Everything below concerns alpha-MSH. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2026-01-21. Where a claim depends on a specific study, the study is described rather than over-claimed.
Melanotan-2 is handled in the laboratory as a lyophilised powder that dissolves readily in water, dimethyl sulfoxide and dimethylformamide, with limited solubility in ethanol. Stock solutions prepared in an organic solvent often precipitate when diluted into aqueous buffer, so gradual dilution with mixing is standard practice. The peptide carries a tryptophan residue and a histidine residue, both sensitive to oxidation and to alkaline conditions. Working solutions are therefore kept near neutral to slightly acidic pH, protected from light, and consumed within the same working session whenever that is practical.
Solid peptide kept dry at minus twenty degrees Celsius, shielded from light and moisture, is generally considered stable for extended periods. Solutions are divided into single-use aliquots and held at minus twenty or minus eighty degrees Celsius, because repeated freeze-thaw cycles promote aggregation and loss of material to container surfaces. Hydrolysis of the backbone and oxidation of tryptophan are the principal degradation routes in aqueous solution, and both accelerate at ambient temperature. Hygroscopic uptake after a vial is opened can also shift the actual mass weighed, which affects any concentration calculated from it.
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.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white powder | Lyophilised material may be hygroscopic |
| Solubility class | Soluble in water, DMSO and DMF | Dilution into aqueous buffer can cause precipitation |
| Storage of solid | Minus 20 degrees C, desiccated, dark | Aliquot to limit repeated opening of the vial |
| Storage of solution | Minus 20 to minus 80 degrees C, aliquoted | Avoid repeated freeze-thaw cycles |
| Identity method | Reversed-phase HPLC with mass spectrometry | Retention time and mass are checked together |
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-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.
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.
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.
Hong Kong has a humid subtropical climate (Köppen Cwa), characteristic of southern China, closely bordering on a tropical monsoon climate. Summers are long, hot, and humid, with occasional showers and thunderstorms and warm air from the southwest. The humid climate of Hong Kong intensifies summer heat. Typhoons occur most often then, sometimes resulting in floods or landslides. Also rarely occurring are waterspouts and tornadoes, which occurred at Hong Kong International Airport on 26 September 2020 and at Victoria Harbour on 28 September 2024. Winters are short, mild and usually sunny at the beginning, becoming cloudy towards February. Frequent cold fronts bring strong, cooling winds from the north and occasionally result in chilly weather. Autumn is the sunniest season, whilst spring is generally cloudy. Snowfall has been extremely rare in Hong Kong; the last reported instance was on Tai Mo Shan in 1975. Hong Kong averages 1,709 hours of sunshine per year. Historic temperature extremes at the Hong Kong Observatory are 36.9 °C (98.4 °F) on 9 August 2026 and 0.0 °C (32.0 °F) on 18 January 1893, record highest daily minimum temperature there was 30.2 °C (86.4 °F) on 12 August 2026 and the lowest daily maximum temperature there was 3.2 °C (37.8 °F) on 16 January 1893. The highest and lowest recorded temperatures in all of Hong Kong are 39.8 °C (104 °F) at Sheung Shui on 9 August 2026, and −6.0 °C (21.2 °F) at Tai Mo Shan on 24 January 2016.
== Taxonomy == The plant is part of the family Lamiaceae. A later described species, named S. sieboldii, in dedication to the German-Dutch botanist and japanologist Philipp Franz von Siebold, is considered to be a synonym.
=== Electrolyte === The electrolyte ensures good electrical conductivity and minimizes iR drop such that the recorded potentials correspond to actual potentials. For aqueous solutions, many electrolytes are available, but typical ones are alkali metal salts of perchlorate and nitrate. In nonaqueous solvents, the range of electrolytes is more limited, and a popular choice is tetrabutylammonium hexafluorophosphate.
