The short version of melanocortin receptor fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-01-21. Anything still debated is marked as such rather than presented as settled.
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.
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.
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 class | Synthetic cyclic heptapeptide | Analog of alpha-MSH with an internal lactam bridge |
| Molecular weight | Approximately 1024 daltons | Free base value; salt forms differ |
| Appearance | White to off-white powder | Usually supplied as a lyophilized solid |
| Solubility | Freely soluble in water | Poorly soluble in nonpolar solvents |
| Typical storage | −20 °C, dry, protected from light | Repeated freeze-thaw cycles degrade peptides |
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.
The peptide acts as a non-selective agonist at melanocortin receptors, showing affinity for MC1R, MC3R, MC4R and MC5R. Activation of MC1R on melanocytes drives the conversion of tyrosine into melanin and shifts production toward the darker eumelanin form. MC4R signalling in the central nervous system is linked to appetite and energy balance, which helps explain why reduced food intake appeared in early human studies. Effects on MC4R and on vascular tone also account for the erectile responses recorded as unexpected findings in those same trials.
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.
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.
Cholecystokinin (CCK or CCK-PZ; from Greek chole 'bile', cysto 'sac', kinin 'move'; hence, 'move the bile-sac', i.e., the gallbladder) is a peptide hormone of the gastrointestinal system responsible for stimulating the digestion of fat and protein. Cholecystokinin, formerly called pancreozymin, is synthesized and secreted by enteroendocrine cells in the duodenum, the first segment of the small intestine. Its presence causes the release of pancreatic juice from the pancreas and bile from the gallbladder.
== P == Pangaea – paleontology – parallel evolution – paraphyletic – parasitism – parasitology – parthenogenesis – passive transport – Patau syndrome – paternity test – PCR – PCR mutagenesis – pentose phosphate pathway – peptide – peptide bond – peripheral protein – peroxisome – Pfeffer cell – phage – phagocytosis – phenotype – phloem – phospholipid – phospholipid bilayer – phosphorylation – photobiology – photolysis – photon – photophosphorylation – photorespiration – photosynthesis – photosynthesis – photosystem I – photosystem II – phycobilin – phycobiliprotein – phycocyanin – phycology – phylogenetics – phylogeny – phylogenetic tree – physiology – pigment – placenta – plankton – plant – plantae – plant physiology – plant sexuality – plasma membrane – plasmid – plasmolysis – plastid – plate tectonics – point mutation – pollenizer – pollination – pollinator – polymerase chain reaction – polypeptide – polyploidy – polysaccharide – population – population dynamics – population ecology – population genetics – potential energy – predation – pregnancy – primary nutritional groups – primary structure – primer – prion – prokaryote – prometaphase – promoter – prophage – prophase – proprioception – proteasome – protein biosynthesis – protein – protein translocation – proteolysis – proteome – proteomics – protist – protista – proton pump – protozoa – pseudopod – pteridophyte – Punnett square – purine – punctuated equilibrium – pyrimidine – pyruvate oxidation –
In October 2013, Basilea received marketing authorisation in twelve European countries, including Germany, for the distribution of the broad-spectrum antibiotic Ceftobiprole for the treatment of bacterial lung infections; in the following two years, the drug was gradually approved in other European countries and non-EU countries. Ceftobiprole has been approved in 32 countries and has been marketed in 21 countries since the end of 2023. In 2020, Basilea sold the group headquarters in Basel to the pension fund of the Swiss bank UBS by way of a sale-leaseback and moved to its new headquarters in Allschwil in mid-2022. The gross proceeds from the sale amounted to around CHF 19 million before fees and transaction costs. In 2021, Basilea Pharmaceutica China Ltd. was sold to the US company PHT International. Basilea was previously active in oncological research, but withdrew from it at the beginning of 2022 and has since been focusing purely on anti-infectives. In 2023, Basilea acquired the rights to the antifungal drug Fosmanogepix from Pfizer. By the end of 2023, Isavuconazole was commercialised in more than 70 countries, including the United States, most EU countries, China and Japan. Isavuconazole's total global sales in the twelve-month period between October 2022 and September 2023 amounted to CHF 406 million. This corresponds to growth of 22 per cent compared to the previous year.
