol/L) Goals should be individualized based on:
=== In the cosmetic industry === Lighter skin complexion has been associated with youth and beauty across various Asian cultures. Recent research by cosmetic companies has been focused on the development of novel whitening agents that selectively suppress tyrosinase activity to reduce hyperpigmentation while avoiding cytotoxicity of healthy melanocytes. Traditional pharmacological agents such as corticosteroids, hydroquinone, and amino numeric chloride lighten skin through the inhibition of melanocyte maturation. However, these agents are associated with adverse effects. Cosmetic companies have been focused on developing novel whitening agents that selectively suppress the activity of tyrosinase to reduce hyperpigmentation while avoiding melanocyte cytotoxicity as tyrosinase is the rate-limiting step of the melanogenesis pathway.
=== Old model of coloration with four primaries === The ancient Greeks, under the influence of Aristotle, Democritus and Plato, considered that there were four basic colors that coincided with the four elements: earth (ochre), sky (blue), water (green) and fire (red), while black and white represented the light of day and the darkness of night. The four-color system is formed by the primaries yellow, green, blue and red, and was supported by Alberti in his "De Pictura" (1436), using the rectangle, rhombus, and color wheel to represent them.
Sources: en.wikipedia.org
The first elections took place in January 1889 and the county council formally came into being on 1 April 1889. On that day its first official meeting was held at the old Shire Hall on Old Elvet in Durham, the courthouse (built 1811) which had served as the meeting place of the quarter sessions which preceded the county council. The first chairman of the council was John Lloyd Wharton, who was the Conservative Member of Parliament for Ripon (in Yorkshire); he had also been chairman of the Durham Quarter Sessions since 1871. Durham was the first county council to be controlled by the Labour Party, which won the most seats in 1919. In 1974, the county was redesignated as a non-metropolitan county under the Local Government Act 1972. As part of those reforms the county ceded territory in the north-east to the new county of Tyne and Wear and in the south-east to the new county of Cleveland, but gained the former Startforth Rural District covering the part of Teesdale south of the River Tees from the North Riding of Yorkshire, and Darlington was brought back under the county council's control. Until 1974, the lower tier of local government comprised numerous boroughs, urban districts and rural districts. The districts were also reorganised in 1974 into eight non-metropolitan districts: Chester-le-Street, Darlington, Derwentside, Durham, Easington, Sedgefield, Teesdale, and Wear Valley. In 1997, Darlington became a unitary authority, removing it from county council control.
There are at least 45 precursor isotopes. In reactor analysis they are conventionally combined into six effective groups, each with an effective half-life (about 55, 22, 6, 2, 0.5, and 0.2 seconds) and an effective yield. The 55-second group is dominated by 87Br, the 22-second group by 88Br and 137I, and the shorter-lived groups have many contributors. The group parameters depend on the fuel isotope, since fission product yields vary with the fissile material. An eight-group structure has also been defined, which uses the same set of half-lives for all fissioning systems, with the three longest-lived groups corresponding to the three dominant long-lived precursors 87Br, 137I and 88Br. The International Atomic Energy Agency (IAEA) publishes eight-group parameters for several actinides; for thermal fission of U-235 they are:
=== February === 1 February – A Statutory Instrument paving the way for the Northern Ireland Executive to be re-established is passed by the House of Commons. Conservative MP Mike Freer announces he is standing down from Parliament at the next election following death threats and an arson attack on his constituency office. Downing Street describes the situation as "an attack on democracy". Addressing a meeting of business leaders, Shadow Chancellor Rachel Reeves says that Labour would not increase corporation tax if elected, but may cut it to boost "competitiveness". Penny Mordaunt, the Leader of the House of Commons, has argued plans to expand the Senedd from 60 to 96 MSs would be the equivalent of expanding the House of Commons from 650 to 2,000 MPs. MP Christina Rees is readmitted to the Labour Party but announces her retirement at the next general election. 2 February – Senior Labour MP Darren Jones confirms that the party has ditched its commitment to spend £28bn a year on green investment schemes if it wins the next general election. 3 February – 2024 Northern Ireland Executive Formation: The Northern Ireland Assembly meets to elect a new Speaker. Edwin Poots, a former leader of the DUP, is chosen to be the Assembly's 7th Speaker. The Northern Ireland Executive is restored after the DUP ends its two year boycott; Sinn Féin's Michelle O'Neill is nominated as First Minister, becoming the first nationalist politician to hold the post, while the DUP's Emma Little-Pengelly is appointed deputy. SDLP MLA Matthew O'Toole is nominated as Leader of the Opposition.
The former presence of 244Pu in the early Solar System has been confirmed, since it manifests itself today as an excess of its daughters, either 232Th (from the alpha decay pathway) or xenon isotopes (from its spontaneous fission). The latter are generally more useful, because the chemistries of thorium and plutonium are rather similar (both are predominantly tetravalent) and hence an excess of thorium would not be strong evidence that some of it was formed as a plutonium daughter. 244Pu has the longest half-life of all transuranic nuclides and is produced only in the r-process in supernovae and colliding neutron stars; when nuclei are ejected from these events at high speed to reach Earth, 244Pu alone among transuranic nuclides has a long enough half-life to survive the journey, and hence tiny traces of live interstellar 244Pu have been found in the deep sea floor. Because 240Pu also occurs in the decay chain of 244Pu, it must thus also be present in secular equilibrium, albeit in even tinier quantities. Astrophysical detection of plutonium is extremely limited, but is found in the spectrum of the extremely chemically peculiar Przybylski's Star. Minute traces of plutonium are usually found in the human body due to the 550 atmospheric and underwater nuclear tests that have been carried out, and to a small number of major nuclear accidents. Most atmospheric and underwater nuclear testing was stopped by the Limited Test Ban Treaty in 1963, which of the nuclear powers was signed and ratified by the United States, United Kingdom and Soviet Union.
Sources: en.wikipedia.org
Dry powder is usually held frozen, shielded from light, and kept away from moisture. Desiccant packaging limits hydrolysis during storage. Solutions are typically aliquoted and frozen once, because repeated thawing shortens useful life.
Mass spectrometry establishes molecular mass, and reversed-phase chromatography reports purity. Peptide mapping or amino acid analysis supports sequence-level confirmation. No single technique covers all failure modes, so laboratories combine results.
Common entries include appearance, purity by chromatographic area, measured mass, and sometimes residual solvents or counter-ion content. Methods and instrument conditions are not always described. The document reflects the supplier's own testing unless an independent laboratory is named.
No. It is a laboratory-made peptide, while the natural hormone is alpha-melanocyte-stimulating hormone, a longer peptide produced by the pituitary gland and by skin cells. Melanotan-2 mimics only a short active region of that hormone and contains non-natural residues such as D-phenylalanine.