Melanotan II comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Updated 2026-01-04. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
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.
| 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 |
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 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.
=== Amino acid biosynthesis === All amino acids are formed from intermediates in the catabolic processes of glycolysis, the citric acid cycle, or the pentose phosphate pathway. From glycolysis, glucose 6-phosphate is a precursor for histidine; 3-phosphoglycerate is a precursor for glycine and cysteine; phosphoenol pyruvate, combined with the 3-phosphoglycerate-derivative erythrose 4-phosphate, forms tryptophan, phenylalanine, and tyrosine; and pyruvate is a precursor for alanine, valine, leucine, and isoleucine. From the citric acid cycle, α-ketoglutarate is converted into glutamate and subsequently glutamine, proline, and arginine; and oxaloacetate is converted into aspartate and subsequently asparagine, methionine, threonine, and lysine.
Muammar Muhammad Abu Minyar al-Gaddafi (c. 1942 – 20 October 2011) was a Libyan military officer, revolutionary, politician, and political theorist who ruled Libya from 1969 until his overthrow by Libyan rebel forces in 2011 during the First Libyan Civil War. He came to power through a bloodless military coup, first becoming Revolutionary Chairman of the Libyan Arab Republic from 1969 to 1977, Secretary General of the General People's Congress from 1977 to 1979, and then the Brotherly Leader of the Great Socialist People's Libyan Arab Jamahiriya from 1979 to 2011. Initially ideologically committed to Arab nationalism and Arab socialism, Gaddafi later ruled according to his own Third International Theory. Gaddafi became an Arab nationalist while at school in Sabha, later enrolling in the Royal Military Academy, Benghazi. He founded a revolutionary group known as the Free Officers movement which deposed the Western-backed Senussi monarchy of Idris I in a 1969 coup. Gaddafi converted Libya into a republic governed by his Revolutionary Command Council. Ruling by decree, he deported Libya's Italian population and ejected its Western military bases. He strengthened ties to Arab nationalist governments and unsuccessfully advocated pan-Arab political union. An Islamic modernist, he introduced Sharia law and promoted Islamic socialism. He nationalized the oil industry and used the increasing state revenues to bolster the military, fund foreign revolutionaries, and implement social programs emphasizing housebuilding, healthcare and education projects.
=== Muscle and fat tissue === Microwave burns show some similarities with electrical burns, as the tissue damage is deep rather than superficial. Adipose tissue shows less degree of damage than muscles and other water-rich tissues. (In contrast, radiant heat, contact burns and chemical burns damage subcutaneous adipose tissue to higher extent than deeper muscle tissue.) Full-thickness biopsy of the area between burned and unburned skin shows layers of more and less damaged tissue (tissue sparing), layers of undamaged fat between damaged muscles; a pattern that is not present in conventional thermal or chemical burns. Cells subjected to electrical burns show microscopic nuclear streaming on histology examination; this feature is not present with microwave burns. Microwaves also deposit more energy to areas with low blood supply and to tissue interfaces. Hot spots may be formed in the tissue, with a consequent higher absorption of microwave energy and even higher temperature achieved, with localized necrosis of the affected tissue following. Sometimes, the affected tissue can even be charred. Muscle tissue destruction can lead to myoglobinuria, with renal failure following in severe cases; this is similar to burns from electric current. Urinalysis and serum CPK, BUN and creatine tests are used to check for this condition.
== NeuCode SILAC == Traditionally the level of multiplexing in SILAC was limited due to the number of SILAC isotopes available. Recently, a new technique called NeuCode (neutron encoding) SILAC, has augmented the level of multiplexing achievable with metabolic labeling (up to 4). The NeuCode amino acid method is similar to SILAC but differs in that the labeling only utilizes heavy amino acids. The use of only heavy amino acids eliminates the need for 100% incorporation of amino acids needed for SILAC. The increased multiplexing capability of NeuCode amino acids is from the use of mass defects from extra neutrons in the stable isotopes. These small mass differences however need to be resolved on high-resolution mass spectrometers.
In 1962, Meurgues' work came to the attention of the botanist Roger Heim. He tasked her with setting up a scientific laboratory in the Muséum national d'histoire naturelle, dedicated to new methods of conservation and presentation of natural history museum collections. This included conservation techniques such as freeze-drying, and resinous injections, the scientific preservation of colours and pigments, as well as improving the interpretation of exhibitions and displays. She organised and directed the laboratory whilst studying for a Diplôme d'études approfondies (Master's degree) in zoology on Calliphoridae, (types of flies) which she completed in 1973. She was promoted to become the museum's assistant professor, and went on collecting expeditions to Kurdistan, Afghanistan, Kashmir, China, Morocco amongst others. Meurgues organised a number temporary exhibitions including: Les pigments végétaux (Vegetable Pigments) in 1963, Orchidées et plantes épiphytes (Orchids and epiphytic plants) in 1966, Météorites, messagères du cosmos (Meteorites, messengers of the cosmos) in 1968, La Nature au microscope électronique (Nature under an electron microscope) in 1971, Le Sahara avant le désert (The Sahara before the desert) in 1974, Les plus beaux coquillages du monde (The most beautiful shells of the world) in 1975, Histoire naturelle de la sexualité (Natural history of sexuality) in 1977 with André Langaney, a leading French science communicator.
