Everything below concerns melanocortin receptor. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2025-10-21. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C50H69N15O9 | Cyclic heptapeptide, C-terminally amidated |
| Approximate molecular mass | 1024 Da | Monoisotopic mass of the free peptide |
| Appearance | White to off-white powder | Typically supplied as a lyophilised solid |
| Solubility class | Soluble in water and polar solvents | Also dissolves in neutral aqueous buffer |
| Common synonyms | Melanotan II, MT-II, MT-2 | Described as a melanocortin agonist in early literature |
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.
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.
Melanotan II is a synthetic cyclic heptapeptide analog derived from the core sequence of alpha-melanocyte-stimulating hormone. Researchers at the University of Arizona synthesized it during the 1980s while studying pigmentation and appetite signaling. The compound is not an approved medicine in any major jurisdiction and appears mainly in laboratory and research-chemical settings. Its structure incorporates a lactam bridge between side chains, which constrains the ring and slows enzymatic breakdown relative to the natural hormone.
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.
=== Restenosis === Paclitaxel is used as an antiproliferative agent for the prevention of restenosis (recurrent narrowing) of coronary and peripheral stents; locally delivered to the wall of the artery, a paclitaxel coating limits the growth of neointima (scar tissue) within stents. Paclitaxel drug-eluting stents for coronary artery placement are sold under the trade name Taxus by Boston Scientific in the United States. Paclitaxel drug-eluting stents for femoropopliteal artery placement are also available.
The rapid expansion of AI infrastructure has significant environmental implications. The energy demands of data centres are projected to grow substantially, potentially conflicting with the UK's net-zero targets and straining grid capacity. Additionally, the water consumption required for cooling data centres has raised sustainability concerns. Beyond domestic impacts, the global AI supply chain relies heavily on the extraction of critical minerals (such as cobalt and lithium) in the Global South, often associated with environmental degradation and human rights abuses. The development of AI models also depends on low-wage "ghost workers" in developing nations for data annotation and content moderation, prompting calls for mandatory human rights due diligence laws. While economic forecasts suggest AI could significantly boost UK GDP and productivity, realising these gains faces a "productivity paradox". Despite experimental evidence of productivity improvements, economy-wide data does not yet reflect an AI-driven boost, largely due to low adoption rates of bespoke systems among traditional businesses and the concentration of economic value among a small percentage of organisations. Furthermore, economists warn of "algorithmic rents", where dominant tech platforms extract wealth, potentially eroding the UK tax base and exacerbating market concentration. The UK's Digital Services Tax (DST) attempts to address this but remains controversial with the US government.
In 2012 and 2014, the Aspen Institute named Santa Fe College one of the ten best community colleges in the U.S. In 2015, the college received the Aspen Prize for Community College Excellence, recognizing it as the top community college in the country. In 2015, the Lawrence W. Tyree Library received the Excellence in Academic Libraries Award from the Association of College & Research Libraries.
Some microorganisms alter net surface charges. Staphylococcus aureus transports D-alanine from the cytoplasm to the surface teichoic acid which reduces the net negative charge by introducing basic amino groups. S. aureus also modifies its anionic membranes via MprF with L-lysine, increasing the positive net charge. The interaction of antimicrobial peptides with membrane targets can be limited by capsule polysaccharide of Klebsiella pneumoniae. Salmonella species reduce the fluidity of their outer membrane by increasing hydrophobic interactions between an increased number of Lipid A acyl tails by adding myristate to Lipid A with 2-hydroxymyristate and forming hepta-acylated Lipid A by adding palmitate. The increased hydrophobic moment is thought to retard or abolish antimicrobial peptide insertion and pore formation. The residues undergo alteration in membrane proteins. In some Gram-negative bacteria, alteration in the production of outer membrane proteins correlates with resistance to killing by antimicrobial peptides. Non-typeable Hemophilus influenzae transports AMPs into the interior of the cell, where they are degraded. Furthermore, H. influenzae remodels its membranes to make it appear as if the bacterium has already been successfully attacked by AMPs, protecting it from being attacked by more AMPs. ATP-binding cassette transporters import antimicrobial peptides and the resistance-nodulation cell-division efflux pump exports antimicrobial peptides.
