This is a working overview of MC1R, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-03-11 and is reviewed periodically as new material appears.
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.
Two structural changes distinguish the synthetic peptide from the natural hormone. A norleucine residue replaces methionine at one position, and a D-configured phenylalanine replaces the natural L-form at another. Both substitutions slow enzymatic breakdown, which extends the molecule's persistence relative to the parent hormone. The lactam bridge further constrains the backbone into a stable conformation. These features are standard design strategies in peptide chemistry and are not unique to this compound; they appear across many research peptides built for improved stability.
The compound was developed in the late 1980s and 1990s by academic researchers investigating photoprotection. The rationale held that stimulating melanin production might reduce ultraviolet damage to skin and lower skin cancer risk. Early work examined receptor binding, pigment response, and short-term tolerability in small studies. That program did not produce an approved drug, and formal development stalled after early-phase trials. Whether induced pigmentation confers meaningful photoprotection remains an open question.
Outside regulated medicine, melanotan II circulates through online vendors as a research chemical, often marketed for tanning. Products sold this way vary widely in purity, concentration, and labeling accuracy, and independent testing has documented discrepancies. Published reports describe both pigment effects and adverse reactions, including nausea, flushing, and darkening of existing moles. Long-term safety data are sparse, and no large controlled trial has established a risk profile. Questions about cumulative effects on melanocytes remain unresolved in the literature.
| 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 |
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.
Melanocortin receptors comprise five subtypes with distinct tissue distributions and functions. Melanotan-2 is described in the literature as a non-selective agonist that engages several of these subtypes, including MC1R, MC3R, MC4R, and MC5R. MC1R is the subtype most directly linked to melanin production in skin cells. Because the compound is not subtype-selective, its observed effects in experimental settings are generally attributed to activity across multiple receptor pathways rather than to a single target.
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.
centromere A specialized DNA sequence within a chromosome that links a pair of sister chromatids. The primary function of the centromere is to act as the site of assembly for kinetochores, protein complexes which direct the attachment of spindle fibers to the centromere and facilitate segregation of the chromatids during mitosis or meiosis.
Left-wing groups which did not agree to the centralisation and abandonment of the soviets by the Bolshevik Party led left-wing uprisings against the Bolsheviks. Such groups included anarchists, Left Socialist-Revolutionaries, Mensheviks and Socialist-Revolutionaries. Amidst this left-wing discontent, the most large-scale events were the workers' Kronstadt rebellion and the anarchist-led Makhnovshchina in Ukraine. In 1922, the 4th World Congress of the Communist International took up the policy of the united front, urging Communists to work with rank and file social democrats while remaining critical of their party leaders, whom they criticised for betraying the working class by supporting the war efforts of their respective capitalist classes. For their part, the social democrats pointed to the dislocation and chaos caused by revolution and later the growing authoritarianism of the Communist parties after they achieved power. When the Communist Party of Great Britain applied to affiliate with the Labour Party in 1920, it was turned down. On seeing the Soviet Union's growing coercive power in 1923, a dying Lenin stated that Russia had reverted to a "bourgeois tsarist machine ... barely varnished with socialism." After Lenin's death in January 1924, the Communist Party of the Soviet Union, increasingly falling under the control of Joseph Stalin, rejected the theory that socialism could not be built solely in the Soviet Union in favour of the concept of socialism in one country.
=== Thyroid disease === Fetal maternal microchimerism may be related to autoimmune thyroid diseases. There have been reports of fetal cells in the lining of the blood and thyroid glands of patients with autoimmune thyroid disease. These cells could become activated after delivery of the baby after immune suppression in the mother is lost, suggesting a role of fetal cells in the pathogenesis of such diseases. Two types of thyroid disease, Hashimoto's thyroiditis (HT) and Graves' disease (GD), show similarities to graft vs host disease which occurs after hematopoietic stem cell transplants. Fetal cells colonize maternal tissues like the thyroid gland and are able to survive many years postpartum. These fetal microchimeric cells in the thyroid show up in the blood of women affected by thyroid diseases.
And while many studies have discussed and illustrated the immunosuppressive effects of CGB on T-cell proliferation, others have shown a contradictory trophic effect, further deepening the notion of an immunosuppressive pregnancy environment brought on by CGB. CGB encourages trophoblast invasion and interstitial theca cell proliferation through the overmodulation of extracellular-regulated kinase (ERK) and AKT signals, and the instigation of leptin production by CGB requires a dialogue between cAMP and p38 signaling pathways in the syncytiotrophoblast. It has also been shown that CGB has a positive impact on the proliferation of CD4+25+ T cells and that it attracts these cells to the endometrium in early pregnancy. Immune cells located at the implantation site actively contribute to embryo implantation. And so, through the modulation of inflammatory-promoting Th1 cells and anti-inflammatory Th2 cells, CGB plays a critically important role in the successful implantation of the embryo to the endometrial wall.