The 1578 death of King Sebastian in battle and the subsequent 1580 death of King Henry without a named heir, precipitated a succession crisis. Philip II of Spain, whose mother was Isabella of Portugal, was one of the candidates for the throne. In 1581 he was acclaimed king of Portugal, creating a personal union between the two kingdoms. This deprived Portugal of an independent foreign policy and led to the Dutch-Portuguese War. In 1641, John, Duke of Braganza, was proclaimed king by the Cortes after an uprising led by some nobles in the year before, ending the Iberian Union under the House of Habsburg, and beginning the rule of the House of Braganza. Following the Portuguese Restoration War, Spain recognised Afonso VI as king of Portugal. During the reign of John V, the large influx of Brazilian gold into the royal treasury, chiefly through the royal fifth, produced a resource curse that weakened industry and cereal production, created a gold rush from Portugal to Brazil, and led to prolonged economic stagnation, permanent reduction of income growth, and the interruption of the institutional and economic progress achieved in the 17th century. After the depletion of gold revenues, Portugal was left with a weak industrial base and backward institutional and educational structures. This condition was exacerbated by Sebastião José de Carvalho e Melo, 1st Marquis of Pombal, who emerged as the country's de facto ruler in the aftermath of the 1755 earthquake and tsunami, one of the kingdom's worst recorded natural disaster.
Sources: en.wikipedia.org
== Hazards == Radium is highly radioactive, as is its immediate decay product, radon gas. When ingested, 80% of the ingested radium leaves the body through the feces, while the other 20% goes into the bloodstream, mostly accumulating in the bones. This is because the body treats radium as calcium and deposits it in the bones, where radioactivity degrades marrow and can mutate bone cells. Exposure to radium, internal or external, can cause cancer and other disorders, because radium and radon emit alpha and gamma rays upon their decay, which kill and mutate cells. Radium is generally considered the most toxic of the radioactive elements. Some of the biological effects of radium include the first case of "radium-dermatitis", reported in 1900, two years after the element's discovery. The French physicist Antoine Becquerel carried a small ampoule of radium in his waistcoat pocket for six hours and reported that his skin became ulcerated. Pierre Curie attached a tube filled with radium to his arm for ten hours, which resulted in the appearance of a skin lesion, suggesting the use of radium to attack cancerous tissue as it had attacked healthy tissue. Handling of radium has been blamed for Marie Curie's death, due to aplastic anemia, though analysis of her levels of radium exposure done after her death find them within accepted safe levels and attribute her illness and death to her use of radiography. A significant amount of radium's danger comes from its daughter radon, which as a gas can enter the body far more readily than can its parent radium.
Mephedrone is a synthetic stimulant drug of the amphetamine and cathinone classes. Slang names include drone and MCAT. It is reported to be manufactured in China and is chemically similar to the cathinone compounds found in the khat plant of eastern Africa. Mephedrone comes in the form of tablets or a powder, which users can swallow, snort, or inject, producing similar effects to MDMA, amphetamines, and cocaine. Mephedrone was first synthesized in 1929, but did not become widely known until it was rediscovered in 2003. By 2007, mephedrone was reported to be available for sale on the Internet; by 2008 law enforcement agencies had become aware of the compound; and, by 2010, it had been reported in most of Europe, becoming particularly prevalent in the United Kingdom. Mephedrone was first made illegal in Israel in 2008, followed by Sweden later that year. In 2010, it was made illegal in many European countries, and, in December 2010, the EU ruled it illegal. Australia, New Zealand, and the US treat it as an analog of other illegal drugs, so it can be controlled by laws similar to the Federal Analog Act. In September 2011, the US temporarily classified mephedrone as illegal, in effect from October 2011. Mephedrone is neurotoxic and has abuse potential, predominantly exerted on serotonin terminals, mimicking that of MDMA with which it shares the same subjective sensations on abusers.
On 7 September 2020, CSL signed agreements with the Australian government to supply the University of Queensland vaccine (V451) and to manufacture (with AstraZeneca) the Oxford University vaccine (AZD1222), which would yield nearly 85 million doses for Australians. The agreement was contingent on the future success of clinical trials of these vaccines. Most of the manufacture would occur in Melbourne, Australia. On 11 December 2020, after a high percentage of the University of Queensland vaccine trial participants returned "false positive" results for HIV, it was decided that vaccine development will not proceed to Phase 2/3 trials. On 23 March 2021, the Therapeutic Goods Administration provisionally approved the first batches, numbering 832,000 doses, of the Oxford–AstraZeneca COVID-19 vaccine manufactured by CSL in its plant in Broadmeadows, Victoria. The Australian Government has contracted CSL to produce 50 million doses of the vaccine.
Jack Schmidt was the first person commissioned to paint the original In-N-Out located in Baldwin Park, California for In-N-Out Burger Inc. His paintings were later reproduced on advertisements, shirts, and other consumer products. The 2022 shirt design was created by Palm Springs, California artist Danny Heller.
