The short version of melanocortin receptor fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2025-09-27. Anything still debated is marked as such rather than presented as settled.
Research interest has centred on photoprotection and pigmentation, with a smaller body of work on appetite and sexual function. Published human data remain limited to small, frequently uncontrolled studies, and the compound has never received marketing approval from a national medicines regulator. Most laboratory work treats it as a pharmacological tool for probing melanocortin signalling in cell culture or animal models. Whether pigmentation changes observed in people translate into measurable protection against ultraviolet-induced DNA damage remains an open question.
Melanotan-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone, the naturally occurring peptide involved in pigmentation signalling. Its sequence is conventionally written as Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, with a lactam bridge joining the aspartate side chain to the lysine side chain. The empirical formula is C50H69N15O9 and the monoisotopic mass lies near 1023.5 daltons. N-terminal acetylation and the D-configured phenylalanine both increase resistance to enzymatic breakdown compared with the parent hormone.
Pharmacologically, melanotan-2 behaves as a non-selective agonist across the melanocortin receptor family. Binding at MC1R on dermal melanocytes promotes eumelanin synthesis, which underlies the tanning response described in early human work. Activity at the centrally expressed MC4R receptor is associated with reported effects on appetite and erectile function. Because the peptide does not discriminate strongly among receptor subtypes, attributing any single observed effect to one receptor pathway is generally not possible without selective antagonists or receptor knockout models.
Outside regulated medicine, melanotan II circulates through online vendors as a research chemical, often marketed for tanning. Products sold this way vary widely in purity, concentration, and labeling accuracy, and independent testing has documented discrepancies. Published reports describe both pigment effects and adverse reactions, including nausea, flushing, and darkening of existing moles. Long-term safety data are sparse, and no large controlled trial has established a risk profile. Questions about cumulative effects on melanocytes remain unresolved in the literature.
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.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | Melanotan II; MT-II; N-acetyl-norleucyl-cyclo[Asp-His-D-Phe-Arg-Trp-Lys] amide | Naming follows peptide convention; the numeral distinguishes it from melanotan-1 |
| Molecular formula | C50H69N15O9 | Includes the lactam bridge; no counter-ion assumed |
| Monoisotopic mass | 1023.53 Da | Free base; salts and counter-ions shift the observed value |
| Appearance | White to off-white lyophilised powder | Batch-to-batch colour variation is not itself proof of impurity |
| Typical analytical method | RP-HPLC purity determination with ESI-MS identity confirmation | Retention time alone does not establish sequence identity |
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.
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.
=== Chemical diversity === As above mentioned, combinatorial chemistry was a key technology enabling the efficient generation of large screening libraries for the needs of high-throughput screening. However, now, after two decades of combinatorial chemistry, it has been pointed out that despite the increased efficiency in chemical synthesis, no increase in lead or drug candidates has been reached. This has led to analysis of chemical characteristics of combinatorial chemistry products, compared to existing drugs or natural products. The chemoinformatics concept chemical diversity, depicted as distribution of compounds in the chemical space based on their physicochemical characteristics, is often used to describe the difference between the combinatorial chemistry libraries and natural products. The synthetic, combinatorial library compounds seem to cover only a limited and quite uniform chemical space, whereas existing drugs and particularly natural products, exhibit much greater chemical diversity, distributing more evenly to the chemical space. The most prominent differences between natural products and compounds in combinatorial chemistry libraries is the number of chiral centers (much higher in natural compounds), structure rigidity (higher in natural compounds) and number of aromatic moieties (higher in combinatorial chemistry libraries).
To test this therapeutic hypothesis, a selective and blood-brain barrier-permeable OGA inhibitor, thiamet-G, was developed. Thiamet-G treatment was able to increase tau O-GlcNAcylation and suppress tau phosphorylation in cell culture and in vivo in healthy Sprague-Dawley rats. A subsequent study showed that thiamet-G treatment also increased tau O-GlcNAcylation in a JNPL3 tau transgenic mouse model. In this model, tau phosphorylation was not significantly affected by thiamet-G treatment, though decreased numbers of neurofibrillary tangles and slower motor neuron loss were observed. Additionally, O-GlcNAcylation of tau was noted to slow tau aggregation in vitro. OGA inhibition with MK-8719 is being investigated in clinical trials as a potential treatment strategy for Alzheimer's disease and other tauopathies including progressive supranuclear palsy.
