salt form raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2026-02-24. Anything still debated is marked as such rather than presented as settled.
Routine characterisation relies on reversed-phase high-performance liquid chromatography with ultraviolet detection near 214 nanometres, using a C18 column and a water-acetonitrile gradient containing trifluoroacetic acid. Electrospray ionisation mass spectrometry confirms the expected molecular mass and can reveal truncated or oxidised by-products that co-elute poorly. Sequence and stereochemistry require additional work, such as peptide mapping or amino acid analysis, because a chromatographic purity figure alone does not distinguish a diastereomer from the target peptide. Independent testing of research-grade material frequently shows measured content below the stated label, so a certificate of analysis is best read together with the method that produced it.
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.
Two structural changes distinguish the synthetic peptide from the natural hormone. A norleucine residue replaces methionine at one position, and a D-configured phenylalanine replaces the natural L-form at another. Both substitutions slow enzymatic breakdown, which extends the molecule's persistence relative to the parent hormone. The lactam bridge further constrains the backbone into a stable conformation. These features are standard design strategies in peptide chemistry and are not unique to this compound; they appear across many research peptides built for improved stability.
The compound was developed in the late 1980s and early 1990s by academic researchers investigating melanocortin signaling and pigmentation. Early work explored whether synthetic analogs could reproduce effects of the natural hormone under controlled conditions. The molecule never advanced through the full regulatory pathway required for approval as a medicine. From the mid-2000s onward it appeared in unregulated consumer markets, often distributed through informal channels. That gap between research origins and commercial availability shapes how the compound is discussed today.
Melanotan-2 is a synthetic peptide designed as an analog of alpha-melanocyte-stimulating hormone, a signaling molecule produced in the pituitary and skin. Its structure is a linear chain of seven amino acids that folds into a ring through an internal lactam bridge joining two side chains. The compound is sometimes written as MT-II or MEL-2 in informal and commercial contexts. It belongs to the melanocortin peptide family, a group of short signaling molecules that share a conserved core sequence recognized by melanocortin receptors.
| 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 |
Identity testing for a cyclic peptide of this size usually relies on reversed-phase high-performance liquid chromatography coupled to mass spectrometry. The mass spectrum confirms molecular weight, while the chromatographic trace indicates the proportion of related impurities. Tandem mass spectrometry can provide sequence-level information when fragmentation data are compared against a reference standard. Nuclear magnetic resonance is sometimes used to confirm the lactam bridge, although it requires more material and greater operator expertise than routine chromatographic methods.
Lyophilised peptide powder is comparatively stable when kept dry, cold and protected from light. Once dissolved, the molecule is exposed to hydrolysis, oxidation and microbial growth, and degradation accelerates at higher temperatures and in alkaline solution. Repeated freeze-thaw cycles concentrate solutes and promote aggregation. Handling guidance for research peptides commonly clusters around freezer temperatures for powder and short refrigerated use for reconstituted solutions, with pH control and sterile technique applied throughout.
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.
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.
On August 29, 1949, the Soviet Union tested its first nuclear weapon at Semipalatinsk in Kazakhstan (see also Soviet atomic bomb project). Scientists in the United States from the Manhattan Project had warned that, in time, the Soviet Union would certainly develop nuclear capabilities of its own. Nevertheless, the effect upon military thinking and planning in the United States was dramatic, primarily because American military strategists had not anticipated the Soviets would "catch up" so soon. However, at this time, they had not discovered that the Soviets had conducted significant nuclear espionage of the project from spies at Los Alamos National Laboratory, the most significant of which was done by the theoretical physicist Klaus Fuchs. The first Soviet bomb was more or less a deliberate copy of the Fat Man plutonium device. In the same year the first US-Soviet nuclear war plan was penned in the US with Operation Dropshot. With the monopoly over nuclear technology broken, worldwide nuclear proliferation accelerated. The United Kingdom tested its first independent atomic bomb in 1952, followed by France developing its first atomic bomb in 1960 and then China developing its first atomic bomb in 1964. While much smaller than the arsenals of the United States and the Soviet Union, Western Europe's nuclear reserves were nevertheless a significant factor in strategic planning during the Cold War.
