A practical reference on melanocortin receptor: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2026-04-18 and is reviewed periodically as new material appears.
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-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controlled human data on melanotan-2 remain sparse, and much of what circulates online derives from small studies or unpublished reports.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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C50H69N15O9 | Cyclic heptapeptide, C-terminally amidated |
| Approximate molecular mass | 1024 Da | Monoisotopic mass of the free peptide |
| Appearance | White to off-white powder | Typically supplied as a lyophilised solid |
| Solubility class | Soluble in water and polar solvents | Also dissolves in neutral aqueous buffer |
| Common synonyms | Melanotan II, MT-II, MT-2 | Described as a melanocortin agonist in early literature |
Receptor studies place melanotan-2 among non-selective melanocortin agonists, binding MC1R, MC3R, MC4R and MC5R rather than a single subtype. Activation of MC1R on cutaneous melanocytes raises tyrosinase activity and shifts pigment synthesis toward eumelanin, which is darker and more photostable than pheomelanin. Central receptors, particularly MC4R, are associated with appetite suppression and with reported effects on sexual function. Because subtype selectivity is low, the same molecule engages pigment, metabolic and vascular pathways at once, and this breadth is a common explanation offered for the range of adverse events described in user reports.
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.
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.
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.
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.
== Medical uses == In the United States empagliflozin/linagliptin is indicated as an adjunct to diet and exercise to improve glycemic control in adults with type 2 diabetes mellitus and to reduce the risk of cardiovascular death in adults with type 2 diabetes mellitus and established cardiovascular disease. In the European Union empagliflozin/linagliptin is indicated in adults aged 18 years and older with type 2 diabetes mellitus:
The Bushies consistently refused." In 2008, Roy Allison, wrote in International Affairs that there was evidence "that the Russian invasion of South Ossetia and then deeper into Georgia was indeed planned and even expected rather than spontaneous and improvised." However, "the exact timing of the intervention during August–September may not have been of Moscow's choosing, if for example South Ossetian forces were impatient to instigate a conflict in July– August to give Russia a pretext for intervention and could not be effectively controlled". Regarding the events of August 7/8, Allison states that "Moscow's insistence that its forces did not cross the Georgian border until Russian peacekeepers in Tskhinvali were in severe jeopardy has gained quite wide acceptance internationally. The Georgian claim has, however, been strengthened by the release of telephone intercepts (lost for a month in the chaos of combat) indicating that at least part of a Russian armoured regiment had crossed into South Ossetia by late on 7 August." In the light of the Russian occupation of uncontested Georgian territory, Russian claim to be carrying out the peacekeeping mission per the Sochi agreements is described as "increasingly surreal". He noted that "international agreements limited Russia's peacekeeping role in South Ossetia to monitoring the ceasefire, with no provision for peace enforcement".
==== Neurodegeneration ==== Research has been conducted on the effects of stem cells on animal models of brain degeneration, such as in Parkinson's disease, Amyotrophic lateral sclerosis, and Alzheimer's disease. Preliminary studies related to multiple sclerosis have been conducted, and a 2020 phase 2 trial found significantly improved outcomes for mesenchymal stem cell treated patients compared to those receiving a sham treatment. In January 2021 the FDA approved the first clinical trial for an investigational stem cell therapy to restore lost brain cells in people with advanced Parkinson's disease. Healthy adult brains contain neural stem cells, which divide to maintain general stem-cell numbers, or become progenitor cells. In healthy adult laboratory animals, progenitor cells migrate within the brain and function primarily to maintain neuron populations for olfaction (the sense of smell). Pharmacological activation of endogenous neural stem cells has been reported to induce neuroprotection and behavioral recovery in adult rat models of neurological disorders.
On 15 May, an armed mob, headed by François-Vincent Raspail, Auguste Blanqui, and Armand Barbès, and assisted by the proletariat-aligned Guard, attempted to overwhelm the Assembly, but were defeated by the bourgeois-aligned battalions of the National Guard. Meanwhile, the national workshops were unable to provide remunerative work for the genuine unemployed, and of the thousands who applied, the greater number were employed in aimless digging and refilling of trenches; soon even this expedient failed, and those for whom work could not be invented were given a half wage of 1 franc a day. On 21 June, Alfred de Falloux decided in the name of the parliamentary commission on labour that the workmen should be discharged within three days and those who were able-bodied should be forced to enlist in the armed forces.
== Description == The Wound Man illustrates various injuries that a person might receive through war, accident, or disease: cuts and bruises from multiple weapons, rashes and pustules, thorn scratches, and the bites of venomous animals. The figure also includes some schematic anatomical outlines of several organs within his unusual, transparent abdomen.
Sources: en.wikipedia.org
=== HCNO-II === The notable difference between the CNO-II cycle and the HCNO-II cycle is that 179F captures a proton instead of decaying, and neon is produced in a subsequent reaction on 189F, leading to the total sequence
=== Cancer === HLA-G has been shown to be associated with tumor escape in cancers, because it causes the immune system to not pay attention to cancer cells. Because it is upregulated in cancer cells, it could serve as a potential target for immunotherapy. Monoclonal antibodies that bind to HLA-G have been used successfully against cancers as part of a strategy to inhibit immune checkpoints. HLA-G has potential utility as a tumor marker due to the large increase in HLA-G in many cancers, including breast cancer, ovarian cancer, and lung cancer. Increased expression of HLA-G has been associated with the metastatic potential of tumor cells.
