This is a working overview of afamelanotide, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2025-11-02. Anything still debated is marked as such rather than presented as settled.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C50H69N15O9 | Free base; salt forms add to total mass |
| Molecular mass | About 1024 daltons | Calculated for the free base |
| Structural class | Cyclic heptapeptide | Contains D-phenylalanine and norleucine |
| Parent hormone | Alpha-melanocyte-stimulating hormone | Endogenous tridecapeptide of 13 residues |
| Receptor profile | Non-selective melanocortin agonist | Interacts with MC1R, MC3R, MC4R and MC5R |
Melanotan-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone, the naturally occurring peptide involved in pigmentation signalling. Its sequence is conventionally written as Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, with a lactam bridge joining the aspartate side chain to the lysine side chain. The empirical formula is C50H69N15O9 and the monoisotopic mass lies near 1023.5 daltons. N-terminal acetylation and the D-configured phenylalanine both increase resistance to enzymatic breakdown compared with the parent hormone.
Pharmacologically, melanotan-2 behaves as a non-selective agonist across the melanocortin receptor family. Binding at MC1R on dermal melanocytes promotes eumelanin synthesis, which underlies the tanning response described in early human work. Activity at the centrally expressed MC4R receptor is associated with reported effects on appetite and erectile function. Because the peptide does not discriminate strongly among receptor subtypes, attributing any single observed effect to one receptor pathway is generally not possible without selective antagonists or receptor knockout models.
Research interest has centred on photoprotection and pigmentation, with a smaller body of work on appetite and sexual function. Published human data remain limited to small, frequently uncontrolled studies, and the compound has never received marketing approval from a national medicines regulator. Most laboratory work treats it as a pharmacological tool for probing melanocortin signalling in cell culture or animal models. Whether pigmentation changes observed in people translate into measurable protection against ultraviolet-induced DNA damage remains an open question.
Melanotan II is a synthetic peptide analog modeled on alpha-melanocyte-stimulating hormone, a naturally occurring signaling peptide involved in pigmentation. Its structure is a cyclic heptapeptide containing two non-natural substitutions, norleucine at position four and D-phenylalanine at position seven. These modifications resist enzymatic breakdown and extend the molecule's activity relative to the native hormone. The compound binds melanocortin receptors and is studied mainly as a pharmacological tool rather than a therapeutic product. It has never received approval as a medicine in any major jurisdiction.
The compound was developed in the late 1980s and 1990s by academic researchers investigating photoprotection. The rationale held that stimulating melanin production might reduce ultraviolet damage to skin and lower skin cancer risk. Early work examined receptor binding, pigment response, and short-term tolerability in small studies. That program did not produce an approved drug, and formal development stalled after early-phase trials. Whether induced pigmentation confers meaningful photoprotection remains an open question.
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 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.
Hours later, White House press secretary Karoline Leavitt said that acquiring Greenland was "a national security priority of the United States", "vital to deter our adversaries in the Arctic region", and added: "The president and his team are discussing a range of options to pursue this important foreign policy goal, and of course, utilizing the US military is always an option at the commander in chief's disposal." Rubio emphasized that any acquisition of Greenland by the US would be negotiated rather than resort to military force, saying Trump's threats were mainly rhetorical and an effort to push Denmark into approving a US-friendly deal. In the following days Trump said the US is "going to do something [there] whether they like it or not", that "We're not going to have Russia or China occupy Greenland. That's what they're going to do if we don't. So we're going to be doing something with Greenland, either the nice way or the more difficult way" and "I would like to make a deal, you know, the easy way. But if we don't do it the easy way, we're going to do it the hard way," that "the fact that they had a boat land there 500 years ago doesn't mean that they own the land. [I'm] sure we had lots of boats go there also." Asked if obtaining Greenland or preserving NATO was his higher priority, he said "it may be a choice."
Mirubactin is a siderophore produced by the bacterium Actinosynnema mirum. A. mirum was first isolated from the Raritan River in New Jersey in 1976, and its full genome sequence was published in 2009. In 2012, mirubactin was isolated and characterized, and the biosynthesis was connected with the gene cluster Amir_2714-Amir_2728, since renamed mrbA-mrbO.
