This is a working overview of melanocortin receptor, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-08-01. Anything still debated is marked as such rather than presented as settled.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Compound class | Synthetic cyclic heptapeptide | Alpha-MSH analogue containing a D-phenylalanine residue |
| Molecular formula | C50H69N15O9 | Average molecular mass approximately 1024.2 g/mol |
| Appearance | White to off-white lyophilised powder | Normally supplied as a freeze-dried solid in a sealed vial |
| Solubility | Freely soluble in water and polar solvents | Dissolves readily in aqueous buffers and in alcohol-water mixtures |
| Receptor targets | MC1R, MC3R, MC4R, MC5R | Acts as a non-selective melanocortin receptor agonist |
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.
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.
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.
Melanotan II is a synthetic peptide analog modeled on alpha-melanocyte-stimulating hormone, a naturally occurring signaling peptide involved in pigmentation. Its structure is a cyclic heptapeptide containing two non-natural substitutions, norleucine at position four and D-phenylalanine at position seven. These modifications resist enzymatic breakdown and extend the molecule's activity relative to the native hormone. The compound binds melanocortin receptors and is studied mainly as a pharmacological tool rather than a therapeutic product. It has never received approval as a medicine in any major jurisdiction.
The compound was developed in the late 1980s and 1990s by academic researchers investigating photoprotection. The rationale held that stimulating melanin production might reduce ultraviolet damage to skin and lower skin cancer risk. Early work examined receptor binding, pigment response, and short-term tolerability in small studies. That program did not produce an approved drug, and formal development stalled after early-phase trials. Whether induced pigmentation confers meaningful photoprotection remains an open question.
Smear layer will fill the orifices of the dentinal tubules, hence forming smear plugs. These smear plugs decrease dentin permeability by 90% and the smear plug alone can prevent adhesive resin penetration into dentinal tubules. The thickness of smear layer can range from 0.5-2 μmeter and for the smear plug, 1 to 10 μmeter. Smear layer poses some threat for optimal bonding to occur. That is why it needs to be removed. For example, smear layer needs to be removed prior to bonding by etch-and-rinse (total etch) adhesives. This will lead to thicker hybrid layer and long, denser resin tags which results in better bond strength.
=== Refraction === The optical component is concerned with producing a reduced inverted image on the retina. The eye's optical system consists of not only two but four surfaces—two on the cornea, two on the lens. Rays are refracted toward the midline. Distant rays, due to their parallel nature, converge to a point on the retina. The cornea admits light at the greatest angle. The aqueous and vitreous humors both have a refractive index of 1.336-1.339, whereas the cornea has a refractive index of 1.376. Because the change in refractive index between cornea and aqueous humor is relatively small compared to the change at the air–cornea interface, it has a negligible refractive effect, typically -6 dioptres. The cornea is considered to be a positive meniscus lens. Some species of birds and chameleons, and one known species of fish, also have corneas which can focus.
Ruthenium has no radioactive isotopes with half-lives much longer than a year and the price of ruthenium is relatively high, making the destruction of 99Tc into a potentially lucrative source of producing a precious metal from an undesirable feedstock.
== Medical uses == In the United States pioglitazone/glimepiride is indicated as an adjunct to diet and exercise to improve glycemic control in adults with type 2 diabetes mellitus who are already treated with a thiazolidinedione and sulfonylurea or who have inadequate glycemic control on a thiazolidinedione alone or a sulfonylurea alone. In the European Union pioglitazone/glimepiride is indicated for the treatment of people with type 2 diabetes mellitus who show intolerance to metformin or for whom metformin is contraindicated and who are already treated with a combination of pioglitazone and glimepiride.
Sources: en.wikipedia.org
== False claims == Since around 2008, GcMAF has been promoted as a cure for cancer, HIV, autism and other conditions. Three out of four of the original studies authored by Yamamoto (published between 2007 and 2009) were retracted by the scientific journals in which they were published in 2014, officially due to irregularities in the way ethical approval was granted. Retraction reasons also included methodological errors in the studies. The integrity of the research, conducted by Nobuto Yamamoto and colleagues, that originally prompted claims regarding cancer and HIV has been questioned. The UK Medicines and Healthcare products Regulatory Agency and Cancer Research UK has warned the public about spurious claims of clinical benefits, misleadingly based on reduced levels of the alpha-N-acetylgalactosaminidase enzyme (also known as nagalase), whose production might be increased in many cancers. In 2014 the Belgian Anticancer Fund communicated serious concerns about published studies on GcMAF by Yamamoto and colleagues. In 2015 the UK Medicines and Healthcare products Regulatory Agency (MHRA) closed a factory in Milton, Cambridgeshire owned by David Noakes' company Immuno Biotech that manufactured GcMAF for cancer treatment. In September 2018 Noakes pleaded guilty in UK to manufacturing a medicinal product without a manufacturer's licence, selling or supplying medicinal products without market authorisation, and money laundering, and sentenced to 15 months of jail.
== Further reading == Semley J. "People Are Already Taking This Unapproved New Weight-Loss Drug". Wired. Gina Kolat, Rebecca Robbins (May 21, 2026). "Experimental Drug Yields Dramatic Weight Loss". People who got the injection, retatrutide, lost 28 percent of their body weight on average after 80 weeks, Eli Lilly said.
