This is a working overview of eumelanin, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2025-12-07. Anything still debated is marked as such rather than presented as settled.
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.
Melanocytes are the pigment-producing cells of the skin, and they carry melanocortin-1 receptors on their surface. When the receptor is activated, cyclic adenosine monophosphate rises inside the cell and raises the activity of enzymes such as tyrosinase, which increases melanin output. Melanotan-2 binds melanocortin-1 receptors in vitro and in animal models, and this binding is generally described as the basis for the tanning effect. Other receptors account for different effects: melanocortin-4 receptors contribute to appetite and erectile signalling, while melanocortin-3 and melanocortin-5 receptors contribute to energy balance and exocrine function.
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 II binds several melanocortin receptor subtypes rather than a single target. MC1R on melanocytes drives melanin synthesis, while MC3R and MC4R participate in energy balance, appetite, and sexual response pathways. This lack of selectivity explains why reported effects extend beyond skin darkening. Substitutions at positions four and seven, including norleucine and D-phenylalanine, increase potency and resistance to peptidases. Understanding which receptor mediates which effect remains an active area of investigation.
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.
| Property | Value | Notes |
|---|---|---|
| Compound class | Synthetic cyclic heptapeptide | Alpha-MSH analogue containing a D-phenylalanine residue |
| Molecular formula | C50H69N15O9 | Average molecular mass approximately 1024.2 g/mol |
| Appearance | White to off-white lyophilised powder | Normally supplied as a freeze-dried solid in a sealed vial |
| Solubility | Freely soluble in water and polar solvents | Dissolves readily in aqueous buffers and in alcohol-water mixtures |
| Receptor targets | MC1R, MC3R, MC4R, MC5R | Acts as a non-selective melanocortin receptor agonist |
No regulatory authority has approved melanotan-2 for human use, and several countries classify it as a prescription-only or controlled substance, which restricts lawful supply. Material sold online is generally labelled as a research chemical and is not required to meet pharmaceutical standards of identity or purity. Published human data consist mainly of small uncontrolled studies, case reports and adverse-event notifications, so the evidence base is descriptive rather than confirmatory. Whether repeated melanocyte stimulation alters long-term naevus behaviour remains an open question that no completed trial has resolved.
Melanotan-2 is a synthetic cyclic heptapeptide designed as a structural analogue of alpha-melanocyte-stimulating hormone, the endogenous tridecapeptide that regulates pigment production. Two modifications distinguish it from the natural hormone: norleucine replaces methionine at the N-terminus, which limits oxidation, and a D-phenylalanine substitution raises receptor affinity. The ring is closed through an aspartate-lysine lactam bridge, giving the molecule a constrained conformation. The free base has a molecular mass near 1024 daltons, and commercial material is usually supplied as an acetate salt. It appears in the literature as a research peptide rather than an approved therapeutic agent.
Receptor studies place melanotan-2 among non-selective melanocortin agonists, binding MC1R, MC3R, MC4R and MC5R rather than a single subtype. Activation of MC1R on cutaneous melanocytes raises tyrosinase activity and shifts pigment synthesis toward eumelanin, which is darker and more photostable than pheomelanin. Central receptors, particularly MC4R, are associated with appetite suppression and with reported effects on sexual function. Because subtype selectivity is low, the same molecule engages pigment, metabolic and vascular pathways at once, and this breadth is a common explanation offered for the range of adverse events described in user reports.
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 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 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.
Maduro's supporters protested against his capture in Caracas, with protesters holding portraits of Maduro and pro-Maduro and pro-Partido Socialista Unido de Venezuela (PSUV) banners. PSUV called for citizens to demand the release of Maduro and Flores. CNN reported that while some Venezuelans celebrated Maduro's ousting, others were skeptical of Trump's motives and condemned the capture of Maduro as a "kidnapping". In the United States, hundreds of people gathered in New York City's Times Square to protest against the operation, with people chanting "Hands off Venezuela" and holding up signs that stated "US Out" and "No Blood for Oil". Outside of New York, hundreds of people in different cities gathered to voice opposition to the strikes. One month after the strikes, the Venezuelan government called for a protest that gathered thousands of supporters for the release of Nicolás Maduro. His son Nicolás Maduro Guerra addressed the crowd, saying that the 3 January "will remain marked like a scar on our face, forever."
