lyophilized powder is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Last reviewed on 2025-11-10. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
Independent verification is central to quality control because the compound is not produced under pharmaceutical manufacturing standards. Third-party laboratories can measure purity, identity, residual solvents, and microbial contamination, though the scope of testing varies between services. Reported analyses of vendor samples have shown batch-to-batch variation in peptide content and the presence of truncated or oxidized species. How much of this variation reflects synthesis conditions versus storage and shipping is not well characterized. No harmonized reference standard exists for the material as sold.
Handling guidance for melanotan II follows general practice for small synthetic peptides rather than a product-specific monograph. Lyophilized powder is typically kept at minus twenty degrees Celsius or colder, protected from light and moisture, because warmth and humidity accelerate degradation. Once reconstituted, solutions are usually refrigerated and used within a short window, as hydrolysis and microbial growth both become concerns. Repeated freeze-thaw cycles are generally avoided. These conventions come from laboratory peptide chemistry and not from formal stability studies on this specific compound.
Analytical confirmation of identity relies on mass spectrometry, most often coupled to liquid chromatography. Reversed-phase high-performance liquid chromatography separates the peptide from related impurities and provides a purity estimate based on peak area. Electrospray ionization mass spectrometry then confirms the expected molecular mass, while tandem mass spectrometry can map the fragment sequence. For research-grade material, these two techniques together form the standard minimum. Purity figures reported by vendors are frequently not traceable to an independent laboratory.
| 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 |
Receptor binding at MC1R on melanocytes raises intracellular cyclic AMP and increases expression of tyrosinase and related enzymes. The downstream result is greater synthesis of eumelanin, the dark pigment, without ultraviolet exposure acting as the trigger. The compound is not selective, however, and also engages MC3R, MC4R and MC5R, which are expressed in the central nervous system and elsewhere. That lack of selectivity is the explanation usually offered for effects reported outside pigmentation, including appetite suppression and nausea. Selectivity remains a central theme in comparative studies of related peptides.
Human data remain limited and mostly short-term. Reports describe small trials and observational accounts rather than large controlled studies, so questions about dose-response relationships and long-term effects on melanocytes stay open. Whether repeated exposure alters naevus behaviour is not settled in the published record. Researchers also note that self-administered use outside clinical settings makes actual exposure difficult to quantify. Statements about efficacy and safety should therefore be read as preliminary rather than established.
Melanotan II is a synthetic cyclic heptapeptide that acts as an agonist at melanocortin receptors. It was designed as a structural analogue of alpha-melanocyte-stimulating hormone, the endogenous peptide involved in pigment production. The analogue carries a lactam bridge that constrains the ring and slows enzymatic breakdown relative to the native hormone. In research literature it appears under several abbreviations, and naming conventions are not fully standardized. Published descriptions usually place it within the broader melanocortin agonist family.
Because the substance circulates mainly through informal markets, verification is a recurring theme in technical discussion. Independent analyses have found that labeled content and actual content can diverge, and that purity varies between samples. Analytical laboratories use reversed-phase chromatography to separate components and mass spectrometry to confirm identity. Isotope-labeled internal standards improve quantification in complex matrices. Such methods describe what a sample contains but say nothing about its sterility, lawful status, or suitability for any use. Open questions remain about how consistently testing is applied across the supply chain.
Regulatory treatment of this peptide varies by country. It holds no marketing authorization as a medicine in the United States, the European Union, or most other jurisdictions. Some countries classify products containing it as prescription-only or unlicensed medicines, which restricts lawful supply. Authorities have issued public notices warning that unregulated products may contain undeclared or incorrect ingredients. The molecule also appears on prohibited lists for competitive sport. These measures address supply oversight rather than any approved therapeutic role.
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.
Quality assessment of research-grade peptide rests mainly on reversed-phase high-performance liquid chromatography for purity and on mass spectrometry for identity confirmation. A single main peak above a stated threshold, commonly ninety-eight percent by peak area, is the usual release criterion applied by suppliers. Independent analyses commissioned by laboratories and consumer organisations have repeatedly reported discrepancies between label claims and measured content, including truncated sequences, residual trifluoroacetate, and lower-than-declared peptide mass. Those findings do not establish that every supplier is unreliable, but they indicate that purity figures printed on a vial are claims requiring verification rather than settled facts.
Regulatory treatment varies by jurisdiction and has changed over time. In several countries the peptide is handled as an unapproved prescription medicine, and import or sale for human use is restricted, while elsewhere it falls under poisons or controlled-substance schedules. Enforcement activity against online vendors has been reported in Australia, New Zealand, the United Kingdom and the United States. Scholarly writing discusses melanotan-2 chiefly as an experimental tool and as a case study in unregulated peptide supply, and its precise legal position in any given country should be checked against current national schedules.