The siege of Coimbra in 1064 or the definitive conquest of Coimbra by Christian forces took place in 1064, from January to July; it ended on 9 July 1064, a Friday, when the king, Ferdinand I of Leon, captured the city from the Muslims. The city of Coimbra had previously been taken from the Christians by Almanzor (or al-Manṣūr) in 987. When the Fitna of al-Andalus broke out and the Umayyad Caliphate of Cordova fragmented into numerous taifa states, Dom Sesnando Davides, lord of Tentúgal proposed the conquest of the city to Ferdinand of Leon. Ferdinand thus began preparations for the campaign in December 1063, after receiving the remains of Saint Isidore of Seville in León. Before he moved against Coimbra however, he made a pilgrimage to Santiago de Compostela. Having prayed there before the tomb of the apostle, St. James of Compostela, for three days and made several donations to the church there, he departed accompanied by his wife Dona Sancha, his sons, the Bishop Crescónio of Santiago, Bishop Vistruário of Lugo, Bishop Suário of Mondonhedo, Bishop Sesnando of Portugal, the abbot Ariano of Cela Nova, abbot Pedro of Guimarães, and a large number of nobles. They advanced through a coastal road that linked Santiago de Compostela to Iria Flavia to Braga, Porto and Coimbra. They arrived before the walls of the city on 20 January 1064. The Muslim garrison fiercely resisted the Christian attacks. The supply situation of the Christians was not favourable and Ferdinand even pondered lifting the siege.
The 4n chain of thorium-232 is commonly called the "thorium series" or "thorium cascade". The series terminates with lead-208, 6 alpha decays and 4 beta decays from thorium. Plutonium-244 (which appears several steps above thorium-232) was present in the early Solar System, and is just long-lived enough (half-life 81.1 Myr) that it should still survive in trace quantities today, though it probably has not been detected. The total energy released from thorium-232 to lead-208, including the energy lost to neutrinos, is 42.65 MeV; from californium-252, 71.11 MeV. The last is the largest of the four chains.
== Structure == The human CRHR1 gene contains 14 exons over 20 kb of DNA, and its full gene product is a peptide composed of 444 amino acids. Excision of exon 6 yields in the mRNA for the primary functional CRF1, which is a peptide composed of 415 amino acids, arranged in seven hydrophobic alpha-helices. The CRHR1 gene is alternatively spliced into a series of variants. These variants are generated through deletion of one of the 14 exons, which in some cases causes a frame-shift in the open reading frame, and encode corresponding isoforms of CRF1. Though these isoforms have not been identified in native tissues, the mutations of the splice variants of mRNA suggest the existence of alternate CRF receptors, with differences in intracellular loops or deletions in N-terminus or transmembrane domains. Such structural changes suggest that the alternate CRF1 receptors have different degrees of capacity and efficiency in binding CRF and its agonists. Though the functions of these CRF1 receptors is yet unknown, they are suspected to be biologically significant. CRF1 is 70% homologous with the second human CRF receptor family, CRF2; the greatest divergence between the two lies at the N-terminus of the protein.
Sources: en.wikipedia.org
== Diagnosis == Echocardiography is the preferred screening test in the diagnosis of PAH as it accurately estimates pulmonary pressures. Other causes of pulmonary hypertension, such as left heart disease (WHO group 2), pulmonary hypertension due to lung disease (such as COPD)(WHO group 3) and pulmonary hypertension due to chronic blood clots in the pulmonary arteries (WHO group 4) need to be ruled out. Some tests which are commonly used include a CT scan of the chest, ventilation perfusion scan or a CT angiography (to rule out pulmonary hypertension due to chronic blood clots), pulmonary function test, and a cardiac MRI. Cardiac MRI is the preferred test to evaluate right ventricular structure and function in PAH. Pulmonary function testing in PAH may show an obstructive or restrictive defect, and the diffusion capacity of carbon monoxide (used as a surrogate for gas exchange in the alveoli) is reduced. A sleep study helps to rule out sleep disordered breathing, such as sleep apnea, which may contribute to PAH. The N-terminal prohormone of brain natriuretic peptide (NT pro-BNP) may be monitored in those with PAH and is prognostic. A right heart catheterization to measure right heart pressure is required for the diagnosis of PAH.
== Signs and symptoms == Symptoms of beriberi include weight loss, emotional disturbances, impaired sensory perception, weakness and pain in the limbs, and periods of irregular heart rate. Edema (swelling of bodily tissues) is common. It may increase the amount of lactic acid and pyruvic acid within the blood. In advanced cases, the disease may cause high-output cardiac failure and death. Symptoms may occur concurrently with those of Wernicke's encephalopathy, a primarily neurological thiamine deficiency-related condition. Beriberi is divided into four categories. The first three are historical and the fourth, gastrointestinal beriberi, was recognized in 2004:
=== Arts critics === Gustav Kobbé (1877), opera scholar and music critic of the New York Herald Clifton Fadiman (1925), book critic for The New Yorker and judge for the Book of the Month Club Edward Downes (1933), music critic, former host on the Metropolitan Opera radio broadcasts, son of music critic Olin Downes Ralph J.
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 seven-amino-acid peptide modeled on alpha-melanocyte-stimulating hormone. It carries two non-natural substitutions and a cyclic bridge that increase its stability relative to the natural hormone. It circulates as a research chemical and is not an approved medicine.