== Possible relevance to primordial chemistry == Methylamine and ammonia will react to form methanediamine when exposed under energetic electrons, just like conditions similar to cold molecular clouds. Since methanediamine is the simplest molecule to contain the N-C-N moiety, it could be a vital intermediate in the abiogenesis of heterocyclic compounds that contain the N-C-N moiety, such as nucleobases.
==== Canada ==== In Canada, codeine is regulated under the Narcotic Control Regulations (NCR), which falls under the Controlled Drugs and Substances Act (CDSA). Regulations state the pharmacists may, without a prescription, sell low-dose codeine products (containing up to 8 mg of codeine per tablet or up to 20 mg per 30 ml in liquid preparation) if the preparation contains at least two additional medicinal ingredients other than a narcotic (S.36.1 NCR). In Canada tablets containing 8 mg of codeine combined with 15 mg of caffeine and 300 mg of acetaminophen are sold as T1s (Tylenol Number 1) without a prescription. A similar tablet called "A.C. & C." (which stands for Acetylsalicylic acid with Caffeine and Codeine) containing 325–375 mg of acetylsalicylic acid (Aspirin) instead of acetaminophen is also available without a prescription. Codeine combined with an antihistamine, and often caffeine, is sold under various trade names and is available without a prescription. These products are kept behind the counter and must be dispensed by a pharmacist who may limit quantities. Names of many codeine and dihydrocodeine products in Canada tend to follow the narcotic content number system (Tylenol With Codeine No. 1, 2, 3, 4 &c) mentioned below in the section on the United States; it came to be in its current form with the Pure Food and Drug Act of 1906. Controlled Drugs and Substances Act (S.C. 1996, c. 19) effective 28 July 2020. Codeine is now classified under Schedule 1, giving it a higher priority in the treatments of offenders of the law.
The first-generation vaccines are manufactured by growing live vaccinia virus in the skin of live animals. Most first-generation vaccines are calf lymph vaccines that were grown on the skin of cows, but other animals were also used, including sheep. The development of freeze-dried vaccine in the 1950s made it possible to preserve vaccinia virus for long periods of time without refrigeration, leading to the availability of freeze-dried vaccines such as Dryvax. The vaccine is administered by multiple puncture of the skin (scarification) with a bifurcated needle that holds vaccine solution in the fork. The skin should be cleaned with water rather than alcohol, as the alcohol could inactivate the vaccinia virus. If alcohol is used, it must be allowed to evaporate completely before the vaccine is administered. Vaccination results in a skin lesion that fills with pus and eventually crusts over. This manifestation of localized vaccinia infection is known as a vaccine "take" and demonstrates immunity to smallpox. After 2–3 weeks, the scab will fall off and leave behind a vaccine scar. First generation vaccines consist of live, unattenuated vaccinia virus. One-third of first-time vaccinees develop side effects significant enough to miss school, work, or other activities, or have difficulty sleeping. 15–20% of children receiving the vaccine for the first time develop fevers of over 102 °F (39 °C). The vaccinia lesion can transmit the virus to other people. Rare side effects include postvaccinal encephalitis and myopericarditis.
Sources: en.wikipedia.org
On an unknown date in 1980, the aircraft registered SSSR-86004 (constructor's number 51483200002 ["002"]) experienced a fire in engine No 4 on departure from Vnukovo on an acceptance testing flight; the crew initially shut down No. 1 in error, then No. 4, but landed safely on the reciprocal runway to the one from which they had departed, after performing a 180° turn. No casualties. The investigation into this fire resulted in a modification to the engine. In 1984, SSSR-86011 (c/n 009) was found to have suffered a tail strike on landing at Simferopol. No casualties. On March 8, 1994, RA-86119 (c/n 087) parked at Delhi airport was struck by debris of crashing Sahara India Boeing 737 (VT-SIA) flown by a trainee; both aircraft were destroyed. All 4 crew on the 737 were killed. Two Aeroflot employees and Russian ground engineer died inside the Il-86 due to a fire and an airport worker was killed on the ground. In 1998, RA-86080 (c/n 051) was found to have been overstressed, most likely by a recent heavy landing, and repairs were considered inexpedient in view of coming retirement. No casualties; aircraft broken up at Sheremetyevo Airport in 2001. On May 1, 2000, RA-86113 (c/n 081) suffered an apparent engine failure and fire on departure from Sochi. The flight crew brought the machine to a safe overweight landing. The failure and fire indications were found to have been spurious. No casualties. On August 26, 2000, RA-86066 (c/n 033) experienced a failure and fire in No 2 engine shortly after take-off from Moscow Sheremetyevo for Barcelona.
