MC1R raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
This page was last updated on 2025-12-16 and is reviewed periodically as new material appears.
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-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.
Independent verification is central to quality control because the compound is not produced under pharmaceutical manufacturing standards. Third-party laboratories can measure purity, identity, residual solvents, and microbial contamination, though the scope of testing varies between services. Reported analyses of vendor samples have shown batch-to-batch variation in peptide content and the presence of truncated or oxidized species. How much of this variation reflects synthesis conditions versus storage and shipping is not well characterized. No harmonized reference standard exists for the material as sold.
Handling guidance for melanotan II follows general practice for small synthetic peptides rather than a product-specific monograph. Lyophilized powder is typically kept at minus twenty degrees Celsius or colder, protected from light and moisture, because warmth and humidity accelerate degradation. Once reconstituted, solutions are usually refrigerated and used within a short window, as hydrolysis and microbial growth both become concerns. Repeated freeze-thaw cycles are generally avoided. These conventions come from laboratory peptide chemistry and not from formal stability studies on this specific compound.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | Melanotan II; MT-II; N-acetyl-norleucyl-cyclo[Asp-His-D-Phe-Arg-Trp-Lys] amide | Naming follows peptide convention; the numeral distinguishes it from melanotan-1 |
| Molecular formula | C50H69N15O9 | Includes the lactam bridge; no counter-ion assumed |
| Monoisotopic mass | 1023.53 Da | Free base; salts and counter-ions shift the observed value |
| Appearance | White to off-white lyophilised powder | Batch-to-batch colour variation is not itself proof of impurity |
| Typical analytical method | RP-HPLC purity determination with ESI-MS identity confirmation | Retention time alone does not establish sequence identity |
Activity is attributed to agonism at melanocortin receptors, particularly MC1R and MC4R. Activation of MC1R on melanocytes increases melanin synthesis, which underlies the reported tanning effect. MC4R engagement in the central nervous system is linked to appetite suppression and to effects on sexual arousal reported in early clinical studies. Those studies were small and were not designed to establish efficacy or long-term safety. Receptor selectivity among the melanocortin subtypes is not absolute, which complicates attribution of any effect to a single pathway.
Regulatory treatment varies between countries. Several national medicines agencies have classified the peptide as unapproved, and customs authorities in some jurisdictions seize shipments on that basis. A few jurisdictions channel supply through prescription-only frameworks that do not list the substance by name. Because the material circulates mainly through online vendors, composition and purity are rarely verified before sale. Surveys of unapproved peptide products have reported labels that did not match measured content in a substantial fraction of samples.
Melanotan II is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone, a naturally occurring peptide involved in pigmentation signalling. Its structure substitutes a lactam bridge between side chains to increase stability relative to the native hormone. The compound is also known by the shorthand MT-II and by several non-proprietary synonyms used in research catalogues. It is not an approved therapeutic product in any major jurisdiction; material sold under this name is typically offered as a laboratory reagent rather than as a medicine.
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.
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.
Lyophilised melanotan-2 is comparatively robust when kept dry, cold and dark, and a desiccated powder stored at minus twenty degrees Celsius or below is generally expected to retain its chemical integrity for extended periods. In solution the peptide is far less stable, with degradation proceeding through oxidation of tryptophan and histidine residues, hydrolysis adjacent to the lactam bridge, and aggregation at higher concentrations. Repeated freeze-thaw cycling accelerates loss of the parent peak. Working aliquots are therefore prepared once, held cold, and used without letting the stock return to ambient temperature.
Quality assessment of research-grade peptide rests mainly on reversed-phase high-performance liquid chromatography for purity and on mass spectrometry for identity confirmation. A single main peak above a stated threshold, commonly ninety-eight percent by peak area, is the usual release criterion applied by suppliers. Independent analyses commissioned by laboratories and consumer organisations have repeatedly reported discrepancies between label claims and measured content, including truncated sequences, residual trifluoroacetate, and lower-than-declared peptide mass. Those findings do not establish that every supplier is unreliable, but they indicate that purity figures printed on a vial are claims requiring verification rather than settled facts.
Irradiation of 241Am by 12C or 22Ne ions yields the isotopes 247Es (einsteinium) or 260Db (dubnium), respectively. Furthermore, the element berkelium (243Bk isotope) had been first intentionally produced and identified by bombarding 241Am with alpha particles, in 1949, by the same Berkeley group, using the same 60-inch cyclotron. Similarly, nobelium was produced at the Joint Institute for Nuclear Research, Dubna, Russia, in 1965 in several reactions, one of which included irradiation of 243Am with 15N ions. Besides, one of the synthesis reactions for lawrencium, discovered by scientists at Berkeley and Dubna, included bombardment of 243Am with 18O.
