melanocortin receptor comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Updated 2025-09-08. 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.
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.
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.
Melanotan-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone. Its sequence incorporates a lactam bridge that constrains the peptide into a ring, which increases resistance to enzymatic breakdown relative to the natural hormone. Researchers at the University of Arizona synthesised the compound in the late 1980s and early 1990s while studying pigmentation pathways. It has never received marketing approval from any national medicines regulator. In the scientific literature it is usually described as a laboratory research reagent rather than a therapeutic product.
| 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.
Structurally, Melanotan-2 retains the core recognition motif of alpha-melanocyte-stimulating hormone while adding a lactam bridge that links two side chains and constrains the molecule into a ring. This modification lowers susceptibility to enzymatic degradation. The compound acts as an agonist at melanocortin receptors, particularly subtypes associated with melanin production. Because the same receptor family influences several physiological processes, researchers note that its activity is not confined to pigmentation alone. Receptor selectivity continues to be examined in published studies.
Melanotan-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone, a naturally occurring peptide involved in pigmentation signalling. Its sequence incorporates modified residues that increase potency and extend biological activity relative to the native hormone. The compound binds receptors of the melanocortin family and is examined mainly in laboratory research. It does not occur naturally and exists only as a manufactured chemical entity produced by solid-phase synthesis.
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.
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.
A brief or only mildly elevated heart rate (heart rate taken while sitting down after recently walking across the room or getting up on the examination table) might be assumed to be due to anxiety or illness rather than exercise-induced inappropriate rapid heart rate due to an ATP shortage in the muscle cells. In the absence of severe symptoms (such as hepatomegaly, cardiomyopathy, hypoglycemia, lactic acidosis, myoglobinuria, rhabdomyolysis, acute compartment syndrome or renal failure), it is understandable that a disease would not be noticed by medical professionals for years, when at rest the patient appears completely normal. Depending on what enzyme is affected, a high-protein or low-fat diet may be recommended along with mild exercise. It is important for people with metabolic myopathies to consult with their doctors for a treatment plan in order to prevent acute muscle breakdowns while exercising that lead to the release of muscle proteins into the bloodstream that can cause kidney damage. A ketogenic diet has a remarkable effect on CNS-symptoms in PDH-deficiency and has also been tried in complex I deficiency. A ketogenic diet has demonstrated beneficial for McArdle disease (GSD-V) as ketones readily convert to acetyl CoA for oxidative phosphorylation, whereas free fatty acids take a few minutes to convert into acetyl CoA. As of 2022, another study on a ketogenic diet and McArdle disease (GSD-V) is underway.
He ruled that only Whitehall could determine what constituted the maintenance of "law and order" in Rhodesia, and that the Rhodesian emergency measures were unlawful as they had been formalised by the Officer Administering the Government, a post-UDI figure who was, in British eyes, unconstitutional. Reid concluded that Madzimbamuto was illegally detained. Harry Davies, one of the Rhodesian judges, announced on 8 August that the Rhodesian courts would not consider this ruling binding as they no longer accepted the Privy Council as part of the Rhodesian judicial hierarchy. Justice J. R. Dendy Young resigned in protest at Davies' ruling on 12 August and four days later was sworn in as Chief Justice of Botswana. The Rhodesian High Court granted full de jure recognition to the post-UDI government on 13 September 1968, while rejecting the appeals of 32 black Rhodesians who had been a month earlier convicted of terrorist offences and sentenced to death. Beadle declared that while he believed the Rhodesian judiciary should respect rulings of the Privy Council "so far as possible", the judgement of 23 July had made it legally impossible for Rhodesian judges to continue under the 1961 constitution. He asserted that the court therefore faced a choice between the 1965 constitution and a legal vacuum, the latter of which he felt he could not endorse.
== Location and classification == BAT's presence in adult humans was discovered in 2003 during FDG-PET scans to detect metastatic cancers. Using these scans and data from human autopsies, several deposits have been identified. In infants, brown adipose tissue deposits include: interscapular, supraclavicular, suprarenal, pericardial, para-aortic and around the pancreas, kidney and trachea. These deposits gradually get more white fat-like during adulthood. In adults, the deposits that are most often detected in FDG-PET scans are the supraclavicular, paravertebral, mediastinal, para-aortic and suprarenal ones. It remains to be determined whether these deposits are 'classical' brown adipose tissue or beige/brite fat.
