The short version of cyclic heptapeptide fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2025-11-14. Anything still debated is marked as such rather than presented as settled.
Regulatory treatment varies by country. In the United States the peptide is not approved as a medicine, and products offered for human use may be treated as unapproved new drugs; some states also restrict sale. Australia, the United Kingdom, and European Union member states apply comparable restrictions to unapproved peptide products. Border agencies have seized shipments labelled as research chemicals. Classification may change over time, and the legal position for personal importation is not clearly settled in most published guidance.
Lyophilised melanotan-2 is supplied as a solid, which is more stable than a solution. The material is hygroscopic, so weighing is done quickly, in low humidity, with the container kept sealed. Reconstitution usually uses water for injection or bacteriostatic water, added down the wall of the vial to limit foaming. A reconstituted solution is held at 2 to 8 °C and kept away from light. Repeated freezing and thawing of the same vial is avoided because ice crystal formation and concentration effects degrade the peptide.
Reversed-phase high-performance liquid chromatography is the routine method for purity assessment. Peptides absorb near 214 nm because of the peptide bond, and a gradient of acetonitrile in water separates the intact peptide from deletion sequences, oxidised products, and earlier-eluting fragments at neutral pH. Electrospray ionisation mass spectrometry provides an orthogonal check: the measured mass must agree with the theoretical value. Amino acid analysis and peptide mapping confirm structure but are used less often. Reference standards remain scarce because the peptide is not described in any pharmacopoeia.
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.
| Property | Value | Notes |
|---|---|---|
| Lyophilised storage | −20 °C, dry, protected from light | Vials are sealed and allowed to reach room temperature before opening |
| Reconstituted storage | 2 to 8 °C, protected from light | Short-term holding; avoid repeated freeze-thaw cycles |
| Reconstitution solvent | Water for injection or bacteriostatic water | Added slowly along the vial wall to reduce foaming and shear |
| Purity measurement | RP-HPLC with area normalisation | Acetonitrile-water gradient monitored at roughly 214 nm |
| Identity confirmation | Electrospray ionisation mass spectrometry | Observed mass compared against the calculated peptide mass |
Melanotan-2 appears on the World Anti-Doping Agency prohibited list within the peptide hormone class, and several national regulators treat it as an unapproved prescription substance. Some countries restrict importation or sale for personal use. Because the compound is widely traded as a research chemical, the practical legal picture differs between jurisdictions and shifts over time. Human safety data covering long periods are limited, and whether repeated pigmentation changes carry any lasting risk to melanocytes remains an open question.
Freeze-dried melanotan-2 is normally kept as a desiccated powder at minus twenty degrees Celsius or lower, shielded from light and moisture. Peptides of this size degrade through hydrolysis, oxidation and deamidation, and each pathway accelerates as temperature and water activity rise. Repeated freeze-thaw cycles promote aggregation and loss of material, so aliquoting a stock solution before freezing is standard laboratory practice. Once dissolved, the solution is markedly less stable than the powder. In laboratory work, solutions are generally refrigerated and used within days rather than kept for months.
Identity and purity are usually assessed by reversed-phase high-performance liquid chromatography, which separates the target peptide from truncated or oxidised impurities. Mass spectrometry, most often coupled to liquid chromatography, confirms molecular mass and detects substitutions that chromatography alone may miss. Amino acid analysis and peptide mapping supply additional structural evidence, while nuclear magnetic resonance is reserved for full structural confirmation. Laboratories that examine samples sold online report wide variation in actual content, with some vials containing little or none of the labelled material.
Melanotan II binds several melanocortin receptor subtypes rather than a single target. MC1R on melanocytes drives melanin synthesis, while MC3R and MC4R participate in energy balance, appetite, and sexual response pathways. This lack of selectivity explains why reported effects extend beyond skin darkening. Substitutions at positions four and seven, including norleucine and D-phenylalanine, increase potency and resistance to peptidases. Understanding which receptor mediates which effect remains an active area of investigation.
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.