=== From organic halides and cyanide salts === Two salt metathesis reactions are popular for laboratory scale reactions. In the Kolbe nitrile synthesis, alkyl halides undergo nucleophilic aliphatic substitution with alkali metal cyanides. Aryl nitriles are prepared in the Rosenmund-von Braun synthesis. In general, metal cyanides combine with alkyl halides to give a mixture of the nitrile and the isonitrile, although appropriate choice of counterion and temperature can minimize the latter. An alkyl sulfate obviates the problem entirely, particularly in nonaqueous conditions (the Pelouze synthesis). In the Kolbe nitrile synthesis (a nucleophilic substitution reaction), an alkanonitrile and an alkali halide are formed from a reactive halocarbons and an alkali cyanide (sodium cyanide or potassium cyanide). The reaction is particularly suitable for primary, allylic, and benzylic halides. Secondary alkyl halides provide lower yields, whereas tertiary halides undergo exclusively elimination reaction instead of substitution. In addition to halides, substrates bearing other good leaving groups may also be employed. In contrast to alkali cyanides, silver cyanide is unsuitable for nitrile synthesis, as it preferentially forms isonitriles. An example of the Kolbe nitrile synthesis is the reaction of methyl iodide with sodium cyanide to yield acetonitrile and sodium iodide:
=== Foam === Topical corticosteroid foams are suitable for treating a range of skin conditions that respond to corticosteroids. These foams are typically simple to apply, which can lead to better patient compliance and, in turn, improve treatment results for those who favor a more convenient and cleaner topical option. Foam can be typically seen with topical steroids marketed for the scalp.
Sources: en.wikipedia.org
=== United Kingdom === In the United Kingdom, following a local newspaper story in October 2005, a parliamentary Early Day Motion was raised calling for Salvia divinorum to be banned there. However, it only received 11 signatures. A second motion raised in October 2008 attracted 18 signatures, and it was reported that Mann had also written to Jacqui Smith, then Home Secretary. The Advisory Council on the Misuse of Drugs, the independent body that advises UK government on drugs, was asked to investigate further. On the 28 January 2016, the Psychoactive Substances Act 2016 was passed. The act came into force on 26 May 2016, across the entire United Kingdom, making S. divinorum illegal to possess with intent to supply, possess on custodial premises, import for human consumption, or produce for human consumption. The two sponsors for the bill were Conservative House of Lords member Michael Bates and Conservative MP Theresa May.
Patients starting morphine may experience nausea and vomiting (generally relieved by a short course of antiemetics such as phenergan). Pruritus (itching) may require switching to a different opioid. Constipation occurs in almost all patients on opioids, and laxatives (lactulose, macrogol-containing or co-danthramer) are typically co-prescribed. Opioid tolerance should not be confused with opioid-induced hyperalgesia. The symptoms of these two conditions can appear very similar but the mechanism of action is different. Opioid-induced hyperalgesia is when exposure to opioids increases the sensation of pain (hyperalgesia) and can even make non-painful stimuli painful (allodynia).
The hydroxide ion OH−, a well known base, is here acting as the conjugate base of the acid water. Acids and bases are thus regarded simply as donors and acceptors of protons respectively. A broader definition of acid dissociation includes hydrolysis, in which protons are produced by the splitting of water molecules. For example, boric acid (B(OH)3) produces H3O+ as if it were a proton donor, but it has been confirmed by Raman spectroscopy that this is due to the hydrolysis equilibrium:
==== Oligoarticular arthritis (Oligoarthritis) ==== Oligoarticular (or pauciarticular) JIA is the most common JIA subtype, and occurs when there are up to four joints involved during the first six months of disease. Two subtypes of oligoarticular arthritis exist: persistent oligoarthritis, where no more than four joints are affected throughout the whole disease course; and extended oligoarthritis, where more than four joints are affected after the first six months of disease. Patients in this subtype are often young, typically aged between 1 and 5 years, and are female preponderant. The most commonly involved joint is the knee, but other affected joints may include the ankles, wrists, elbows, and others. 50% of cases involve mono-arthritis, only involving the knee. The anti-nuclear antigen (ANA) is positive in up to 80% of patients with oligoarthritis and is associated with a higher risk of associated eye disease (uveitis), particularly in younger patients. There is no adult counterpart disease to oligoarticular JIA. The prefixes oligo- and pauci- mean 'few'.
Industrial nitrogen fixation by the Haber process is mostly used as fertiliser, although excess nitrogen–bearing waste, when leached, leads to eutrophication of freshwater and the creation of marine dead zones, as nitrogen-driven bacterial growth depletes water oxygen to the point that all higher organisms die. Furthermore, nitrous oxide, which is produced during denitrification, attacks the atmospheric ozone layer. Many saltwater fish manufacture large amounts of trimethylamine oxide to protect them from the high osmotic effects of their environment; conversion of this compound to dimethylamine is responsible for the early odour in unfresh saltwater fish. In animals, free radical nitric oxide (derived from an amino acid), serves as an important regulatory molecule for circulation. Nitric oxide's rapid reaction with water in animals results in the production of its metabolite nitrite. Animal metabolism of nitrogen in proteins, in general, results in the excretion of urea, while animal metabolism of nucleic acids results in the excretion of urea and uric acid. The characteristic odour of animal flesh decay is caused by the creation of long-chain, nitrogen-containing amines, such as putrescine and cadaverine, which are breakdown products of the amino acids ornithine and lysine, respectively, in decaying proteins.
Sources: en.wikipedia.org
No. It is a synthetic analogue carrying four amino acid changes, a lactam ring and an amidated C-terminus. The natural hormone is a linear thirteen-amino-acid peptide processed from proopiomelanocortin.
Afamelanotide is the linear analogue [Nle4-D-Phe7]-alpha-MSH, sometimes called melanotan I, while melanotan II is cyclic and carries three further substitutions. The two are distinct molecules and are not interchangeable in analytical testing.
Binding to the four melanocortin receptor subtypes is well documented in vitro. The relative contribution of each subtype to whole-body effects in humans is far less certain.
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.