The short version of MC1R fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2026-07-05 and is reviewed periodically as new material appears.
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.
Identity and purity are usually assessed by reversed-phase high-performance liquid chromatography, which separates the target peptide from truncated or oxidised impurities. Mass spectrometry, most often coupled to liquid chromatography, confirms molecular mass and detects substitutions that chromatography alone may miss. Amino acid analysis and peptide mapping supply additional structural evidence, while nuclear magnetic resonance is reserved for full structural confirmation. Laboratories that examine samples sold online report wide variation in actual content, with some vials containing little or none of the labelled material.
Melanotan-2 appears on the World Anti-Doping Agency prohibited list within the peptide hormone class, and several national regulators treat it as an unapproved prescription substance. Some countries restrict importation or sale for personal use. Because the compound is widely traded as a research chemical, the practical legal picture differs between jurisdictions and shifts over time. Human safety data covering long periods are limited, and whether repeated pigmentation changes carry any lasting risk to melanocytes remains an open question.
| Property | Value | Notes |
|---|---|---|
| Compound class | Synthetic cyclic heptapeptide | Alpha-MSH analogue containing a D-phenylalanine residue |
| Molecular formula | C50H69N15O9 | Average molecular mass approximately 1024.2 g/mol |
| Appearance | White to off-white lyophilised powder | Normally supplied as a freeze-dried solid in a sealed vial |
| Solubility | Freely soluble in water and polar solvents | Dissolves readily in aqueous buffers and in alcohol-water mixtures |
| Receptor targets | MC1R, MC3R, MC4R, MC5R | Acts as a non-selective melanocortin receptor agonist |
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.
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.
Solid peptide kept dry at minus twenty degrees Celsius, shielded from light and moisture, is generally considered stable for extended periods. Solutions are divided into single-use aliquots and held at minus twenty or minus eighty degrees Celsius, because repeated freeze-thaw cycles promote aggregation and loss of material to container surfaces. Hydrolysis of the backbone and oxidation of tryptophan are the principal degradation routes in aqueous solution, and both accelerate at ambient temperature. Hygroscopic uptake after a vial is opened can also shift the actual mass weighed, which affects any concentration calculated from it.
Routine characterisation relies on reversed-phase high-performance liquid chromatography with ultraviolet detection near 214 nanometres, using a C18 column and a water-acetonitrile gradient containing trifluoroacetic acid. Electrospray ionisation mass spectrometry confirms the expected molecular mass and can reveal truncated or oxidised by-products that co-elute poorly. Sequence and stereochemistry require additional work, such as peptide mapping or amino acid analysis, because a chromatographic purity figure alone does not distinguish a diastereomer from the target peptide. Independent testing of research-grade material frequently shows measured content below the stated label, so a certificate of analysis is best read together with the method that produced it.
The internal dynamics of protons are complicated, because they are determined by the quarks' exchanging gluons, and interacting with various vacuum condensates. Lattice QCD provides a way of calculating the mass of a proton directly from the theory to any accuracy, in principle. The most recent calculations claim that the mass is determined to better than 4% accuracy, even to 1% accuracy (see Figure S5 in Dürr et al.). These claims are still controversial, because the calculations cannot yet be done with quarks as light as they are in the real world. This means that the predictions are found by a process of extrapolation, which can introduce systematic errors. It is hard to tell whether these errors are controlled properly, because the quantities that are compared to experiment are the masses of the hadrons, which are known in advance. These recent calculations are performed by massive supercomputers, and, as noted by Boffi and Pasquini: "a detailed description of the nucleon structure is still missing because ... long-distance behavior requires a nonperturbative and/or numerical treatment ..." More conceptual approaches to the structure of protons are: the topological soliton approach originally due to Tony Skyrme and the more accurate AdS/QCD approach that extends it to include a string theory of gluons, various QCD-inspired models like the bag model and the constituent quark model, which were popular in the 1980s, and the SVZ sum rules, which allow for rough approximate mass calculations.
