A practical reference on melanocortin receptor: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2026-05-01. Anything still debated is marked as such rather than presented as settled.
Research interest has centred on photoprotection and pigmentation, with a smaller body of work on appetite and sexual function. Published human data remain limited to small, frequently uncontrolled studies, and the compound has never received marketing approval from a national medicines regulator. Most laboratory work treats it as a pharmacological tool for probing melanocortin signalling in cell culture or animal models. Whether pigmentation changes observed in people translate into measurable protection against ultraviolet-induced DNA damage remains an open question.
Melanotan-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone, the naturally occurring peptide involved in pigmentation signalling. Its sequence is conventionally written as Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, with a lactam bridge joining the aspartate side chain to the lysine side chain. The empirical formula is C50H69N15O9 and the monoisotopic mass lies near 1023.5 daltons. N-terminal acetylation and the D-configured phenylalanine both increase resistance to enzymatic breakdown compared with the parent hormone.
Pharmacologically, melanotan-2 behaves as a non-selective agonist across the melanocortin receptor family. Binding at MC1R on dermal melanocytes promotes eumelanin synthesis, which underlies the tanning response described in early human work. Activity at the centrally expressed MC4R receptor is associated with reported effects on appetite and erectile function. Because the peptide does not discriminate strongly among receptor subtypes, attributing any single observed effect to one receptor pathway is generally not possible without selective antagonists or receptor knockout models.
Published human data come mostly from small, short studies rather than large controlled trials. Reported outcomes include increased skin pigmentation and, in some reports, effects on appetite and libido, but sample sizes are small and follow-up is limited. Whether long-term use produces durable pigment changes or adverse effects is not established. Because products sold outside pharmacies are not standardized, the actual content of any given vial is often unknown. Independent testing of such material is uncommon.
Melanotan II is a synthetic cyclic heptapeptide analog derived from the core sequence of alpha-melanocyte-stimulating hormone. Researchers at the University of Arizona synthesized it during the 1980s while studying pigmentation and appetite signaling. The compound is not an approved medicine in any major jurisdiction and appears mainly in laboratory and research-chemical settings. Its structure incorporates a lactam bridge between side chains, which constrains the ring and slows enzymatic breakdown relative to the natural hormone.
Melanotan II binds several melanocortin receptor subtypes rather than a single target. MC1R on melanocytes drives melanin synthesis, while MC3R and MC4R participate in energy balance, appetite, and sexual response pathways. This lack of selectivity explains why reported effects extend beyond skin darkening. Substitutions at positions four and seven, including norleucine and D-phenylalanine, increase potency and resistance to peptidases. Understanding which receptor mediates which effect remains an active area of investigation.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | Melanotan II; MT-II; N-acetyl-norleucyl-cyclo[Asp-His-D-Phe-Arg-Trp-Lys] amide | Naming follows peptide convention; the numeral distinguishes it from melanotan-1 |
| Molecular formula | C50H69N15O9 | Includes the lactam bridge; no counter-ion assumed |
| Monoisotopic mass | 1023.53 Da | Free base; salts and counter-ions shift the observed value |
| Appearance | White to off-white lyophilised powder | Batch-to-batch colour variation is not itself proof of impurity |
| Typical analytical method | RP-HPLC purity determination with ESI-MS identity confirmation | Retention time alone does not establish sequence identity |
Receptor-binding studies classify melanotan II as a non-selective melanocortin agonist. It interacts with MC1R, MC3R, MC4R and MC5R, with reported affinities in the low nanomolar range and no strong subtype preference. Activation of MC1R on dermal melanocytes shifts pigment synthesis toward eumelanin, the dark polymer deposited in melanosomes and transferred to keratinocytes. Because the same peptide engages MC4R in the hypothalamus, it also appears in animal work on food intake and erectile response, which is why it is discussed in both pigment and metabolic research. Which receptor populations dominate after systemic exposure in humans is not fully established.
Published pharmacokinetic information is limited and comes mainly from small studies rather than registrational trials. Plasma half-life is usually described as short, on the order of tens of minutes, followed by rapid tissue distribution and clearance of the intact peptide. Metabolites and low concentrations of parent compound have been reported in urine, a detail relevant to anti-doping and forensic testing. Whether repeated exposure changes receptor sensitivity or clearance over time remains an open question. Values differ noticeably between analytical assays, so published numbers should be read as approximate rather than definitive.
Melanotan II is a synthetic cyclic heptapeptide with the sequence Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, corresponding to a molecular formula of C50H69N15O9 and a monoisotopic mass near 1024 daltons. It was designed as a structural analogue of alpha-melanocyte-stimulating hormone, a peptide hormone produced by cleavage of proopiomelanocortin. A lactam bridge between the aspartate and lysine side chains closes the ring, and the C-terminal amide removes a free carboxyl group. Both modifications increase resistance to enzymatic degradation compared with the linear parent hormone. Four substitutions distinguish it from afamelanotide, the linear analogue studied under the name melanotan I.
