Everything below concerns cyclic heptapeptide. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2026-01-06. 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.
Regulatory treatment varies between countries. Several national medicines agencies have classified the peptide as unapproved, and customs authorities in some jurisdictions seize shipments on that basis. A few jurisdictions channel supply through prescription-only frameworks that do not list the substance by name. Because the material circulates mainly through online vendors, composition and purity are rarely verified before sale. Surveys of unapproved peptide products have reported labels that did not match measured content in a substantial fraction of samples.
Melanotan II is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone, a naturally occurring peptide involved in pigmentation signalling. Its structure substitutes a lactam bridge between side chains to increase stability relative to the native hormone. The compound is also known by the shorthand MT-II and by several non-proprietary synonyms used in research catalogues. It is not an approved therapeutic product in any major jurisdiction; material sold under this name is typically offered as a laboratory reagent rather than as a medicine.
Activity is attributed to agonism at melanocortin receptors, particularly MC1R and MC4R. Activation of MC1R on melanocytes increases melanin synthesis, which underlies the reported tanning effect. MC4R engagement in the central nervous system is linked to appetite suppression and to effects on sexual arousal reported in early clinical studies. Those studies were small and were not designed to establish efficacy or long-term safety. Receptor selectivity among the melanocortin subtypes is not absolute, which complicates attribution of any effect to a single pathway.
| 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 |
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.
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.
Structurally, Melanotan-2 retains the core recognition motif of alpha-melanocyte-stimulating hormone while adding a lactam bridge that links two side chains and constrains the molecule into a ring. This modification lowers susceptibility to enzymatic degradation. The compound acts as an agonist at melanocortin receptors, particularly subtypes associated with melanin production. Because the same receptor family influences several physiological processes, researchers note that its activity is not confined to pigmentation alone. Receptor selectivity continues to be examined in published studies.
Melanotan-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone, a naturally occurring peptide involved in pigmentation signalling. Its sequence incorporates modified residues that increase potency and extend biological activity relative to the native hormone. The compound binds receptors of the melanocortin family and is examined mainly in laboratory research. It does not occur naturally and exists only as a manufactured chemical entity produced by solid-phase synthesis.
Outside regulated medicine, melanotan II circulates through online vendors as a research chemical, often marketed for tanning. Products sold this way vary widely in purity, concentration, and labeling accuracy, and independent testing has documented discrepancies. Published reports describe both pigment effects and adverse reactions, including nausea, flushing, and darkening of existing moles. Long-term safety data are sparse, and no large controlled trial has established a risk profile. Questions about cumulative effects on melanocytes remain unresolved in the literature.
Melanotan II is a synthetic peptide analog modeled on alpha-melanocyte-stimulating hormone, a naturally occurring signaling peptide involved in pigmentation. Its structure is a cyclic heptapeptide containing two non-natural substitutions, norleucine at position four and D-phenylalanine at position seven. These modifications resist enzymatic breakdown and extend the molecule's activity relative to the native hormone. The compound binds melanocortin receptors and is studied mainly as a pharmacological tool rather than a therapeutic product. It has never received approval as a medicine in any major jurisdiction.
Melanotan-2 is frequently confused with afamelanotide, a linear analogue authorised in the European Union for erythropoietic protoporphyria. The two compounds differ in chain length, ring structure and receptor selectivity, so findings for one cannot be transferred directly to the other. Published controlled human data on melanotan-2 remain sparse, and much of what circulates online derives from small studies or unpublished reports. Questions about effect size, dose-response behaviour and long-term safety therefore remain unresolved.
Melanotan-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone. Its sequence incorporates a lactam bridge that constrains the peptide into a ring, which increases resistance to enzymatic breakdown relative to the natural hormone. Researchers at the University of Arizona synthesised the compound in the late 1980s and early 1990s while studying pigmentation pathways. It has never received marketing approval from any national medicines regulator. In the scientific literature it is usually described as a laboratory research reagent rather than a therapeutic product.
The peptide acts as a non-selective agonist at melanocortin receptors, showing affinity for MC1R, MC3R, MC4R and MC5R. Activation of MC1R on melanocytes drives the conversion of tyrosine into melanin and shifts production toward the darker eumelanin form. MC4R signalling in the central nervous system is linked to appetite and energy balance, which helps explain why reduced food intake appeared in early human studies. Effects on MC4R and on vascular tone also account for the erectile responses recorded as unexpected findings in those same trials.
. In normal liquids, most of this crossover takes place at frequencies between GHz and THz, sometimes called hypersound. At sub-GHz frequencies, a normal liquid cannot sustain shear waves: the zero-frequency limit of the shear modulus is 0. This is sometimes seen as the defining property of a liquid. However, like the bulk modulus K, the shear modulus G is also frequency-dependent and exhibits a similar crossover at hypersound frequencies. According to linear response theory, the Fourier transform of K or G describes how the system returns to equilibrium after an external perturbation; for this reason, the dispersion step in the GHz to THz region is also called relaxation. As a liquid is supercooled toward the glass transition, the structural relaxation time exponentially increases, which explains the viscoelastic behavior of glass-forming liquids.
