This is a working overview of cyclic heptapeptide, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2025-07-26 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 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.
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.
| 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 |
does not tell us whether or not the spreading will speed up or slow down in the latter stages when the fraction of susceptible people in the community has dropped significantly after recovery or vaccination.
== History == Harith Rajagopalan, MD, PhD, and Jay Caplan established Fractyl Health, initially named Fractyl Laboratories, in 2010. The company's Revita device gained CE marking in April 2016 and became commercially available in the UK in January 2020. In April 2021, the US Food and Drug Administration (FDA) gave Revita breakthrough device designation to treat type 2 diabetes. The company changed its name to Fractyl Health in June 2021. In April 2022, the FDA approved an investigational device exemption trial for Revita. It became available commercially in Germany in early 2023. The FDA issued additional breakthrough device designation to Revita in July 2024 for weight maintenance in certain people with type 2 diabetes or obesity. Fractyl had an initial public offering on the Nasdaq in February 2024. As of February 2025, the company's REMAIN-1 study is evaluating Revita for patients with obesity to support weight maintenance after use of a GLP-1 drug. In January 2025, Fractyl announced it would focus research for Revita on obesity and people on GLP-1s, citing rising demand driven by the popularity of GLP-1s. The company also laid off some employees focused on type 2 diabetes treatment.
It is hypothesized to function by changing its lowest luminescent state from n–π* to π–π* when coordinating to a metal. When the Dansyl group DNS binds to a metal, it loses a sulfonamide hydrogen, causing fluorescence quenching via a PET or reverse PET mechanism in which an electron is transferred either to or from the metal that is bound. Small molecule sensors for zinc have been reported. One example is "ZX1", a compound comprising a dipicolylamine (DPA) Zinc binding subunit that has greater affinity for Zinc than other species found in solution such as Ca and Mg. GFZnP OMe is an alternate, GFP-based fluorescent Zn2+ sensor is published for two-photon microscopy and related biological and microscop application. It composed of an 8-methoxyquinoline scaffold. It has excellent photophysical characteristics including a 37-fold fluorescence enhancement with l(ex) = 440 nm and l(em) = 505 nm. The two-photon cross-section is as high as 73 GM at 880 nm. GFZnP BIPY features a 2,2'-bipyridine chelator moiety. It was effective at physiologically relevant pH-range and excellent photophysical characteristics are reported, including a 53-fold fluorescence enhancement with excitation and emission maxima at 422 nm and 492 nm, respectively. High two-photon cross-section of 3.0 GM at 840 nm as well as excellent metal ion selectivity are reported. In vitro experiments on HEK 293 cell culture were carried out using two-photon microscopy demonstrating the applicability.
In May 1972, President Richard M. Nixon and Soviet Premier Leonid Brezhnev negotiated an easing of relations known as détente, creating a temporary "thaw" in the Cold War. The two nations planned a joint mission to dock the last US Apollo craft with a Soyuz, known as the Apollo-Soyuz Test Project (ASTP). To prepare, the US designed a docking module for the Apollo that was compatible with the Soviet docking system, which allowed any of their craft to dock with any other (e.g. Soyuz-to-Soyuz as well as Soyuz-to-Salyut). The module was also necessary as an airlock to allow the men to visit each other's craft, which had incompatible cabin atmospheres. The USSR used the Soyuz 16 mission in December 1974 to test modifications of the Soyuz atmosphere and the docking adapter to prepare for ASTP. The joint mission began when Soyuz 19 was first launched on July 15, 1975, at 12:20 UTC, and the Apollo craft was launched with the docking module six and a half hours later. The two craft rendezvoused and docked on July 17 at 16:19 UTC. The three astronauts conducted joint experiments with the two cosmonauts, and the crew shook hands, exchanged gifts, and visited each other's craft.
Sources: en.wikipedia.org
=== Mutations === Mutations in myostatin do more than just affect the amount of muscle mass an organism can produce; they also have variable effects on other phenotypes for different species. For example, a Belgian Blue bovine with a mutation that inhibits myostatin production will exhibit a dramatic increase in muscle mass but will also lead to dystocia. Other species with myostatin deficiency mutation such as humans or Whippet dogs do not get obstructed labor.
Officials from the Panamanian military were frequently given courses at the school free of charge. Noriega was proud of his relationship with the school, and wore its crest on his military uniform for the rest of his career.
X-linked chronic granulomatous disease (CGD) autosomal recessive cytochrome b-negative CGD autosomal recessive cytochrome b-positive CGD type I autosomal recessive cytochrome b-positive CGD type II atypical granulomatous disease
=== PlayStation 3 version === While the Windows and Xbox 360 versions of The Orange Box were developed and published by Valve, the development of the PlayStation 3 port was outsourced to the Electronic Arts studio EA UK. In an interview with Edge magazine before the game's release, Valve co-founder Gabe Newell commented, "I think the people who have The Orange Box on the PS3 are going to be happy with their game experience. We've done the PC and 360 versions here and EA has a team doing the PS3 version – and they'll make the PS3 version a good product; EA got the job done in putting a lot of people with PS3 experience on the project. But I think it's harder to get it to the same standard as the 360 and PC versions". Despite this, he noted that Valve will probably handle PlayStation 3 versions of its products in the future.
