A practical reference on cyclic heptapeptide: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2026-03-15. Anything still debated is marked as such rather than presented as settled.
Melanotan-2, also written Melanotan II, is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone. Its sequence is Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, and the lactam bridge between the aspartate and lysine side chains constrains the peptide into a ring. This structural change increases receptor affinity and metabolic stability relative to the native hormone. The compound was created in the 1980s as a research tool for studying pigmentation biology.
Melanocytes are the pigment-producing cells of the skin, and they carry melanocortin-1 receptors on their surface. When the receptor is activated, cyclic adenosine monophosphate rises inside the cell and raises the activity of enzymes such as tyrosinase, which increases melanin output. Melanotan-2 binds melanocortin-1 receptors in vitro and in animal models, and this binding is generally described as the basis for the tanning effect. Other receptors account for different effects: melanocortin-4 receptors contribute to appetite and erectile signalling, while melanocortin-3 and melanocortin-5 receptors contribute to energy balance and exocrine function.
Early published reports described melanotan-2 as a tanning agent without sun protection, which means darkening is not the same as protection against ultraviolet radiation. Later studies explored the peptide in erectile dysfunction, hemorrhagic shock, and some skin conditions. No regulator in the United States or Europe has approved it for clinical use. Many products labelled melanotan-2 are sold without approval and their identity and purity are unverified. Its long-term safety in humans remains an open question.
The compound was developed in the late 1980s and 1990s by academic researchers investigating photoprotection. The rationale held that stimulating melanin production might reduce ultraviolet damage to skin and lower skin cancer risk. Early work examined receptor binding, pigment response, and short-term tolerability in small studies. That program did not produce an approved drug, and formal development stalled after early-phase trials. Whether induced pigmentation confers meaningful photoprotection remains an open question.
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.
| Property | Value | Notes |
|---|---|---|
| Compound class | Synthetic cyclic heptapeptide | Alpha-MSH analogue containing a D-phenylalanine residue |
| Molecular formula | C50H69N15O9 | Average molecular mass approximately 1024.2 g/mol |
| Appearance | White to off-white lyophilised powder | Normally supplied as a freeze-dried solid in a sealed vial |
| Solubility | Freely soluble in water and polar solvents | Dissolves readily in aqueous buffers and in alcohol-water mixtures |
| Receptor targets | MC1R, MC3R, MC4R, MC5R | Acts as a non-selective melanocortin receptor agonist |
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.
David Neal, the former Independent Chief Inspector of Borders and Immigration, has described the Home Office is dysfunctional and in urgent need of reform, citing problems with immigration as an example. 12 March – A spokesman for the prime minister describes the remarks allegedly made by Frank Hester about Diane Abbott as "racist and wrong". A recall petition opens in the Blackpool South constituency following Scott Benton's 35 day suspension from Parliament. 13 March – Sunak tells Prime Minister's Questions he will not return £10m donated to the Conservative Party by Frank Hester, because he has apologised and "his remorse should be accepted". The UK government announces a scheme to offer failed asylum seekers £3,000 if they agree to move to Rwanda voluntarily. The UK government announces a ban on foreign state ownership of British newspapers and news magazines following controversy over a potential purchase of The Telegraph by a consortium backed by the United Arab Emirates. Middlesbrough MP Andy McDonald regains the Labour whip. 14 March – Russia is reported to have jammed the GPS signal of an RAF plane carrying Defence Secretary Grant Shapps back to the UK from Poland the previous day for around 30 minutes as the plane flew near the border of the Russian territory of Kaliningrad. Speaking in the House of Commons, Secretary of State for Levelling Up, Housing and Communities Michael Gove outlines the UK government's new definition of extremism, and names five groups that would be assessed against the new criteria.
Rönnberg also filmed himself firing various guns at a shooting range to make the gun animations more authentic. Throughout the mod's development, Team Psykskallar released "videocasts" on the Mod DB page for Cry of Fear, which were medium-length videos that documented the team's development on the mod, as well as showcased new and improved features. The videos consisted of various team members, but most notably Rönnberg, Marchant, and Sydtangen.