=== Glycosyltransferase === OGT catalyzes the addition of a single N-acetylglucosamine through an O-glycosidic linkage to serine or threonine and an S-glycosidic linkage to cysteine residues of nucleocytoplasmic proteins. Since both phosphorylation and O-GlcNAcylation compete for similar serine or threonine residues, the two processes may compete for sites, or they may alter the substrate specificity of nearby sites by steric or electrostatic effects. Two transcript variants encoding cytoplasmic and mitochondrial isoforms have been found for this gene. OGT glycosylates many proteins including: Histone H2B, AKT1, PFKL, KMT2E/MLL5, MAPT/TAU, Host cell factor C1, and SIN3A. O-GlcNAc transferase is a part of a host of biological functions within the human body. OGT is involved in the resistance of insulin in muscle cells and adipocytes by inhibiting the Threonine 308 phosphorylation of AKT1, increasing the rate of IRS1 phosphorylation (at serine 307 and serine 632/635), reducing insulin signaling, and glycosylating components of insulin signals. Additionally, O-GlcNAc transferase catalyzes intracellular glycosylation of serine and threonine residues with the addition of N-acetylglucosamine. Studies show that OGT alleles are vital for embryogenesis, and that OGT is necessary for intracellular glycosylation and embryonic stem cell vitality. O-GlcNAc transferase also catalyzes the posttranslational modification that modifies transcription factors and RNA polymerase II, however the specific function of this modification is mostly unknown.
=== Films === The Devil We Know (2018): a documentary detailing the health dangers of PFAS. Dark Waters (2019): a thriller movie based on the corporate defense of PFAS and DuPont. Contaminated: The Carpet Industry's Toxic Legacy (2026): documentary about the history of PFAS and the carpet industry. Everywhere & Forever: Blood. Water. And the Politics of PFAS (2025): a documentary about PFAS and the struggles to manage the contamination. Revealed: How to Poison A Planet (2024): a documentary detailing the negative externalities from PFAS creation.
Russian officials claimed that one person was killed in a Ukrainian drone strike in Belgorod Oblast. Canada imposed new sanctions on Russian individuals and entities for facilitating the illegal transfer of North Korean weapons, including ballistic missiles, for use in the invasion of Ukraine. The EU agreed to allow Ukraine to use the interest earned from seized Russian assets, totalling approximately 2.5 billion to 3 billion euros ($2.7 billion to $3.3 billion) annually, disbursed twice per year. Institutions will keep all interest earned between February 2022 and February 2024, possibly for reconstruction purposes, according to European Commission sources. More than 3,000 Ukrainian prisoners have applied to join the Ukrainian military.
=== United Kingdom === In the United Kingdom (UK) there are two varieties of registered healthcare scientist in hospitals - Clinical Scientists and Biomedical Scientists (BMS). There is a strict and formal post graduate training programme for both careers followed by statutory registration for each with the Health & Care Professions Council UK (HCPC), for the safety and assurance of the customers - the patients. They are two similar but distinct careers with parallel but different training paths and different entry requirements. The role of Clinical Scientists is to improve the health and well-being of patients and the public by practising alongside doctors, nurses, and other health and social care professionals in the delivery of healthcare. Their aim is to provide expert scientific and clinical advice to clinician colleagues, to aid in the diagnosis, treatment and management of patient care. Examples of the type of work they undertake include:
Sources: en.wikipedia.org
No. It is a laboratory-made peptide, while the natural hormone is alpha-melanocyte-stimulating hormone, a longer peptide produced by the pituitary gland and by skin cells. Melanotan-2 mimics only a short active region of that hormone and contains non-natural residues such as D-phenylalanine.
No approved regulatory indication exists in major markets. An approval exists for a different peptide, afamelanotide, which is used for a rare photosensitivity disorder called erythropoietic protoporphyria. Melanotan-2 itself remains a research compound with no cleared clinical role.
Melanocortin-1 receptors on melanocytes are the receptor most closely linked to pigment production. The peptide is not selective, however, and also activates melanocortin-3, melanocortin-4, and melanocortin-5 receptors. That lack of selectivity is the usual explanation offered for both its range of observed effects and its off-target effects.
No regulator in a major market has approved it for human use. It appears in research settings and in products marketed outside pharmacy channels. Legal status for personal possession varies by country.