If you have been reading about melanocortin receptors and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Last reviewed on 2025-12-25. Where a claim depends on a specific study, the study is described rather than over-claimed.
The compound was developed in the late 1980s and early 1990s by academic researchers investigating melanocortin signaling and pigmentation. Early work explored whether synthetic analogs could reproduce effects of the natural hormone under controlled conditions. The molecule never advanced through the full regulatory pathway required for approval as a medicine. From the mid-2000s onward it appeared in unregulated consumer markets, often distributed through informal channels. That gap between research origins and commercial availability shapes how the compound is discussed today.
Melanotan-2 is a synthetic peptide designed as an analog of alpha-melanocyte-stimulating hormone, a signaling molecule produced in the pituitary and skin. Its structure is a linear chain of seven amino acids that folds into a ring through an internal lactam bridge joining two side chains. The compound is sometimes written as MT-II or MEL-2 in informal and commercial contexts. It belongs to the melanocortin peptide family, a group of short signaling molecules that share a conserved core sequence recognized by melanocortin receptors.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular class | Synthetic cyclic heptapeptide | Analog of alpha-MSH with an internal lactam bridge |
| Molecular weight | Approximately 1024 daltons | Free base value; salt forms differ |
| Appearance | White to off-white powder | Usually supplied as a lyophilized solid |
| Solubility | Freely soluble in water | Poorly soluble in nonpolar solvents |
| Typical storage | −20 °C, dry, protected from light | Repeated freeze-thaw cycles degrade peptides |
Regulatory treatment varies between countries. Several national medicines agencies have classified the peptide as unapproved, and customs authorities in some jurisdictions seize shipments on that basis. A few jurisdictions channel supply through prescription-only frameworks that do not list the substance by name. Because the material circulates mainly through online vendors, composition and purity are rarely verified before sale. Surveys of unapproved peptide products have reported labels that did not match measured content in a substantial fraction of samples.
Melanotan II is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone, a naturally occurring peptide involved in pigmentation signalling. Its structure substitutes a lactam bridge between side chains to increase stability relative to the native hormone. The compound is also known by the shorthand MT-II and by several non-proprietary synonyms used in research catalogues. It is not an approved therapeutic product in any major jurisdiction; material sold under this name is typically offered as a laboratory reagent rather than as a medicine.
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.
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.
The peptide was developed during the 1980s by researchers investigating melanocortin signalling and skin pigmentation pathways. Early work focused on analogues of alpha-melanocyte-stimulating hormone that would resist enzymatic breakdown more effectively than the parent molecule. Melanotan-2 emerged from that programme as a shortened, cyclised variant. Reports describing its synthesis and receptor activity later appeared in the scientific literature. Commercial availability grew through unregulated channels rather than through pharmaceutical approval.
Many psychoactive medications can cause withdrawal symptoms upon discontinuation from administration. Paroxetine has among the highest incidence rates and severity of withdrawal syndrome of any medication of its class. Common withdrawal symptoms for paroxetine include nausea, dizziness, lightheadedness and vertigo; insomnia, nightmares, and vivid dreams; feelings of electricity in the body, as well as rebound depression and anxiety. A liquid formulation of paroxetine is available and allows a very gradual decrease of the dose, which may prevent discontinuation syndrome. Another recommendation is to temporarily switch to fluoxetine, which has a longer half-life and thus decreases the severity of discontinuation syndrome. In 2002, the U.S. FDA published a warning regarding "severe" discontinuation symptoms among those terminating paroxetine treatment, including paraesthesia, nightmares, and dizziness. The agency also warned of case reports describing agitation, sweating, and nausea. In connection with a Glaxo spokesperson's statement that withdrawal reactions occur only in 0.2% of patients and are "mild and short-lived", the International Federation of Pharmaceutical Manufacturers Associations said GSK had breached two of the federation's codes of practice. Paroxetine prescribing information posted at GlaxoSmithKline has been updated related to the occurrence of a discontinuation syndrome, including serious discontinuation symptoms.
Polyglutamic acid (PGA) is a polymer of the amino acid glutamic acid (GA). Depending on where the individual monomers connect, PGA can be gamma PGA (poly-γ-glutamic acid, γ-PGA), the form where the peptide bonds are between the amino group of GA and the carboxyl group at the end of the GA side chain, or alpha PGA, the form where the alpha-carboxyl is used to form the peptide bond. Gamma PGA is formed by bacterial fermentation. It is a major constituent of the Japanese food nattō and has a wide range of uses. Alpha PGA has been investigated as a drug delivery system.
