This is a working overview of afamelanotide, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-03-02. Anything still debated is marked as such rather than presented as settled.
Published research on the compound remains limited. Much of the human data comes from small, early-stage studies rather than large controlled trials, and several questions about effects and variability between individuals remain open. Investigators have examined receptor activity, pigment pathways, and related physiological responses in laboratory and animal models. Findings from those models do not automatically translate to human outcomes. Reviews frequently note the scarcity of rigorous clinical evidence and call for better-characterized study material.
Because the substance circulates mainly through informal markets, verification is a recurring theme in technical discussion. Independent analyses have found that labeled content and actual content can diverge, and that purity varies between samples. Analytical laboratories use reversed-phase chromatography to separate components and mass spectrometry to confirm identity. Isotope-labeled internal standards improve quantification in complex matrices. Such methods describe what a sample contains but say nothing about its sterility, lawful status, or suitability for any use. Open questions remain about how consistently testing is applied across the supply chain.
Regulatory treatment of this peptide varies by country. It holds no marketing authorization as a medicine in the United States, the European Union, or most other jurisdictions. Some countries classify products containing it as prescription-only or unlicensed medicines, which restricts lawful supply. Authorities have issued public notices warning that unregulated products may contain undeclared or incorrect ingredients. The molecule also appears on prohibited lists for competitive sport. These measures address supply oversight rather than any approved therapeutic role.
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.
| Property | Value | Notes |
|---|---|---|
| Regulatory status | Not approved as a medicine | No marketing authorization in major jurisdictions |
| Scheduling example | Prescription-only supply in some countries | Handled as an unlicensed medicine where restricted |
| Sports classification | Prohibited peptide | Appears on anti-doping prohibited lists |
| Reported presentation | Lyophilized vial | Nominal content varies between vendors |
| Detection approach | Liquid chromatography–tandem mass spectrometry | Used in anti-doping and forensic testing |
Identification in laboratories relies on reversed-phase liquid chromatography coupled with tandem mass spectrometry, with product-ion spectra compared against a certified reference standard. High-resolution mass spectrometry supplies accurate mass confirmation, and peptide mapping after enzymatic digestion separates melanotan II from closely related analogues. Quantitation of seized material is complicated by unknown counter-ions and residual trifluoroacetate left from purification. Immunoassays raised against alpha-melanocyte-stimulating hormone can cross-react, so chromatographic confirmation is normally required. Urinary detection windows are short, and reported limits of detection differ substantially between laboratories.
Melanotan II holds no marketing authorisation from the Food and Drug Administration, the European Medicines Agency, the UK Medicines and Healthcare products Regulatory Agency or Australia's Therapeutic Goods Administration. Products sold under that name are treated as unapproved new drugs, and their sale or import is prohibited in several jurisdictions. Other countries classify the peptide as a prescription-only medicine or place it among controlled substances, so the legal position changes with the destination market. No pharmacopoeial monograph supplies an official specification, because the material is not a licensed pharmaceutical. Consequently, products offered online are not manufactured to a shared public standard.
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 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.
Verification of a purchased sample requires documentation linking a batch to a certificate of analysis, and that document should be read for the methods used rather than the headline purity figure. A single chromatographic percentage does not establish identity. Independent laboratories can perform identity and content assays, but no such test establishes that a product is suitable for human use. Claims about efficacy rest largely on small, early studies rather than on replicated controlled trials, and that gap remains open.
Identity testing for a cyclic peptide of this size usually relies on reversed-phase high-performance liquid chromatography coupled to mass spectrometry. The mass spectrum confirms molecular weight, while the chromatographic trace indicates the proportion of related impurities. Tandem mass spectrometry can provide sequence-level information when fragmentation data are compared against a reference standard. Nuclear magnetic resonance is sometimes used to confirm the lactam bridge, although it requires more material and greater operator expertise than routine chromatographic methods.
Lyophilised peptide powder is comparatively stable when kept dry, cold and protected from light. Once dissolved, the molecule is exposed to hydrolysis, oxidation and microbial growth, and degradation accelerates at higher temperatures and in alkaline solution. Repeated freeze-thaw cycles concentrate solutes and promote aggregation. Handling guidance for research peptides commonly clusters around freezer temperatures for powder and short refrigerated use for reconstituted solutions, with pH control and sterile technique applied throughout.
