Everything below concerns cyclic heptapeptide. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2026-05-30. Numbers and descriptions here follow the published literature rather than marketing material.
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 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.
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.
| 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 |
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.
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.
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.
== Synthesis == The first reported syntheses of fluoroalanine in 1976 involved treating cysteine with difluorine under an inert atmosphere. This produced a mixture of 3-fluoroalanine and 3,3-difluoroalanine, with the former as the major component.
=== Analogs === Some analog substances have been created which mimic caffeine's properties with either function or structure or both. Of the latter group are the xanthines DMPX and 8-chlorotheophylline, which is an ingredient in dramamine. Members of a class of nitrogen substituted xanthines are often proposed as potential alternatives to caffeine. Many other xanthine analogues constituting the adenosine receptor antagonist class have also been elucidated. Some other caffeine analogs:
== Sources == Schmitt, Michael; Mayerhöfer, Thomas; Popp, Jürgen; Kleppe, Ingo; Weisshartannée, Klaus (2013). Handbook of Biophotonics, Chap.3 Light–Matter Interaction. Wiley. doi:10.1002/9783527643981.bphot003. ISBN 978-3-527-64398-1. S2CID 93908151. Pavone, Francesco S.; Campagnola, Paul J. (2016). Second Harmonic Generation Imaging, 2nd edition. CRC Taylor&Francis. ISBN 978-1-4398-4914-9. Campagnola, Paul J.; Clark, Heather A.; Mohler, William A.; Lewis, Aaron; Loew, Leslie M. (2001). "Second harmonic imaging microscopy of living cells" (PDF). Journal of Biomedical Optics. 6 (3): 277–286. Bibcode:2001JBO.....6..277C. doi:10.1117/1.1383294. hdl:2047/d20000323. PMID 11516317. S2CID 2376695. Campagnola, Paul J.; Loew, Leslie M (2003). "Second-harmonic imaging microscopy for visualizing biomolecular arrays in cells, tissues and organisms" (PDF). Nature Biotechnology. 21 (11): 1356–1360. doi:10.1038/nbt894. PMID 14595363. S2CID 18701570. Archived from the original (PDF) on 2016-03-04. Stoller, P.; Reiser, K.M.; Celliers, P.M.; Rubenchik, A.M. (2002). "Polarization-modulated second harmonic generation in collagen". Biophys. J. 82 (6): 3330–3342. Bibcode:2002BpJ....82.3330S. doi:10.1016/s0006-3495(02)75673-7. PMC 1302120. PMID 12023255. Han, M.; Giese, G.; Bille, J. F. (2005). "Second harmonic generation imaging of collagen fibrils in cornea and sclera". Opt. Express. 13 (15): 5791–5797. Bibcode:2005OExpr..13.5791H. doi:10.1364/opex.13.005791. PMID 19498583. König, Karsten (2018). Multiphoton Microscopy and Fluorescence Lifetime Imaging - Applications in Biology and Medicine.
Reticular fibers, reticular fibres or reticulin is a type of fiber in connective tissue composed of type III collagen secreted by reticular cells. They are mainly composed of reticulin protein and form a network or mesh. Reticular fibers crosslink to form a fine meshwork (reticulin). This network acts as a supporting mesh in soft tissues such as liver, bone marrow, and the tissues and organs of the lymphatic system.
Sources: en.wikipedia.org
Rattlesnakes are native to the Americas from southern Canada to central Argentina, with the majority of species inhabiting arid regions. The large majority of species live in the American Southwest and Mexico. Four species may be found east of the Mississippi River, and two in South America. In the United States, the state with the most types of rattlesnakes is Arizona, with 13. Rattlesnakes are found in almost every habitat type capable of supporting terrestrial ectothermic vertebrates, but individual species may have extremely specific habitat requirements, living where certain plant associations occur or within a narrow range of elevations. Most species live near open, rocky areas. Rocks offer them cover from predators, plentiful prey (e.g. rodents, lizards, insects, etc. that live amidst the rocks), and open basking areas. However, rattlesnakes can also be found in a wide variety of other habitats, including prairies, marshes, deserts, and forests. Rattlesnakes prefer a temperature range between 80 and 90 °F (27 and 32 °C), but can survive temperatures below freezing, recovering from brief exposure to temperatures as low as 4 °F (−16 °C), and surviving for several days in temperatures as low as 37 °F (3 °C). The most probable ancestral area of rattlesnakes is the Sierra Madre Occidental region in Mexico. The most probable vegetation or habitat of the ancestral area appears to be pine-oak forests.