Eusociality is the highest level of social organization. These societies have an overlap of adult generations, the division of reproductive labor and cooperative caring of young. Usually insects, such as bees, ants and termites, have eusocial behavior, but it is demonstrated in two rodent species: the naked mole-rat and the Damaraland mole-rat. Presociality is when animals exhibit more than just sexual interactions with members of the same species, but fall short of qualifying as eusocial. That is, presocial animals can display communal living, cooperative care of young, or primitive division of reproductive labor, but they do not display all of the three essential traits of eusocial animals. Humans and some species of Callitrichidae (marmosets and tamarins) are unique among primates in their degree of cooperative care of young. Harry Harlow set up an experiment with rhesus monkeys, presocial primates, in 1958; the results from this study showed that social encounters are necessary in order for the young monkeys to develop both mentally and sexually. A fission–fusion society is a society that changes frequently in its size and composition, making up a permanent social group called the "parent group". Permanent social networks consist of all individual members of a community and often varies to track changes in their environment. In a fission–fusion society, the main parent group can fracture (fission) into smaller stable subgroups or individuals to adapt to environmental or social circumstances.
Barker often appeared in fiction as himself, usually in a cameo appearance, in shows including The Nanny, The Bold and the Beautiful Futurama, and How I Met Your Mother.In 1996, Barker played himself in the Adam Sandler comedy Happy Gilmore. In one scene, Barker beats up Gilmore after an altercation arising from their teaming up in a Pro-Am Golf Tournament. According to Sandler, the original choice for that scene was Ed McMahon, but Sandler said that McMahon was not fond of the script and they got Barker because of Chuck Norris training Barker in the martial arts. Barker also played himself in the animated series Family Guy, starting in 2001 with the episode "Screwed the Pooch" with his last appearance being in 2008 in the episode "Tales of a Third Grade Nothing". In 2007, during a CBS prime-time special commemorating Barker's career, the fight scene from Happy Gilmore was shown, after which Sandler made a surprise appearance on stage to read a poem paying tribute to Barker. In 2015, during Comedy Central's "Night of Too Many Stars" benefit show to battle autism, Barker and Sandler reunited for a video featuring the two of them in a follow-up fight at the hospital, which ends with both of them dying and going to heaven. However, Barker did play characters apart from himself in Bonanza, as a character named Mort in the 1960 episode "Denver McKee", and as a small business owner named Bob Barnacle in "Sanctuary!", an episode of the Nickelodeon animated series SpongeBob SquarePants.
Penicillins, like other β-lactam antibiotics, block not only the division of bacteria, including cyanobacteria, but also the division of cyanelles, the photosynthetic organelles of the glaucophytes, and the division of chloroplasts of bryophytes. In contrast, they have no effect on the plastids of the highly developed vascular plants. This supports the endosymbiotic theory of the evolution of plastid division in land plants. Some bacteria produce enzymes that break down the β-lactam ring, called β-lactamases, which make the bacteria resistant to penicillin. Therefore, some penicillins are modified or given with other drugs for use against antibiotic-resistant bacteria or in immunocompromised patients. The use of clavulanic acid or tazobactam, β-lactamase inhibitors, alongside penicillin gives penicillin activity against β-lactamase-producing bacteria. β-Lactamase inhibitors irreversibly bind to β-lactamase preventing it from breaking down the beta-lactam rings on the antibiotic molecule. Alternatively, flucloxacillin is a modified penicillin that has activity against β-lactamase-producing bacteria due to an acyl side chain that protects the beta-lactam ring from β-lactamase.
Sources: en.wikipedia.org
Gam-COVID-Vac is a viral vector vaccine based on two recombinant replication-defective human adenoviruses: Ad26 (serotype 26) and Ad5 (serotype 5) replicated in HEK 293 cells. The viruses contain the gene that encodes the full-length spike protein (S) of SARS-CoV-2 to stimulate an immune response. Adenoviral vectors for expression of the SARS-CoV-2 spike protein have also been used in two other COVID-19 vaccines. One is the Janssen COVID-19 vaccine, which uses the Ad26COV2 viral vector based on the human virus Ad26. For this vaccine, the cell line PER.C6 is used to replicate the vector. Another one, the Oxford–AstraZeneca COVID‑19 vaccine, uses chimpanzee adenovirus (ChAdOx1) as the vector. For both the Oxford-AstraZeneca COVID-19 and Gam-COVID-Vac vaccines the producer cells for the production of non-replicating adenoviral vectors were obtained from the HEK 293 cell line. Each dose of Gam-COVID-Vac contains (1.0 ± 0.5) × 1011 virus particles. Both Ad26 and Ad5 were modified to remove the E1 gene to prevent replication outside the HEK 293 cells. For the production of the vaccine, to propagate adenoviral vectors in which the E1 gene was deleted, HEK 293 cells are used, which express several adenoviral genes, including E1. However, although rare, homologous recombination between the inserted cellular sequence and the vector sequence can restore the replication capacity to the vector, with less than 100 replicating adenovirus particles per dose of the vaccine.