Organic geochemists also have an interest in studying the diagenesis of biogenic substances in petroleum and how they are transformed in sediment and fossils. While 90% of this organic material is insoluble in common organic solvents – called kerogen – 10% is in a form that is soluble and can be extracted, from where biogenic compounds can then be isolated. Saturated linear fatty acids and pigments have the most stable chemical structures and are therefore suited to withstanding degradation from the diagenesis process and being detected in their original forms. However, macromolecules have also been found in protected geological regions. Typical sedimentation conditions involve enzymatic, microbial and physicochemical processes as well as increased temperature and pressure, which lead to transformations of biogenic substances. For example, pigments that arise from dehydrogenation of chlorophyll or hemin can be found in many sediments as nickel or vanadyl complexes. A large proportion of the isoprenoids in sediments are also derived from chlorophyll. Similarly, linear saturated fatty acids discovered in the Messel oil shale of the Messel Pit in Germany arise from organic material of vascular plants. Additionally, alkanes and isoprenoids are found in soluble extracts of Precambrian rock, indicating the probable existence of biological material more than three billion years ago. However, there is the potential that these organic compounds are abiogenic in nature, especially in Precambrian sediments.
Paleolithic hunting and gathering people ate varying proportions of vegetables (including tubers and roots), fruit, seeds (including nuts and wild grass seeds) and insects, meat, fish, and shellfish. However, there is little direct evidence of the relative proportions of plant and animal foods. Although the term "paleolithic diet", without references to a specific timeframe or locale, is sometimes used with an implication that most humans shared a certain diet during the entire era, that is not entirely accurate. The Paleolithic was an extended period of time, during which multiple technological advances were made, many of which had impact on human dietary structure. For example, humans probably did not possess the control of fire until the Middle Paleolithic, or tools necessary to engage in extensive fishing. On the other hand, both these technologies are generally agreed to have been widely available to humans by the end of the Paleolithic (consequently, allowing humans in some regions of the planet to rely heavily on fishing and hunting). In addition, the Paleolithic involved a substantial geographical expansion of human populations. During the Lower Paleolithic, ancestors of modern humans are thought to have been constrained to Africa east of the Great Rift Valley. During the Middle and Upper Paleolithic, humans greatly expanded their area of settlement, reaching ecosystems as diverse as New Guinea and Alaska, and adapting their diets to whatever local resources were available.
Sources: en.wikipedia.org
== Desalting and Buffer Exchange vs. Dialysis == Dialysis is useful for many of the same desalting and buffer exchange applications performed with gel filtration chromatography, as both methods are based on similar molecular weight cut-off limits. Gel filtration has the advantage of speed (a few minutes vs. hours for dialysis) along with the ability to remove contaminants from relatively small-volume samples compared to dialysis which is an important feature when working with toxic or radioactive substances. Dialysis, on the other hand, is much less dependent on sample size as related to device format. For dialysis applications, achieving a high percentage sample recovery and molecule removal is generally straight forward with little optimization. For gel filtration applications it is important to select a column size and format that is suitable for your sample.
In addition to the Bedouin, the 18th and 19th centuries also witnessed large migrations of Druze from Mount Lebanon to the Jabal Hauran, which gradually became known as the Jabal al-Druze ('mountain of the Druze'). Persistent migrations of Druze from Mount Lebanon, Wadi al-Taym and the Galilee, caused by the increased turbulence they faced, continued throughout the 18th century: historian Kais Firro stated that "each sign of danger in their traditional lands of settlement seemed to instigate a new Druze migration to the Hauran". During the final years of the decade-long Egyptian administration of Syria, the Druze of Jabal Hauran launched their first revolt against the authorities, in response to a conscription order by Ibrahim Pasha. By then, their numbers in the region had been swollen by migration. The 1860 Mount Lebanon civil war between the Druze and Christians and the resulting French military intervention caused another large exodus of Druze to Jabal Hauran. The relationship between the Druze and Christians in As-Suwayda Governorate has been marked by harmony and peaceful coexistence, Before 2011, more than 55,000 Christians, primarily Greek Orthodox members of the Greek Orthodox Church of Antioch, Melkite, and Latin Catholic, lived in As-Suwayda Governorate, where they had several ancient churches. Many of them are members of Christian Arab tribes affiliated with the Ghassanids. Outside of the As-Suwayda Governorate, Christians and Druze coexist in several mixed villages and towns such as Jaramana, Sahnaya, and Jdeidat Artouz.
