The short version of melanocortin receptors fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-03-14. Anything still debated is marked as such rather than presented as settled.
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.
| 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 |
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.
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.
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.
==== Insurances Covering Gender Affirmative Care ==== Numerous insurances within the United States cover gender affirming care, which includes hormone replacement therapy (HRT) and surgery. However, this coverage is conditional and dependent on many factors, such as plan benefits, employer, and the state. In California most insurers are forbidden from banning gender affirming care coverage; however, insurers in other states don't have this restriction and can exclude coverage of gender affirming care. Each specific plan and policy will specify the coverage of gender affirming care. Most insurers covering gender affirming care will cover generic and FDA approved hormone replacement therapy. If a clinician recommends a brand name hormone replacement therapy, insurance will conditionally accept it based on recommendation, cost, policy, and healthcare needs. Some insurers that cover gender affirming care include Anthem Blue Cross and Blue Shield, Cigna, Aetna, Medicare, Tricare and UnitedHealthcare.
Former faculty member Ernest Lyon was a United States ambassador to Liberia and the founder of the Maryland Industrial and Agricultural Institute for Colored Youths. Noted African American historian and pioneering scholar Dr. Benjamin A. Quarles served on its faculty for many decades. Physician-scientist Charles R. Drew, known for his work on blood transfusion, was Morgan College's first athletic director. African-American historian Rosalyn Terborg-Penn wrote on women's suffrage. Flora E. Strout, Morgan College teacher and principal, wrote the school's anthem. Notable faculty currently teaching at Morgan State University include bestselling author and filmmaker MK Asante, and scholar Raymond Winbush.
== Employment == Biochemists are typically employed in the life sciences, where they work in the pharmaceutical or biotechnology industry in a research role. They are also employed in academic institutes, where in addition to pursuing their research, they may also be involved with teaching undergraduates, training graduate students, and collaborating with post-doctoral fellows. Because of a biochemists' background in both biology and chemistry, they may also be employed in the medical, industrial, governmental, and environmental fields. Slightly more than half of the biological scientists are employed by the Federal State and local governments. The field of medicine includes nutrition, genetics, biophysics, and pharmacology; industry includes beverage and food technology, toxicology, and vaccine production; while the governmental and environmental fields includes forensic science, wildlife management, marine biology, and viticulture. The average income of a biochemist was $82,150 in 2017. The range of the salaries begin around 44,640 to 153,810, reported in 2017. The United States Federal Government in 2005 reported the average salaries in different fields associated with biochemistry and being a biochemist. General biological scientists in nonsupervisory, supervisory, and managerial positions earned an average salary of $69,908; microbiologists, $80,798; ecologists, $72,021; physiologists, $93,208; geneticists, $85,170; zoologists, $101,601; and botanists, $62,207.
== In popular culture == The fictional character Dexter Morgan uses Etorphine M-99 to capture and sedate his victims in the television series, Dexter, although this was retroactively changed to ketamine in the sequel series, Dexter: New Blood, only for etorphine to return in the succeeding series, Dexter: Original Sin and Dexter: Resurrection. In the film The Meg etorphine is used to neutralise the first megalodon. The fictional character Katherine Dutta uses etorphine to murder her victims in the television series Lewis, Lewis: Down Among the Fearful. In an Agatha Raisin book, a fictional veterinarian is murdered with the Immobilon he planned to use to sedate a horse for an operation.
== External links == Clinical trial number NCT01681953 for "A Placebo-Controlled Phase 3 Trial of Repeated Lamazym Treatment of Subjects With Alpha-Mannosidosis" at ClinicalTrials.gov Clinical trial number NCT02998879 for "Trial on Safety and Efficacy of Velmanase Alfa Treatment in Pediatric Patients With Alpha-Mannosidosis (rhLaman-08)" at ClinicalTrials.gov alpha-Mannosidase at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
Sources: en.wikipedia.org
=== Vertebrates === Serotonin, also referred to as 5-hydroxytryptamine (5-HT), is a neurotransmitter most known for its involvement in mood disorders in humans. It is also a widely present neuromodulator among vertebrates and invertebrates. Serotonin has been found having associations with many physiological systems such as cardiovascular, thermoregulation, and behavioral functions, including: circadian rhythm, appetite, aggressive and sexual behavior, sensorimotor reactivity and learning, and pain sensitivity. Serotonin's function in neurological systems along with specific behaviors among vertebrates found to be strongly associated with serotonin will be further discussed. Two relevant case studies are also mentioned regarding serotonin development involving teleost fish and mice. In mammals, 5-HT is highly concentrated in the substantia nigra, ventral tegmental area and raphe nuclei. Lesser concentrated areas include other brain regions and the spinal cord. 5-HT neurons are also shown to be highly branched, indicating that they are structurally prominent for influencing multiple areas of the CNS at the same time, although this trend is exclusive solely to mammals.
== Life and physiology == At birth, earthworms emerge small but fully formed, lacking only their sex structures which develop in about 60 to 90 days. They attain full size in about one year. Scientists predict that the potential lifespan under field conditions is four to eight years, while the actual lifespan is probably no more than a few months because of intense predation and environmental hazards.
