cyclic heptapeptide is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Last reviewed on 2026-08-01. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
| 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 |
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.
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.
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 a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone, the naturally occurring peptide involved in pigmentation signalling. Its sequence is conventionally written as Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, with a lactam bridge joining the aspartate side chain to the lysine side chain. The empirical formula is C50H69N15O9 and the monoisotopic mass lies near 1023.5 daltons. N-terminal acetylation and the D-configured phenylalanine both increase resistance to enzymatic breakdown compared with the parent hormone.
Pharmacologically, melanotan-2 behaves as a non-selective agonist across the melanocortin receptor family. Binding at MC1R on dermal melanocytes promotes eumelanin synthesis, which underlies the tanning response described in early human work. Activity at the centrally expressed MC4R receptor is associated with reported effects on appetite and erectile function. Because the peptide does not discriminate strongly among receptor subtypes, attributing any single observed effect to one receptor pathway is generally not possible without selective antagonists or receptor knockout models.
One specialized form of fresh-produce train that existed in the UK was the milk train, which, using specialized chilled, glass-lined wagons, remained in service until 1981. Like many railways around the world, modern UK railways do ship specialized refrigerated containers on intermodal trains, with such trains now taking over the role again from long-distance trucking on hub-to-hub routes to reduce carbon footprint. DB Cargo UK runs Europe's longest-distance single-operator handled train from Valencia, Spain to Barking in East London twice weekly, in partnership with Eddie Stobart Logistics and retailer Tesco's, shipping fresh fruit and produce 1,800 km (1,118 mi) in refrigerated ISO containers.
Further work was needed to develop a ration that did not require re-hydration (thus not requiring additional preparation time and water). Further effort, led by Dr. Rauno A. Lampi, Chief of Food Systems Equipment Division at the Natick Soldier Research, Development and Engineering Center, concentrated on the refinement of the retort pouch to contain a wet ration with a three-to-ten year shelf life that could be easily shipped, carried in the field, opened and consumed straight out of the package if necessary with no further heat or water. The resulting MRE went into special issue starting in 1981 and standard issue in 1986, using a limited menu of twelve entrées.
Since the insulin pump needs to be worn most of the time, pump users need strategies to participate in activities that may damage the pump, such as rough sports and activities in the water. Some users may find that wearing the pump all the time (together with the infusion set tubing) is uncomfortable or unwieldy. Possibility of insulin pump malfunctioning, and having to resort back to multiple daily injections until a replacement becomes available. However most pump manufacturers will have a program that will get a new pump to the user within 24 hours or allow the user to buy a second pump as a backup for a small fee. Users may experience scar tissue buildup around the inserted cannula, resulting in a hard bump under the skin after the cannula is removed. The scar tissue does not heal particularly fast, so years of wearing the pump and changing the infusion site will cause the user to start running out of viable "spots" to wear the pump. In addition, the areas with scar tissue buildup generally have lower insulin sensitivity and may affect basal rates and bolus amounts. In some extreme cases the insulin delivery will appear to have no/little effect on lowering blood glucose levels and the site must be changed. Users may experience allergic reactions and other skin irritation from the adhesive on the back of an infusion set. Experience may vary according to the individual, the pump manufacturer, and the type of infusion set used. A larger supply of insulin may be required in order to use the pump.
Much of the literature, however, suggests a curvilinear or even quadratic relationship between spatial performance and circulating testosterone, where both hypo- and hypersecretion (deficient- and excessive-secretion) of circulating androgens have negative effects on cognition.
Sources: en.wikipedia.org
Silicon single crystals may be produced today in commercial facilities with extremely high purity and with few lattice defects. This method defined the Avogadro constant as the ratio of the molar volume, Vm, to the atomic volume Vatom:
=== Analogues === Pyridopyrroloquinoxaline serotonin 5-HT2A receptor agonists such as the psychedelic IHCH-7113 and the non-hallucinogenic IHCH-7086, IHCH-7079, and ITI-1549 have been derived via structural modification of lumateperone.