Episcleritis is a benign, self-limiting inflammatory disease affecting part of the eye called the episclera. The episclera is a thin layer of tissue that lies between the conjunctiva and the connective tissue layer that forms the white of the eye (sclera). Episcleritis is a common condition, and is characterized by the abrupt onset of painless eye redness. There are two types of episcleritis, nodular and simple. Nodular episcleritis lesions have raised surface. Simple episcleritis lesions are flat. There are two subtypes. In diffuse simple episcleritis, inflammation is generalized. In sectoral simple episcleritis, the inflammation is restricted to one region. Most cases of episcleritis have no identifiable cause, although about a third of cases are associated with various systemic diseases. Often people with episcleritis experience it recurrently. Treatment focuses on decreasing discomfort, and includes lubricating eye drops. More severe cases may be treated with topical corticosteroids or oral anti-inflammatory medications (NSAIDs).
The black mamba (Dendroaspis polylepis) is a large and highly venomous snake species native to much of Sub-Saharan Africa. It is the second-longest venomous snake species in the world and is the fastest-moving land snake, capable of moving at 4.3 to 5.4 metres per second (16–20 km/h, 10–12 mph). The black mamba is the most feared snake in Africa because of its size, aggression, venom toxicity and speed of onset of symptoms following envenomation, and is classified as a snake of medical importance by the World Health Organization. This species of snake shows tenacity, fearlessness, and aggression when cornered or threatened, during breeding season, or when defending its territory. They are also known to have up to a 100% rate of envenomation; the probability of dry bites (no venom injected) in black mamba strikes is almost non-existent. The venom of the black mamba is a protein of low molecular weight and as a result is able to spread rapidly within the bitten tissue. The venom is the most rapid-acting venom of any snake species and consists mainly of highly potent neurotoxins; it also contains cardiotoxins, fasciculins, and calciseptine. Based on the median lethal dose (LD50) values in mice, the black mamba LD50 from all published sources is as follows:
Montclair-Boonton Line to Montclair State University station, with connecting service west to Hackettstown. Morris and Essex Lines, consisting of the Morristown Line to Dover via Morristown and the Gladstone Branch to Gladstone. Northeast Corridor Line to Trenton North Jersey Coast Line to Long Branch and Bay Head Raritan Valley Line to Raritan and High Bridge NJT normally uses tracks 1 to 4 exclusively, as these four tracks end at bumper blocks to their east. NJT shares tracks 5 through 12 with Amtrak, and occasionally uses tracks 13 to 16, which are shared with Amtrak and the LIRR.
Compounds containing one or more elements which can exist in a variety of charge/oxidation states will have a stoichiometry that depends on which oxidation states are present, to ensure overall neutrality. This can be indicated in the name by specifying either the oxidation state of the elements present, or the charge on the ions. Because of the risk of ambiguity in allocating oxidation states, IUPAC prefers direct indication of the ionic charge numbers. These are written as an arabic integer followed by the sign (... , 2−, 1−, 1+, 2+, ...) in parentheses directly after the name of the cation (without a space separating them). For example, FeSO4 is named iron(2+) sulfate (with the 2+ charge on the Fe2+ ions balancing the 2− charge on the sulfate ion), whereas Fe2(SO4)3 is named iron(3+) sulfate (because the two iron ions in each formula unit each have a charge of 3+, to balance the 2− on each of the three sulfate ions). Stock nomenclature, still in common use, writes the oxidation number in Roman numerals (... , −II, −I, 0, I, II, ...). So the examples given above would be named iron(II) sulfate and iron(III) sulfate respectively. For simple ions the ionic charge and the oxidation number are identical, but for polyatomic ions they often differ. For example, the uranyl(2+) ion, UO2+2, has uranium in an oxidation state of +6, so would be called a dioxouranium(VI) ion in Stock nomenclature.
=== Reconstituted Transitional National Legislative Assembly (2021–present) === As a result of a 2018 peace agreement that came into effect in February 2020, a Reconstituted Transitional National Legislative Assembly with 550 members was nominated in May 2021. The membership is as follows:
Sources: en.wikipedia.org
Copper-free click chemistry is a bioorthogonal reaction first developed by Carolyn Bertozzi as an activated variant of an azide alkyne Huisgen cycloaddition, based on the work by Karl Barry Sharpless et al. Unlike CuAAC, Cu-free click chemistry has been modified to be bioorthogonal by eliminating a cytotoxic copper catalyst, allowing reaction to proceed quickly and without live cell toxicity. Instead of copper, the reaction is a strain-promoted alkyne-azide cycloaddition (SPAAC). It was developed as a faster alternative to the Staudinger ligation, with the first generations reacting over sixty times faster. The bioorthogonality of the reaction has allowed the Cu-free click reaction to be applied within cultured cells, live zebrafish, and mice.
