A practical reference on MC1R: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2026-05-14 and is reviewed periodically as new material appears.
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.
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 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-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.
| 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.
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.
Hormones in cattle had been studied in North America for 50 years prior to the ban, accompanied by long-term use in over 20 countries. Canada and the United States asserted that these practices provided empirical evidence of long-term safety. The EU had already established other measures that restricted the import of North American beef. The primary North American product affected by the new ban was edible offal. A series of "hormone scandals" emerged in Italy in the late 1970s and early 1980s. The first, in 1977, was the discovery of premature puberty in northern Italian schoolchildren. Investigators cast suspicion on school lunches that used illegal hormone-treated meat. No concrete evidence was found–no samples of the suspect meals were available for analysis. In 1980 diethylstilbestrol (DES), another illegal synthetic hormone, was discovered in veal-based baby foods. Little or no scientific evidence supported these restrictions. However, consumer groups successfully influenced the European Parliament to enact regulations in the 1980s, and influenced public perceptions. In the US at the time, consumer organizations evinced little interest prior to the 1980s, and regulations were driven by a coalition of export-oriented industry and farming interests, opposed only by organic farming groups. Until 1980, the use of growth hormones was completely prohibited in Italy, Denmark, the Netherlands, and Greece. Germany, the EU's largest beef producer at the time, prohibited only exogenous growth hormones.
In other places, such as Australia, suvorexant is a prescription-only medicine and is not a controlled drug. Suvorexant is not available in generic formulations. Besides suvorexant, other orexin receptor antagonists like lemborexant and daridorexant have also been introduced.
=== Screenwriting === For her screenplay Look for Water, which she co-wrote with Dominic Mah, she was invited to the Sundance Screenwriters' Lab in June 2008. The screenplay has also received the Tribeca Film Festival L'Oreal Woman of Worth Vision Award, a Sundance CineReach grant, and a Sundance Institute Annenberg Feature Film Fellowship Grant.
=== Carbon nanomaterials === Barron investigated the impact of a fullerene on wide range of systems. Initial work was concerned with the toxicity on various cell types. The results of this work demonstrated that inclusion of C60 into a peptide structure drastically lowered any toxicity effects. In his later work, Barron studied catalysis with growth of single walled carbon nanotubes (SWCNTs) pioneering the concept of amplification of a CNT. Other work includes measuring electrical properties of individual CNTs, and using them to absorbs cadmium, cobalt, copper, mercury, nickel and lead from contaminated water.
Sources: en.wikipedia.org
From the finding that this regulation starts working on a high activity level after weaning and the enhanced activity subsists during the uphill period of life, until sexual hormones dampen the enhancer regulation in the catecholaminergic and serotonergic neurons in the brain stem, and this event signifies the transition from developmental longevity into postdevelopmental longevity, the downhill period of life. Despite findings by Knoll that selegiline can prolong lifespan in rodents by 35% however, other studies have had conflicting findings and have even found increased mortality with selegiline in rodents. In humans with Parkinson's disease, selegiline has been associated with cardiovascular and psychiatric complications and has not been found to reduce mortality in long-term studies. As such, the claimed anti-aging and longevity benefits of selegiline have yet to be substantiated in humans and are controversial and uncertain.
Stargirl and her team were briefly introduced in the Arrowverse crossover "Crisis on Infinite Earths" in January 2020, through archive footage from "The Justice Society" episode. Stargirl is set on a new Earth-2, created during the crossover. Stargirl from the pre-Crisis Earth-1 had previously appeared in three episodes of season two of Legends of Tomorrow, portrayed by Sarah Grey, between October 2016 and February 2017. Regarding any proper crossovers with the Arrowverse, Johns and Bassinger were keen on the idea. Johns said that "right now the main concern is making sure that this show is great, that these characters are great, that they have their own stories and they get the proper screen time and the proper episodes to develop on their own. So hopefully in the future we can do something fun, but the first season is all about making sure that Stargirl is the best show it can possibly be". Bassinger added that there had already been preliminary discussion about crossing over with The Flash, and she was hopeful to be able to crossover with Melissa Benoist on Supergirl. John Wesley Shipp reprised his role as an alternate version of Jay Garrick from The Flash. Johns said Shipp's appearance helped connect "our universe directly with the other shows, and also shows that were part of a grander universe. It opens up the door to opportunities for us to eventually interact with those Arrowverse characters, and that was important".
