The short version of melanocortin receptor fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2025-08-01. Anything still debated is marked as such rather than presented as settled.
Melanotan-2 is handled in the laboratory as a lyophilised powder that dissolves readily in water, dimethyl sulfoxide and dimethylformamide, with limited solubility in ethanol. Stock solutions prepared in an organic solvent often precipitate when diluted into aqueous buffer, so gradual dilution with mixing is standard practice. The peptide carries a tryptophan residue and a histidine residue, both sensitive to oxidation and to alkaline conditions. Working solutions are therefore kept near neutral to slightly acidic pH, protected from light, and consumed within the same working session whenever that is practical.
Solid peptide kept dry at minus twenty degrees Celsius, shielded from light and moisture, is generally considered stable for extended periods. Solutions are divided into single-use aliquots and held at minus twenty or minus eighty degrees Celsius, because repeated freeze-thaw cycles promote aggregation and loss of material to container surfaces. Hydrolysis of the backbone and oxidation of tryptophan are the principal degradation routes in aqueous solution, and both accelerate at ambient temperature. Hygroscopic uptake after a vial is opened can also shift the actual mass weighed, which affects any concentration calculated from it.
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 |
|---|---|---|
| Appearance | White to off-white powder | Lyophilised material may be hygroscopic |
| Solubility class | Soluble in water, DMSO and DMF | Dilution into aqueous buffer can cause precipitation |
| Storage of solid | Minus 20 degrees C, desiccated, dark | Aliquot to limit repeated opening of the vial |
| Storage of solution | Minus 20 to minus 80 degrees C, aliquoted | Avoid repeated freeze-thaw cycles |
| Identity method | Reversed-phase HPLC with mass spectrometry | Retention time and mass are checked together |
Identity testing for a cyclic peptide of this size usually relies on reversed-phase high-performance liquid chromatography coupled to mass spectrometry. The mass spectrum confirms molecular weight, while the chromatographic trace indicates the proportion of related impurities. Tandem mass spectrometry can provide sequence-level information when fragmentation data are compared against a reference standard. Nuclear magnetic resonance is sometimes used to confirm the lactam bridge, although it requires more material and greater operator expertise than routine chromatographic methods.
Lyophilised peptide powder is comparatively stable when kept dry, cold and protected from light. Once dissolved, the molecule is exposed to hydrolysis, oxidation and microbial growth, and degradation accelerates at higher temperatures and in alkaline solution. Repeated freeze-thaw cycles concentrate solutes and promote aggregation. Handling guidance for research peptides commonly clusters around freezer temperatures for powder and short refrigerated use for reconstituted solutions, with pH control and sterile technique applied throughout.
Verification of a purchased sample requires documentation linking a batch to a certificate of analysis, and that document should be read for the methods used rather than the headline purity figure. A single chromatographic percentage does not establish identity. Independent laboratories can perform identity and content assays, but no such test establishes that a product is suitable for human use. Claims about efficacy rest largely on small, early studies rather than on replicated controlled trials, and that gap remains open.
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.
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.
The young Appalachians reached elevations similar to today's Alps and Rockies—both of which are significantly younger mountain ranges—before 240 million years of natural erosion by water, wind, ice, and gravity gradually morphed them into the lower, rugged peaks typically seen today. Considering their extensive length, the Appalachians contain a diverse selection of biomes ranging from the temperate broadleaf and mixed Appalachian-Blue Ridge forest in the south to the boreal Eastern Canadian forest in the north. Conifers like red spruce and balsam fir dominate the north and high elevations, while deciduous trees like sugar maple and beech are more prevalent further south and oak-chestnut forests reign between. The climate ranges from humid subtropical to subarctic, with a few peaks in the Presidential Range of New Hampshire's White Mountains having a true tundra climate; many locations are also oceanic or humid continental. Mammals like black bear, white-tailed deer, squirrels, raccoons, and skunks are common throughout the range, while others like moose are more regionally limited. Birds, fish, shellfish, amphibians like salamanders, and other invertebrates are also abound in the profoundly ecologically diverse region. Once-largely extirpated species like the bobcat and coyote have also made a resurgence in recent years. The Appalachian Mountains are a barrier to east–west travel, as they form a series of alternating ridgelines and valleys oriented in opposition to most highways and railroads running east–west.