Sources: en.wikipedia.org
=== Storage === Semen can be stored in diluents such as the Illini Variable Temperature (IVT) diluent, which have been reported to be able to preserve high fertility of semen for over seven days. The IVT diluent is composed of several salts, sugars and antibacterial agents and gassed with CO2. Semen cryopreservation can be used for far longer storage durations. For human sperm, the longest reported successful storage with this method is 21 years.
"Machine Cleans Blood While You Wait"—1950 article on early use of dialysis machine at Bellevue Hospital New York City—an example of how complex and large early dialysis machines were Home Dialysis Museum—History and pictures of dialysis machines through time Introduction to Dialysis Machines—Tutorial describing the main subfunctions of dialysis systems. "First Nations man conducts own dialysis treatments to avoid move to the city"—CBC News (November 30, 2016)
== Foreign policy issues == Aden was located in a vital strategic location, on the main shipping routes between the Red Sea and the Indian Ocean. During the days of Empire, the value of the port was in providing key communications and bunkering facility between the Suez Canal and India. Even after the independence of India, Aden continued to be regarded as a vital asset in Britain's worldwide defence network. By 1958, Aden was the second-busiest harbour in the world, after New York City, described as having importance that "cannot be overestimated" while protecting British oil interests in the region. The Little Aden oil refinery was essential to the economy of Aden as it could process 5 million tons of crude oil annually and formed one of the Colony's only exports. The safety of this refinery was a clear priority for the government of Aden. "As a temporary expedient, the Aden base has the merits of a stabiliser at a moment when the Yemen is split by civil war, when the Saudi Royal house has not yet made itself a name for consistent rule, when the Iraqi and Syrian governments are prone to overnight revolutions and when Egypt's relations with both of them are uncertain". For much of Aden's later history, relations with the United Arab Republic (UAR) were of primary consideration. Its 1958 establishment was described as having "increased the importance of Aden as a British military base in this troubled corner of the world". However even before the formation of the UAR, Arab nationalism had been growing in the awareness of Adeni's.
Recent studies found a clear association between long-term oral (or intravenous) anticoagulant treatment (OAC) and reduced bone quality due to reduction of active osteocalcin. OAC might lead to an increased incidence of fractures, reduced bone mineral density or content, osteopenia, and increased serum levels of undercarboxylated osteocalcin. Furthermore, OAC is often linked to undesired soft-tissue calcification in both children and adults. This process has been shown to be dependent upon the action of K vitamins. Vitamin K deficiency results in undercarboxylation of MGP. Also in humans on OAC treatment, two-fold more arterial calcification was found as compared to patients not receiving vitamin K antagonists. Among consequences of anticoagulant treatment: increased aortic wall stiffness, coronary insufficiency, ischemia, and even heart failure. Arterial calcification might also contribute to systolic hypertension and ventricular hypertrophy. Anticoagulant therapy is usually instituted to avoid life-threatening diseases, and high vitamin K intake interferes with anticoagulant effects. Patients on warfarin (Coumadin) or being treated with other vitamin K antagonists are therefore advised not to consume diets rich in K vitamins.
== Applications == Photoactivated peptides have shown potential for various applications, including cancer therapy, other light-controlled drugs, and as tools to probe molecular interactions in intact cells and whole organisms. Initial studies demonstrated that these peptides could effectively kill B-cell lymphoma cancer cells. Specifically, a synthetic short peptide was alkylated with azobenzene crosslinkers and used to photo-stimulate mitochondrial membrane depolarization and cytochrome c release in permeabilized cells, initiating the intrinsic apoptosis pathway. Analogs of Gramicidin S containing a diarylethene fragment have also been developed, exhibiting a clear, reversible change in antimicrobial activity. In their inactive, UV-inducible photoform, these analogs are harmless to bacteria cells; however, upon activation with visible (amber) light, they become bactericidal. Additionally, a photoswitchable analogue of the orexin-B peptide has been developed, enabling control of orexin receptors with light in vivo at nanomolar concentrations. Photoswitchable peptides have been designed to inhibit protein-protein interactions in a light-controlled manner. They have been successfully applied to inhibit clathrin-mediated endocytosis in mammalian cells and in yeast. This same design principle has been applied to inhibit protein-protein interactions involved in cancer and can potentially be used for any interaction mediated by a helical motif.