== Localisation and precursors == Systemin and AtPEP1 are found in the cell cytosol. The precursor to tomato systemin is transcribed as a 200 amino acid polypeptide. It does not contain a putative signal sequence suggesting that it is synthesised on free ribosomes in the cytosol. The precursor to AtPEP1 is a 92 amino acid polypeptide and also lacks a signal sequence. In tomato, mRNA encoding the precursor for systemin is present at very low levels in unwounded leaves but accumulates upon wounding, particularly in the cells surrounding the sieve elements of the phloem in vascular bundles of mid veins. The precursor accumulates exclusively in the phloem parenchyma cells of leaves in tomato after wounding. The precursor to potato systemin is also localised in a similar manner suggesting it is under the same cell-type-specific regulation in both species. HypSys are localised in the cell wall. The precursor for tobacco HypSys is transcribed as a 165 amino acid polypeptide which has no structural homology to the precursor for systemin in tomato. The structural properties of HypSys, containing hydroxyproline and being glycosylated, indicate that they are synthesised through the secretory system. The precursor to HypSys in tomato is a 146 amino acid polypeptide, exclusively synthesised within the vascular bundles of leaves and petioles associated with parenchyma cells of phloem bundles. Unlike systemin, it is primarily associated with the cell wall. The precursors to HypSys appear to represent a distinct subfamily of hydroxyproline-rich proteins found in cell walls.
Including the continued aerial slaughter over Orote Field, Japanese losses exceeded 350 planes on the first day of battle. About 30 American planes were lost, and there was little damage to American ships; even the damaged South Dakota was able to remain in formation to continue her anti-aircraft duties.
Sources: en.wikipedia.org
In MHC class II, phagocytes such as macrophages and immature dendritic cells take up entities by phagocytosis into phagosomes—though B cells exhibit the more general endocytosis into endosomes—which fuse with lysosomes whose acidic enzymes cleave the uptaken protein into many different peptides. Via physicochemical dynamics in molecular interaction with the particular MHC class II variants borne by the host, encoded in the host's genome, a particular peptide exhibits immunodominance and loads onto MHC class II molecules. These are trafficked to and externalized on the cell surface. In MHC class I, any nucleated cell normally presents cytosolic peptides, mostly self peptides derived from protein turnover and defective ribosomal products. During viral infection, intracellular microorganism infection, or cancerous transformation, such proteins degraded in the proteosome are as well loaded onto MHC class I molecules and displayed on the cell surface. T lymphocytes can detect a peptide displayed at 0.1–1% of the MHC molecules.
== Rise to prominence (1970–1976) == In 1971, Mahathir announced his plan to rejoin UMNO, stating he would make a formal statement at an appropriate time; that same year, he also met Prime Minister Abdul Razak Hussein during a visit to Morib. Mahathir rejoined UMNO on 7 March 1972. Recognizing his potential and sharp political acumen, Razak appointed Mahathir as a Senator for Kedah in 1973. Around the same time, Mahathir also became the chairman of Food Industries of Malaysia (FIMA) Sdn. Bhd. In January 1973, as chairman of the FIMA, Mahathir visited a government factory in Pekan Nanas. He faced peaceful protests from over 200 workers demanding better working conditions and wage improvements. After Mahathir spoke to the workers and promised to review their grievances, they dispersed peacefully. He remained chairman of FIMA until 1981, when he became prime minister and was succeeded by Basir Ismail. Mahathir rose quickly in the Abdul Razak government, returning to UMNO's Supreme Council in 1973. He returned to the House of Representatives in the 1974 election, winning the Kedah-based seat of Kubang Pasu unopposed. He was appointed to Cabinet in September 1974 as the Minister for Education. During his tenure, Mahathir rolled out a new school curriculum for both primary and secondary schools, designed to provide holistic education and cultivate well-rounded individuals. Around this time, he also ceased his private medical practice. In 1975, Mahathir ran for one of the three vice-presidencies of UMNO.
The stylised lily, or fleur-de-lis (lily flower) has long been associated with royalty, although it may originally have been derived from the form of an iris. It has also been associated with the head of a spear. Its three parts have been associated with the three classes of mediaeval society, or alternatively faith, wisdom and chivalry. Whatever its exact derivation, it has come to be associated with France and the French monarchy since the earliest Frankish kings. Consequently, it became incorporated into not only French heraldry but also into many heraldic devices in jurisdictions where there had been historic French influence, such as Quebec and New Orleans. In modern times it appears in many forms, symbolic and decorative, and can be used on compasses to indicate the direction north, as well as the Scouting movement.
PSSM is most prevalent in American Quarter Horses and their related breeds (Paint horse, Appaloosa, Appendix Quarter Horse), Draft horse breeds (especially Belgian Draft and Percherons), and Warmblood breeds. The Belgian Draft been shown to have a 36% prevalence of PSSM. Other breeds that have been diagnosed with PSSM include the Arabian, Lipizzaner, Morgan, Mustang, Peruvian Paso, Rocky Mountain Horse, Standardbred, Tennessee Walking Horse, Thoroughbred, and National Show Horse. It has been suggested that the GSY1 mutation provided some benefit to hard working animals with poor-quality diets, and is now damaging members of those "thrifty" breeds that are managed with moderate to low levels of work and diets high in non-structural carbohydrates. PSSM Type 1 (homozygous or heterozygous for the GSY1 mutation) is more common in Quarter Horses and their related breeds, and draft breeds, while PSSM Type 2 (negative for the GSY1 mutation) is more commonly seen in other breeds, including warmbloods. There is no sex predilection to the disease.