Rosiglitazone (trade name Avandia) is an antidiabetic drug in the thiazolidinedione class. It works as an insulin sensitizer, by binding to the PPAR in fat cells and making the cells more responsive to insulin. It is marketed by the pharmaceutical company GlaxoSmithKline (GSK) as a stand-alone drug or for use in combination with metformin or with glimepiride. First released in 1999, annual sales peaked at approximately $2.5 billion in 2006; however, following a meta-analysis in 2007 that linked the drug's use to an increased risk of heart attack, sales plummeted to just $9.5 million in 2012. The drug's patent expired in 2012. It was patented in 1987 and approved for medical use in 1999. Despite rosiglitazone's effectiveness at decreasing blood sugar in type 2 diabetes mellitus, its use decreased dramatically as studies showed apparent associations with increased risks of heart attacks and death. Adverse effects alleged to be caused by rosiglitazone were the subject of over 13,000 lawsuits against GSK; as of July 2010, GSK had agreed to settlements on more than 11,500 of these suits. Some reviewers recommended rosiglitazone be taken off the market, but an FDA panel disagreed, and it remains available in the US. From November 2011 until November 2013, the US federal government did not allow Avandia to be sold without a prescription from a certified doctor; moreover, patients were required to be informed of the risks associated with its use, and the drug had to be purchased by mail order through specified pharmacies.
In the 1970s, biscuit manufacturers began using micro-aeration to process chocolate for moulded products. This was a cost-saving measure: with less chocolate, the same volume of coated biscuit could be maintained. In 1981 or 1983, Cadbury released Wispa, an aerated chocolate with a more chunky shape than Aero bars, made using a secret, non-patented process. The launch of Wispa was successful, but it soon encountered manufacturing difficulties and was temporarily withdrawn from the market. While Wispa was off the market, Rowntree's developed and launched a chunky Aero which they successfully launched and was still being sold as of 2008. Wispa was discontinued in the early 2000s so Cadbury could bring in a new aerated chocolate product aligned with the Cadbury Dairy Milk brand: Dairy Milk Bubbly. Following an internet campaign in 2007, Cadbury reintroduced Wispa. Today, Aero is manufactured by Nestlé, the brand having been acquired by Nestlé during a 1988 takeover of Rowntree's. As of 2023, other brands of aerated chocolate includes Mirage and Galaxy.
In ancient India, various teachings about well-being are found in the Hindu tradition, formulated in the first two millennia BCE in the Vedas, Upanishads, and the Smriti literature. They include the ideas that a person should fulfill their duty relative to their social role and stage of life, and that one should attain knowledge about how the self and the world are ultimately one. A central element of the Buddhist conception of well-being is the avoidance of suffering. The Buddha (roughly 6th century BCE) identified craving as the root cause of suffering, proposing a set of practical recommendations, such as right conduct and mindfulness, to overcome it. In ancient China, Confucius (6th to 5th century BCE) emphasized the role of social virtues in leading a good life, with a particular focus on benevolence or humaneness. In the Taoist tradition, Laozi (6th century BCE) saw living in harmony with the natural order of the universe through effortless, spontaneous action as the ideal form of life. During the medieval period in the West, Christian thinkers associated well-being with spiritual salvation. Augustine (354–430 CE) argued that humans are not fully in control of their well-being and instead depend on divine grace. He maintained that true happiness is achievable only in the afterlife. Thomas Aquinas (1225–1274 CE) similarly emphasized the role of the divine, proposing that a beatific vision of God is the highest form of well-being.
The work published by Banting, Best, Collip and Macleod represented the preparation of purified insulin extract suitable for use on human patients. Although Paulescu discovered the principles of the treatment, his saline extract could not be used on humans; he was not mentioned in the 1923 Nobel Prize. Ian Murray was particularly active in working to correct "the historical wrong" against Nicolae Paulescu. Murray was a professor of physiology at the Anderson College of Medicine in Glasgow, United Kingdom, the head of the department of Metabolic Diseases at a leading Glasgow hospital, vice-president of the British Association of Diabetes, and a founding member of the International Diabetes Federation. Murray wrote:
Sources: en.wikipedia.org
=== Receptor tyrosine kinase === Much like for G protein-coupled receptors, dimerization is essential for receptor tyrosine kinases (RTK) to perform their function in signal transduction, affecting many different cellular processes. RTKs typically exist as monomers, but undergo a conformational change upon ligand binding, allowing them to dimerize with nearby RTKs. The dimerization activates the cytoplasmic kinase domains that are responsible for further signal transduction.
He wrote: "Its development in this theatre has suffered for various reasons. Sired by the English out of an American mother, the Mustang has no parent in the Army Air Corps to appreciate and push its good points. It does not fully satisfy good people on both sides of the Atlantic who seem more interested in pointing with pride to the development of a 100% national product..." Nevertheless, during the British service development program of the Mustang I at Rolls-Royce's airfield at Hucknall, a close relationship was developed between NAA, the RAF Air Fighting Development Unit and Rolls-Royce Flight Test Establishment at Hucknall. Following extensive communication between Hitchcock (based in England), Rolls Royce engineers and Phillip Legarra at NAA regarding the promising outlook of a Merlin Mustang, along with the subsequent work in progress by Rolls Royce on the Mustang X, NAA representatives including Mustang designer Schmued visited the UK to examine and discuss the project in detail. The promising calculations and modification progress by Rolls Royce led in July 1942 to a contract being let for two NAA Merlin prototypes, briefly designated XP-78, but soon to become the XP-51B. Based on the Packard V-1650-3 duplicating the Merlin 61's performance, NAA estimated for the XP-78 a top speed of 445 mph (387 kn; 716 km/h) at 28,000 feet (8,500 m), and a service ceiling of 42,000 feet (13,000 m). Initial flights of what was known to Rolls-Royce as the Mustang X were completed at Hucknall in October 1942.
