The short version of melanocortin receptor fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-03-13. Anything still debated is marked as such rather than presented as settled.
Melanotan-2 is frequently confused with afamelanotide, a linear analogue authorised in the European Union for erythropoietic protoporphyria. The two compounds differ in chain length, ring structure and receptor selectivity, so findings for one cannot be transferred directly to the other. Published controlled human data on melanotan-2 remain sparse, and much of what circulates online derives from small studies or unpublished reports. Questions about effect size, dose-response behaviour and long-term safety therefore remain unresolved.
Melanotan-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone. Its sequence incorporates a lactam bridge that constrains the peptide into a ring, which increases resistance to enzymatic breakdown relative to the natural hormone. Researchers at the University of Arizona synthesised the compound in the late 1980s and early 1990s while studying pigmentation pathways. It has never received marketing approval from any national medicines regulator. In the scientific literature it is usually described as a laboratory research reagent rather than a therapeutic product.
The peptide acts as a non-selective agonist at melanocortin receptors, showing affinity for MC1R, MC3R, MC4R and MC5R. Activation of MC1R on melanocytes drives the conversion of tyrosine into melanin and shifts production toward the darker eumelanin form. MC4R signalling in the central nervous system is linked to appetite and energy balance, which helps explain why reduced food intake appeared in early human studies. Effects on MC4R and on vascular tone also account for the erectile responses recorded as unexpected findings in those same trials.
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.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic cyclic heptapeptide | Alpha-MSH analogue with a lactam ring |
| Molecular formula | C50H69N15O9 | Commonly cited value for the neutral peptide |
| Molecular weight | 1024.18 g/mol | Calculated for the free molecule |
| Appearance | White to off-white powder | Typically supplied as a lyophilised solid |
| Solubility | Soluble in water, DMSO and ethanol | Dissolution in pure water is often slow |
No regulatory authority has approved melanotan-2 for human use, and several countries classify it as a prescription-only or controlled substance, which restricts lawful supply. Material sold online is generally labelled as a research chemical and is not required to meet pharmaceutical standards of identity or purity. Published human data consist mainly of small uncontrolled studies, case reports and adverse-event notifications, so the evidence base is descriptive rather than confirmatory. Whether repeated melanocyte stimulation alters long-term naevus behaviour remains an open question that no completed trial has resolved.
Melanotan-2 is a synthetic cyclic heptapeptide designed as a structural analogue of alpha-melanocyte-stimulating hormone, the endogenous tridecapeptide that regulates pigment production. Two modifications distinguish it from the natural hormone: norleucine replaces methionine at the N-terminus, which limits oxidation, and a D-phenylalanine substitution raises receptor affinity. The ring is closed through an aspartate-lysine lactam bridge, giving the molecule a constrained conformation. The free base has a molecular mass near 1024 daltons, and commercial material is usually supplied as an acetate salt. It appears in the literature as a research peptide rather than an approved therapeutic agent.
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.
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.
Some academics, such as Stéphane Courtois (The Black Book of Communism), Steven Rosefielde (Red Holocaust), and Rudolph Rummel (Death by Government), wrote of mass, excess deaths under Marxist–Leninist regimes. These authors defined the political repression by communists as a "Communist democide", "Communist genocide", "Red Holocaust", or followed the "victims of Communism" narrative. Some of them compared Communism to Nazism and described deaths under Marxist–Leninist regimes (civil wars, deportations, famines, repressions, and wars) as being a direct consequence of Marxism–Leninism. Some of these works, in particular The Black Book of Communism and its 93 or 100 millions figure, are cited by political groups and Members of the European Parliament. Without denying the tragedy of the events, other scholars criticise the interpretation that sees communism as the main culprit as presenting a biased or exaggerated anti-communist narrative. Several academics propose a more nuanced analysis of Marxist–Leninist rule, stating that anti-communist narratives have exaggerated the extent of political repression and censorship in communist states and drawn comparisons with what they see as atrocities that were perpetrated by capitalist countries, particularly during the Cold War. These academics include Mark Aarons, Noam Chomsky, Jodi Dean, Kristen Ghodsee, Seumas Milne, and Michael Parenti. Ghodsee, Nathan J.
He played a career-high 21 games during the season and averaged 19 disposals, six marks and three rebound 50s for the year. Despite Essendon's poor performances in the 2015 season, Michael averaged 21 disposals, seven marks and six rebound 50s over 19 matches. He was awarded with his first All-Australian selection, and finished runner-up in the W.S. Crichton Medal. Hurley, along with 33 other Essendon players, was found guilty of using a banned performance-enhancing substance, thymosin beta-4, as part of Essendon's sports supplements program during the 2012 season. He and his teammates were initially found not guilty in March 2015 by the AFL Anti-Doping Tribunal, but a guilty verdict was returned in January 2016 after an appeal by the World Anti-Doping Agency. He was suspended for two years which, with backdating, ended in November 2016; as a result, he served approximately fourteen months of his suspension and missed the entire 2016 AFL season. During his suspension, he signed a five-year contract extension to stay with Essendon until the end of 2022. In 2017, he was named in the All-Australian Team. Prior to the 2021 AFL season, Hurley contracted an infection in his hip. The infection became life-threatening, leaving him bedridden for a month, during which he lost 10kg, and afterwards, had to learn to walk again. He went through multiple stints in hospital, and underwent a hip replacement, missing the entire 2021 season.