Along with mirtazapine, although to a lesser extent in comparison, mianserin has sometimes been described as a noradrenergic and specific serotonergic antidepressant (NaSSA). However, the actual evidence in support of this label has been regarded as poor.
But threats continue to grow as outsiders envy what they have, and Jenna must grapple with how far her faith will allow her to go. As the series opens, Ian has slipped back into a coma, more refugees have gathered outside the gates, and the Homesteaders set up a trading post. The city government has set up their own compound called Raven Rock, with FEMA resources and government operatives. They begin recruiting and arming gang members and thugs from town for an eventual attack on the Homestead. The Homesteaders engage in daily training and drills, including the women, who become experienced with various types of weapons and battle tactics. Tom Reynolds, an engineer and friend of Ian, and his pregnant wife Jacq, a therapist, arrive at the gates and are admitted by Jenna. Abe and Clare's romance buds but they must decide how to reconcile their different worldviews and their loyalties to their parents, who have continued to clash. Georgie, who had been adopted by the Eriksson's six months prior after Jeff found her hiding in a drug den during a DEA raid, is alone in the woods when she sees a man attempt to grab her. Jeff is enraged and decides to retaliate against those they believe to be responsible at the behest of a soldier named Bing, creating more enemies. Bing and an accomplice leave the Homestead and join the city government forces, giving them critical secrets about the Homestead along with a traitor who feeds them information from the inside. Ian's brother Cain, who is also wealthy, arrives via helicopter at Jenna's invitation.
Potassium arsenite (KAsO2) is an inorganic compound that exists in two forms, potassium meta-arsenite (KAsO2) and potassium ortho-arsenite (K3AsO3). It is composed of arsenite ions (AsO3−3 or AsO−2) with arsenic always existing in the +3 oxidation state. Like many other arsenic containing compounds, potassium arsenite is highly toxic and carcinogenic to humans. Potassium arsenite forms the basis of Fowler’s solution, which was historically used as a medicinal tonic, but was removed from market due to serious adverse effects. Potassium arsenite is still, however, used as a rodenticide.
Sources: en.wikipedia.org
Several modern western scholars argue that there are inconsistencies in the list of twelve links, and regard it to be a later synthesis of several older lists and elements, some of which can be traced to the Vedas. The doctrine of dependent origination appears throughout the early Buddhist texts. It is the main topic of the Nidāna Saṃyutta of the Theravada school's Saṃyutta Nikāya (henceforth SN). A parallel collection of discourses also exists in the Chinese Saṁyukta Āgama (henceforth SA).
== Sources == Sadava, David E; Hillis, David M; Heller, H Craig; Berenbaum, May (2011). Life: The Science of Biology. Macmillan. ISBN 978-1-4292-4644-6. Han, Seong S.; Ashley, Ruth; Hann, Gary (1974). Cell Biology. University of Michigan. OCLC 1532651.
The core of comparative genome analysis is the establishment of the correspondence between genes (orthology analysis) or other genomic features in different organisms. Intergenomic maps are made to trace the evolutionary processes responsible for the divergence of two genomes. A multitude of evolutionary events acting at various organizational levels shape genome evolution. At the lowest level, point mutations affect individual nucleotides. At a higher level, large chromosomal segments undergo duplication, lateral transfer, inversion, transposition, deletion and insertion. Entire genomes are involved in processes of hybridization, polyploidization and endosymbiosis that lead to rapid speciation. The complexity of genome evolution poses many exciting challenges to developers of mathematical models and algorithms, who have recourse to a spectrum of algorithmic, statistical and mathematical techniques, ranging from exact, heuristics, fixed parameter and approximation algorithms for problems based on parsimony models to Markov chain Monte Carlo algorithms for Bayesian analysis of problems based on probabilistic models. Many of these studies are based on the detection of sequence homology to assign sequences to protein families.
Todd appeared in more than 100 theatrical and television films and played opposite many major Hollywood stars. His film credits include: Platoon (1986), Night of the Living Dead (1990), Candyman (1992), The Crow (1994), The Rock (1996), Wishmaster (1997), the Final Destination series (2000–2025), Minotaur (2006), and Beg (2010). Todd was the voice of The Fallen in Transformers: Revenge of the Fallen (2009) and was also in the Rel Dowdell film Changing the Game. Todd was a special guest of the Weekend of Horror Creation Entertainment on May 23, 2010, and Screamfest LA. Todd portrayed Reverend Zombie in Hatchet II, which was released in a limited number of theatres on October 1, 2010. His signature baritone voice narrated several works, including the 2021 documentary Invisible Threads: From Wireless to War. Todd returned as William Bludworth, when he filmed Final Destination Bloodlines in 2024.
Sources: en.wikipedia.org
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.
No approved regulatory indication exists in major markets. An approval exists for a different peptide, afamelanotide, which is used for a rare photosensitivity disorder called erythropoietic protoporphyria. Melanotan-2 itself remains a research compound with no cleared clinical role.
Melanocortin-1 receptors on melanocytes are the receptor most closely linked to pigment production. The peptide is not selective, however, and also activates melanocortin-3, melanocortin-4, and melanocortin-5 receptors. That lack of selectivity is the usual explanation offered for both its range of observed effects and its off-target effects.
No regulatory agency has authorised melanotan-2 as a medicine for any indication. It circulates mainly as a research chemical or through unregulated channels. As a result, identity, purity and content are not independently guaranteed.