This is a working overview of melanocortin receptors, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2025-11-12. Anything still debated is marked as such rather than presented as settled.
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.
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.
Structurally, Melanotan-2 retains the core recognition motif of alpha-melanocyte-stimulating hormone while adding a lactam bridge that links two side chains and constrains the molecule into a ring. This modification lowers susceptibility to enzymatic degradation. The compound acts as an agonist at melanocortin receptors, particularly subtypes associated with melanin production. Because the same receptor family influences several physiological processes, researchers note that its activity is not confined to pigmentation alone. Receptor selectivity continues to be examined in published studies.
Melanotan-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone, a naturally occurring peptide involved in pigmentation signalling. Its sequence incorporates modified residues that increase potency and extend biological activity relative to the native hormone. The compound binds receptors of the melanocortin family and is examined mainly in laboratory research. It does not occur naturally and exists only as a manufactured chemical entity produced by solid-phase synthesis.
The peptide was developed during the 1980s by researchers investigating melanocortin signalling and skin pigmentation pathways. Early work focused on analogues of alpha-melanocyte-stimulating hormone that would resist enzymatic breakdown more effectively than the parent molecule. Melanotan-2 emerged from that programme as a shortened, cyclised variant. Reports describing its synthesis and receptor activity later appeared in the scientific literature. Commercial availability grew through unregulated channels rather than through pharmaceutical approval.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C50H69N15O9 | Cyclic heptapeptide, C-terminally amidated |
| Approximate molecular mass | 1024 Da | Monoisotopic mass of the free peptide |
| Appearance | White to off-white powder | Typically supplied as a lyophilised solid |
| Solubility class | Soluble in water and polar solvents | Also dissolves in neutral aqueous buffer |
| Common synonyms | Melanotan II, MT-II, MT-2 | Described as a melanocortin agonist in early literature |
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.
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.
Published human data come mostly from small, short studies rather than large controlled trials. Reported outcomes include increased skin pigmentation and, in some reports, effects on appetite and libido, but sample sizes are small and follow-up is limited. Whether long-term use produces durable pigment changes or adverse effects is not established. Because products sold outside pharmacies are not standardized, the actual content of any given vial is often unknown. Independent testing of such material is uncommon.
Melanotan II is a synthetic cyclic heptapeptide analog derived from the core sequence of alpha-melanocyte-stimulating hormone. Researchers at the University of Arizona synthesized it during the 1980s while studying pigmentation and appetite signaling. The compound is not an approved medicine in any major jurisdiction and appears mainly in laboratory and research-chemical settings. Its structure incorporates a lactam bridge between side chains, which constrains the ring and slows enzymatic breakdown relative to the natural hormone.
More recent publications have defined the usually recommended doses as 50 mg DMT and 100 mg harmaline orally. Besides DMT with harmaline, the properties and effects of oral DMT in combination with harmine have also been studied by Jonathan Ott. He found that the threshold dose was 20 or 30 mg DMT and 120 mg harmine orally. Shulgin also reported in TiHKAL that 35 to 40 mg DMT and 140 to 190 mg harmine were unmistakably active, whereas smaller doses of 30 mg DMT and 120 to 140 mg harmine orally were inactive. In notable contrast to harmaline, harmine does not have its own psychoactive effects when used at doses of up to at least 300 mg orally. In pharmahuasca, the harmala alkaloid is usually taken first and then DMT is taken 15 to 20 minutes later, although a shorter or longer interval may also be employed. The onset of oral DMT with an MAOI is within 1 hour and its duration is 4 to 6 hours.
A scenario is a set of related concepts pertinent to the origin of life (abiogenesis), such as the iron-sulfur world. Many alternative abiogenesis scenarios have been proposed by scientists in a variety of fields from the 1950s onwards in an attempt to explain how the complex mechanisms of life could have come into existence. These include hypothesized ancient environments that might have been favourable for the origin of life, and possible biochemical mechanisms.