Sources: en.wikipedia.org
Mahathir criticised the awarding of import permits for foreign cars, which he claimed were causing Proton's domestic sales to suffer, and attacked Abdullah for cancelling the construction of a second causeway between Malaysia and Singapore. Mahathir complained that his views were not getting sufficient airing by the Malaysian press. In response, he began writing a column for Malaysiakini and starting his own blog. He unsuccessfully sought election from his local party division to be a delegate to UMNO's general assembly in 2006, where he planned to initiate a challenge to Abdullah's leadership. Mahathir had previously missed the UMNO General Assembly twice since 2006 for health reasons. After the 2008 election, in which UMNO lost its two-thirds majority in parliament, Mahathir resigned from the party. When Abdullah was replaced by his deputy Najib Razak in 2009, Mahathir re-joined the party and urged all former members to follow his move. Before the 2013 general election, Mahathir promised to keep the government in check and ensure it fulfilled its manifesto promises, vowing to protest and fight against it if it failed.
=== Other honours === Crick was elected a Fellow of the Royal Society (FRS) in 1959, a Fellow of the International Academy of Humanism, and a Fellow of CSICOP. In 1987, Crick received the Golden Plate Award of the US Academy of Achievement. The inscription on the helices of a DNA sculpture (which was donated by James Watson) outside Thirkill Court, Clare College, Cambridge, reads: "The structure of DNA was discovered in 1953 by Francis Crick and James Watson while Watson lived here at Clare." and on the base: "The double helix model was supported by the work of Rosalind Franklin and Maurice Wilkins." Another sculpture entitled Discovery, by artist Lucy Glendinning, was installed on 13 December 2005 in Abington Street, Northampton. According to the late Lynn Wilson, chairman of the Wilson Foundation, "The sculpture celebrates the life of a world class scientist who must surely be considered the greatest Northamptonian of all time — by discovering DNA he unlocked the whole future of genetics and the alphabet of life." Westminster City Council unveiled a green plaque to Francis Crick on the front façade of 56 St George's Square, Pimlico, London SW1 on 20 June 2007; Crick lived in the first floor flat, together with Robert Dougall of BBC radio and later TV fame, a former Royal Navy associate. At a meeting of the executive council of the Committee for Skeptical Inquiry (CSI) (formerly CSICOP) in Denver, Colorado in April 2011, Crick was selected for inclusion in CSI's Pantheon of Skeptics.
All I can personally do, at least for now, is stuff like this." Laidlaw also contributed to Valve's puzzle series Portal, which is set in the Half-Life universe. He disliked the crossover, feeling it "made both universes smaller", and said later: "I just had to react as gracefully as I could to the fact that it was going there without me. It didn't make any sense except from a resource-restricted point of view."
== Requirements == The formal requirements to begin gender-affirming hormone therapy vary widely depending on geographic location and specific institution. Gender-affirming hormones can be prescribed by a wide range of medical providers including, but not limited to, primary care physicians, endocrinologists, and gynecologists. Requirements to be prescribed these hormones generally include a minimum age. According to the Endocrine Society, there has been little research on taking cross-sex hormones before the age of about 14. Historically, many health centers required a psychiatric evaluation and/or a letter from a therapist before beginning hormone replacement therapy. Many centers now use an informed consent model that does not require any routine formal psychiatric evaluation, but rather focuses on reducing barriers to care while ensuring a person can understand the risks and benefits of treatment. Some LGBT health organizations, including Chicago's Howard Brown Health Center and Planned Parenthood, advocate for this type of informed consent model. The World Professional Association for Transgender Health (WPATH) Standards of Care, 7th edition, note that both of these approaches to care are appropriate.
== History == Chloroeremomycin was discovered by Eli Lilly in the 1980s. In the 1990s, researchers at Eli Lilly developed biphenyl-chloroeremomycin, now known as oritavancin, as a functionalized derivative of chloroeremomycin to combat rising antibacterial resistance to vancomycin. The chloroeremomycin gene cluster was sequenced by van Wageningen et al in 1998. After the publication, many groups expressed the genes and conducted experiments to understand how chloroeremomycin and, by extension, vancomycin are biosynthesized.
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 peptide designed as an analog of alpha-melanocyte-stimulating hormone. It acts on melanocortin receptors and is best known from research into pigmentation. It is not an approved pharmaceutical product.