Lyophilised melanotan-2 is comparatively robust when kept dry, cold and dark, and a desiccated powder stored at minus twenty degrees Celsius or below is generally expected to retain its chemical integrity for extended periods. In solution the peptide is far less stable, with degradation proceeding through oxidation of tryptophan and histidine residues, hydrolysis adjacent to the lactam bridge, and aggregation at higher concentrations. Repeated freeze-thaw cycling accelerates loss of the parent peak. Working aliquots are therefore prepared once, held cold, and used without letting the stock return to ambient temperature.
The Prachachat Party issued a statement asking the Election Commission to investigate irregularities in Pattani and Narathiwat Constituency 4, and the Bhumjaithai candidate in Narathiwat Constituency 3 asked for a recount in that constituency. Former Election Commission member Somchai Srisutthiyakorn criticized the commission's failure to comply with regulations in Chonburi Constituency 1, stating that election showed serious signs of fraud. He further stated that even a recount might not be enough due to the possibility of tampering with improperly sealed boxes and suggested that a repeat election might have to be held in the constituency. On 12 February, the Election Commission rejected the requests for recounts in Chonburi and Maha Sarakham, stating that its investigation did not find credible evidence. In the same press briefing, it ordered new elections for three polling stations: one in Bangkok where ballots were damaged by rain, and two in Nan and Udon Thani, where polling station officials incorrectly tore ballots. It also ordered a recount of the votes in Pathum Thani Constituency 7, which had been subject to complaints that officials failed to properly count votes in view of the public. Further recounts at eight stations and a fresh election at one station were announced on 17 February, and nine more on 24 February.
Reactions of acids are often generalized in the form HA ⇌ H+ + A−, where HA represents the acid and A− is the conjugate base. This reaction is referred to as protolysis. The protonated form (HA) of an acid is also sometimes referred to as the free acid. Acid–base conjugate pairs differ by one proton, and can be interconverted by the addition or removal of a proton (protonation and deprotonation, respectively). The acid can be the charged species and the conjugate base can be neutral in which case the generalized reaction scheme could be written as HA+ ⇌ H+ + A. In solution there exists an equilibrium between the acid and its conjugate base. The equilibrium constant K is an expression of the equilibrium concentrations of the molecules or the ions in solution. Brackets indicate concentration, such that [H2O] means the concentration of H2O. The acid dissociation constant Ka is generally used in the context of acid–base reactions. The numerical value of Ka is equal to the product (multiplication) of the concentrations of the products divided by the concentration of the reactants, where the reactant is the acid (HA) and the products are the conjugate base and H+.
Schering AG filed for a patent for NETA in June 1957, and the patent was issued in December 1960. The drug was first marketed, by Parke-Davis as Norlestrin in the United States, in March 1964. This was a combination formulation of 2.5 mg NETA and 50 μg ethinylestradiol and was indicated as an oral contraceptive. Other early brand names of NETA used in oral contraceptives included Minovlar and Anovlar. Norethisterone acetate is the INNTooltip International Nonproprietary Name, BANMTooltip British Approved Name, and JANTooltip Japanese Accepted Name of NETA while norethindrone acetate is its USANTooltip United States Adopted Name and USPTooltip United States Pharmacopeia. NETA is marketed under a variety of brand names throughout the world including Primolut-Nor (major), Aygestin (USTooltip United States), Gestakadin, Milligynon, Monogest, Norlutate (USTooltip United States, CATooltip Canada), Primolut N, SH-420 (UKTooltip United Kingdom), Sovel, and Styptin among others.
== Synthesis == [18F]FDG was first synthesized via electrophilic fluorination with [18F]F2. Subsequently, a "nucleophilic synthesis" was devised with the same radioisotope. As with all radioactive 18F-labeled radioligands, the fluorine-18 must be made initially as the fluoride anion in a cyclotron. Synthesis of complete [18F]FDG radioactive tracer begins with synthesis of the unattached fluoride radiotracer, since cyclotron bombardment destroys organic molecules of the type usually used for ligands, and in particular, would destroy glucose. Cyclotron production of fluorine-18 may be accomplished by bombardment of neon-20 with deuterons, but usually is done by proton bombardment of 18O-enriched water, causing a (p-n) reaction (sometimes called a "knockout reaction" – a common type of nuclear reaction with high probability where an incoming proton "knocks out" a neutron) in the 18O. This produces "carrier-free" dissolved [18F]fluoride ([18F]F−) ions in the water. The 109.8-minute half-life of fluorine-18 makes rapid and automated chemistry necessary after this point. Anhydrous fluoride salts, which are easier to handle than fluorine gas, can be produced in a cyclotron. To achieve this chemistry, the [18F]F− is separated from the aqueous solvent by trapping it on an ion-exchange column, and eluted with an acetonitrile solution of 2,2,2-cryptand and potassium carbonate. Evaporation of the eluate gives [(crypt-222)K]+ [18F]F− (2) .