== Mechanism of carcinogenicity == Aflatoxin B1 is a potent genotoxic hepatocarcinogen with its exposure strongly linked to the development of hepatocellular carcinoma, liver tumors, especially given co-infection with hepatitis B virus. These effects seem to be largely mediated by mutations at guanine in codon 249 of the p53 gene, a tumor suppressing gene, and at several guanine residues in the 12th and 13th codons of the ras gene, a gene whose product controls cellular proliferation signals. Aflatoxin B1 must first be metabolized into its reactive electrophilic form, aflatoxin B1-8,9-exo-epoxide by cytochrome p450. This active form then intercalates between DNA base residues and forms adducts with guanine residues, most commonly aflatoxin B1-N7-Gua. These adducts may then rearrange or become removed from the backbone altogether, forming an apurinic site. These adducts and alterations represent lesions which, upon DNA replication, cause the insertion of a mis-matched base in the opposing strand. Up to 44% of hepatocellular carcinomas in regions with high aflatoxin exposure bear a GC → TA transversion at codon 249 of p53, a characteristic mutation seen with this toxin.
The Office of the Inspector General also found that because the EPA's perchlorate reference dose is conservative and protective of human health further reducing perchlorate exposure below the reference dose does not effectively lower risk. Because of ammonium perchlorate's adverse effects upon children, Massachusetts set its maximum allowed limit of ammonium perchlorate in drinking water at 2 parts per billion (2 ppb = 2 micrograms per liter). Perchlorate affects only thyroid hormone. Because it is neither stored nor metabolized, effects of perchlorate on the thyroid gland are reversible, though effects on brain development from lack of thyroid hormone in fetuses, newborns, and children are not. Toxic effects of perchlorate have been studied in a survey of industrial plant workers who had been exposed to perchlorate, compared to a control group of other industrial plant workers who had no known exposure to perchlorate. After undergoing multiple tests, workers exposed to perchlorate were found to have a significant systolic blood pressure rise compared to the workers who were not exposed to perchlorate, as well as a significant decreased thyroid function compared to the control workers. A study involving healthy adult volunteers determined that at levels above 0.007 milligrams per kilogram per day (mg/(kg·d)), perchlorate can temporarily inhibit the thyroid gland's ability to absorb iodine from the bloodstream ("iodide uptake inhibition", thus perchlorate is a known goitrogen).
Limitations While it is an exceptional tool, constraints do arise, particularly in practical applications. In some cases, the need for externally added reagents arises to integrate dienophiles into biomolecules. A compromise in stability can also occur due to the instability of the fastest alkenes because of isomerization of trans-cyclooctenes to cis. Regardless, the reaction continues to be widely used as a result of the critical role it plays in several applications.
Sources: en.wikipedia.org
Full-fat soybean meal, made from whole soybeans. It has a high metabolizable energy concentration. (For example, metabolizable energy for swine in this product is about 3.69 megacalories (i.e. 15.4 MJ) per kg dry matter.) Crude protein concentration is about 38 percent (as fed). This kind of product is sometimes fed to various classes of livestock. Defatted soybean meal, containing no hulls. This product has an intermediate energy concentration. (For example, Balaji metabolizable energy for swine in this product is about 3.38 megacalories (i.e. 14.1 MJ) per kg dry matter.) Crude protein concentration is about 48 percent. This percentage [which is commonly used in describing the product] is calculated at the typical as-fed moisture content of 88 percent. Thus, crude protein concentration expressed on a dry matter basis is 54 percent. This product is commonly fed to swine, broilers and layers. Defatted soybean meal, containing soybean hulls. The hulls are readily digestible by ruminant livestock. This product is often fed as a protein supplement for domestic ruminants. Ruminant-metabolizable energy concentration is about 3.0 megacalories (i.e. about 12.5 MJ) per kg dry matter, and crude protein concentration is about 44 percent. The latter percentage [which is commonly used in describing the product] is calculated at the typical as-fed moisture content of 90 percent. Thus, crude protein concentration on a dry matter basis is 49 percent.