=== Discovery and early studies === Proteins have been studied and recognized since the 1700s by Antoine Fourcroy and others, who often collectively called them "albumins", or "albuminous materials" (Eiweisskörper, in German). Gluten, for example, was first separated from wheat in published research around 1747, and later determined to exist in many plants. In 1789, Antoine Fourcroy recognized three distinct varieties of animal proteins: albumin, fibrin, and gelatin. Vegetable (plant) proteins studied in the late 1700s and early 1800s included gluten, plant albumin, gliadin, and legumin. Proteins were first described by the Dutch chemist Gerardus Johannes Mulder and named by the Swedish chemist Jöns Jacob Berzelius in 1838. Mulder carried out elemental analysis of common proteins and found that nearly all proteins had the same empirical formula, C400H620N100O120P1S1. He came to the erroneous conclusion that they might be composed of a single type of (very large) molecule. The term "protein" to describe these molecules was proposed by Mulder's associate Berzelius; protein is derived from the Greek word πρώτειος (proteios), meaning "primary", "in the lead", or "standing in front", + -in. Mulder went on to identify the products of protein degradation such as the amino acid leucine for which he found a (nearly correct) molecular weight of 131 Da. Early nutritional scientists such as the German Carl von Voit believed that protein was the most important nutrient for maintaining the structure of the body, because it was generally believed that "flesh makes flesh".
Sources: en.wikipedia.org
West Indian limes began to take over from lemons, when Spain's alliance with France against Britain in the Napoleonic Wars made the supply of Mediterranean lemons problematic, and because they were more easily obtained from Britain's Caribbean colonies and were believed to be more effective because they were more acidic. It was the acid, not the (then-unknown) Vitamin C that was believed to cure scurvy. The West Indian limes were significantly lower in Vitamin C than the previous lemons and further were not served fresh but rather as lime juice, which had been exposed to light and air, and piped through copper tubing, all of which significantly reduced the Vitamin C. A 1918 animal experiment using representative samples of the Navy and Merchant Marine's lime juice showed that it had virtually no antiscorbutic power at all. The belief that scurvy was fundamentally a nutritional deficiency, best treated by consumption of fresh food, particularly fresh citrus or fresh meat, was not universal in the 19th and early 20th centuries, and thus sailors and explorers continued to have scurvy into the 20th century. For example, the Belgian Antarctic Expedition of 1897–1899 became seriously affected by scurvy when its leader, Adrien de Gerlache, initially discouraged his men from eating penguin and seal meat. In the Royal Navy's Arctic expeditions in the mid-19th century, it was widely believed that scurvy was prevented by good hygiene on board ship, regular exercise, and maintaining crew morale, rather than by a diet of fresh food.
methylarsonite + glutathione disulfide + H2O Thus, the two substrates of this enzyme are methylarsonate and glutathione, whereas its 3 products are methylarsonite, glutathione disulfide, and H2O. This enzyme belongs to the family of oxidoreductases, specifically those acting on phosphorus or arsenic in donor with disulfide as acceptor. The systematic name of this enzyme class is gluthathione:methylarsonate oxidoreductase. This enzyme is also called MMA(V) reductase.
These increases in coagulation factors may contribute to the development of stroke (see under § Side effects), but a precise association cannot be made at this stage. In a variety of clinical studies upon which FDA approval is based, Neumega showed effectivity in reducing thrombocytopenia in oncologic patients treated with myelosuppressant chemotherapeutic drugs as measured by significantly decreased need of platelet transfusions. Neumega is manufactured and sold by Wyeth. The drug is formulated in single-use vials containing 5 mg of oprelvekin (specific activity approximately 8 million units/mg) as a sterile, lyophilized powder. The FDA approved the drug in 1997.
In July 2012, the government made a review of the mandatory death penalty applied to certain drug trafficking or murder offences. In the midst of this review, a moratorium was imposed on all the 35 pending executions in Singapore at that time (7 for murder and 28 for drug trafficking). During that period of the review of the mandatory death penalty, one convicted murderer, Pathip Selvan s/o Sugumaran, who made headlines for the violent murder of his girlfriend in 2008, won his appeal in October 2012 and was re-sentenced to 20 years' imprisonment for culpable homicide. Wang Zhijian, a Chinese national who committed the 2008 Yishun triple murders, was sentenced to death for a conviction of murder under Section 300(a) of the Penal Code in November 2012, and another unnamed death row convict died of natural causes while in prison. In November 2012, capital punishment laws in Singapore were revised such that the mandatory death penalty for those convicted of drug trafficking or murder was lifted under certain specific conditions. Judges were empowered with the discretion to sentence such offenders to life imprisonment with the possibility of parole after 20 years. These changes were approved by Parliament and set to take effect in January of the following year. In January 2013, the law was again amended to make the death penalty no longer mandatory for certain capital offences.