== Preparations by size == Plasmid preparation can be divided into five main categories based on the scale of the preparation: minipreparation, midipreparation, maxipreparation, megapreparation, and gigapreparation. The choice of which method to use will depend on the amount of plasmid DNA required, as well as the specific application for which it will be used. Kits are available from varying manufacturers to purify plasmid DNA, which are named by size of bacterial culture and corresponding plasmid yield. In increasing order they are: miniprep, midiprep, maxiprep, megaprep, and gigaprep. The plasmid DNA yield will vary depending on the plasmid copy number, type and size, the bacterial strain, the growth conditions, and the kit.
Often molecules do form multilayers, that is, some are adsorbed on already adsorbed molecules, and the Langmuir isotherm is not valid. In 1938 Stephen Brunauer, Paul Emmett, and Edward Teller developed a model isotherm that takes that possibility into account. Their theory is called BET theory, after the initials in their last names. They modified Langmuir's mechanism as follows:
Sources: en.wikipedia.org
==== Sub-gingival margins ==== A gingivectomy can also be done to increase the clinical crown height of teeth. This is suitable in treatment planning for teeth with inadequate tissue for retention of prosthetic restorations as a result of subgingival carious lesions or coronal fractures. Surgical treatment resets the margin while maintaining the biological width and clinical attachment.
In the nine-year Report it is stated that the bears had been seen in the zoological gardens to couple freely, but previously to 1848 most had rarely conceived. In the reports published since this date three species have produced young (hybrids in one case), ... A bear shot in autumn 1986 in Michigan was thought by some to be an American black bear/grizzly bear hybrid, because of its unusually large size and its proportionately larger brain case and skull. DNA testing was unable to determine whether it was a large American black bear or a grizzly bear.
Work on the game began with a Kickstarter funding campaign in 2015, before the developers were acquired by Microsoft Studios in 2018, supporting the developers to work on a version for the Xbox One. We Happy Few received mixed reviews from critics.
== Chain Home, Chain Home Low, Chain Home Extra Low, ROTOR and tropo-scatter stations == Notes: Some of the Chain Home Low sites were co-located with the larger Chain Home radars. Chain Home Extra Low equipment was co-located with "Chain Home" and "Chain Home Low" as well as at separate sites, but were of a less permanent nature, usually with mobile equipment. ROTOR was the post war Radar interception system created from existing radar installations. NARS, the North Atlantic Radio System, was an extension of the US Distant Early Warning system tropo-scatter communications network. ACE High provided long-range communications for NATO.
A similar promotion was held in September 2011, near the start of a traditional school year, encouraging the use of the game as an educational tool for science and mathematics. Valve wrote that they felt that Portal "makes physics, math, logic, spatial reasoning, probability, and problem-solving interesting, cool, and fun", a necessary feature to draw children into learning. This was tied to Digital Promise, a United States Department of Education initiative to help develop digital tools for education, which Valve is part of. Portal: Still Alive was announced for Xbox Live Arcade at the 2008 E3 convention, and was released on October 22, 2008. It features the original game, 14 new challenges, and new achievements. The additional content was based on levels from the map pack Portal: The Flash Version created by We Create Stuff and contains no additional story-related levels. According to Valve spokesman Doug Lombardi, Microsoft had previously rejected Portal on the platform due to its large size. Portal: Still Alive was well received by reviewers. 1UP.com's Andrew Hayward stated that, with the easier access and lower cost than paying for The Orange Box, Portal is now "stronger than ever". IGN editor Cam Shea ranked it fifth on his top 10 list of Xbox Live Arcade games. He stated that it was debatable whether an owner of The Orange Box should purchase this, as its added levels do not add to the plot. However, he praised the quality of the new maps included. The game ranked 7th in a later list of top Xbox Live Arcade titles compiled by IGN's staff in September 2010.
Sources: en.wikipedia.org
It is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone, containing seven amino acids with a lactam ring and a D-configured phenylalanine residue. It is supplied as a lyophilised powder for laboratory research.
The natural hormone is a linear tridecapeptide that is rapidly degraded in circulation. Melanotan-2 is shortened, cyclised, N-terminally acetylated, and carries a D-amino acid substitution, all of which slow enzymatic breakdown.
No national medicines regulator has approved melanotan-2 for therapeutic or cosmetic use. In several jurisdictions it is treated as an unapproved prescription medicine, and its legal classification differs from country to country.
The lyophilized powder is generally held at minus twenty degrees Celsius or below, away from light and moisture. Reconstituted solutions are typically refrigerated and used quickly. These practices derive from general peptide handling rather than a formal stability study.