{\displaystyle {\begin{aligned}y:\ &\rho \left({\partial _{t}u_{y}}+u_{x}{\partial _{x}u_{y}}+u_{y}{\partial _{y}u_{y}}+u_{z}{\partial _{z}u_{y}}\right)\\&\quad =-{\partial _{y}p}+\mu \left({\partial _{x}^{2}u_{y}}+{\partial _{y}^{2}u_{y}}+{\partial _{z}^{2}u_{y}}\right)+{\frac {1}{3}}\mu \ \partial _{y}\left({\partial _{x}u_{x}}+{\partial _{y}u_{y}}+{\partial _{z}u_{z}}\right)+\rho g_{y}\\\end{aligned}}}
Qatar: The Ministry of Foreign Affairs of Qatar called for restraint and de-escalation and emphasized support for international law and the UN charter. It also offered to contribute to mediation efforts to reach an "immediate peaceful solution". Singapore: The Ministry of Foreign Affairs of Singapore expressed "grave concern" about the intervention and urged restraint by all parties. Senior Minister Lee Hsien Loong stated that the US strikes in Venezuela, would have worrying long-term consequences to the international system and small countries in particular. Taiwan: The Ministry of Foreign Affairs stated that it is closely monitoring the developments in Venezuela, and would continue to cooperate with democratic allies and work together for regional and global security, stability, and prosperity. Thailand: The Ministry of Foreign Affairs stated that it is closely monitoring the situation and urges all parties involved to resolve the conflict peacefully in accordance with the UN Charter and international law, exercising restraint to avoid further escalation, prioritizing civilian protection and respecting Venezuelans' will. Vietnam: The Ministry of Foreign Affairs expressed deep concern about the Venezuelan situation. The Vietnamese authority also called all sides to respect international law and the United Nations Charter, including the principle of respect for national sovereignty, and to refrain from the use or threat of force in international relations.
In an investigative report published by The Insider news-outlet in 2024, journalist Yuriy Matsarsky stated:"...Captagon produced in underground labs—and in actual Syrian pharmaceutical facilities—is distributed to the fighters of Bashar Assad's army. Interestingly, however, the quantities the country produces far exceed its own military's demand. ... By some estimates, this business gives Syria more money than its entire legal export, and the regime constantly works to increase its profits, primarily by expanding its market reach. To this end, criminal gangs associated with Damascus or Hezbollah have built distribution networks for Captagon in countries where the drug was not previously popular."
Sources: en.wikipedia.org
== Protein structure == The monomer protein, consisting of 54 amino acid residues, is the smallest of the sweet proteins with a molecular weight of 6.5 kDa. The amino acid sequence of brazzein, adapted from the Swiss-Prot biological database of protein, is as follows: QDKCKKVYEN YPVSKCQLAN QCNYDCKLDK HARSGECFYD EKRNLQCICD YCEY The structure of brazzein was determined by proton nuclear magnetic resonance (NMR) at a pH of 5.2 and 22 °C. Brazzein has four evenly spaced disulfide bonds and no sulfhydryl groups. 3D analysis of brazzein showed one alpha-helix and three strands of anti-parallel beta sheet. This is not superficially similar to either of the other two sweet-tasting proteins, monellin and thaumatin. However, a recent 3D study shows that these three proteins possess similar "sweet fingers" believed to elicit the sweet taste. Residues 29–33 and 39–43, plus residue 36, as well as the C-terminus were found to be involved in the sweet taste of the protein. The charge of the protein also plays an important role in its interaction with the sweet taste receptor. Based on this knowledge a synthesised improved brazzein, called pGlu-1-brazzein, was reported to be twice as sweet as the natural counterpart.