Solid peptide material is generally stable when kept cold and dry. Common practice is storage at -20 degrees Celsius or lower, with desiccant and protection from light. Repeated freeze-thaw cycles and exposure to moisture are associated with degradation, aggregation, or loss of material. Once dissolved, stability depends on solvent, concentration, and temperature, and solutions are usually treated as short-lived unless stability data support longer periods. Handling notes typically emphasise minimising time at ambient temperature.
Identity and purity are assessed with chromatographic and mass spectrometric techniques. Reversed-phase high-performance liquid chromatography separates the target peptide from related impurities and degradation products, and the resulting retention time is compared against a reference standard. Mass spectrometry, often coupled to liquid chromatography, confirms molecular mass. Amino acid analysis or peptide mapping can provide additional sequence-level confirmation when required. Results are only as reliable as the reference materials used alongside them.
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.
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.
acetyl-CoA + L-glutamate → CoA + N-acetyl-L-glutamate NAGS, a member of the N-acetyltransferase family of enzymes, is present in both prokaryotes and eukaryotes, although its role and structure differ widely depending on the species. NAG can be used in the production of ornithine and arginine, two important amino acids, or as an allosteric cofactor for carbamoyl phosphate synthase (CPS1). In mammals, NAGS is expressed primarily in the liver and small intestine, and is localized to the mitochondrial matrix.
Most commonly 2,5-diketopiperazines are generated by cyclisation of dipeptides. In addition to the many methods of peptide synthesis, the Ugi reaction can be applied. Dipeptides with an ester terminus spontaneously cyclize often. Racemization can be problematic. The Ugi reaction using an isonitrile, amino acid, aldehyde and amine, can produce a dipeptide in equally high yield and optical purity, to that formed by standard peptide couplings. Commonly, an isonitrile is chosen to give a labile terminal amide to enable cyclization. For example, the direct 2,5-DKP ring formation via such an activated leaving group using the stable, easily accessible and versatile convertible isonitrile 1-isocyano-2-(2,2-dimethoxyethyl)-benzene 4 gave a one-pot synthesis of N-substituted 2,5-diketopiperazine's 7.
=== Role in neonatal immunity across species === The function of FcRn in neonatal immunity differs across species. In humans, FcRn in the placenta transfers maternal IgG to the fetus during gestation. In rodents, maternal IgG is delivered postnatally through FcRn-mediated uptake in the neonatal gut. Species like piglets and foals, which lack prenatal IgG transfer due to their placental structure, depend entirely on intestinal FcRn to absorb IgG from colostrum shortly after birth. These species-specific mechanisms reflect evolutionary adaptations in FcRn expression and function across mammals.
== Chemistry == 1,2-Diarylethylamines contain the substructure ArCH2CH(Ar')NRR', where Ar, Ar' = aryl and R, R' = H or organyl. A chiral center exists at the ethylamine carbon atom bearing the two aryl groups. The enantiomers often have a large difference in pharmacological activity. For example, (+)-(S)-diphenidine has 40 times higher affinity than (−)-(R)-form for the NMDA receptor. According to a review by Jason Wallach and Simon Brandt (2018), most psychoactive 1,2-diarylethylamines reported in the scientific literature contain non-heteroaromatic aryl groups (i.e., both rings are carbocyclic). Some exceptions include lanicemine and an analogue N-ethyl-lanicemine, which feature a heteroaromatic pyridyl ring. Additional heteroaromatic analogues have been disclosed in the patent literature.
November 29 Twitter co-founder Jack Dorsey steps down as its chief executive, saying it is "finally time for me to leave". Parag Agrawal is named his successor. The Attorney General of New York Office releases lengthy documents which prove that CNN host Chris Cuomo abused journalistic ethics in a manner that was much greater than what had been reported earlier in the year. According to the documents, during Andrew Cuomo's sexual harassment scandal, Chris used his connections in the media both to obtain information about his brother's accusers as well as to uncover the possibility that new accusers could come out against the former New York governor. November 30 Former White House Chief of Staff Mark Meadows announces that he will testify to and cooperate with the January 6 committee. 2021 Oxford High School shooting – Four students are killed and seven other people are injured in a mass shooting at Oxford High School in Oxford Township, Michigan. CNN announces that it has indefinitely suspended Chris Cuomo while a law firm conducts an independent investigation that the network hired to look into the matter.