== Etymology == The genus name, Rotheca, seemingly comes from the Malaysian words "cheriga", which means small, and "thekku", which means teak. The species epithet comes from the French word "myriades", which means ten thousand, and a Latinization of the Greek "oides", which means to see. Some say that the species epithet came about because it resembles another species in Myrica, so the name refers to the leaf shape. 'Ugandense' is a cultivar of this species which shows purplish-blue flowers with flashy stamens. It was originally named Clerodendrum myricoides 'Ugandense', but a 1998 study led to its current status as Rotheca myricoides 'Ugandense".
Management focuses on relieving symptoms and reducing long-term risks. A healthy lifestyle and weight control are recommended for general management. In addition, hormonal contraception can help regulate menstrual cycles and reduce acne and excess hair growth. Metformin, a common antidiabetic drug, increases insulin sensitivity. For fertility, ovulation can be induced with letrozole, among other methods. In addition, those affected can be monitored for cardiometabolic risks, and during pregnancy.
== History == EGF was the second growth factor to be identified. Initially, human EGF was known as urogastrone. Stanley Cohen discovered EGF while working with Rita Levi-Montalcini at the Washington University in St. Louis during experiments researching nerve growth factor. For these discoveries Levi-Montalcini and Cohen were awarded the 1986 Nobel Prize in Physiology or Medicine.
Sources: en.wikipedia.org
=== 1955 === February 24: The Baghdad Pact is founded by Iran, Iraq, Pakistan, Turkey, and the United Kingdom. It is committed to resisting Communist expansion in the Middle East. March: Soviet aid to Syria begins. The Syrians will remain allies of the Soviets until the end of the Cold War. April 18: The Asia-Africa Conference (also known as the Bandung Conference) is first held in Bandung, Indonesia. April: The Non-Aligned Movement is pioneered by Jawaharlal Nehru of India, Sukarno of Indonesia, Tito of Yugoslavia, Gamal Abdel Nasser of Egypt and Kwame Nkrumah of Ghana (then known as the Gold Coast). This movement is designed to be a bulwark against the 'dangerous polarization' of the world at that time and to restore the balance of power with smaller nations. May 5: The Allies end the military occupation of West Germany. May 6: The United States begins formal diplomatic relations with West Germany, followed soon after by the United Kingdom and France. May 9: West Germany joins NATO and begins rearmament. May 14: The Warsaw Pact is founded in Eastern Europe and includes East Germany, Czechoslovakia, Poland, Hungary, Romania, Albania, Bulgaria, and the Soviet Union. It acts as the Communist military counterpart to NATO. May 15: The Austrian State Treaty is signed by the Allied powers. July 18: President Dwight D. Eisenhower of the United States, Prime Minister Anthony Eden of the United Kingdom, Premier Nikolai A. Bulganin of the Soviet Union, and Prime Minister Edgar Faure of France, known as the 'Big Four', attend the Geneva Summit.
While the 1967 riots are seen as a turning point in the city's fortunes, Detroit's decline began in the 1950s, during which the city lost almost a tenth of its population. Powerful historical forces buffeted Detroit's single-industry economy, and Detroit's federally supported comeback strategies did little to help. State and local governments responded to the riot with a dramatic increase in minority hiring, including the State Police hiring blacks for the first time, and Detroit more than doubling the number of black police. The Michigan government used its reviews of contracts issued by the state to secure an increase in nonwhite employment. Between August 1967 and the end of the 1969–1970 fiscal year, minority group employment by the contracted companies increased by 21.1 percent. In the aftermath of the riot, the Greater Detroit Board of Commerce launched a campaign to find jobs for ten thousand "previously unemployable" persons, a preponderant number of whom were black. By October 12, 1967, Detroit firms had reportedly hired about five thousand African-Americans since the beginning of the jobs campaign. According to Sidney Fine, "that figure may be an underestimate." The Michigan Historical Review writes that "Just as the riots following the assassination of Martin Luther King Jr.