=== Knoxville and Slavery === By 1860, slaves comprised 22% of Knoxville's population, which was higher than the percentage across East Tennessee (approximately 10%) but lower than the rest of the South (about one-third). Most of Knox County's farms were small (only one was larger than 1,000 acres (4.0 km2)) and typically focused on livestock or other products that weren't labor-intensive. The city was home to a chapter of the American Colonization Society, led by St. John's Episcopal Church rector Thomas William Humes. While Knoxville was far less dependent on slavery than the rest of the South, most of the city's leaders, even those who opposed secession, were pro-slavery at the onset of the Civil War. Some, such as J.G.M. Ramsey, had always been pro-slavery. However, numerous prominent Knoxvillians, including Brownlow, Oliver Perry Temple, and Horace Maynard, had been pro-emancipation in the 1830s, but, for reasons not fully understood, were pro-slavery by the 1850s. Temple later wrote that he and others abandoned their anti-slavery stance due to the social ostracism abolitionists faced in the South. Historian Robert McKenzie, however, argues that the aggression of northern abolitionists toward Southerners pushed many Southern abolitionists toward pro-slavery views, though he points out that no one explanation neatly explains this shift. In any case, by the late-1850s, most of Knoxville's leaders were pro-slavery. The views of Brownlow and Ramsey, bitter enemies on many fronts, were virtually identical on the issue of slavery.
Sources: en.wikipedia.org
=== Terminal alkyne protecting groups === For alkynes there are in any case two types of protecting groups. For terminal alkynes it is sometimes important to mask the acidic hydrogen atom. This normally proceeds from deprotonation (via a strong base like methylmagnesium bromide or butyllithium in tetrahydrofuran/dimethylsulfoxide) and subsequently reaction with chlorotrimethylsilane to a terminally TMS-protected alkyne. Cleavage follows hydrolytically – with potassium carbonate in methanol – or with fluoride ions like for example with tetrabutylammonium fluoride.
Glycine + tetrahydrofolate + NAD+ ⇌ CO2 + NH+4 + N5,N10-methylene tetrahydrofolate + NADH + H+ In the second pathway, glycine is degraded in two steps. The first step is the reverse of glycine biosynthesis from serine with serine hydroxymethyl transferase. Serine is then converted to pyruvate by serine dehydratase. In the third pathway of its degradation, glycine is converted to glyoxylate by D-amino acid oxidase. Glyoxylate is then oxidized by hepatic lactate dehydrogenase to oxalate in an NAD+-dependent reaction. The half-life of glycine and its elimination from the body varies significantly based on dose. In one study, the half-life varied between 0.5 and 4.0 hours.
S2F10 + Cl2 → 2 SF5Cl The analogous reaction with bromine is reversible and yields SF5Br. The reversibility of this reaction can be used to synthesize S2F10 from SF5Br. It reacts with SO2 to form pentafluorosulfur fluorosulfonate (SF5OSO2F) in the presence of ultraviolet radiation. Ammonia is oxidised by S2F10 into NSF3.
Sources: en.wikipedia.org
Purity is normally stated as an area percentage from high-performance liquid chromatography, for example ninety-five or ninety-eight percent. That figure describes the proportion of ultraviolet-absorbing material eluting as the main peak. It says nothing about water content, counterions, residual solvents or mass fraction of the peptide itself.
Peptides are commonly isolated as acetate or trifluoroacetate salts, and the counterion contributes to total mass. Two vials with identical peptide content can therefore differ in weight and in measured response. Residual trifluoroacetate is also relevant in cell-based work because it can influence membrane behaviour.
Degradation products are often closely related to the parent molecule, making them hard to resolve with a single method. Counterion variability adds a further source of scatter between laboratories. Because no pharmacopoeial monograph exists for melanotan-2, groups rely on method-specific validation rather than a shared reference standard.
It is a synthetic cyclic heptapeptide and a non-selective melanocortin receptor agonist. Structurally it is modelled on alpha-melanocyte-stimulating hormone, a peptide that occurs naturally in the body.