The patagium is the wing membrane, which reaches from the arm and finger bones to the side of the body and the hindlimbs. The extent to which the tail of a bat is attached to a patagium can vary by species, with some having completely free tails or even no tails. For bat embryos, only the hindfeet experience apoptosis (programmed cell death), while the forefeet retain webbing between the fingers that become the wing membranes. These structures include connective tissue, elastic fibres, nerves, muscles, and blood vessels. The muscles keep the membrane taut as the animal flies. While the skin on the body of the bat is covered in hair and sweat glands with an epidermis, a dermis, and a fatty subcutaneous layer, the patagium is an extremely thin double layer of epidermis separated by a connective tissue centre rich with collagen and elastic fibres. The surface of the wings is equipped with touch-sensitive receptors on small bumps called Merkel cells. Each bump has a tiny hair in the centre, allowing the bat to detect and adapt to changing airflow; the primary use is to judge the most efficient speed at which to fly, and possibly also to avoid stalls. Insectivorous bats may also use tactile hairs when manoeuvring to capture flying insects. While delicate, the membranes can heal quickly and regrow when torn. Photoluminescence has been reported in at least six North American species based on 60 museum specimens. The wings, uropatagium (around the tail), and hind limbs of these bats glowed green when exposed to UV light.
She argued that women, unlike men, did not have locker room experiences in school where they compared each other's genitals, which is one reason so many women wonder if their genitals are normal. Scholar Catherine Blackledge stated that having a vagina meant she would typically be treated less well than her vagina-less counterparts and subject to inequalities (such as job inequality), which she categorized as being treated like a second-class citizen.
Indium is created by the long-lasting (up to thousands of years) s-process (slow neutron capture) in low-to-medium-mass stars (range in mass between 0.6 and 10 solar masses). When a silver-109 atom captures a neutron, it transmutes into silver-110, which then undergoes beta decay to become cadmium-110. Capturing further neutrons, it becomes cadmium-115, which decays to indium-115 by another beta decay. This explains why the radioactive isotope is more abundant than the stable one. The stable indium isotope, indium-113, is one of the p-nuclei, the origin of which is not fully understood; although indium-113 is known to be made directly in the s- and r-processes (rapid neutron capture), and also as the daughter of very long-lived cadmium-113, which has a half-life of about eight quadrillion years, this cannot account for all indium-113. Indium is the 68th most abundant element in Earth's crust at approximately 50 ppb. This is similar to the crustal abundance of silver, bismuth and mercury. It very rarely forms its own minerals, or occurs in elemental form. Fewer than 10 indium minerals such as roquesite (CuInS2) are known, and none occur at sufficient concentrations for economic extraction. Instead, indium is usually a trace constituent of more common ore minerals, such as sphalerite and chalcopyrite. From these, it can be extracted as a by-product during smelting. While the enrichment of indium in these deposits is high relative to its crustal abundance, it is insufficient, at current prices, to support extraction of indium as the main product.
Sources: en.wikipedia.org
(2026) describe molars of Helarctos malayanus praemalayanus from the Pleistocene strata of the Tham Hai Cave (Vietnam), and interpret the fossil record from Southeast Asia as indicative of larger body size of Middle Pleistocene sun bears compared to their extant relatives. Probable fossil material of the Asian black bear, representing the first known record of a member of this lineage from northeastern Iberian Peninsula, is described from the Middle Pleistocene strata from Llers Quarry (Spain) by Rufí et al. (2026). Gutiérrez-Carbajal et al. (2026) reconstruct the evolutionary history of cave bears from southwestern Europe on the basis of data from enamel proteomic analysis, recovering Ursus dolinensis as a basal member of the cave bear lineage. Kochnev et al. (2026) study the variation of the size and shape of the hard palate and choanae of Ursus kanivetz and Ursus rossicus, and report possible evidence of a link between the hard palate form and the climate. A study on the ecology of cave bears from Galería 1 inside the Cueva de Guantes (Palencia, Spain) as indicated by isotopic composition of tooth enamel and bone collagen is published by Rodríguez-Franco et al. (2026). Hasegawa et al. (2026) study the distribution of brown bears in the Japanese Archipelago during the Late Pleistocene, reporting remains of exceptionally large individuals from Aomori, Nagano, Shizuoka and Oita. Estraviz-López et al.