Firstly, the NADH + H+ generated by glycolysis has to be transferred to the mitochondrion to be oxidized, and thus to regenerate the NAD+ necessary for glycolysis to continue. However the inner mitochondrial membrane is impermeable to NADH and NAD+. Use is therefore made of two "shuttles" to transport the electrons from NADH across the mitochondrial membrane. They are the malate-aspartate shuttle and the glycerol phosphate shuttle. In the former the electrons from NADH are transferred to cytosolic oxaloacetate to form malate. The malate then traverses the inner mitochondrial membrane into the mitochondrial matrix, where it is reoxidized by NAD+ forming intra-mitochondrial oxaloacetate and NADH. The oxaloacetate is then re-cycled to the cytosol via its conversion to aspartate which is readily transported out of the mitochondrion. In the glycerol phosphate shuttle electrons from cytosolic NADH are transferred to dihydroxyacetone to form glycerol-3-phosphate which readily traverses the outer mitochondrial membrane. Glycerol-3-phosphate is then reoxidized to dihydroxyacetone, donating its electrons to FAD instead of NAD+. This reaction takes place on the inner mitochondrial membrane, allowing FADH2 to donate its electrons directly to coenzyme Q (ubiquinone) which is part of the electron transport chain which ultimately transfers electrons to molecular oxygen O2, with the formation of water, and the release of energy eventually captured in the form of ATP.
=== Genotoxicity === WHO concluded that patulin is genotoxic based on variable genotoxicity data, however it is considered a group 3 carcinogen by the International Agency for Research on Cancer (IARC) since data was inconclusive.
==== Early career (1999–2004) ==== After having a slow start with a season high of 15 Disposals and 4 Marks, in his second season he suffered an injury and missed most of Essendons games. In McVeigh's third season however, it was clear that the game had grown on him as he stood up as an up-and-coming youngster. After playing 23 games in his third year of playing including the Grand Final against the Brisbane Lions in which Essendon lost, McVeigh had some promising stats with a consistent 11 – 18 in over half of every game he played. McVeigh also went on to play the next 3 seasons in stellar form with Essendon who reached 3 consecutive semi-finals in which McVeigh played in all.
Sources: en.wikipedia.org
Competition between RNA may have favored the emergence of cooperation between different RNA chains, opening the way for the formation of the first protocell. Eventually, RNA chains developed with catalytic properties that help amino acids bind together (a process called peptide-bonding). These amino acids could then assist with RNA synthesis, giving those RNA chains that could serve as ribozymes the selective advantage. The ability to catalyze one step in protein synthesis, aminoacylation of RNA, has been demonstrated in a short (five-nucleotide) segment of RNA. In 2014, a group of researchers managed to produce all four components of RNA by simulating an asteroid impact in primordial conditions. In March 2015, NASA scientists reported that, for the first time, complex DNA and RNA organic compounds of life, including uracil, cytosine, and thymine, have been formed in the laboratory under conditions found only in outer space, using starting chemicals, like pyrimidine, found in meteorites. Pyrimidine, like polycyclic aromatic hydrocarbons (PAHs), may have been formed in red giant stars or in interstellar dust and gas clouds, according to the scientists. That same month, researchers were able to produce over 50 aminoacids in a laboratory setting by using only hydrogen sulfide, hydrogen cyanide (presumably produced after outer space meteorites reacted with atmospheric nitrogen) and ultraviolet light.