Between 560 and 550 BCE a decade-long war was fought between Kroton and Epizephyrian Locris. The war was resolved by the battle on the Sagra River, which saw the alliance between the people of Reggio and Locri emerge victorious. In 510 BCE the Crotonians attacked Sybaris, and fought the Sybarites by the River Trionto, in a clash pitting 100,000 Crotonians against 300,000 Sybarites. The Dorians won the battle and occupied Sybaris, sacking it over 70 days and diverting the Crati River onto the ruins of the city. In 444 BCE Athenian and Peloponnesian colonists founded Turi on the site of the destroyed Sybaris at the behest of Pericles in the détente plan related to the Thirty Years' Peace in the Peloponnesian War. In 338 BCE, Locri asked Dionysius of Syracuse for help against the expansion of Reggio (no longer their allieds) and Croton. The Syracusans intervened by defeating the Crotonians on the narrowest point of the river Sagra, current Allaro, and occupying Croton for ten years, an event that ended the Crotonians' power; a similar fate befell Reggio, which resisted the numerous attacks of Dionysius of Syracuse, but in 386 BCE after eleven months of siege, was taken by the Syracusans, also weakened in its political power. Rhegion was the birthplace of one of the famed nine lyric poets, Ibycus and Metauros was the birthplace of another, Stesichorus, who was amongst the western world's first lyric poets. Kroton spawned many victors during the ancient Olympics and other Panhellenic Games.
Sources: en.wikipedia.org
=== Civil society === Reactions also came from European civil society organisations. Transparency International described the incident as "the most egregious case" of alleged corruption the European Parliament has ever seen. The founder of the Good Lobby commented that "[w]hatever its final outcome, [the] Qatar 'corruption' scandal has unveiled an inconvenient, and for most Europeans already obvious, truth. Money does buy influence in the EU", and that "[t]he EU Parliament and most of its members have historically resisted stricter integrity rules and [an] effective enforcement system." As news broke of the investigation, the honorary board of the implicated NGO, Fight Impunity, resigned en masse. The board members included high-profile European policymakers including Federica Mogherini (former EU High Representative in the Juncker Commission), Bernard Cazeneuve (formerly Prime Minister of France), Dimitris Avramopoulos (former EU Commissioner for Migration, Home Affairs and Citizenship in the Juncker Commission), Cecilia Wikström (former MEP) and Emma Bonino (former EU Commissioner for Health and Consumer Protection in the Santer Commission). The honorary board has no executive or managerial role, so there is no suspicion or accusations against any member of the board. Visentini originally voluntarily stood down temporarily as president of the International Trade Union Congress but a specially convened Extraordinary Meeting of the General Council voted to suspend him of all of his duties.
==== Indonesia ==== In Indonesia, Mister Donut is operated under management of Indomaret, a subsidiary of Salim Group. The first store was opened in 2015, with 7 standalone outlets and 1,350 stands inside Indomaret outlets, mostly located in the city center, malls, airports, rail stations, or shop-in-shops at every Indomaret outlet.
=== Toxicity === In 2009, one case of sympathomimetic toxicity was reported in the UK after a person took 0.2 g of mephedrone orally, and after this did not achieve the desired effect, intramuscularly injected 3.8 g mixed with water into his thighs. Shortly afterwards, the user "developed palpitations, blurred tunnel vision, chest pressure and sweating". The patient was treated with 1 mg of lorazepam and the sympathomimetic features decreased and the user was discharged within six hours of arrival. One case of serotonin syndrome has been reported, where the patient was already prescribed fluoxetine and olanzapine, and then took 40 tablets containing mephedrone in one night. He was treated with lorazepam and discharged 15 hours after admission. Both enantiomers of methcathinone, which differs only in the lack of the methyl group on the phenyl ring when compared to mephedrone, have been shown to be toxic to rat dopamine neurons, and the S-enantiomer was also toxic against serotonin neurons. Simon Gibbons and Mire Zloh of the School of Pharmacy, University of London stated, based on the chemical similarities between methcathinone and mephedrone, "it is highly likely that mephedrone will display neurotoxicity". However, Brunt and colleagues stated, "extreme caution" should be used when inferring the toxicity of mephedrone from methcathinone, noting some of the toxicity associated with methcathinone is due to manganese impurities related to its synthesis, rather than the compound itself.
APCs naturally have a role in fighting tumors, via stimulation of B and cytotoxic T cells to respectively produce antibodies against tumor-related antigen and kill malignant cells. Dendritic cells, presenting tumor-specific antigen to T cells, are key to this process. Cancer therapies have included treating the patient with increased numbers of dendritic cells or cancer-specific T cells. However, newer therapies have turned to genetically engineered artificial antigen-presenting cells designed to prime the immune system to attack malignant cells. Some artificial APCs are derived from human cells; others are acellular, containing MHC proteins, co-stimulatory molecules and the necessary peptides. The APC activator IMP321 is being tested in clinical trials to accelerate the immune reaction to eliminate metastatic breast cancer or melanoma. Antigen: protease degradation on YouTube – PMAP animation Antigen-Presenting+Cells at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
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.
The lyophilized powder is generally held at minus twenty degrees Celsius or below, away from light and moisture. Reconstituted solutions are typically refrigerated and used quickly. These practices derive from general peptide handling rather than a formal stability study.