=== Microemulsion === In February 2011, Canadian researchers at the University of Calgary's Schulich School of Engineering announced a microchip for blood tests. Dubbed a microemulsion, a droplet of blood captured inside a layer of another substance. It can control the exact size and spacing of the droplets. The new test could improve the efficiency, accuracy, and speed of laboratory tests while also doing it cheaply.
Sources: en.wikipedia.org
As the elastic walls of the vagina stretch or contract, with support from the pelvic muscles, to wrap around the inserted penis (or other object), this creates friction for the penis and helps to cause a man to experience orgasm and ejaculation, which in turn enables fertilization. An area in the vagina that may be an erogenous zone is the G-spot. It is typically defined as being located at the anterior wall of the vagina, a couple or few inches in from the entrance, and some women experience intense pleasure, and sometimes an orgasm, if this area is stimulated during sexual activity. A G-spot orgasm may be responsible for female ejaculation, leading some doctors and researchers to believe that G-spot pleasure comes from the Skene's glands, a female homologue of the prostate, rather than any particular spot on the vaginal wall; other researchers consider the connection between the Skene's glands and the G-spot area to be weak. The G-spot's existence (and existence as a distinct structure) is still under dispute because reports of its location can vary from woman to woman, it appears to be nonexistent in some women, and it is hypothesized to be an extension of the clitoris and therefore the reason for orgasms experienced vaginally.
Stratum basale (basal layer) Stratum spinosum (spinous layer) Stratum granulosum (granular layer) Stratum corneum (keratinized/superficial layer) Depending on the region of the mouth the epithelium may be keratinized or non-keratinized. Non-keratinized squamous epithelium covers the soft palate, lips, cheeks and the floor of the mouth. Keratinized squamous epithelium is present in the gingiva and hard palate. Keratinization is the differentiation of keratinocytes in the granular layer into dead surface cells to form the stratum corneum. The cells terminally differentiate as they migrate to the surface (from the basal layer where the progenitor cells are located to the dead superficial surface). The lamina propria is a fibrous connective tissue layer that consists of a network of type I and III collagen and elastin fibers. The main cells of the lamina propria are the fibroblasts, which are responsible for the production of the extracellular matrix. The basement membrane forms the border between the epithelial layer and the lamina propria.
== Animal models == Four different mouse models with COL3A1 defects have been reported. Inactivation of the murine COL3A1 gene using homologous recombination technique led to a shorter life span in homozygous mutant mice. The mice died prematurely from a rupture of major arteries mimicking the human vEDS phenotype. These mice also had a severe malformation of the brain. Another study discovered mice with a naturally occurring large deletion of the COL3A1 gene. These mice died suddenly due to thoracic aortic dissections. The third type of mutant mice were transgenic mice with a Gly182Ser mutation. These mice developed severe skin wounds, demonstrated vascular fragility in the form of reduced tensile strength and died prematurely at the age of 13–14 weeks. The fourth mouse model with defective COL3A1 gene is the tight skin mouse (Tsk2/+), which resembles the human systemic sclerosis.
Sources: en.wikipedia.org
Purity is normally stated as an area percentage from high-performance liquid chromatography, for example ninety-five or ninety-eight percent. That figure describes the proportion of ultraviolet-absorbing material eluting as the main peak. It says nothing about water content, counterions, residual solvents or mass fraction of the peptide itself.
Peptides are commonly isolated as acetate or trifluoroacetate salts, and the counterion contributes to total mass. Two vials with identical peptide content can therefore differ in weight and in measured response. Residual trifluoroacetate is also relevant in cell-based work because it can influence membrane behaviour.
Degradation products are often closely related to the parent molecule, making them hard to resolve with a single method. Counterion variability adds a further source of scatter between laboratories. Because no pharmacopoeial monograph exists for melanotan-2, groups rely on method-specific validation rather than a shared reference standard.
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.