Nicolás Maduro has been criticized for authoritarian rule since Hugo Chávez hand-picked him as the next president of Venezuela in 2013. According to Reuters, "Maduro ruled Venezuela with a heavy hand ... presiding over deep economic and social crises and resisting pressure from domestic opponents and foreign governments for political change", and was "long accused by critics both at home and abroad of being a dictator who jailed or persecuted political opponents and repeatedly staged sham elections". Mark Weisbrot states that Venezuela has faced an economic crisis since the oil glut of the 2010s, due to its export-dependent economy. For years, the US government pressured Maduro, considering him an "illegitimate leader". Unilateral US sanctions on Venezuela began in the 2010s, and escalated through 2025. According to a 2019 report by Mark Weisbrot and Jeffrey Sachs, sanctions caused Venezuela a loss of $38 billion between 2016 and 2019, prevented the government from resolving the crisis using fiscal and monetary policy changes, and in combination with preexisting negative trends resulted in an estimated 40,000 excess deaths between 2017 and 2018. The report's methodology and conclusions were criticized by other economists. Maduro's victory in the 2018 Venezuelan presidential election was disputed and 45 countries did not accept the results, causing a presidential crisis that divided the international community from 2019 to 2023. In May 2020, Venezuelan dissidents backed by Silvercorp USA attempted to infiltrate Venezuela by sea and overthrow Maduro in Operation Gideon.
=== Magnetotaxis === The movement and orientation of "Ca. M. multicellularis" appears to be altered by many external stimuli as it undergoes magnetotaxis, photokinesis, negative phototaxis and potentially helical klinotaxis. The organism contains multiple internal magnetosomes, membrane-bound structures containing magnetic nanocrystals. In "Ca. M. multicellularis" these crystals are greigite (Fe3S4) but in most other species of multicellular magnetotactic bacteria (MMB) the crystals are magnetite (Fe3O4). These magnetosomes are organised in linear chains that allow the consortium to orient itself along the Earth's geomagnetic field. In samples from the Southern Hemisphere, "Ca. M. multicellularis" exhibits a preference for south-facing orientation while swimming. In weak magnetic fields, under 80 μT, "Ca. M. multicellularis" behaves differently to other magnetotactic bacteria. Under fields close to or weaker than Earth's geomagnetic field, its trajectories appear significantly scattered away from the exact magnetic field line. In these situations, movement relies mostly on a combination of other environmental factors and the direction of the magnetic field line does not fully control the final swimming direction.
=== Pregnancy and breastfeeding === The safety of using omeprazole has not been established in pregnant or breastfeeding women. Epidemiological data do not show an increased risk of major birth defects after maternal use of omeprazole during pregnancy.
== Properties == Native silk fibre is both strong and tough, and silkworm silk spun under controlled conditions approaches spider dragline silk in strength. Regenerated silk rarely matches it, because reprocessing disrupts the ordered molecular alignment produced during natural spinning, and the reconstituted material is correspondingly weaker. The extent of this loss depends on the format and the beta-sheet content, and matching the properties of native silk in regenerated form has not yet been fully resolved. Purified fibroin is well tolerated by living tissue and supports the attachment and growth of many cell types. The mild reaction associated with modern silk biomaterials results largely from purification: when sericin and other residues are removed the response is slight, whereas their presence provokes a stronger reaction. This is a large part of why degumming is emphasised in device manufacture. Many synthetic implants remain essentially inert in the body; silk does not. Protease enzymes such as chymotrypsin cleave it into peptides and amino acids that the body can absorb. The rate of degradation is not fixed; it can be set from a few weeks to more than a year by adjusting the beta-sheet content, the format and the porosity. This allows a scaffold to be designed so that it degrades at approximately the rate at which new tissue forms. Surgical silk is sometimes described as non-degradable, a term that reflects the slow loss of strength of a thick braided suture rather than any permanence of the protein itself.
Sources: en.wikipedia.org
== Research misconduct == In September 2024, Masliah's work came under intense scrutiny when an investigation led by the journal Science exposed extensive image manipulation across 132 of his published research papers. A 286-page dossier compiled by forensic analysts and neuroscientists pointed to repeated instances of Western blot manipulation, image reuse, and other forms of digital editing across decades of his research. These allegations involved crucial studies related to Alzheimer's and Parkinson's disease, particularly surrounding the alpha-synuclein protein. The dossier was sent to the HHS Office of Research Integrity, which requested that the National Institute on Aging (NIA) start a research misconduct investigation in May 2023. The NIA started their investigation in December 2023. In September 2024, the NIH confirmed that Masliah was no longer leading the Division of Neuroscience at the NIA, following the conclusion of their investigation. The controversy includes papers that have influenced clinical trials and investment decisions in the pharmaceutical industry. 238 active patents cite papers by Masliah that contain anomalous images and data. A notable impact on the pharmaceutical industry concerns the experimental Parkinson's drug prasinezumab, developed by Prothena Biosciences in collaboration with Roche. A Phase II study reported in August 2022 found no statistically significant effect from the drug vs placebo on measures of Parkinson's disease progression. Several papers foundational to the development of prasinezumab were flagged for image manipulation.
