melanocortin receptor raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2026-01-04. Anything still debated is marked as such rather than presented as settled.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C50H69N15O9 | Free base; salt forms add to total mass |
| Molecular mass | About 1024 daltons | Calculated for the free base |
| Structural class | Cyclic heptapeptide | Contains D-phenylalanine and norleucine |
| Parent hormone | Alpha-melanocyte-stimulating hormone | Endogenous tridecapeptide of 13 residues |
| Receptor profile | Non-selective melanocortin agonist | Interacts with MC1R, MC3R, MC4R and MC5R |
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.
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 that acts as an agonist at melanocortin receptors. It was designed as a structural analogue of alpha-melanocyte-stimulating hormone, the endogenous peptide involved in pigment production. The analogue carries a lactam bridge that constrains the ring and slows enzymatic breakdown relative to the native hormone. In research literature it appears under several abbreviations, and naming conventions are not fully standardized. Published descriptions usually place it within the broader melanocortin agonist family.
Receptor binding at MC1R on melanocytes raises intracellular cyclic AMP and increases expression of tyrosinase and related enzymes. The downstream result is greater synthesis of eumelanin, the dark pigment, without ultraviolet exposure acting as the trigger. The compound is not selective, however, and also engages MC3R, MC4R and MC5R, which are expressed in the central nervous system and elsewhere. That lack of selectivity is the explanation usually offered for effects reported outside pigmentation, including appetite suppression and nausea. Selectivity remains a central theme in comparative studies of related peptides.
Melanotan-2 is a synthetic linear peptide built from seven amino acids arranged in a short chain. Its sequence is commonly written as Ac-Nle-Asp-His-D-Phe-Arg-Trp-Lys-NH2, which includes a modified N-terminus and an amidated C-terminus. The molecule belongs to the melanocortin family and acts as a receptor agonist. Structural features such as the D-phenylalanine residue and the Nle substitution are associated with increased stability against enzymatic degradation relative to the natural parent peptide.
The compound emerged from research programs in the 1980s that examined analogues of alpha-melanocyte-stimulating hormone for pigmentation and photoprotection. Investigators modified the native sequence to extend activity duration and potency. A related analogue, afamelanotide, was developed within the same broad line of inquiry and eventually gained approval in certain jurisdictions for a rare light-sensitivity condition. Melanotan-2 itself did not progress through the same regulatory route and has no approved therapeutic indication.
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.
Amphetamine-Dextroamphetamine is known to hamper appetite. Amphetamine-Dextroamphetamine is used to treat Attention deficit hyperactivity disorder (ADHD) and is usually under the trade name "Adderall" or "Mydayis". Amphetamine sulfate (also known as amfetamine) – US FDA-approved for the treatment of exogenous obesity under the brand name "Evekeo". Methylphenidate Cocaine Caffeine Glucomannan Leptin Lisdexamfetamine - US FDA approved for the treatment of binge-eating disorder in adults under the brand name "Vyvanse". Methamphetamine hydrochloride – USFDA-approved for the treatment of obesity (as a short-term) under the brand name "Desoxyn". Nicotine Liraglutide as brand name Saxenda Semaglutide (brand name Ozempic/Wegovy) GLP-1 agonist Tirzepatide (Brand Name Mounjaro, Zepbound) Metformin Opiates/opioids such as heroin, morphine, codeine, oxycodone, fentanyl, etc. Anti-obesity medication
== Isomeric ratio == When the generator is left unused, 99Mo decays to 99mTc, which in turn decays to 99Tc. The half-life of 99Tc is far longer than its metastable isomer, so the ratio of 99Tc to 99mTc increases over time. Both isomers are carried out by the elution process and react equally well with the ligand, but the 99Tc is an impurity useless to imaging (and cannot be separated). The generator is washed of 99Tc and 99mTc at the end of the manufacturing process of the generator, but the ratio of 99Tc to 99mTc then builds up again during transport or any other period when the generator is left unused. The first few elutions will have reduced effectiveness because of this high ratio.
The first performance in Los Angeles in 1954 was introduced with a tribute to Thomas from Aldous Huxley. Thomas spent the last nine or ten days of his third tour in New York mostly in the company of Reitell, with whom he had an affair. During this time, Thomas fractured his arm falling down a flight of stairs when drunk. Reitell's doctor, Milton Feltenstein, put his arm in plaster and treated him for gout and gastritis. After returning home, Thomas worked on Under Milk Wood in Laugharne. Aeronwy, his daughter, noticed that his health had "visibly deteriorated...I could hear his racking cough. Every morning he had a prolonged coughing attack...The coughing was nothing new but it seemed worse than before." She also noted that the blackouts that Thomas was experiencing were "a constant source of comment" amongst his Laugharne friends. Thomas sent the original manuscript to Douglas Cleverdon on 15 October 1953. It was copied and returned to Thomas, who lost it in a pub in London and required a duplicate to take to America. Thomas flew to the States on 19 October 1953 for what would be his final tour. He died in New York before the BBC could record Under Milk Wood. Richard Burton starred in the first broadcast in 1954, and was joined by Elizabeth Taylor in a subsequent film. In 1954, the play won the Prix Italia for literary or dramatic programmes.