1993/1947) Learning for Work (Miscellaneous Provisions) Order 1993 (S.I. 1993/1949) Act of Adjournal (Consolidation Amendment) (Courses for Drink-drive Offenders) 1993 (S.I. 1993/1955) Act of Sederunt (Sheriff Court Ordinary Cause Rules) 1993 (S.I. 1993/1956) Double Taxation Relief (Taxes on Income) (General) (Manufactured Overseas Dividends) Regulations 1993 (S.I. 1993/1957) Dartford–Thurrock Crossing (Amendment) Regulations 1993 (S.I. 1993/1961) Harwich Haven Harbour Revision Order 1993 (S.I. 1993/1962) A4 Trunk Road (Great West Road, Hounslow) (Prescribed Routes) Order 1993 (S.I. 1993/1963) London South Circular Trunk Road (A205) (Westhorne Avenue, Lewisham) (Prohibition of Use of Gaps in Central Reserve) Order 1993 (S.I. 1993/1964) Civil Aviation (Route Charges for Navigation Services) Regulations 1993 (S.I. 1993/1965) Importation of Bovine Semen (Amendment) Regulations 1993 (S.I. 1993/1966) Animals and Animal Products (Import and Export) (Amendment) Regulations 1993 (S.I. 1993/1967) Criminal Justice Act 1993 (Commencement No. 1) Order 1993 (S.I. 1993/1968) Education (Teachers) (Amendment) Regulations 1993 (S.I. 1993/1969) Clyde Port Authority (Dissolution) Order 1993 (S.I. 1993/1970) Education Act 1993 (Commencement No. 1 and Transitional Provisions) Order 1993 (S.I. 1993/1975) Education (London Oratory School) (Exemption from Pay and Conditions Orders) Order 1993 (S.I. 1993/1976) Further Education (Attribution of Surpluses and Deficits) (The Ridge College) Regulations 1993 (S.I.
Sources: en.wikipedia.org
=== Available forms === Two arsenic-containing stereoisomers exist in a 3:1 molar ratio. Since melarsoprol is insoluble in water, dosage occurs via a 3.6% propylene glycol intravenous injection. To avoid the risk of injection site reactions, melarsoprol must be given slowly. Melarsoprol used for the treatment of African trypanosomiasis with CNS involvement is given under a complicated dosing schedule. The dosing schedule for children and adults is 2–3.6 mg/kg/day intravenously for three days, then repeated every seven days for a total of three series. To monitor for relapse, follow-up is recommended every six months for at least two years.
Mescaline has a wide array of suggested medical usage, including treatment of depression, anxiety, PTSD, nicotine dependence, and alcoholism. However, its status as a Schedule I controlled substance in the Convention on Psychotropic Substances limits availability of the drug to researchers. Because of this, very few studies concerning mescaline's activity and potential therapeutic effects in people have been conducted since the early 1970s. However, the drug is under development by Journey Colab under the code name JOUR-5700 and by Biomind Labs under the code names BMND04, BMND06, and BMND09 for various medical applications, such as treatment of alcoholism.
The potato tuber moth (Phthorimaea operculella) is an oligophagous insect that prefers to feed on plants of the family Solanaceae such as tobacco plants. Female P. operculella use the leaves to lay their eggs and the hatched larvae will eat away at the mesophyll of the leaf.
His distribution policy lasted for at least a few centuries, but scholars are unsure if the policy continued thereafter. Wine was not as freely distributed as olive oil, but was sold for a very low price starting around 300 CE.
Sources: en.wikipedia.org
No. It is a laboratory-made peptide, while the natural hormone is alpha-melanocyte-stimulating hormone, a longer peptide produced by the pituitary gland and by skin cells. Melanotan-2 mimics only a short active region of that hormone and contains non-natural residues such as D-phenylalanine.
No approved regulatory indication exists in major markets. An approval exists for a different peptide, afamelanotide, which is used for a rare photosensitivity disorder called erythropoietic protoporphyria. Melanotan-2 itself remains a research compound with no cleared clinical role.
Melanocortin-1 receptors on melanocytes are the receptor most closely linked to pigment production. The peptide is not selective, however, and also activates melanocortin-3, melanocortin-4, and melanocortin-5 receptors. That lack of selectivity is the usual explanation offered for both its range of observed effects and its off-target effects.
It is a synthetic cyclic peptide designed as an analog of alpha-melanocyte-stimulating hormone. It acts on melanocortin receptors and is best known from research into pigmentation. It is not an approved pharmaceutical product.