==== Liver damage ==== Nicotinic acid in medicinal doses can cause modest elevations in serum transaminase and unconjugated bilirubin, both biomarkers of liver injury. The increases usually resolve even when drug intake is continued. However, less commonly, the sustained release form of the drug can lead to serious hepatotoxicity, with onset in days to weeks. Early symptoms of serious liver damage include nausea, vomiting and abdominal pain, followed by jaundice and pruritus. The mechanism is thought to be a direct toxicity of elevated serum niacin. Lowering dose or switching to the immediate release form can resolve symptoms. In rare instances the injury is severe, and progresses to liver failure.
=== Fragmentation === After Bolesław III divided Poland among his sons in his Testament of 1138, internal fragmentation eroded the Piast monarchical structures in the 12th and 13th centuries. In 1180, Casimir II the Just, who sought papal confirmation of his status as a senior duke, granted immunities and additional privileges to the Polish Church at the Congress of Łęczyca. Around 1220, Wincenty Kadłubek wrote his Chronica seu originale regum et principum Poloniae, another major source for early Polish history. In 1226, one of the regional Piast dukes, Konrad I of Masovia, invited the Teutonic Knights to help him fight the Baltic Prussian pagans. The Teutonic Order destroyed the Prussians but kept their lands, which resulted in centuries of warfare between Poland and the Teutonic Knights, and later between Poland and the German Prussian state. The first Mongol invasion of Poland began in 1240; it culminated in the defeat of Polish and allied Christian forces and the death of the Silesian Piast Duke Henry II the Pious at the Battle of Legnica in 1241. In 1242, Wrocław became the first Polish municipality to be incorporated, as the period of fragmentation brought economic development and growth of towns. New cities were founded and existing settlements were granted town status per Magdeburg Law. In 1264, Bolesław the Pious granted Jewish liberties in the Statute of Kalisz.
Sources: en.wikipedia.org
Myozyme costs an average of US$300,000 a year and must be taken for the patient's entire life, so some American health insurers have refused to pay for it. In August 2006, Health Canada approved Myozyme for the treatment of Pompe disease. In June 2007, the Canadian Common Drug Review issued its recommendations regarding public funding for Myozyme therapy. Their recommendation was to provide funding to treat a tiny subset of Pompe patients (Infants less one year of age with cardiomyopathy). In May 2010, the FDA approved Lumizyme for the treatment of late-onset Pompe disease. Lumizyme and Myozyme have the same generic ingredient (alglucosidase alfa) and manufacturer (Genzyme Corporation). The difference between these two products is in the manufacturing process. Myozyme is made using a 160-L bioreactor, while Lumizyme uses a 4000-L bioreactor. Because of the difference in the manufacturing process, the FDA claims that the two products are biologically different. Myozyme is FDA approved for replacement therapy for infantile-onset Pompe disease. In July 2021, the European Medicines Agency (EMA) recommended the authorization of avalglucosidase alfa. Avalglucosidase alfa (Nexviazyme) was approved for medical use in the United States in August 2021, and in the European Union in June 2022. In December 2022, the EMA recommended the authorization of cipaglucosidase alfa. The approval was given in June 2023. In the EU, the therapy is available to all age groups without restrictions on weight of patients.
President of League of Communists of Serbia Slobodan Milošević visited Kosovo in April 1987 and promised rapid action in order to protect peace and the Serbs of Kosovo. Ethnic tensions in Kosovo heated up when a Kosovo Albanian soldier opened fire on his fellow soldiers in Paraćin, in an event known as the Paraćin massacre. Then President of Serbia Ivan Stambolić wanted to make compromise, rather than fast solution. He found himself in a clash with Milošević. This conflict culminated with 8th Session and replacement of Stambolić with Petar Gračanin as President of Serbia.
== External links == Mercaptans (or Thiols) at The Periodic Table of Videos (University of Nottingham) Applications, Properties, and Synthesis of ω-Functionalized n-Alkanethiols and Disulfides – the Building Blocks of Self-Assembled Monolayers by D. Witt, R. Klajn, P. Barski, B.A. Grzybowski at Northwestern University. Mercaptan, by The Columbia Electronic Encyclopedia What is Mercaptan? Archived 2008-12-20 at the Wayback Machine, by Columbia Gas of Pennsylvania and Maryland. What Is the Worst Smelling Chemical? Archived 2011-06-06 at the Wayback Machine, by About Chemistry.
=== Industrial scale === In a similar fashion to some laboratory methods, acetamide is produced by dehydrating ammonium acetate or via the hydration of acetonitrile, a byproduct of the production of acrylonitrile:
For the next several years, the band refused to perform together, out of respect for him. In 2005, Cantrell, Kinney, and Inez reunited for a benefit concert for victims of the 2004 Indian Ocean tsunami, with several vocalists filling in for Staley. Following positive response, the band decided to reunite formally in 2006. Comes with the Fall vocalist William DuVall, a member of Cantrell's solo touring band who often sang Staley's parts on the Alice in Chains songs that Cantrell performed, was announced to sing Staley's part for the reunion shows. In an interview with MTV News, Kinney noted that the band would use the reunion concerts to pay tribute to the songs and to Staley. The band used to have an intermission to include a five-minute filmed tribute to Staley in between sets. DuVall has since become Staley's full-time replacement in the band, contributing to three full-length releases.
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 and an analogue of alpha-melanocyte-stimulating hormone. The molecule is produced by chemical synthesis rather than extracted from a biological source.