== Other hydroxylations == The function of the remainder of the hydroxylated E2 metabolites (6α-, 6β-, 7α-, 12β-, 15α-, 15β-, and 16β-OHE2) remain to be elucidated. Some of these metabolites, such as 15α-OHE2, are excreted in relatively large amounts in pregnant women, possibly serving as an indicator of good fetal health.
Aminoacylases are expressed in the kidney, where they recycle N-acyl-L-amino acids as L-amino acids and aid in urea cycle regulation. N-acyl-L-amino acids are formed when L-amino acids have their N-terminus covalently bonded to an acyl group. The acyl group provides stability for the amino acid, making it more resistant to degradation. Additionally, N-acyl-L-amino acids cannot be used directly as building blocks for proteins and must first be converted to L-amino acids by aminoacylase. Again, the L-amino acid products can be used for biosynthesis or catabolized energy. Aminoacylase is involved in the regulation of the urea cycle. N-acetyl-L-glutamate is an allosteric activator of carbamoyl phosphate synthetase, a crucial enzyme that commits NH4+ molecules to the urea cycle. The urea cycle gets rid of excess ammonia (NH4+) in the body, a process that must be up-regulated during times of increased protein catabolism, as amino acid breakdown produces large amounts of NH4+. When amino acid catabolism increases, N-Acetylglutamate synthase is up-regulated, producing more N-acetyl-L-glutamate, which up-regulates carbamoyl phosphate synthetase and allows it to dispose of the excess NH4+ from catabolism. Aminoacylase is up-regulated during times of nutrient deficit or starvation, causing N-acetyl-L-glutamate breakdown, which down-regulates carbamoyl phosphate synthetase and the rest of the urea cycle.
Ranged combat is first-person, with character points assigned to the firearms skill determining the shot's accuracy and how long it takes to target an opponent. Melee combat is third-person, with access to weapons such as katanas and sledgehammers for melee combat, or pistols, crossbows, and flamethrowers for firearm combat. If a player sneaks up on an opponent, they can perform an instant kill; weapons provide unique instant kill animations. The player can block attacks manually or automatically by leaving their character idle. They can use stealth in missions by sneaking past guards and security cameras, picking locks, and hacking computers to locate alternative routes. Each clan has specific Disciplines, which can be used in combat and to create approaches to quests. Although some powers overlap clans, no two clans share the same three Disciplines. More physical vampires can enhance themselves to become fast and lethal killers or summon spirit allies to attack their foes; others can mentally dominate their targets to force their cooperation or render themselves invisible to hide from detection; and others can boil their opponent's blood from afar. The ability Blood Buff (which temporarily upgrades physical abilities) is common to all vampires. Several abilities can be active at the same time. Blood is a primary currency in Bloodlines, used to activate Disciplines and abilities.
=== Common === Empagliflozin increases the risk of genital fungal infections. The risk is highest in people with a prior history of genital fungal infections. Empagliflozin has been thought to be associated with increased risk of urinary tract infections. Reviews of clinical trials have shown there is no significant risk of developing urinary tract infections while taking empagliflozin when compared to placebo or other diabetic medications. Empagliflozin reduces systolic and diastolic blood pressure and can increase the risk of low blood pressure, which can cause fainting and/or falls. The risk is higher in older people, people taking diuretics, and people with reduced kidney function. Slight increases in Low-density lipoprotein (LDL) cholesterol can be seen with empagliflozin, in the range of 2–4% from baseline. Empagliflozin may cause a temporary decline in kidney function and, in rare cases, acute kidney injury, so it should be used cautiously in patients with kidney impairment. Some evidence suggests it may be safely used in people with significantly reduced kidney function (eGFR ≥ 20 mL/min/1.73 m2) while still providing renal benefits. However, given that this conclusion is largely based on a single major trial, further research is recommended to establish long-term safety and efficacy in this population.
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. Melanotan-2 is manufactured synthetically. The naturally occurring peptide in the same family is alpha-melanocyte-stimulating hormone, which the body produces as part of normal endocrine and neural signalling.