=== Transportation companies === Canadian Airlines (1987–2001) (IATA airline code CP) Canadian Pacific Railway, reporting mark CP Central Pacific Railroad, a network of lines between California and Utah, US Chemins de Fer de Provence, a French public railway company Comboios de Portugal, a Portuguese state-owned train company CP Air or Canadian Pacific Air Lines (1942–1987), a Canadian airline CP Ships, a Canadian shipping company, part of TUI Group Cathay Pacific, a Hong Kong–based major airline
Whereas in the course of human affairs history has shown that it may become necessary for a people to resolve the political affiliations which have connected them with another people and to assume amongst other nations the separate and equal status to which they are entitled: And Whereas in such event a respect for the opinions of mankind requires them to declare to other nations the causes which impel them to assume full responsibility for their own affairs: Now Therefore, We, The Government of Rhodesia, Do Hereby Declare: That it is an indisputable and accepted historic fact that since 1923 the Government of Rhodesia have exercised the powers of self-government and have been responsible for the progress, development and welfare of their people; That the people of Rhodesia having demonstrated their loyalty to the Crown and to their kith and kin in the United Kingdom and elsewhere through two world wars, and having been prepared to shed their blood and give of their substance in what they believed to be the mutual interests of freedom-loving people, now see all that they have cherished about to be shattered on the rocks of expediency; That the people of Rhodesia have witnessed a process which is destructive of those very precepts upon which civilization in a primitive country has been built, they have seen the principles of Western democracy, responsible government and moral standards crumble elsewhere, nevertheless they have remained steadfast; That the people of Rhodesia fully support the requests of their government for sovereign independence but have witnessed the consistent refusal of the Government of the United Kingdom to accede to their entreaties; That the Government of the United Kingdom have thus demonstrated that they are not prepared to grant sovereign independence to Rhodesia on terms acceptable to the people of Rhodesia, thereby persisting in maintaining an unwarrantable jurisdiction over Rhodesia, obstructing laws and treaties with other states and the conduct of affairs with other nations and refusing assent to laws necessary for the public good, all this to the detriment of the future peace, prosperity and good government of Rhodesia; That the Government of Rhodesia have for a long period patiently and in good faith negotiated with the Government of the United Kingdom for the removal of the remaining limitations placed upon them and for the grant of sovereign independence; That in the belief that procrastination and delay strike at and injure the very life of the nation, the Government of Rhodesia consider it essential that Rhodesia should attain, without delay, sovereign independence, the justice of which is beyond question; Now Therefore, We The Government of Rhodesia, in humble submission to Almighty God who controls the destinies of nations, conscious that the people of Rhodesia have always shown unswerving loyalty and devotion to Her Majesty the Queen and earnestly praying that we and the people of Rhodesia will not be hindered in our determination to continue exercising our undoubted right to demonstrate the same loyalty and devotion, and seeking to promote the common good so that the dignity and freedom of all men may be assured, Do, By This Proclamation, adopt, enact and give to the people of Rhodesia the Constitution annexed hereto;
Coagulative necrosis is characterized by the formation of a gelatinous (gel-like) substance in dead tissues in which the architecture of the tissue is maintained, and can be observed by light microscopy. Coagulation occurs as a result of protein denaturation, causing albumin to transform into a firm and opaque state. This pattern of necrosis is typically seen in hypoxic (low-oxygen) environments, such as infarction. Coagulative necrosis occurs primarily in tissues such as the kidney, heart and adrenal glands. Severe ischemia most commonly causes necrosis of this form. Liquefactive necrosis (or colliquative necrosis), in contrast to coagulative necrosis, is characterized by the digestion of dead cells to form a viscous liquid mass. This is typical of bacterial, or sometimes fungal, infections because of their ability to stimulate an inflammatory response. The necrotic liquid mass is frequently creamy yellow due to the presence of dead leukocytes and is commonly known as pus. Hypoxic infarcts in the brain presents as this type of necrosis, because the brain contains little connective tissue but high amounts of digestive enzymes and lipids, and cells therefore can be readily digested by their own enzymes. Gangrenous necrosis can be considered a type of coagulative necrosis that resembles mummified tissue. It is characteristic of ischemia of lower limb and the gastrointestinal tracts. Both dry gangrene and gas gangrene can lead to this type of necrosis. If superimposed infection of dead tissues occurs, then liquefactive necrosis ensues (wet gangrene).
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.
No. No major regulatory agency has granted a marketing authorisation for melanotan II as a medicine. Products sold under this name are generally presented as laboratory reagents and are not subject to the batch-release testing applied to approved drugs.