=== Mass spectrometry === MALDI-TOF (Matrix-assisted laser desorption/ionization - time of flight) is a specific type of mass spectrometry that is able to identify microorganisms. A pure culture is isolated and spread directly on a stainless steel or disposable target. The cells are lysed and overlaid with a matrix, which forms protein complexes with the bacterial proteins. The MALDI fires a laser and ionizes the protein complexes, which break off and travel up the vacuum where they are detected based on mass and charge. The resulting protein spectra is compared to a known database of previously catalogued organisms, resulting in rapid diagnosis of microorganisms. Recent studies have suggested that these tests can become specific enough to diagnose down to the sub-species level by observing novel biomarkers. The MALDI-TOF identification method requires pure cultures that are less than 72 hours old. This places the organism in log phase with an abundance of ribosomal proteins, which are the most common proteins detected in the spectra. Identifications with this technology can also be impacted if the culture is exposed to cold temperatures, as this would change the typical protein distribution.
Sources: en.wikipedia.org
== Clinical significance == Gastroesophageal reflux disease (GERD) is a common disorder that occurs when stomach acid repeatedly flows back into the esophagus, this backwash of acid (reflux) also known as heartburn can irritate the lining of the esophagus. Most people are able to manage the discomfort of GERD with lifestyle changes and medications, notably proton pump inhibitors, and H2 blockers. Antacids may also be used to neutralise gastric acid. Sometimes, surgery may be needed to ease symptoms. Chronic inflammation of the gastric mucosa can lead to atrophic gastritis resulting in a decreased secretion of gastric acid, and consequent digestive problems. In hypochlorhydria and achlorhydria, gastric acid is either low or absent, respectively. This can potentially lead to less protection against ingested pathogens such as Vibrio or Helicobacter bacteria. In Zollinger–Ellison syndrome gastrin levels are increased, leading to excess gastric acid production, which can cause gastric ulcers. Hypercalcemia also increases gastrin and gastric acid and can cause ulcers. In diseases featuring excess vomiting, hypochloremic metabolic alkalosis (decreased blood acidity by H+ and chlorine depletion) may develop.
While no other government actively supported the Boer cause, individuals from several countries volunteered and formed Foreign Volunteer Units. These primarily came from Europe, particularly the Netherlands, Germany and Sweden-Norway. Other countries such as France, Italy, Ireland (then part of the United Kingdom), and restive areas of the Russian Empire, including Congress Poland and Georgia, also formed smaller volunteer corps. Finns fought in the Scandinavian Corps. Two volunteers, George Henri Anne-Marie Victor de Villebois-Mareuil of France and Yevgeny Maximov of Russia, became veggeneraals (fighting generals) of the South African Republic.
Professional divers are screened for risk factors during initial and periodical medical examination for fitness to dive. In most cases recreational divers are not medically screened, but are required to provide a medical statement before acceptance for training in which the most common and easy to identify risk factors must be declared. If these factors are declared, the diver may be required to be examined by a medical practitioner, and may be disqualified from diving if the conditions indicate. Asthma, Marfan syndrome, and COPD pose a very high risk of pneumothorax. In some countries these may be considered absolute contraindications, while in others the severity may be taken into consideration. Asthmatics with a mild and well controlled condition may be permitted to dive under restricted circumstances.
Anise tea, made from either the seeds or the leaves Asiatic penny-wort leaf, in South Asia and Southeast Asia Artichoke tea Commiphora gileadensis tea, in the Hijaz region of western Arabia. Bael fruit tea Barley tea, East Asian drink with roasted barley Bee balm Boldo, used in South America Burdock; the seeds, leaves, and roots have been used Butterfly pea flower tea (from Clitoria ternatea), also called "Blue tea" since it produces a blue infusion Caraway, tea made from the seeds Catnip, tea used as a relaxant, sedative, and to calm Chamomile, both Matricaria chamomilla and Chamaemelum nobile can be used Che dang, bitter tea made from Ilex causue leaves Chinese knotweed tea Chrysanthemum tea, made from dried flowers Cinnamon tea Clover tea, made from the blossoms Cerasse, bitter Jamaican herb Citrus peel, including bergamot, lemon and orange peel Dandelion coffee, which does not contain caffeine despite the name Dill tea Dried lime tea, made from dried limes common in western Asia Echinacea tea Elderberry European mistletoe (Viscum album), (steep in cold water for 2–6 hours) Essiac tea, blended herbal tea Fennel Gentian Ginger tea, made from the ginger root, can be made into herbal tea, known in the Philippines as salabat Ginkgo biloba Ginseng tea, a common tea in China and Korea, commonly used as a stimulant and as a caffeine substitute Goji berry tea Hawthorn Hibiscus tea (often blended with rose hip), a common tea in the Middle East or Asia Honeybush, similar to rooibos and grows in a nearby area of South Africa, but tastes slightly sweeter.
The 1987 report of National Cholesterol Education Program, Adult Treatment Panels suggests the total blood cholesterol level should be: < 200 mg/dL normal blood cholesterol, 200–239 mg/dL borderline-high, > 240 mg/dL high cholesterol. The American Heart Association provides a similar set of guidelines for total (fasting) blood cholesterol levels and risk for heart disease: Statins are effective in lowering LDL cholesterol and widely used for primary prevention in people at high risk of cardiovascular disease, as well as in secondary prevention for those who have developed cardiovascular disease. The average global mean total cholesterol for humans has remained at about 4.6 mmol/L (178 mg/dL) for men and women, both crude and age standardized, for nearly 40 years from 1980 to 2018, with some regional variations and reduction of total cholesterol in Western nations. More current testing methods determine LDL ("bad") and HDL ("good") cholesterol separately, allowing cholesterol analysis to be more nuanced. The desirable LDL level is considered to be less than 100 mg/dL (2.6 mmol/L).
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 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.