Soy sauce allergy not caused by soy or wheat allergy is rare. Most varieties of soy sauce contain wheat, to which some people have a medical intolerance. However, protein hydrolysis (fermentation or industrial) breaks down gluten, so some soy sauces may end up tolerable to gluten-intolerant individuals with no detectable gluten left. Japanese tamari soy sauce is traditionally wheat-free, and some tamari available commercially today is wheat- and gluten-free. Acid-hydrolyzed vegetable protein is non-allergenic due to the completeness of protein breakdown.
=== Fuselage === Circular-section structure of frames and stringers with a continuous main deck and lower decks fore and aft of the centre section. Rectangular windows in most interframe bays, eight ICAO Type 1a passenger doors on the main deck and three more on the lower deck portside; two freight hold doors and a galley supply door on the lower deck starboard. The main deck houses the flightdeck, two wardrobes, eight toilets, two pantries and a three-section passenger cabin. The lower deck houses three entry vestibules/luggage stores with hydraulic boarding stairs to ground level and fixed stairs to the main deck, a midships galley linked with the main deck by an electric lift, two freight holds (fore and aft of the passenger facilities), an avionics bay and two technical bays. The entire accommodation is pressurised and air-conditioned with "earphones for music or on-board cinema."
The topic of IAQ has become popular due to the greater awareness of health problems caused by mold and triggers to asthma and allergies. In the US, the Environmental Protection Agency (EPA) has developed an "IAQ Tools for Schools" program to help improve the indoor environmental conditions in educational institutions. The National Institute for Occupational Safety and Health conducts Health Hazard Evaluations (HHEs) in workplaces at the request of employees, authorized representative of employees, or employers, to determine whether any substance normally found in the place of employment has potentially toxic effects, including indoor air quality. A variety of scientists work in the field of indoor air quality, including chemists, physicists, mechanical engineers, biologists, bacteriologists, epidemiologists, and computer scientists. Some of these professionals are certified by organizations such as the American Industrial Hygiene Association, the American Indoor Air Quality Council and the Indoor Environmental Air Quality Council. In the UK, under the Department for Environment Food and Rural Affairs, the Air Quality Expert Group considers current knowledge on indoor air quality and provides advice to government and devolved administration ministers. At the international level, the International Society of Indoor Air Quality and Climate (ISIAQ), formed in 1991, organizes two major conferences, the Indoor Air and the Healthy Buildings series.
In 2014, Guinness released Guinness Blonde, a lager brewed in Latrobe, Pennsylvania using a combination of Guinness yeast and American ingredients. When Guinness opened their new brewery in Baltimore, Maryland in August 2018 they recreated "Blonde" to "Baltimore Blonde" by adjusting the grain mixture and adding Citra for a citrus flavour and removed the Mosaic hops. Guinness released a lager in 2015 called Hop House 13. It was withdrawn from sale in the UK in May 2021, following poor sales, but remains on sale in Ireland. In 2020, Guinness announced the introduction of a zero alcohol canned stout, Guinness 0.0. It was withdrawn from sale almost immediately after launch, due to contamination. It was relaunched in 2021 starting with pubs in mid July with cans following in late August. In September 2021, Guinness Nitrosurge was released in pint sized cans which contain no widget. Similar to the Surger, nitrogen is activated using ultrasonic frequencies. Nitrosurge uses a special device attached to the top of the can which activates the nitrogen as it is being poured.
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.
No. Melanotan-2 is manufactured synthetically. The naturally occurring peptide in the same family is alpha-melanocyte-stimulating hormone, which the body produces as part of normal endocrine and neural signalling.