Sources: en.wikipedia.org
The gamma decay from a metastable state is referred to as isomeric transition (IT), or internal transition, though it resembles shorter-lived "prompt" gamma decays in all external aspects with the exception of the longer life. This is generally associated with a high nuclear spin change, or "forbiddenness", which would be required in gamma emission to reach the ground state; this is even more true of beta decays. A low transition energy both slows the transition rate and makes it more likely that only highly forbidden decays are available, so most long-lived isomers have a relatively low excitation energy above the ground state (in the extreme case of thorium-229m, low excitation alone causes the measurably long life). In 210m83Bi, the forbiddenness of available beta and gamma decays is so high that alpha decay is observed exclusively, though even that is slower than for the ground state. For most lighter isomers including 180m73Ta, alpha decay is not practically available, but others are not quite so forbidden as those two. The first nuclear isomer and decay-daughter system (uranium X2/uranium Z, now known as 234m91Pa/23491Pa) was discovered by Otto Hahn in 1921. Metastable isomers can be produced through any nuclear reaction, including radioactive decay, neutron capture, nuclear fission, and bombardment by accelerated charged particles. A nucleus produced this way generally starts its existence in an excited state that loses its excess energy through the emission of one or more gamma rays or conversion electrons.
== History == Two research teams independently identified mouse colony stimulating factors in the 1960s: Ray Bradley at University of Melbourne and Donald Metcalf at Walter and Eliza Hall Institute, from Australia, and Yasuo Ichikawa, Dov Pluznik and Leo Sachs at the Weizmann Institute of Science, Israel. In 1980 Antony Burgess and Donald Metcalf discovered that mouse lung conditioned medium contained at least two different CSFs - GM-CSF, which they had purified in 1977 and a G-CSF which stimulated the production of colonies of neutrophils. In 1983, Donald Metcalf's research team, led by Nicos Nicola, isolated the murine cytokine from medium conditioned with lung tissue obtained from endotoxin-treated mice. In 1985, Karl Welte, Erich Platzer, Janice Gabrilove, Roland Mertelsmann and Malcolm Moore at the Memorial Sloan Kettering Cancer Center (MSK) purified human G-CSF produced by bladder cancer cell line 5637 from conditioned medium. In 1986, Karl Welte's team at MSK patented the method of producing and using human G-CSF under the name "human hematopoietic pluripotent colony stimulating factor" or "human pluripotent colony stimulating factor" (P-CSF). Also in 1986, two independent research groups working with pharmaceutical companies cloned the G-CSF gene that made possible large-scale production and its clinical use: Shigekazu Nagata's team in collaboration with Chugai Pharmaceutical Co. from Japan, and Lawrence Souza's team at Amgen in collaboration with Karl Welte's research team members from Germany and the USA.
Focke-Wulf formally merged with Weserflug in 1964, becoming Vereinigte Flugtechnische Werke (VFW), which after several further mergers became the European Aeronautic Defence and Space Company N.V. (EADS). EADS was later renamed as Airbus. In early 2021 Focke Wulf Aircraft was re-registered as a trademark across the EU, the UK and Australia as a retailer of aviation watches and associated official Focke Wulf merchandise.
The laboratory analysis of homocysteine itself is complicated because most homocysteine (possibly above 85%) is bound to other thiol amino acids and proteins in the form of disulphides (e.g., cysteine in cystine-homocysteine, homocysteine in homocysteine-homocysteine) via disulfide bonds. Since as an equilibrium process the proportion of free homocysteine is variable a true value of total homocysteine (free + bound) is useful for confirming diagnosis and particularly for monitoring of treatment efficacy. To this end it is prudent to perform total homocyst(e)ine analysis in which all disulphide bonds are subject to reduction prior to analysis, traditionally by HPLC after derivatisation with a fluorescent agent, thus giving a true reflection of the quantity of homocysteine in a plasma sample.
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.
Solutions are best kept cold, protected from light, and buffered to a pH that limits hydrolysis. Dividing a stock into single-use aliquots avoids repeated freeze-thaw cycles, which measurably reduce the intact parent peak over time.