The Hong Kong Rugby Football Union was founded in 1953. Rugby is long established, partly as a result of its being a British colony. Hong Kong Sevens is held annually in Hong Kong and is considered the premier tournament on the World Rugby Sevens Series competition. Hong Kong national rugby union team is ranked 23rd in the world with a peak rating of 21st (2018–2022). Hong Kong is one of the best teams in Asia and has finished first place in the Asia Rugby Championship in 2018, 2019, 2022, 2023, 2024, and 2025. They qualified for the 2027 Rugby World Cup for the first time by winning the 2025 Asia Rugby Championship. The Hong Kong national rugby sevens team is widely regarded as the best rugby sevens team in Asia and a regular participant in the Rugby World Cup Sevens. Hong Kong has won the Asian Sevens Series a record 8 times and the Asian Games 2 times.
Bukele registered as a presidential pre-candidate on 26 June 2023 with Nuevas Ideas; Ulloa registered as Bukele's vice-presidential pre-candidate. Nuevas Ideas nominated Bukele and Ulloa as their presidential and vice-presidential candidates on 9 July. The party began registering Bukele and Ulloa's candidacies with the TSE on 26 October, the last day to do so. On 3 November 2023, the TSE registered their candidacies amidst opposition requests to reject Bukele's candidacy. On 30 November 2023, the Legislative Assembly granted Bukele and Ulloa leaves of absence to focus on their re-election campaign. The leave went into effect the following day and Bukele's presidential powers were suspended. The Legislative Assembly named Claudia Rodríguez de Guevara, Bukele's presidential secretary, as the presidential designate; Rodríguez was the first woman in Salvadoran history to hold presidential power. Her appointment was criticized by some lawyers and opposition politicians as unconstitutional. Including Bukele, there were six presidential candidates in the 2024 election. His primary opponents were ARENA's Joel Sánchez, a businessman, and the FMLN's Manuel Flores, a former legislator. Bukele led Sánchez and Flores by large margins in opinion polling before the election. Bukele promised to maintain the gang crackdown, invest in infrastructure projects, and promote economic growth during his second term. On 4 February 2024, he won re-election with 84.65 percent of the vote. Bukele was the first Salvadoran president to be re-elected since Maximiliano Hernández Martínez in 1944.
== Release == Episode One was sold in both retail stores and Valve's online Steam distribution system, where it was sold at a discount price. It was also distributed by Electronic Arts as a standalone release. It was available for pre-load and pre-purchase through Steam on May 1, 2006, with Half-Life Deathmatch: Source and Half-Life 2: Deathmatch immediately available for play as part of the package. Episode One was rereleased in the compilation The Orange Box for Mac, PC, Xbox 360, and PlayStation 3. About 1.4 million retail copies of Episode One had been sold by 2008. In November 2024, Valve delisted Episode One and Episode Two from the Steam Store and incorporated them into Half-Life 2.
Sources: en.wikipedia.org
The gastric juice also contains digestive enzymes produced by other cells in the gastric glands – gastric chief cells. Gastric chief cells secrete an inactivated pepsinogen. Once in the stomach lumen gastric acid activates the proenzyme to pepsin.
== Pumps used in high-pressure chromatography == Pumps used in high-pressure chromatography such as HPLC and ion chromatography are much like small piston metering pumps. For wear resistance and chemical resistance to solvents, etc., typically the pistons are made of artificial sapphire and the ball check valves have ruby balls and sapphire seats. To produce good chromatograms, it is desirable to have a pumping flow rate as constant as possible. Either a single piston pump with a quick refill is used or a double pump head with coordinated piston strokes is used to provide as constant a pumping rate as possible.