Sources: en.wikipedia.org
Bluebottle fly adults feed on nectar, and they are pollinators of flowers. They are especially attracted to flowers that have strong odors, such as those that have adapted to smell like rotting meat. Plants pollinated by the fly include the skunk cabbage (Symplocarpus foetidus), American pawpaw (Asimina triloba), dead horse arum (Helicodiceros muscivorus), goldenrod and some species of the carrot family. These insects tend to fly in packs in order to detect possible food sources more efficiently. If one fly detects food, it disperses a pheromone, which will alert the others to the meal.
The principal Cossack émigré leader after 1945 was Nikolai Nazarenko, the self-proclaimed president of the World Federation of the Cossack National Liberation Movement of Cossackia, who enjoyed a prominence in New York as the organizer of the annual Captive Nations parade held every July. In 1978, Nazarenko dressed in his Don Cossack uniform led the Captive Days day parade in New York city, and told a journalist: "Cossackia is a nation of 10 million people. In 1923 the Russians officially abolished Cossackia as a nation. Officially, it no longer exists...America should not spend billions supporting the Soviets with trade. We don't have to be afraid of the Russian army because half of it is made up of Captive Nations. They can never trust the rank and file". The journalist Hal McKenzie described Nazarenko as having "cut a striking figure with his white fur cap, calf-length coat with long silver-sheathed dagger and ornamental silver cartridge cases on his chest". Nazarenko was also the president of Cossack American Republican National Federation, which in turn was part of the National Republican Heritage Groups Council, and he attracted much controversy in the 1980s owing to his wartime career and certain statements he made about Jews. The American journalist Christopher Simpson in his 1988 book Blowback: America's Recruitment of Nazis and Its Effects on the Cold War called Nazarenko a leading Republican activist who made "explicit pro-Nazi, anti-semitic" statements in his speeches.
Insecticides are pesticides used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. The major use of insecticides is in agriculture, but they are also used in home and garden settings, industrial buildings, for vector control, and control of insect parasites of animals and humans. Acaricides, which kill mites and ticks, are not strictly insecticides, but are usually classified together with insecticides. Some insecticides (including common bug sprays) are effective against other non-insect arthropods as well, such as scorpions, spiders, etc. Insecticides are distinct from insect repellents, which repel but do not kill.
Pasteur's research led to Ignaz Semmelweis and Joseph Lister researching the importance of sanitized hands in medical work. In the 1840s, Semmelweis' observations and ideas surrounding sanitary techniques were rejected and his book on the topic condemned by the medical community due to its conflict with the prevailing theory and practice of humorism at the time. After Lister's publications, which supported hand washing and sanitation with germ theory, doctors started sanitizing their hands in the 1870s; mandatory handwashing was not incorporated into common health practice until as late as the 1980s. The discovery of the connection of microorganisms to disease came later in the nineteenth century, when Italian anatomist Filippo Pacini isolated the cholera bacterium Vibrio cholerae in 1854 in Florence during the Asiatic Cholera Pandemic of 1846–63 and clearly linked the presence of the bacterium in the intestinal mucosa of dead cholera patients to the disease. Although Pacini's work was available to the international scientific community via French and English translations, the discovery of the cholera-causing agent is often attributed to the German physician Robert Koch who rediscovered it in 1884. Koch is credited for introducing the science of microorganisms including bacteria to the medical field. Koch, a pioneer in medical microbiology, worked on cholera, anthrax and tuberculosis. In his research into tuberculosis Koch finally proved the germ theory, for which he received a Nobel Prize in 1905.