In April 2023, British boxer Amir Khan was banned for two years after an anti-doping test revealed the presence of enobosarm following his fight against Kell Brook in February 2022. On May 1, 2024, American boxer Ryan Garcia tested positive for the performance-enhancing substance Ostarine the day before and the day of his upset win over Devin Haney last month, per a Voluntary Anti-Doping Association letter sent to all parties Wednesday and obtained by ESPN. The samples were taken prior to the fight, but the results weren't known until later. Garcia's A-sample also screened positive for 19-norandrosterone, but its presence is unconfirmed at this time. Garcia floored Haney three times during the majority decision victory, but that result could possibly be overturned because his B-sample tested positive on May 22, 2024. Garcia's fate now rests in the hands of the New York State Athletic Commission, which will adjudicate any suspensions and financial penalties. Sanctions also include the possibility of his win over Haney being overturned to a no-contest or having it changed to a disqualification. Despite his "B" samples returning positive results, Garcia has maintained his innocence and has cited substance contamination.
Somatostatin receptor antagonists (or somatostatin inhibitors) are a class of chemical compounds that work by imitating the structure of the neuropeptide somatostatin, which is an endogenous hormone found in the human body. The somatostatin receptors are G protein-coupled receptors. Somatostatin receptor subtypes in humans include sstr1, 2A, 2 B, 3, 4, and 5. While normally expressed in the gastrointestinal (GI) tract, pancreas, hypothalamus, and central nervous system (CNS), they are expressed in different types of tumours. The predominant subtype in cancer cells is the ssrt2 subtype, which is expressed in neuroblastomas, meningiomas, medulloblastomas, breast carcinomas, lymphomas, renal cell carcinomas, paragangliomas, small cell lung carcinomas, and hepatocellular carcinomas. As a radiopharmaceutical compound that is selective for somatostatin receptors, there is research being done for these radiolabeled compounds to act as diagnostic tests in PET scans for neuroendocrine tumors and other tumors not previously targeted with radiolabeled somatostatin receptor agonists, and to act as radiopharmaceutical therapeutic compound, more specifically to conduct peptide radionuclide receptor therapy. Some non-radiopharmaceutical compounds that are developed as competitive inhibitors of somatostatin, such as the hormone antagonist cyclosomatostatin.
The United States recovered from the Apollo 1 fire, fixing the fatal flaws in an improved version of the Block II command module. The US proceeded with unpiloted test launches of the Saturn V launch vehicle (Apollo 4 and Apollo 6) and the Lunar Module (Apollo 5) during the latter half of 1967 and early 1968. The first Saturn V flight was an unqualified success, and although the second suffered some non-catastrophic engine failures, it was considered a partial success and the launcher achieved human rating qualification. Apollo 1's mission to check out the Apollo Command and Service Module in Earth orbit was accomplished by Grissom's backup crew on Apollo 7, launched on October 11, 1968. The eleven-day mission was a total success, as the spacecraft performed a virtually flawless mission, paving the way for the United States to continue with its lunar mission schedule. The Soviet Union also fixed the parachute and control problems with Soyuz, and the next piloted mission Soyuz 3 was launched on October 26, 1968. The goal was to complete Komarov's rendezvous and docking mission with the un-piloted Soyuz 2. Ground controllers brought the two craft to within 200 meters (660 ft) of each other, then cosmonaut Georgy Beregovoy took control. He got within 40 meters (130 ft) of his target, but was unable to dock before expending 90 percent of his maneuvering fuel, due to a piloting error that put his spacecraft into the wrong orientation and forced Soyuz 2 to automatically turn away from his approaching craft.