==== Combustion ==== The combustion of all carbon-based fuels, such as methane (natural gas), petroleum distillates (gasoline, diesel, kerosene, propane), coal, wood and generic organic matter produces carbon dioxide and, except in the case of pure carbon, water. As an example, the chemical reaction between methane and oxygen:
A substance that has been tested in a laboratory and has gotten approval from the U.S. Food and Drug Administration (FDA) to be tested in people. A drug may be approved by the FDA for use in one disease or condition but be considered investigational in other diseases or conditions. Also called experimental drug. (NCI) A pharmaceutical form of an active ingredient or placebo being tested or used as a reference in a clinical trial, including a product with a marketing authorization when used or assembled (formulated or packaged) in a way different from the approved form, or when used for an unapproved indication, or when used to gain further information about an approved use. (ICH E6) Investigational New Drug
People with irritable bowel syndrome (IBS) typically report that they suffer with abdominal cramps and constipation. In some patients, chronic constipation is interspersed with brief episodes of diarrhoea; while a minority of patients with IBS have only diarrhoea. The presentation of symptoms is usually months or years and commonly patients consult different doctors, without great success, and doing various specialized investigations. It notices a strong correlation of the reported symptoms with stress; indeed diarrhoeal discharges are associated with emotional phenomena. IBS blood is present only if the disease is associated with haemorrhoids. Research conducted on irritable bowel syndrome in the 2000s, faecal incontinence and the gastrointestinal complications of HIV have used the Bristol scale as a diagnostic tool easy to use, even in research which lasted for 77 months. Historically, this scale of assessment of the faeces has been recommended by the consensus group of Kaiser Permanente Medical Care Program (San Diego, California, US) for the collection of data on functional bowel disease (FBD). More recently, according to the latest revision of the Rome III Criteria, six clinical manifestations of IBS can be identified:
Sources: en.wikipedia.org
Len Butt (1910–1994), footballer, who played over 370 games, including 150 for Macclesfield Town Sir Alex Ferguson (born 1941), former footballer who played 317 league games and manager of Manchester United for 26 years Chris Nicholl (1946–2024), footballer who played 706 games Terry Nicholl (born 1952 in Wilmslow), footballer, played over 450 games Andy Fanshawe (1963–1992), a British mountaineer, attended Wilmslow Grammar School Liz Blatchford (born 1980 in Wilmslow), professional triathlete Danny Whitaker (born 1980 in Wilmslow), footballer, played 671 games, including 400 for Macclesfield Town Park Ji-sung (born 1981), footballer, played 318 games and 134 league games for Manchester United David Horsey (born 1985), golfer who currently plays on the European Tour, lives in Wilmslow Seren Bundy-Davies (born 1994), track and field sprinter at 400 metres, attended Wilmslow High School Sam James (born 1994 in Wilmslow), rugby union player who has played over 250 games; currently with Sale Sharks Millie Turner (born 1996 in Wilmslow), football defender, who has played 180 games for Women's Super League club Manchester United
==== Economy ==== According to the World Bank's Lebanon Rapid Damage and Needs Assessment (RDNA) 2025 report, the conflict cost Lebanon a total of US$14 billion. Physical damages amounted to $6.8 billion, while decreased productivity, lost revenue, and operational costs amounted to $7.2 billion. With $4.6 billion in damages, the housing sector suffered the most losses, followed by the commerce, industry, and tourism sector with losses of $3.4 billion. The conflict caused Lebanon's real GDP to decline by 7.1% in 2024. The World Bank added that reconstruction costs amounted to $11 billion.
== Predicted properties == Other than nuclear properties, no properties of meitnerium or its compounds have been measured; this is due to its extremely limited and expensive production and the fact that meitnerium and its parents decay very quickly. Properties of meitnerium metal remain unknown and only predictions are available.
=== Exercise === The plasma concentration of apelin is shown to increase during exercise. Paradoxically, exogenous apelin in healthy volunteers reduced VO2 peak (peak oxygen consumption) in an endurance test.
Sources: en.wikipedia.org
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.
No approved regulatory indication exists in major markets. An approval exists for a different peptide, afamelanotide, which is used for a rare photosensitivity disorder called erythropoietic protoporphyria. Melanotan-2 itself remains a research compound with no cleared clinical role.
Melanocortin-1 receptors on melanocytes are the receptor most closely linked to pigment production. The peptide is not selective, however, and also activates melanocortin-3, melanocortin-4, and melanocortin-5 receptors. That lack of selectivity is the usual explanation offered for both its range of observed effects and its off-target effects.
The lyophilised solid is best kept cold, dry and dark, typically at minus twenty degrees Celsius. Moisture and repeated warming cycles are the main causes of degradation. Solutions prepared from the powder are less stable and are normally used quickly.