where A is mass number, Z is atomic number, mH is the atomic mass of a hydrogen atom, mn is the mass of a neutron, and c is the speed of light. Thus, the mass of an atom is less than the mass of its constituent protons and neutrons, assuming the average binding energy of its electrons is negligible. The binding energy B is expressed in energy units, using Einstein's mass-energy equivalence relationship. The binding energy also provides an estimate of the total energy released from fission. The curve of binding energy is characterized by a broad maximum near mass number 60 at 8.6 MeV, then gradually decreases to 7.6 MeV at the highest mass numbers. Mass numbers higher than 238 are rare. At the lighter end of the scale, peaks are noted for helium-4, and the multiples such as beryllium-8, carbon-12, oxygen-16, neon-20 and magnesium-24. Binding energy due to the nuclear force approaches a constant value for large A, while the Coulomb acts over a larger distance so that electrical potential energy per proton grows as Z increases. Fission energy is released when a A is larger than approx. 60. Fusion energy is released when lighter nuclei combine. Carl Friedrich von Weizsäcker's semi-empirical mass formula may be used to express the binding energy as the sum of five terms, which are the volume energy, a surface correction, Coulomb energy, a symmetry term, and a pairing term:
Sources: en.wikipedia.org
where the employee is in a position to objectively demonstrate that a report to her/his employer will prove ineffective, where the employee has to anticipate dismissal, where the employee must assume that the competent authority will be hindered in investigating the irregularity, or where there is a direct and serious hazard to life, to health, to safety, or to the environment. The draft does not improve on protection against dismissal for employees who report irregularities to their employer. The amendment does not provide for employees to anonymously file their observations of irregularities.
=== Chiral discrimination === Easson and Stedman (1933) advanced a drug-receptor interaction model to account for the differential pharmacodynamic activity between enantiomeric pairs. In this model the more active enantiomer (the eutomer) take part in a minimum of three simultaneous intermolecular interactions with the receptor surface (good fit), Figure. A., where as the less active enantiomer (distomer) interacts at two sites only (bad fit), Figure B. [Refer image for Figure: Easson-Stedman model]. Thus the "fit" of the individual enantiomers to the receptor site differs, as does the energy of interaction. This is a simplistic model but used to explain the biological discrimination between enantiomeric pairs.
As the name for the element of atomic number 96 we should like to propose "curium", with symbol Cm. The evidence indicates that element 96 contains seven 5f electrons and is thus analogous to the element gadolinium, with its seven 4f electrons in the regular rare earth series. On this basis element 96 is named after the Curies in a manner analogous to the naming of gadolinium, in which the chemist Gadolin was honored. The first curium samples were barely visible, and were identified by their radioactivity. Louis Werner and Isadore Perlman made the first substantial sample of 30 μg curium-242 hydroxide at University of California, Berkeley in 1947 by bombarding americium-241 with neutrons. Macroscopic amounts of curium(III) fluoride were obtained in 1950 by W. W. T. Crane, J. C. Wallmann and B. B. Cunningham. Its magnetic susceptibility was very close to that of GdF3 providing the first experimental evidence for the +3 valence of curium in its compounds. Curium metal was produced only in 1950 by reduction of CmF3 with barium.
== Use and effects == In his book PiHKAL (Phenethylamines I Have Known and Loved), Alexander Shulgin lists MDDMA's dose as greater than 150 mg orally and its duration as unknown. Findings on the effects of MDDMA are very mixed. In two reports, with 150 mg and 1,000 mg both orally, no effects whatsoever occurred. In another report, 550 mg orally resulted in very negative effects. Finally, two people who used 200 mg orally found that it produced very pleasant effects for 20 minutes, wore off, but then resurged to produce even stronger effects 4 hours later. The higher-dose reports were communicated to Shulgin anonymously and he was uncertain whether the actual substance employed was indeed MDDMA. More research seems necessary to characterize MDDMA, but Shulgin expected that a "pretty hefty dose" would be required for it to produce effects.
Sources: en.wikipedia.org
Low temperature slows hydrolysis and oxidation, the two main routes by which the peptide backbone and side chains are modified. A lyophilised powder stored at −20 °C is more stable than one kept at room temperature, and once the material is dissolved the degradation rate rises, making refrigeration more important.
Liquid chromatography coupled to mass spectrometry is the most common approach because it combines a retention time with a mass measurement. A chromatographic peak alone cannot establish which peptide is present, so mass determination or amino acid analysis is used as an orthogonal confirmation alongside the separation.
This depends on buffer, pH, and concentration, and published stability data for this peptide are limited. In practice laboratories work through a refrigerated solution within a few weeks and discard samples that show cloudiness or visible particles. Freezing and thawing repeatedly is generally discouraged.
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.