=== Primordial synthesis === The formation of amino acids and peptides is assumed to have preceded and perhaps induced the emergence of life on earth. Amino acids can form from simple precursors under various conditions. Surface-based chemical metabolism of amino acids and very small compounds may have led to the build-up of amino acids, coenzymes and phosphate-based small carbon molecules. Amino acids and similar building blocks could have been elaborated into proto-peptides, with peptides being considered key players in the origin of life.
==== Noble and non-noble kava ==== Scholars make a distinction between the so-called noble and non-noble kava. The latter category comprises the so-called tudei (or "two-day") kavas, medicinal kavas, and wild kava (Piper wichmanii, the ancestor of domesticated Piper methysticum). Traditionally, only noble kavas have been used for regular consumption, due to their more favourable composition of kavalactones and other compounds that produce more pleasant effects and have lower potential for causing negative side effects, such as nausea, or "kava hangover". The perceived benefits of noble cultivars explain why only these cultivars were spread around the Pacific by Polynesian and Melanesian migrants, with presence of non-noble cultivars limited to the islands of Vanuatu, from which they originated. More recently, it has been suggested that the widespread use of tudei cultivars in the manufacturing of several kava products might have been the key factor contributing to the rare reports of adverse reactions to kava observed among the consumers of kava-based products in Europe. Tudei varieties have traditionally not been grown in Hawaii and Fiji, but in recent years there have been reports of farmers attempting to grow "isa" or "palisi" non-noble cultivars in Hawaii, and of imports of dried tudei kava into Fiji for further re-exporting. The tudei cultivars may be easier and cheaper to grow: while it takes up to 5 years for noble kava to mature, non-noble varieties can often be harvested just one year after being planted.
Telisotuzumab vedotin, sold under the brand name Emrelis, is an antibody drug conjugate used for the treatement of non-small cell lung cancer. Telisotuzumab vedotin is a c-Met-directed antibody and microtubule inhibitor conjugate. It was developed by AbbVie. The most common adverse reactions include peripheral neuropathy, fatigue, decreased appetite, and peripheral edema. The most common grade 3 or 4 laboratory abnormalities include decreased lymphocytes, increased glucose, increased alanine aminotransferase, increased gamma glutamyl transferase, decreased phosphorus, decreased sodium, decreased hemoglobin, and decreased calcium. Telisotuzumab vedotin was approved for medical use in the United States in May 2025. The US Food and Drug Administration considers it to be a first-in-class medication.
=== Military use === Fenethylline is a major stimulant, sometimes dubbed the "jihad drug", used by some jihadist fighters. It quickly produces a euphoric intensity in users, allowing them to stay awake for a very long time, remaining more calm and focused under the effects of the drug, which allows the senses to stay at more operational levels. It also helps to subdue feelings of fear and hunger during lengthy operations. Psychiatrist Robert Keisling said that the drug "gives you a sense of well-being and euphoria", along with the thought that "you're invincible and that nothing can harm you." Those who go on jihad missions take high doses to prepare, says a former fighter associated with the Muslim Brotherhood. He described the effect: "They go blank. Their heart rate spikes. They lose all connection to their emotions and thoughts." Some commented on this effect as a "zombie-like detachment". An illegal Syrian manufacturer told New York Magazine in 2015 of the effect the drug had on fighters: "[If] someone takes many pills, like 30 or so, they become violent and crazy, paranoid, unafraid of anything. They'll have a thirst for fighting and killing and will shoot at whatever they see. They lose any feeling or empathy for the people in front of them and can kill them without caring at all." According to some commentators, fighters taking the drug in Syria were better able to tolerate the pain of being shot. A drug control officer in the central city of Homs told Reuters that protestors and fighters were able to resist painful interrogations better while on fenethylline.
Sources: en.wikipedia.org
It is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone, containing seven amino acids with a lactam ring and a D-configured phenylalanine residue. It is supplied as a lyophilised powder for laboratory research.
The natural hormone is a linear tridecapeptide that is rapidly degraded in circulation. Melanotan-2 is shortened, cyclised, N-terminally acetylated, and carries a D-amino acid substitution, all of which slow enzymatic breakdown.
No national medicines regulator has approved melanotan-2 for therapeutic or cosmetic use. In several jurisdictions it is treated as an unapproved prescription medicine, and its legal classification differs from country to country.
It is a synthetic cyclic peptide designed as an analog of alpha-melanocyte-stimulating hormone. It acts on melanocortin receptors and is best known from research into pigmentation. It is not an approved pharmaceutical product.