==== National Blue Ribbon Schools of Excellence ==== Beacon Heights Elementary School, Riverdale, 2003–04 Columbia Park Elementary School, Landover, 1987–88 Fort Foote Elementary School, Fort Washington, 2000–01 Glenarden Woods Elementary School, Glenarden, 2005–06 Greenbelt Center Elementary School, Greenbelt, 1991–92 Heather Hills Elementary School, Bowie, 1989–90 Templeton Elementary School, Riverdale, 1998–99 Whitehall Elementary School, Bowie, 2011–12 Kenmoor Middle School, Landover, 1988–89 Dora Kennedy French Immersion, Greenbelt, 2013–14 Kettering Middle School, Upper Marlboro, 1992–93 Martin Luther King, Jr. Middle School, Beltsville, 1992–93 Eleanor Roosevelt High School, Greenbelt, 1990–91 & 1997–98 Suitland High School, Forestville, 1988–89
== Testing == The meat industry strives to produce meat with standardized and guaranteed tenderness, since these characteristics are sought for by the consumers. For that purpose a number of objective tests of tenderness have been developed, gauging meat resistance to shear force, most commonly used being Slice Shear Force test and Warner–Bratzler Shear Force test.
Sources: en.wikipedia.org
Random freeze: the genetic code was randomly created. For example, early tRNA-like ribozymes may have had different affinities for amino acids, with codons emerging from another part of the ribozyme that exhibited random variability. Once enough peptides were coded for, any major random change in the genetic code would have been lethal; hence it became "frozen". Stereochemical affinity: the genetic code is a result of a high affinity between each amino acid and its codon or anti-codon; the latter option implies that pre-tRNA molecules matched their corresponding amino acids by this affinity. Later during evolution, this matching was gradually replaced with matching by aminoacyl-tRNA synthetases. Optimality: the genetic code continued to evolve after its initial creation, so that the current code maximizes some fitness function, usually some kind of error minimization. Hypotheses have addressed a variety of scenarios:
The details of the Hill & Knowlton public relations campaign, including the incubator testimony, were published in John R. MacArthur's Second Front: Censorship and Propaganda in the Gulf War, and came to public attention when an Op-ed by MacArthur was published in The New York Times. This prompted a reexamination by Amnesty International, which had promoted an account alleging even greater numbers of babies torn from incubators than the fake testimony. After finding no evidence to support it, the organization issued a retraction. Bush repeated the incubator allegations on television. The Iraqi Army did commit well-documented crimes during its occupation, such as the summary execution without trial of three brothers, after which their bodies were stacked and left to decay in a street. Iraqi troops ransacked and looted private homes; one residence was repeatedly defecated in. A resident later commented: "The whole thing was violence for the sake of violence, destruction for the sake of destruction ... Imagine a surrealistic painting by Salvador Dalí". Bush repeatedly compared Saddam Hussein to Hitler.
=== Macrocycles === Macrocycles are a traditional component in supramolecular chemistry. The macrocyclic effect enhances otherwise weak interactions. Cyclodextrins, calixarenes, cucurbiturils, and crown ethers allow the incorporation of alkali metal cations. More complex, 3-dimenesion receptors include cyclophanes, and cryptands. Supramolecular metallocycles and metallacrowns are related components. Common metallocycle shapes in these types of applications include triangles, squares, and pentagons, each bearing functional groups that connect the pieces via "self-assembly."
=== Inflammatory bowel disease === There is only a little evidence of its effectiveness in treating functional symptoms in inflammatory bowel disease from small studies that are susceptible to bias. The low-FODMAP diet is not recommended for ulcerative colitis due to risk of disruption of nutritional status and insufficient evidence of beneficial effects.
==== Employees and DuPont exposed community ==== In 2010, the three members of the C8 Science Panel published a review of the epidemiological evidence on PFOA exposure in Environmental Health Perspectives. Insufficient evidence exists to conclude PFOA causes adverse health effects in humans, but consistent evidence exists on associations with higher cholesterol and uric acid. Whether or not these potential effects result in an increase in cardiovascular disease is unknown. Further data on the 69,030 member cohort that is being studied by the panel is scheduled for release through 2012. A 2011 epidemiological study demonstrated "probable link" between PFOA and kidney cancer, testicular cancer, thyroid disease, high cholesterol, pre-eclampsia and ulcerative colitis. Facial birth defects, an effect observed in rat offspring, occurred with the children of two out of seven female DuPont employees from the Washington Works facility from 1979 to 1981. Bucky Bailey is one of the affected individuals; DuPont, however, does not accept any liability from the toxicity of PFOA. While 3M sent DuPont results from a study that showed birth defects to rats administered PFOA and DuPont moved the women out of the Teflon production unit, subsequent animal testing led DuPont to conclude there was no reproductive risk to women, and they were returned to the production unit. However, data released in March 2009 on the community around DuPont's Washington Works plant showed "a modest, imprecise indication of an elevation in risk ... above the 90th percentile ...
Sources: en.wikipedia.org
It is a synthetic seven-amino-acid peptide modeled on alpha-melanocyte-stimulating hormone. It carries two non-natural substitutions and a cyclic bridge that increase its stability relative to the natural hormone. It circulates as a research chemical and is not an approved medicine.
Melanotan-1, also called afamelanotide, is a shorter linear analog with a different amino acid sequence and no lactam ring. It has been evaluated in formal clinical programs, while melanotan-2 has not. The two are distinct molecules and are not interchangeable.
No. Bremelanotide is a related but distinct cyclic peptide that reached approved status for one specific clinical indication. Melanotan-2 is a separate molecule with its own sequence and properties. Shared ancestry in the melanocortin family does not make them the same substance.
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.