Structurally, Melanotan-2 retains the core recognition motif of alpha-melanocyte-stimulating hormone while adding a lactam bridge that links two side chains and constrains the molecule into a ring. This modification lowers susceptibility to enzymatic degradation. The compound acts as an agonist at melanocortin receptors, particularly subtypes associated with melanin production. Because the same receptor family influences several physiological processes, researchers note that its activity is not confined to pigmentation alone. Receptor selectivity continues to be examined in published studies.
Melanotan-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone, a naturally occurring peptide involved in pigmentation signalling. Its sequence incorporates modified residues that increase potency and extend biological activity relative to the native hormone. The compound binds receptors of the melanocortin family and is examined mainly in laboratory research. It does not occur naturally and exists only as a manufactured chemical entity produced by solid-phase synthesis.
5 April COVID-19 pandemic: Preclinical data for a new vaccine developed at the Medical University of Vienna indicates it is effective against all SARS-CoV-2 variants known to date, including Omicron. A study presents a mechanism by which the hypothesized potential dark-energy-explaining quintessence, if true, would smoothly cause the accelerating expansion of the Universe to inverse to contraction, possibly within the cosmic near-future (100 My) given current data. It concludes that its end-time scenario theory fits "naturally with cyclic cosmologies [(each a theory of cycles of universe originations and ends, rather than the theories of one Big Bang beginning of the Universe/multiverse, to which authors were major contributors)] and recent conjectures about quantum gravity".
=== Child development === Iron-deficiency anemia is associated with poor neurological development, including decreased learning ability and altered motor functions. This is because iron deficiency impacts the development of the cells of the brain called neurons. When the body is low on iron, the red blood cells get priority on iron, and it is shifted away from the neurons of the brain. Exact causation has not been established, but there is a possible long-term impact from these neurological issues.
Cambridge beat Oxford to win both the 2024 men's and women's Boat Races, giving Cambridge their first consecutive men's victory and their seventh consecutive women's victory. 31 March Charles III makes his first public appearance since being diagnosed with cancer when he attends the Easter Sunday service at Windsor. The UK government says it will work alongside the Northern Ireland Executive to maintain stability at Stormont.
The key intermediate step of these cyclometalation reactions involves the metal-mediated cleavage of the C–H bond and simultaneous formation of the metal–C bond of the substrate. Upon addition of substrate, the N-acyl motif acts as an internal proton acceptor in the concerted metal-deprotonation (CMD) of the transition state for this inner-sphere process. According to this model, the rate and selectivity of the C–H functionalization are impacted by the basicity of the MPAA ligand. The resulting experimental data of steric and electronic alteration of the MPAA ligands align with this model. In 2023, the first experimental observations to support the proposed mechanism were reported, which were previously unattainable due to the lack of well-defined isolated palladium-MPAA complexes.
== Clinical data == In a 12 week randomised clinical trial, subjects receiving AOD9604 lost, on average, 1.8 kg more than those receiving placebo. Development of AOD9604 was halted following poor efficacy in a later 24 week trial.
Sources: en.wikipedia.org
== Human pathology == Accumulation of excess homogentisic acid and its oxide, named alkapton, is a result of the failure of the enzyme homogentisic acid 1,2-dioxygenase (typically due to a mutation) in the degradative pathway of tyrosine, consequently associated with alkaptonuria.
Parliament elections, take place every five years, and votes for Members of the European Parliament (MEP) in member states must be organised by proportional representation or a single transferable vote. There are 750 MEPs and their numbers are "degressively proportional" according to member state size. This means – although the council is meant to be the body representing member states – in the Parliament citizens of smaller member states have more voice than citizens in larger member states. MEPs divide, as they do in national Parliaments, along political party lines: the conservative European People's Party is currently the largest, and the Party of European Socialists leads the opposition. Parties do not receive public funds from the EU, as the Court of Justice held in Parti écologiste "Les Verts" v European Parliament that this was entirely an issue to be regulated by the member states. The Parliament's powers include calling inquiries into maladministration or appoint an Ombudsman pending any court proceedings. It can require the Commission respond to questions and by a two-thirds majority can censure the whole Commission (as happened to the Santer Commission in 1999). In some cases, the Parliament has explicit consultation rights, which the Commission must genuinely follow.
Pyrimidine nucleosides include cytidine, uridine, and thymidine. The synthesis of pyrimidine nucleotides begins with the formation of uridine monophosphate (UMP). This process requires aspartate, glutamine, bicarbonate, and two molecules of ATP to provide energy. Additionally, phosphoribosyl pyrophosphate (PRPP) provides the ribose-phosphate backbone. Unlike purine synthesis, in which the nitrogenous base is built upon PRPP, pyrimidine synthesis forms the base first and attaches it to PRPP later in the process. Once UMP is synthesized, it undergoes phosphorylation using ATP to form uridine-triphosphate (UTP). UTP can then be converted into cytidine-triphosphate (CTP) in a reaction catalyzed by CTP synthetase, which utilizes glutamine as an amine donor. The synthesis of thymidine nucleotides requires the reduction of UMP to deoxyuridine monophosphate (dUMP) via ribonucleotide reductase (see next section). dUMP is then methylated by thymidylate synthase to produce thymidine monophosphate (TMP). The regulation of pyrimidine synthesis is tightly controlled. ATP, a purine nucleotide, activates pyrimidine synthesis, while CTP, a pyrimidine nucleotide, acts as an inhibitor. This regulatory feedback ensures balanced purine and pyrimidine levels, which is essential for DNA and RNA synthesis. Deficiencies in enzymes involved in pyrimidine synthesis can lead to metabolic disorders such as orotic aciduria.