Tea and toast syndrome is a form of malnutrition commonly experienced by elderly people who cannot prepare meals and tend to themselves. The term is not intrinsic to tea or bread products only; rather, it describes limited dietary patterns that lead to reduced calories resulting in a deficiency of vitamins and other nutrients. This can contribute to a gradual loss of wellness and muscle due to poor protein intake. In elderly individuals with a low GFR, the syndrome may manifest itself as hyponatremia, a low concentration of the electrolyte sodium in the bloodstream. This is attributed to drinking a large amount of water while consuming a diet poor in salt and protein. Hyponatremia can lead to various neurological problems ranging from headaches and a decreased ability to think, to seizures and coma in the most severe cases.
Approximately two billion years ago, a free-living cyanobacterium entered an early eukaryotic cell, either as food or as an internal parasite, but managed to escape the phagocytic vacuole it was contained in and persist inside the cell. This event is called endosymbiosis, or "cell living inside another cell with a mutual benefit for both". The external cell is commonly referred to as the host while the internal cell is called the endosymbiont. The engulfed cyanobacteria provided an advantage to the host by providing sugar from photosynthesis. Over time, the cyanobacterium was assimilated, and many of its genes were lost or transferred to the nucleus of the host. Some of the cyanobacterial proteins were then synthesized by the host cell and imported back into the chloroplast (formerly the cyanobacterium), allowing the host to control the chloroplast. Chloroplasts which can be traced back directly to a cyanobacterial ancestor (i.e. without a subsequent endosymbiotic event) are known as primary plastids ("plastid" in this context means almost the same thing as chloroplast). Chloroplasts that can be traced back to another photosynthetic eukaryotic endosymbiont are called secondary plastids or tertiary plastids (discussed below). Whether primary chloroplasts came from a single endosymbiotic event or multiple independent engulfments across various eukaryotic lineages was long debated.
Sources: en.wikipedia.org
=== Other uses in arts, entertainment, and media === Link (film), a 1986 horror movie featuring a super-intelligent, murderous orangutan WBT-FM, a radio station in Charlotte, North Carolina, US, that used call sign WLNK 1997–2025
=== Dependence and withdrawal === Dextromethorphan is considered less addictive than other common cough suppressants, such as the opiate codeine. Since it acts as a serotonin reuptake inhibitor, users report that regular recreational use over a long period of time can cause withdrawal symptoms similar to those of antidepressant discontinuation syndrome. Additionally, disturbances have been reported in sleep, senses, movement, mood, and thinking.
Neal Benowitz, a professor of medicine at UC San Francisco who is an expert on ephedrine and other stimulants, agreed that "These [levels] are what you'd see from someone taking cold or allergy medicines and are unlikely to have any effect on performance." Following Exum's revelations the IAAF acknowledged that at the 1988 Olympic Trials the USOC indeed followed the correct procedures in dealing with eight positive findings for ephedrine and ephedrine-related compounds in low concentration. The federation also reviewed in 1988 the relevant documents with the athletes' names undisclosed and stated that "the medical committee felt satisfied, however, on the basis of the information received that the cases had been properly concluded by the USOC as 'negative cases' in accordance with the rules and regulations in place at the time and no further action was taken".
=== Economic policy === Ford's government cancelled the basic income pilot project. He opposes the laying off of government workers. He supports the use of attrition to eliminate government jobs that he believes are not needed. Ford believes in hiring independent auditors to audit government spending. Jay Goldberg of the Canadian Taxpayers Federation labelled Ford's spending excessive and noted Ontario's large debt increases under his government. In June 2019, Rod Phillips, who served as Minister of the Environment, Conservation and Parks, replaced Vic Fedeli as Ontario's finance minister. Andrea Khanjin was appointed as Parliamentary Assistant to the Minister of the Environment, Conservation and Parks in June 2018. Starting in January 2019, those who are working full-time and earning less than $30,000 a year would pay no provincial income tax, in the new LIFT program but minimum wage would be frozen at $14 per hour. They eliminated 3 legislative offices including the Environmental Commissioner of Ontario (ECO), child and youth advocate and French language services commissioner positions. The surtax on the highest earning Ontarians that would have generated about $275 million in revenue, was cancelled. The proposed French language university was cancelled as were three university satellite campuses. Fedeli served as minister until he was moved to economic development in June 2019 in a major cabinet shuffle.
=== Pilonidal sinus === Pilonidal sinus (PNS): a sinus tract, or small channel, that may originate from the source of infection and open to the surface of the skin. Material from the cyst drains through the pilonidal sinus. A pilonidal cyst is usually painful, but if it is a draining sinus, the pressure is relieved and the patient might not feel pain.
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 cyclic heptapeptide modelled on alpha-melanocyte-stimulating hormone. A lactam bridge links two side chains, forming a ring that stabilises the molecule against proteolysis. It belongs to the broader melanocortin peptide family.