While some birds are essentially territorial or live in small family groups, other birds may form large flocks. The principal benefits of flocking are safety in numbers and increased foraging efficiency. Defence against predators is particularly important in closed habitats like forests, where ambush predation is common and multiple eyes can provide a valuable early warning system. This has led to the development of many mixed-species feeding flocks, which are usually composed of small numbers of many species; these flocks provide safety in numbers but increase potential competition for resources. Costs of flocking include bullying of socially subordinate birds by more dominant birds and the reduction of feeding efficiency in certain cases. Some species have a mixed system with breeding pairs maintaining territories, while unmated or young birds live in flocks where they secure mates prior to finding territories. Birds sometimes also form associations with non-avian species. Plunge-diving seabirds associate with dolphins and tuna, which push shoaling fish towards the surface. Some species of hornbills have a mutualistic relationship with dwarf mongooses, in which they forage together and warn each other of nearby birds of prey and other predators.
== Functions and binding properties == Such a broad pattern in gene expression over such a wide range of sensory and non-sensory fluids or tissues is in strong agreement with a very general basic function for this gene family, i.e. in relation with lipid transport and metabolism. A role of CSPs in general immunity, insecticide resistance and xenobiotic degradation has been recently brought up by Xuan et al. (2015), who showed a drastic and remarkable up-regulation of CSP genes in many various tissues over exposure to abamectin insecticide molecule [32]. Increased load of CSPs (pherokines) in fly hemolymph is observed after microbial or viral infection [33]. The particular role of CSP proteins in lipid transport in relation with insecticide resistance has been brought up by Liu et al. (2016) in whiteflies [34]. Liu et al. showed insecticide-mediated up regulation and interaction of the protein with C18-lipid (linoleic acid), suggesting a metabolic role of CSP in insect defense rather than olfaction or chemical communication [34]. The first member of this soluble protein family has been reported by Nomura et al. (1982) as up-regulated factor (p10) in the regenerating legs of the American cockroach Periplaneta americana [35]. The same protein was identified in the antennae and legs from P. americana at the adult sexually mature stage with some apparent differences between males and females, rather suggesting a “chemodevol” function for this protein, contributing both to tissue development and recognition of sex-specific signals such as sex pheromones [2].
thiol 1. Any of a class of organosulfur compounds consisting of a sulfur atom attached to a hydrogen atom and any other organic substituent, with the general formula R–SH. Thiols are the sulfur analogues of alcohols. Also thiol derivative and mercaptan. 2. The –SH functional group itself. Also sulfhydryl, sulfanyl, and mercapto.
The cyclol model was consistent with the general properties then attributed to folded proteins. (1) Centrifugation studies had shown that folded proteins were significantly denser than water (~1.4 g/mL) and, thus, tightly packed; Wrinch assumed that dense packing should imply regular packing. (2) Despite their large size, some proteins crystallize readily into symmetric crystals, consistent with the idea of symmetric faces that match up upon association. (3) Proteins bind metal ions; since metal-binding sites must have specific bond geometries (e.g., octahedral), it was plausible to assume that the entire protein also had similarly crystalline geometry. (4) As described above, the cyclol model provided a simple chemical explanation of denaturation and the difficulty of cleaving folded proteins with proteases. (5) Proteins were assumed to be responsible for the synthesis of all biological molecules, including other proteins. Wrinch noted that a fixed, uniform structure would be useful for proteins in templating their own synthesis, analogous to the Watson-Francis Crick concept of DNA templating its own replication. Given that many biological molecules such as sugars and sterols have a hexagonal structure, it was plausible to assume that their synthesizing proteins likewise had a hexagonal structure. Wrinch summarized her model and the supporting molecular-weight experimental data in three review articles.
Sources: en.wikipedia.org
Only a small number of early-stage human studies have been reported, and most were limited in size and duration. No large late-stage program has established a general efficacy or safety profile. The evidence base is therefore thin compared with approved medicines.
The peptide is listed as prohibited in competitive sport, so laboratories develop detection methods and monitor for its presence. Its appearance in enforcement reports reflects that classification rather than any approved athletic use. Analytical work in this area focuses on identifying the molecule and its breakdown products in biological samples.
Chromatographic separation combined with mass spectrometry identifies the peptide and estimates its amount in a sample. Testing can confirm whether the expected molecule is present and at what concentration. It cannot establish how a product was manufactured or whether it meets any purity standard.
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.