== Regulation == United States: GRAS nutrient supplement (21 CFR 184.1930); dietary‑supplement labelling expresses content in μg RAE or International Units. European Union: Permitted as vitamin A source in fortified foods under Regulation (EC) 1925/2006; cosmetic concentrations limited as per SCCS opinion. Codex Alimentarius: Listed as an approved vitamin A fortificant for sugar, cereal flours and edible oils.
==== Men's lacrosse ==== The lacrosse club team was founded in the mid-1960s. In the 1960s, Arizona was a Division I varsity program, coached by Carl Runk, an Arizona graduate and football player. In 1998, Runk retired after twenty-eight years at Towson University in Maryland.
Sources: en.wikipedia.org
Around the time, an expert concludes that "AI art is everywhere right now", with even experts not knowing what it will mean, a news outlet establishes that "AI-generated art booms" and reports about issues of copyright and automation of professional artists, a news outlet investigates how online communities (e.g. their rules) confronted with many such artworks react, a news outlet raised concerns over deepfakes, a magazine highlights possibilities of enabling "new forms of artistic expression", an editorial notes that it may be seen as a welcome "augmentation of human capability". Moreover, additional functionalities – such as enabling the use of user-provided concepts (like an object or a style) learned from few images for novel personalized art generated from the associated word/s (2 Aug) or expanding beyond the borders of artistic images in the same style (31 Aug) – are reported. On 22 August, Stable Diffusion is released as free and open source software.
=== Solvent choice === An eluotropic series, which orders solvents by how much they move compounds, can help select a mobile phase. Solvents are divided into solvent selectivity groups. Using solvents with different elution strengths or different selectivity groups can often give very different results. While single-solvent mobile phases can sometimes give good separation, some cases may require solvent mixtures. In normal-phase TLC, the most common solvent mixtures include ethyl acetate/hexanes (EtOAc/Hex) for less-polar compounds and methanol/dichloromethane (MeOH/DCM) for more polar compounds. Different solvent mixtures and solvent ratios can help give better separation. In reverse-phase TLC, solvent mixtures are typically water with a less-polar solvent: Typical choices are water with tetrahydrofuran (THF), acetonitrile (ACN), or methanol.
Caricain (EC 3.4.22.30, papaya peptidase A, papaya peptidase II, papaya proteinase, papaya proteinase III, papaya proteinase 3, proteinase omega, papaya proteinase A, chymopapain S, Pp) is an enzyme. This enzyme catalyses the following chemical reaction: Hydrolysis of proteins with broad specificity for peptide bonds, similar to those of papain and chymopapain This enzyme is isolated from the papaya plant, Carica papaya.
==== Improving institutional decision-making ==== The advancement of AI in economic and military domains could precipitate unprecedented political challenges. Some scholars have compared AI race dynamics to the cold war, where the careful judgment of a small number of decision-makers often spelled the difference between stability and catastrophe. AI researchers have argued that AI technologies could also be used to assist decision-making. For example, researchers are beginning to develop AI forecasting and advisory systems.
== History == 2C-EF was originally named by Alexander Shulgin in his 1991 book PiHKAL (Phenethylamines I Have Known and Loved). However, he only speculated about it and never actually synthesized or tested it himself. Subsequently, 2C-EF was synthesized and tested by others such as Daniel Trachsel.
Sources: en.wikipedia.org
It is a synthetic cyclic heptapeptide modelled on alpha-melanocyte-stimulating hormone. A lactam bridge links two side chains, forming a ring that stabilises the molecule against proteolysis. It belongs to the broader melanocortin peptide family.
No national medicines agency has approved melanotan-2 for clinical use. Afamelanotide, a related but distinct peptide, holds a marketing authorisation in the European Union for a rare photosensitivity disorder. Melanotan-2 itself is handled as a laboratory chemical.
Its broad activity across melanocortin receptors makes it a tool for probing pigmentation, appetite and vascular signalling. Early trials recorded skin darkening and other effects that were not the original focus of the work. Those observations generated hypotheses that later studies have examined.
Laboratory confirmation typically combines retention time matching on a chromatographic system with mass measurement. A reference standard of known identity is needed for a meaningful comparison. Sequence-level techniques can add further confirmation.