The Kingdom of Kucha, the most populous oasis in the Tarim Basin, occupied a strategic position on the Northern Silk Road, which brought it prosperity, and made it a wealthy center of trade and culture. Kucha was part of the Silk Road economy, and was in contact with the rest of Central Asia, including Sogdiana and Bactria, and thus also with the cultures of India, Iran, and coastal areas of China. Early visitors are known, such as Maes Titianus. Since the 2nd century CE, under the auspices of the Han dynasty and the Kushan Empire, numerous great Buddhist missionaries passed through the Tarim Basin on their way to China, such as the Parthian An Shigao, the Yuezhis Lokaksema and Zhi Qian, or the Indian Chu Sho-fu (竺朔佛). Culture flourished, and Indian Sanskrit scriptures were being translated by the Kuchean monk and translator Kumarajiva (344–413 CE), himself the son of a Buddhist man from Kashmir and a Kuchean princess, sister of the King. The 1st Style, sometimes called "First Indo-Iranian style" to denote influences from India and Central Asia, covers a period from 300 to 500 CE, and is characterized by Gandharan themes and orange and green hues, having a strong flavour of India: female dancers and musicians are often naked or half-naked with full breasts. The art of these paintings is quite refined, and forms the "Classical" period of the art of Kizil: the shades are delicate, the lines are fine and elegant, the colors blend progressively to give a sense of texture and volume.
Sources: en.wikipedia.org
=== In silico technique === Synthetic biology in silico and the various strategies are interconnected. The development of complex designs, whether they are metabolic pathways, fundamental cellular processes, or chassis genomes, is one of the major difficulties faced by the four synthetic-biology methods outlined above. Because of this, synthetic biology has a robust in silico branch, similar to systems biology, that aims to create computational models for the design of common biological components or synthetic circuits, which are essentially simulations of synthetic organisms. The practical application of simulations and models through bioengineering or other fields of synthetic biology is the long-term goal of in silico synthetic biology. Many of the computational simulations of synthetic organisms up to this point possess little to no direct analogy to living things. Due to this, in silico synthetic biology is regarded as a separate group in this article. It is sensible to integrate the five areas under the umbrella of synthetic biology as one unified area of study. Even though they focus on various facets of life, such as metabolic regulation, essential elements, or biochemical makeup, these five strategies all work toward the same end: creating new types of living organisms. Additionally, the varied methodologies begin with numerous methodological approaches, which leads to the diversity of synthetic biology approaches.
The vertical bars ("|") in the above list are not separators in the sense of the Backus–Naur form but are part of the format. Multiple identifiers can be concatenated, also separated by vertical bars.
Britain had expected a swift victory against a mostly unmilitarised and predominantly agricultural-based opponent. Britain was the world's most technologically advanced military. The results caused many both domestically and internationally to question the dominance of the British Empire, especially as nations like the US, Germany, and Japan had become major powers.
=== First aid === Pre-hospital care for lung barotrauma includes basic life support of maintaining adequate oxygenation and perfusion, assessment of airway, breathing and circulation, neurological assessment, and managing any immediate life-threatening conditions. High-flow oxygen up to 100% is considered appropriate for diving accidents. Large-bore venous access with isotonic fluid infusion is recommended to maintain blood pressure and pulse.
== Decaffeinated coffee == Friedlieb Ferdinand Runge performed the first isolation of caffeine from coffee beans in 1820, after the German poet Goethe heard about his work on belladonna extract, and requested he perform an analysis on coffee beans. Though Runge was able to isolate the compound, he did not learn much about the chemistry of caffeine itself, nor did he seek to use the process commercially to produce decaffeinated coffee.
Sources: en.wikipedia.org
It is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone, containing seven amino acids with a lactam ring and a D-configured phenylalanine residue. It is supplied as a lyophilised powder for laboratory research.
The natural hormone is a linear tridecapeptide that is rapidly degraded in circulation. Melanotan-2 is shortened, cyclised, N-terminally acetylated, and carries a D-amino acid substitution, all of which slow enzymatic breakdown.
No national medicines regulator has approved melanotan-2 for therapeutic or cosmetic use. In several jurisdictions it is treated as an unapproved prescription medicine, and its legal classification differs from country to country.
No regulator in a major market has approved it for human use. It appears in research settings and in products marketed outside pharmacy channels. Legal status for personal possession varies by country.