Microscopically, each liver lobe is seen to be made up of hepatic lobules. The lobules are roughly hexagonal, and consist of plates of hepatocytes, and sinusoids radiating from a central vein towards an imaginary perimeter of interlobular portal triads. The central vein joins to the hepatic vein to carry blood out from the liver. A distinctive component of a lobule is the portal triad, which can be found running along each of the lobule's corners. The portal triad consists of the hepatic artery, the portal vein, and the common bile duct. The triad may be seen on a liver ultrasound, as a Mickey Mouse sign with the portal vein as the head, and the hepatic artery, and the common bile duct as the ears. Histology, the study of microscopic anatomy, shows two major types of liver cells: parenchymal cells and nonparenchymal cells. About 70–85% of the liver volume is occupied by parenchymal hepatocytes. Nonparenchymal cells constitute 40% of the total number of liver cells but only 6.5% of its volume. The liver sinusoids are lined with two types of cell, sinusoidal endothelial cells, and phagocytic Kupffer cells. Hepatic stellate cells are nonparenchymal cells found in the perisinusoidal space, between a sinusoid and a hepatocyte. Additionally, intrahepatic lymphocytes are often present in the sinusoidal lumen.
Sources: en.wikipedia.org
ligand An ion, functional group, or other molecule that binds to a central metal atom to form a coordination complex. Such bonding can range from covalent to ionic, but generally involves formal donation of one or more of the ligand's electron pairs to the metal.
==== Legislature ==== The U.S. Congress is a bicameral legislature made up of the Senate and the House of Representatives. The Senate has 100 members—two residents from each state and elected by that state's voters for a six-year term. The House of Representatives has 435 voting members, elected for a two-year term by the constituency of the congressional district in which they reside. District boundaries are generally drawn by state legislatures or redistricting commissions under state law. Every U.S. congressional district must be as nearly equal in population as practicable; each sends one representative to Congress. Election years for senators are staggered so that only one-third of them will be up for election every two years. U.S. representatives are all up for election at the same time every two years. The U.S. Congress makes federal law, declares war, has the power of the purse, and has the power of impeachment. The Senate gives advice and consent to the ratification of treaties by a two-thirds vote of senators present. One of the foremost non-legislative functions of Congress is the power to investigate and oversee the executive branch. Congressional oversight is usually delegated to committees and is facilitated by Congress' power to issue subpoenas. Much of the work of Congress is performed by a collection of committees, each appointed for a specific purpose or function. Committee membership is by tradition and statute bipartisan, but all committees are chaired by a member of the majority party, who sets the committee agenda.
The white shark is an apex predator that opportunistically feeds on fish, cephalopods (like squid), marine mammals, sea birds, and sea turtles. Diet differs based on size and age; individuals over 3 m (10 ft) can feed on marine mammals, while juveniles are limited to smaller prey like fish and cephalopods. White sharks prefer prey with high fat content, but even large individuals are recorded to eat low-fat foods. Marine mammals preyed on include seals and cetaceans (like dolphins). White sharks are also recorded to bite sea otters but do not usually consume them. The seasonal availability of seals drives white shark migration to certain locations. Targeted species include gray seals, harbor seals, northern elephant seals, California sea lions, Cape fur seals and New Zealand fur seals. White sharks mainly hunt seals by ambush and normally target newly weaned young, as they have thick blubber but are still small and inexperienced. Adults are more difficult to overpower and can injure the shark with their teeth and claws; bull elephant seals are particularly formidable, being as massive as adult white sharks. Some species will harass the shark to drive it away. Observations off California show that white sharks typically ambush seals from below, seizing them near the surface and dragging them under. The strike location often depends on the prey's anatomy: earless seals (like elephant seals) are usually struck near the head or hind flippers, while eared seals (like sea lions) are grabbed behind the torso.
Respiration involves drawing water into the mantle cavity through an aperture, passing it through the gills, and expelling it through the siphon. Ingress is achieved by contraction of radial muscles in the mantle wall, and flapper valves shut when strong, circular muscles expel the water through the siphon. Extensive connective tissue lattices support the respiratory muscles and allow them to inflate the respiratory chamber. The lamella structure of the gills allows for high oxygen uptake, up to 65% in water at 20 °C (68 °F). Respiration can also play a role in locomotion, as an octopus can propel its body shooting water out of the siphon. The thin skin absorbs additional oxygen. When resting, around 41% of oxygen absorption is through the skin, reduced to 33% when the octopus swims, despite the amount of oxygen absorption increasing as water flows over the body. When it is resting after a meal, skin absorption can drop to 3%.
The relative stability of metal ion-protein binding, which affects the conformational stability of metal cofactor-containing proteins in (denaturing) solution, is reflected by the Irving–Williams series.
Sources: en.wikipedia.org
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.
Melanotan-1, also called afamelanotide, is a shorter linear analog with a different amino acid sequence and no lactam ring. It has been evaluated in formal clinical programs, while melanotan-2 has not. The two are distinct molecules and are not interchangeable.
No. Bremelanotide is a related but distinct cyclic peptide that reached approved status for one specific clinical indication. Melanotan-2 is a separate molecule with its own sequence and properties. Shared ancestry in the melanocortin family does not make them the same substance.
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.