Sources: en.wikipedia.org
During the Edo period of Japan, the consumption of polished white rice, once largely restricted to the upper classes, began to spread among lower-ranking samurai and urban townspeople, often forming the bulk of their diet with few side dishes. This dietary shift contributed to the rising prevalence of beriberi, particularly in major cities such as Kyoto, Nagoya, Edo (modern Tokyo), and Osaka by the late 17th century. In contrast, rural populations and farmers, who relied on mixed grains and less refined brown rice with higher thiamine content, were largely spared from the disease. With the onset of the Meiji era and its accompanying economic growth, refined white rice became more widely accessible across social classes. The resulting popularization of a polished white rice diet contributed to the nationwide spread of beriberi, which came to be regarded as a disease endemic to Japan.
=== Broadcasters === Robert Siegel (1968), host of All Things Considered on National Public Radio Jim Gardner (1970), anchor for WPVI-TV news in Philadelphia Christopher Kimball (1973), celebrity chef, editor-in-chief of Cook's Illustrated and host of America's Test Kitchen George Whipple III (1977), lawyer and society correspondent for NY1 Pimm Fox (1982), Bloomberg Radio and Bloomberg Television anchorman Fred Katayama (1982), anchor on Reuters Television James Rubin (1982), Sky News anchorman; former assistant secretary of state for public affairs in the Clinton Administration; spokesman for the presidential campaigns of Wesley Clark and John Kerry; husband of Christiane Amanpour George Stephanopoulos (1982), ABC News personality; senior advisor to U.S.
The Purple Book, formally titled Compendium of Macromolecular Terminology and Nomenclature, contains the nomenclature of polymers. The first edition was first published in 1991. The second and latest edition was published in December 2008 and is also available for download.
Sources: en.wikipedia.org
== January 20, 1982 (Wednesday) == Musician Ozzy Osbourne was treated for rabies after allegedly biting the head off a live bat during a concert at Veterans Auditorium in Des Moines, Iowa. A spokesman for Broadlawn Medical Center reported that the patient registered as John M. Osbourne "was given a rabies shot and rabies vaccine and a tetanus shot as well," and that the medical report gave the history "Patient bit head off bat." Des Moines police lieutenant Derald Leaming said "I told his manager if he bit the head off any animals while he was here, he'd be arrested. We would have arrested him on the spot if we'd seen anything like that," while two other officers said that he had seen Osbourne "put a couple of birds in his mouth but he let them loose", and that although the police didn't see a bat, that they "did see raw liver on the floor." Born: Pete Buttigieg, American politician, U.S. Secretary of Transportation from 2021 to 2025, 2020 candidate for the Democratic Party nomination for U.S. president; in South Bend, Indiana Died: Marc Demeyer, 31, Belgian professional bicyclist known for winning individual stages twice in the Tour de France (1978 and 1979) and twice in the 1977 Giro d'Italia, died of a heart attack.
Vasodilators are increased (such as nitric oxide and carbon monoxide) reducing afterload with compensatory increase in cardiac output, mixed venous oxygen saturation. Renin is increased (as well as sodium retention in kidneys) secondary to a fall in systemic vascular resistance. FibroTest is a biomarker for fibrosis that may be used instead of a biopsy. Other laboratory studies performed in newly diagnosed cirrhosis may include:
== External links == The MEROPS online database for peptidases and their inhibitors: A01.004 beta-Secretase: Molecule of the Month Archived 2012-11-21 at the Wayback Machine, by David Goodsell, RCSB Protein Data Bank Human BACE1 genome location and BACE1 gene details page in the UCSC Genome Browser. Overview of all the structural information available in the PDB for UniProt: P56817 (Human Beta-secretase 1) at the PDBe-KB.
Sources: en.wikipedia.org
No regulatory agency has authorised melanotan-2 as a medicine for any indication. It circulates mainly as a research chemical or through unregulated channels. As a result, identity, purity and content are not independently guaranteed.
Melanotan-1, also called afamelanotide, is a linear analogue with greater selectivity for MC1R and has received approval in some jurisdictions for a specific photosensitivity disorder. Melanotan-2 is cyclic, less selective, and reaches central receptors more readily. The two are often confused in online discussion despite different pharmacology and regulatory status.
Alpha-MSH is an endogenous tridecapeptide derived from pro-opiomelanocortin. Melanotan-2 reproduces its core receptor-binding sequence inside a shortened, stabilised ring. The result is a molecule with a longer effective half-life and higher potency than the parent hormone.
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.