Since lithium-ion batteries are intercalation batteries, information on the chemistry and electronic structure going on in the bulk during operation are of interest. For this, soft x-ray information can be obtained using hard X-ray Raman scattering. Fixed energy methods (FEXRAV) have been developed and applied to the study of the catalytic cycle for the oxygen evolution reaction on iridium oxide. FEXRAV consists of recording the absorption coefficient at a fixed energy while varying at will the electrode potential in an electrochemical cell during the course of an electrochemical reaction. It allows to obtain a rapid screening of several systems under different experimental conditions (e.g., nature of the electrolyte, potential window), preliminary to deeper XAS experiments. The soft X-Ray regime (i.e. with photon energy < 1000 eV) can be profitably used for investigating heterogeneous solid-gas reaction. In this case, it is proved that XAS can be sensitive both to the gas phase and to the solid surface states.
Sources: en.wikipedia.org
== Secondary ion mass spectrometry == Secondary ion mass spectrometry (SIMS) is a method very similar to FAB in that a beam of particles is fired against the surface of a sample in order to cause sputtering, in which the molecules of the sample ionize and leave the surface, thus allowing for the ions or the sample to be analyzed. The primary difference is that in SIMS, an ion beam is fired against the surface, but in FAB, an atom beam is fired against the surface. The other primary difference, of more interest to this page, is that, unlike FAB, SIMS is typically performed on a solid sample with little sample preparation required. The main consideration with SIMS is ensuring that the sample is stable under ultra-high vacuum, or pressures less than 10−8 torr. The nature of the ultra-high vacuum is that it ensures the sample remains constant during analysis as well as ensuring the high energy ion beam strikes the sample. Ultra-high vacuum solves many of the problems that need to be considered during sample preparation. When preparing the sample for analysis, another thing that should be considered is the thickness of the film. Typically, if a thin monolayer can be deposited onto the surface of a noble metal, analysis should be successful. If the film thickness is too large, which is common in real world analysis, the problem can be solved by methods such as depositing a perforated silver foil over a nickel grid onto the film surface. This yields similar results to thin films deposited directly onto a noble metal.
=== First radiation protection regulations === A leaflet published by the German Radiological Society (DRG) in 1913 was the first systematic approach to radiation protection. The physicist and co-founder of the society, Bernhard Walter (1861-1950), was one of the pioneers of radiation protection. The International Commission on Radiological Protection (ICRP) and the International Commission on Radiation Units and Measurements (ICRU) were established at the Second International Congress of Radiology in Stockholm in 1928. In the same year, the first international radiation protection recommendations were adopted and each country represented was asked to develop a coordinated radiation control program. The United States representative, Lauriston Taylor of the US Bureau of Standards (NSB), formed the Advisory Committee on X-Ray and Radium Protection, later renamed the National Committee on Radiation Protection and Measurements (NCRP). The NCRP received a Congressional charter in 1964 and continues to develop guidelines to protect individuals and the public from excessive radiation. In the years that followed, numerous other organizations were established by almost every president.
Megakaryocyte and platelet production is regulated by thrombopoietin, a hormone produced in the kidneys and liver. Each megakaryocyte produces between 1,000 and 3,000 platelets during its lifetime. An average of 1011 platelets are produced daily in a healthy adult. Reserve platelets are stored in the spleen and are released when needed by splenic contraction induced by the sympathetic nervous system.
Sources: en.wikipedia.org
No regulatory agency has authorised melanotan-2 as a medicine for any indication. It circulates mainly as a research chemical or through unregulated channels. As a result, identity, purity and content are not independently guaranteed.
Melanotan-1, also called afamelanotide, is a linear analogue with greater selectivity for MC1R and has received approval in some jurisdictions for a specific photosensitivity disorder. Melanotan-2 is cyclic, less selective, and reaches central receptors more readily. The two are often confused in online discussion despite different pharmacology and regulatory status.
Alpha-MSH is an endogenous tridecapeptide derived from pro-opiomelanocortin. Melanotan-2 reproduces its core receptor-binding sequence inside a shortened, stabilised ring. The result is a molecule with a longer effective half-life and higher potency than the parent hormone.
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.