Everything below concerns afamelanotide. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2025-08-29. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
| 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 |
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.
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.
This period is also marked by the appearance of the self-portraits of painters in long tunics and highboots armed with short daggers, such as the painter of the Cave of the Statues or the several painters of the "Cave of the Painters", with often their own identifying labels in Sanskrit. The clothing style and type of these painters has often been described as Sasanian, but has recently been proposed as being rather Hephthalite, due to the similarities with the Hephthalite figures in Dilberjin Tepe, Balalyk Tepe or Bamiyan, and because the Hepthalites did control the Tarim Basin for nearly a century around this time period.
=== Physical === Most of the physical properties of astatine have been estimated (by interpolation or extrapolation), using theoretically or empirically derived methods. For example, halogens get darker with increasing atomic weight—fluorine is nearly colorless, chlorine is yellow-green, bromine is red-brown, and iodine is dark gray/violet. Astatine is sometimes described as probably being a black solid (assuming it follows this trend), or as having a metallic appearance (if it is a metalloid or a metal). Because it has a lower vapor pressure than iodine, astatine sublimes, as expected. Half of a given quantity of astatine will vaporize in approximately an hour if put on a clean glass surface at room temperature. The absorption spectrum of astatine in the middle ultraviolet region has lines at 224.401 and 216.225 nm, suggestive of 6p to 7s transitions. The structure of solid astatine is unknown. As an analog of iodine it may have an orthorhombic crystalline structure composed of diatomic astatine molecules, and be a semiconductor (with a band gap of 0.7 eV). Alternatively, if condensed astatine forms a metallic phase, as has been predicted, it may have a monatomic face-centered cubic structure; in this structure, it may well be a superconductor, like the similar high-pressure phase of iodine. Metallic astatine is expected to have a density of 8.91–8.95 g/cm3. Evidence for (or against) the existence of diatomic astatine (At2) is sparse and inconclusive.
Phenelzine requires attention to dietary tyramine and clinically important drug interactions, but severe tyramine-related hypertensive reactions are uncommon when dietary and medication precautions are followed. Modern food standards have substantially reduced tyramine levels in many foods compared with the 1950s and 1960s, making excessive tyramine ingestion less likely than in earlier decades. The highest-risk foods are generally those that are fermented, matured, or spoiled, including some aged cheeses, some artisan beers, fermented meats, and fermented products such as soy sauce, miso, tempeh, sauerkraut, Marmite, and kimchi. Because inhibition of monoamine oxidase reduces the breakdown of dietary tyramine in the gastrointestinal tract and liver, excessive tyramine intake can raise blood pressure through peripheral norepinephrine release. If this causes a marked blood-pressure rise, the reaction is usually self-limiting and typically reaches its maximum within about 2 hours. Modern guidance advises against rapid blood-pressure reduction outside appropriate medical supervision, because overtreatment can cause hypotensive overshoot; sublingual nifedipine is specifically discouraged. The Cambridge Prescriber's Guide recommends benzodiazepine administration with blood-pressure monitoring, with emergency clinicians using clinical judgment in severe cases and considering short-acting agents such as phentolamine when additional treatment is needed.
August 2016, Amnesty International released a report tackling the issue of torture and ill-treatment in Syrian government prisons which amount to crimes against humanity. Since the crisis began in March 2011, the international organization estimated that 17,723 people have died in custody in Syria – an average rate of more than 300 deaths each month. According to the report, governmental forces have used torture to scare the opponents. But today, they use it as a part of systematic attack against opposition members. According to testimonies of some survivors, detainees were subjected to numerous kind of torture aiming at dehumanizing them, and in many cases killing them. Amnesty international said that those, who are responsible for these atrocities, must be brought to justice. In Sednaya Prison alone, up to 13,000 detainees were executed extrajudicially in secret between 2011 and 2015, mostly through mass-hangings. This was part of Assad's push to eliminate all dissent to his rule. On 6 July 2020, families of detainees in Syrian government prisons found the pictures of their dead relatives in the media graphics of a forensic police photographer-turned-whistleblower, codenamed, Caesar. The photos are among tens of thousands of images of torture victims, smuggled out of Syria in 2013. Numerous European citizens were also revealed to be among the torture victims.
Sources: en.wikipedia.org
Natural food freezing (using winter frosts) had been in use by people in cold climates for centuries. In 1861 Thomas Sutcliffe Mort established at Darling Harbour in Sydney, Australia, the world's first freezing works, which later became the New South Wales Fresh Food and Ice Company. Mort financed experiments by Eugene Dominic Nicolle, a French born engineer who had arrived in Sydney in 1853 and registered his first ice-making patent in 1861. The first trial shipment of frozen meat to London was in 1868. Although their machinery was never used in the frozen meat trade, Mort and Nicolle developed commercially viable systems for domestic trade. The financial return on that investment was minimal for Mort. Regular shipments of frozen meat from Australia and New Zealand to Europe began in 1881, with a consignment of frozen New Zealand sheep exported to London on board the Dunedin. By 1885 a small number of chickens and geese were being shipped from Russia to London in insulated cases using this technique. By March 1899, the "British Refrigeration and Allied Interests" reported that a food importing business, "Baerselman Bros", was shipping some 200,000 frozen geese and chickens per week from three Russian depots to New Star Wharf, Lower Shadwell, London over three or four winter months. This trade in frozen food was enabled by the introduction of Linde cold air freezing plants in three Russian depots and the London warehouse. The Shadwell warehouse stored the frozen goods until they were shipped to markets in London, Birmingham, Liverpool and Manchester.
=== 2019 recall of Ranitidine products === In 2019, Dr. Reddy's recalled all ranitidine products in the US market due to contamination with the carcinogen N-nitrosodimethylamine (NDMA). Months later, all brands of ranitidine were recalled and it was taken off the US market, as the carcinogen was an unavoidable byproduct.
=== Battery electrolyte === Chitosan is being investigated as an electrolyte for rechargeable batteries with good performance and low environmental impact due to rapid biodegradability, leaving recycleable zinc. The electrolyte has excellent physical stability up to 50 °C, electrochemical stability up to 2 V with zinc electrodes, and accommodates redox reactions involved in the Zn-MnO2 alkaline system. As of 2022 results were promising, but the battery needed testing on a larger scale and under actual use conditions.
Because water-soluble B vitamins are eliminated in the urine, taking large doses of most B vitamins usually only produces transient side effects (with the only exception being pyridoxine). General side effects may include restlessness, nausea, and insomnia. These side effects are almost always caused by dietary supplements and not food.
=== Polypeptide hormones, toxins, and antimicrobial peptides === Many hormones, toxins, inhibitors, or antimicrobial peptides interact specifically with transmembrane protein complexes. They can also accumulate at the lipid bilayer surface, prior to binding their protein targets. Such polypeptide ligands are often positively charged and interact electrostatically with anionic membranes. Some water-soluble proteins and peptides can also form transmembrane channels. They usually undergo oligomerization, significant conformational changes, and associate with membranes irreversibly. 3D structure of one such transmembrane channel, α-hemolysin, has been determined. In other cases, the experimental structure represents a water-soluble conformation that interacts with the lipid bilayer peripherally, although some of the channel-forming peptides are rather hydrophobic and therefore were studied by NMR spectroscopy in organic solvents or in the presence of micelles.
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.
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.