Sources: en.wikipedia.org
Despite the UN arms embargo on Bosnia, the ISI under General Javed Nasir airlifted anti-tank weapons and missiles to Bosnian mujahideen, shifting the tide in favour of Bosnian Muslims. ISI, under Nasir's leadership, supported Chinese Muslims in Xinjiang, rebel groups in the Philippines, and religious groups in Central Asia. Since 2001, the Pakistan military has been engaged in counterinsurgency and internal security operations in the Khyber Pakhtunkhwa province, primarily targeting Tehrik-e-Taliban Pakistan and associated militant groups. Major military operations conducted during this period include Operation Enduring Freedom, Operation al-Mizan, Operation Zalzala, Operation Sherdil, Operation Rah-e-Haq, Operation Rah-e-Rast, and Operation Rah-e-Nijat.
== Pharmacology == Pimecrolimus is an ascomycin macrolactam derivative. It has been shown in vitro that pimecrolimus binds to FKBP1A and also inhibits calcineurin. Thus pimecrolimus inhibits T-cell activation by inhibiting the synthesis and release of cytokines from T-cells. Pimecrolimus also prevents the release of inflammatory cytokines and mediators from mast cells. Pimecrolimus, like tacrolimus, belongs to the ascomycin class of macrolactam immunosuppressives, acting by the inhibition of T-cell activation by the calcineurin pathway and inhibition of the release of numerous inflammatory cytokines, thereby preventing the cascade of immune and inflammatory signals. Pimecrolimus has a similar mode of action to that of tacrolimus but is more selective, with no effect on dendritic (Langerhans) cells. It has lower permeation through the skin than topical steroids or topical tacrolimus although they have not been compared with each other for their permeation ability through mucosa. In addition, in contrast with topical steroids, pimecrolimus does not produce skin atrophy.
Chick-fil-A, Inc. ( CHIK-fil-AY, a play on the American English pronunciation of "filet") is an American fast food restaurant chain and the largest chain specializing in chicken sandwiches. Headquartered in College Park, Georgia, Chick-fil-A operates restaurants across 48 states, as well as in the District of Columbia and Puerto Rico. The company also has operations in Canada, the United Kingdom, and Singapore, and previously had restaurants in South Africa. The restaurant has a breakfast, a lunch, and a dinner menu. The chain also provides catering services. Chick-fil-A calls its specialty the "original chicken sandwich". It is a piece of deep-fried breaded boneless chicken breast served on a toasted bun with two slices of dill pickle, or with lettuce, tomato, and cheese. Many of the company's values are influenced by the Christian religious beliefs of its late founder, S. Truett Cathy (1921–2014), a devout Southern Baptist. Reflecting a commitment to Sunday Sabbatarianism, all Chick-fil-A restaurants are closed for business on Sundays, and Christmas Day, as well as Thanksgiving for US and Canadian locations. The company's conservative opposition to same-sex marriage has caused controversy; the company began to loosen its stance on this issue from 2019. Even among numerous controversies and boycott attempts, the 2022 American Customer Satisfaction Index found that Chick-fil-A remained the country's favorite fast food chain for the eighth consecutive year, and it has the highest per store sales of any fast food chain in the nation.
acquired bowel herniation (this becomes a risk for larger donor sites (>4 cm)). About 20 cases have been reported in the literature from 1945 until 1989 and only a few hundred cases have been reported worldwide meralgia paresthetica (injury to the lateral femoral cutaneous nerve also called Bernhardt-Roth's syndrome) pelvic instability fracture (extremely rare and usually with other factors) injury to the clunial nerves (this will cause posterior pelvic pain which is worsened by sitting) injury to the ilioinguinal nerve infection minor hematoma (a common occurrence) deep hematoma requiring surgical intervention seroma ureteral injury pseudoaneurysm of iliac artery (rare) tumor transplantation cosmetic defects (chiefly caused by not preserving the superior pelvic brim) chronic pain Bone grafts harvested from the posterior iliac crest in general have less morbidity, but depending on the type of surgery, may require a flip while the patient is under general anesthesia.
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.
The lyophilised solid is best kept cold, dry and dark, typically at minus twenty degrees Celsius. Moisture and repeated warming cycles are the main causes of degradation. Solutions prepared from the powder are less stable and are normally used quickly.