Sources: en.wikipedia.org
== Evolution == Similar to any other protein, enzymes change over time through mutations and sequence divergence. Given their central role in metabolism, enzyme evolution plays a critical role in adaptation. A key question is therefore whether and how enzymes can change their enzymatic activities alongside. It is generally accepted that many new enzyme activities have evolved through gene duplication and mutation of the duplicate copies although evolution can also happen without duplication. One example of an enzyme that has changed its activity is the ancestor of methionyl aminopeptidase (MAP) and creatine amidinohydrolase (creatinase) which are clearly homologous but catalyze very different reactions (MAP removes the amino-terminal methionine in new proteins while creatinase hydrolyses creatine to sarcosine and urea). In addition, MAP is metal-ion dependent while creatinase is not, hence this property was also lost over time. Small changes of enzymatic activity are extremely common among enzymes. In particular, substrate binding specificity (see above) can easily and quickly change with single amino acid changes in their substrate binding pockets. This is frequently seen in the main enzyme classes such as kinases. Artificial (in vitro) evolution is now commonly used to modify enzyme activity or specificity for industrial applications (see below).
== Structure == Lumican is a proteoglycan Class II member of the small leucine-rich proteoglycan (SLRP) family that includes decorin, biglycan, fibromodulin, keratocan, epiphycan, and osteoglycin. Like the other SLRPs, lumican has a molecular weight of about 40 kilodaltons and has four major intramolecular domains:
== Medical uses == Escitalopram is approved by the US Food and Drug Administration (FDA) for the treatment of major depressive disorder in adolescents and adults, and generalized anxiety disorder (GAD) in adults, in dosage from 5 to 20 mg. In European countries including the United Kingdom, it is approved for depression and anxiety disorders; these include: generalized anxiety disorder, social anxiety disorder (SAD), obsessive–compulsive disorder (OCD), and panic disorder with or without agoraphobia. In Australia it is approved for major depressive disorder.
=== British English === In British English a spatula is similar in shape to a palette knife, without holes, in a flexible or detachable blade. It is used in medical examinations, for holding down the tongue or taking cell samples. The term is also commonly used in cookery to refer to a scraper, as in American English.
You must know that, for my part, there would be none, determined as I am to leave the command in this next Congress, but who can mitigate the ambition of our leaders and the fear of inequality among the lowly people? Don't you think that England would be jealous of the choice made in a Bourbon? How much would not be opposed by all the new American states, and the United States that seem destined by Providence to plague America with miseries in the name of Liberty? It seems to me that I already see a general conspiracy against this poor Colombia, already too envied by all the Republics America has. All the presses would be in motion calling for a new crusade against the accomplices of treason against freedom, addicts of the Bourbons and violators of the American system. In the South, the Peruvians would ignite the flame of discord; by the Isthmus those of Guatemala and Mexico, and by the Antilles the Americans and the liberals of all parts. Santo Domingo would not stay idle and call his brothers to make common cause against a prince of France. They would all become enemies without Europe doing anything to support us, because the New World is not worth the expense of a Holy Alliance; At least, we have reason to judge so, due to the indifference with which we have been seen to undertake and fight for the emancipation of half the world, which very soon will be the most productive source of European prosperity.
Sources: en.wikipedia.org
No. It is a synthetic analogue carrying four amino acid changes, a lactam ring and an amidated C-terminus. The natural hormone is a linear thirteen-amino-acid peptide processed from proopiomelanocortin.
Afamelanotide is the linear analogue [Nle4-D-Phe7]-alpha-MSH, sometimes called melanotan I, while melanotan II is cyclic and carries three further substitutions. The two are distinct molecules and are not interchangeable in analytical testing.
Binding to the four melanocortin receptor subtypes is well documented in vitro. The relative contribution of each subtype to whole-body effects in humans is far less certain.
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.