== Life and work == Emanuel Gil-Av was born 1916 in Pensa of Tzarist Russia. After the death of his father, a physician, the family moved first to Central Europe and in 1928 to Tel-Aviv, Israel, where Gil-Av attended High School. Gil-Av studied petroleum chemistry at the University of Strasbourg. In 1940 he escaped the German occupation to England where he worked at first in the chemical laboratory of Chaim Weizmann, followed by the Petrochemical Ltd. in Manchester. After World War II, he moved to Palestine and he joined the Daniel Sieff Institute in Rehovot which was later on to become the Weizmann Institute of Science. In 1951 he earned his PhD under the supervision of Ernst David Bergmann. In his study of oil shale deposits, Gil-Av developed complex-forming stationary phases employing silver(I) ions for selective olefin separations by gas chromatography (GC). In co-operation with the centre of peptide chemistry at the Weizmann Institute of Science, he developed methods of the gas-chromatographic resolution of racemic α-amino acids. By coating a glass capillary column with the chiral stationary phase (CSP) N-trifluoroacetyl-L-isoleucine lauryl ester, Gil-Av et al. carried out in 1966 the first gas-chromatographic enantioseparation of racemic amino acids as N-trifluoroacetyl-O-alkyl derivatives. Many racemic compounds, amenable for enantioselective interaction via hydrogen bonding with the CSP, could be analytically enantioseparated by GC.
In January 2018, a class action lawsuit was filed against LifeVantage in Connecticut alleging that the company and its chief executive officer Darren Jensen, chief sales officer Justin Rose, and chief marketing officer Ryan Goodwin were operating an illegal pyramid scheme in violation of the RICO Act, federal securities laws, and the Connecticut Unfair Trade Practices Act.
Lurasidone is taken by mouth and should be taken with a meal of at least 350 calories to ensure maximum absorption. It has an estimated absorption rate of 9 to 19%. Studies have shown that when lurasidone is taken with food, absorption increases about twofold. Peak blood plasma concentrations are reached after one to three hours. About 99% of the circulating substance are bound to plasma proteins. Efficacy data for lurasidone have been evaluated for doses of 20 mg to 120 mg daily. In schizophrenia, lurasidone has a recommended dose range of 40-160 mg. In bipolar depression, lurasidone has a slightly lower recommended dose range of 20-120 mg. Lurasidone is extensively metabolised by CYP3A4 leading to contraindication of both strong inhibitors as well as strong inducers of this enzyme, but has negligible affinity to other cytochrome P450 enzymes. It is transported by P-glycoprotein and ABCG2 and also inhibits these carrier proteins in vitro. It also inhibits the solute carrier protein SLC22A1, but no other relevant transporters. Main metabolism pathways are oxidative N-dealkylation between the piperazine and cyclohexane rings, hydroxylation of the norbornane ring, and S-oxidation.:59 Other pathways are hydroxylation of the cyclohexane ring and reductive cleavage of the isothiazole ring followed by S-methylation. The two relevant active metabolites are the norbornane hydroxylation products called ID-14283 and ID-14326, the former reaching pharmacologically relevant blood plasma concentrations.
=== Groupings and organizations === Lucha Libre AAA Worldwide, a Mexican wrestling promotion Asian Athletics Association, the continental athletics authority in Asia Amateur Athletic Association of England, the Athletic Association in England Arkansas Activities Association, for high school sports Montreal AAA, an amateur athletic association Triple-A (baseball), a North American Minor League Baseball classification level Senior ice hockey § Senior AAA hockey leagues
Sources: en.wikipedia.org
No. It is a synthetic analogue carrying four amino acid changes, a lactam ring and an amidated C-terminus. The natural hormone is a linear thirteen-amino-acid peptide processed from proopiomelanocortin.
Afamelanotide is the linear analogue [Nle4-D-Phe7]-alpha-MSH, sometimes called melanotan I, while melanotan II is cyclic and carries three further substitutions. The two are distinct molecules and are not interchangeable in analytical testing.
Binding to the four melanocortin receptor subtypes is well documented in vitro. The relative contribution of each subtype to whole-body effects in humans is far less certain.
It is a synthetic cyclic heptapeptide and an analogue of alpha-melanocyte-stimulating hormone. The molecule is produced by chemical synthesis rather than extracted from a biological source.