This is a working overview of cyclic heptapeptide, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2025-08-26 and is reviewed periodically as new material appears.
The peptide was developed during the 1980s by researchers investigating melanocortin signalling and skin pigmentation pathways. Early work focused on analogues of alpha-melanocyte-stimulating hormone that would resist enzymatic breakdown more effectively than the parent molecule. Melanotan-2 emerged from that programme as a shortened, cyclised variant. Reports describing its synthesis and receptor activity later appeared in the scientific literature. Commercial availability grew through unregulated channels rather than through pharmaceutical approval.
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.
Research interest has centred on photoprotection and pigmentation, with a smaller body of work on appetite and sexual function. Published human data remain limited to small, frequently uncontrolled studies, and the compound has never received marketing approval from a national medicines regulator. Most laboratory work treats it as a pharmacological tool for probing melanocortin signalling in cell culture or animal models. Whether pigmentation changes observed in people translate into measurable protection against ultraviolet-induced DNA damage remains an open question.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C50H69N15O9 | Synthetic cyclic heptapeptide |
| Molecular mass | Approximately 1024 g/mol | Depends on counter-ion content |
| Appearance | White to off-white powder | Commonly supplied as a lyophilised solid |
| Solubility | Freely soluble in water | Also dissolves in common aqueous buffers |
| Typical storage | -20 degrees Celsius, desiccated | Protect from light and repeated freeze-thaw |
Melanotan II binds several melanocortin receptor subtypes rather than a single target. MC1R on melanocytes drives melanin synthesis, while MC3R and MC4R participate in energy balance, appetite, and sexual response pathways. This lack of selectivity explains why reported effects extend beyond skin darkening. Substitutions at positions four and seven, including norleucine and D-phenylalanine, increase potency and resistance to peptidases. Understanding which receptor mediates which effect remains an active area of investigation.
Published human data come mostly from small, short studies rather than large controlled trials. Reported outcomes include increased skin pigmentation and, in some reports, effects on appetite and libido, but sample sizes are small and follow-up is limited. Whether long-term use produces durable pigment changes or adverse effects is not established. Because products sold outside pharmacies are not standardized, the actual content of any given vial is often unknown. Independent testing of such material is uncommon.
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.
In September 2024, Israel intensified its operations with two waves of electronic device attacks targeting Hezbollah's communication systems, and later assassinated the group's leading figures, including Secretary-General Hassan Nasrallah, and his successor, Hashem Safieddine. On 1 October, the Israeli military began an invasion of southern Lebanon, although it had been conducting limited ground operations for some time. Israeli operations led to the significant dismantling of Hezbollah's military infrastructure in southern Lebanon and the destruction of a large portion of its missile stockpile. A 60-day ceasefire agreement was brokered and took effect on 27 November 2024. The ceasefire required Hezbollah to move its fighters north of the Litani River, approximately 30 kilometres (19 miles) from the Israeli border, while Israel began withdrawing its forces from southern Lebanon. The Lebanese Army was tasked with deploying around 5,000 soldiers to monitor the situation and maintain peace in the region. The ceasefire is being monitored by a panel of five countries, led by the United States, though Israel retains the right to strike at immediate threats in Lebanon during this period. The ceasefire was extended to 18 February 2025, at which time the Israel Defense Forces (IDF) withdrew from most of southern Lebanon. Airstrikes resumed on 2 March 2026 between Hezbollah and Israel following the 2026 Iran war and the killing of Ali Khamenei. On 16 April, President Trump announced that Israel and Lebanon agreed to a 10-day truce.
=== Radiation shielding === 238U is also used as a radiation shield – its alpha radiation is easily stopped by the non-radioactive casing of the shielding and the uranium's high atomic weight and high number of electrons are highly effective in absorbing gamma rays and X-rays. It is not as effective as ordinary water for stopping fast neutrons. Both metallic depleted uranium and depleted uranium dioxide are used for radiation shielding. Uranium is about five times better as a gamma ray shield than lead, so a shield with the same effectiveness can be packed into a thinner layer. DUCRETE, a concrete made with uranium dioxide aggregate instead of gravel, is being investigated as a material for dry cask storage systems to store radioactive waste.
The iron storage disorder hereditary hemochromatosis (HHC) is an autosomal recessive genetic disorder that usually results from defects in this gene. The disease-causing genetic variant most commonly associated with hemochromatosis is p. C282Y. About 1/200 of people of Northern European origin have two copies of this variant; they, particularly males, are at high risk of developing hemochromatosis. This variant may also be one of the factors modifying Wilson's disease phenotype, making the symptoms of the disease appear earlier. Allele frequencies of HFE C282Y in ethnically diverse western European white populations are 5-14% and in North American non-Hispanic whites are 6-7%. C282Y exists as a polymorphism only in Western European white and derivative populations, although C282Y may have arisen independently in non-whites outside Europe. HFE H63D is cosmopolitan but occurs with greatest frequency in individuals of European descent. Allele frequencies of H63D in ethnically diverse western European populations are 10-29%. and in North American non-Hispanic whites are 14-15%. At least 42 mutations involving HFE introns and exons have been discovered, most of them in persons with hemochromatosis or their family members. Most of these mutations are rare. Many of the mutations cause or probably cause hemochromatosis phenotypes, often in compound heterozygosity with HFE C282Y. Other mutations are either synonymous or their effect on iron phenotypes, if any, has not been demonstrated.
== Animal welfare == The welfare of animals used in Burger King products has been a subject of company activity, as well as a source of controversy. In 2001, Burger King entered into an agreement with People for the Ethical Treatment of Animals (PETA) following a corporate campaign regarding the treatment of poultry by its suppliers. The agreement established a framework for implementing animal welfare standards, including third-party compliance monitoring. In 2006, PETA, acting as a shareholder in Burger King's parent company, brought a resolution before the board advocating for the adoption of controlled atmosphere killing (CAK) as a more humane and cost-effective slaughter method. In response, Burger King announced new supplier policies in 2007, prioritizing CAK and committing to incremental use of cage-free eggs and crate-free pork. These changes were recognized by advocacy groups as establishing a higher industry standard for animal welfare compliance.
=== Factors found not to correlate with fibromyalgia === Studies on personality and fibromyalgia have shown inconsistent results. Although some have suggested that fibromyalgia patients are more likely to have specific personality traits, it appears that, in comparison to other diseases, when anxiety and depression are statistically controlled for, personality has less relevance, and does not differ from healthy controls.
Sources: en.wikipedia.org
=== Disorders of glycogen metabolism === The most common disease in which glycogen metabolism becomes abnormal is diabetes, in which, because of abnormal amounts of insulin, liver glycogen can be abnormally accumulated or depleted. Restoration of normal glucose metabolism usually normalizes glycogen metabolism, as well. In hypoglycemia caused by excessive insulin, liver glycogen levels are high, but the high insulin levels prevent the glycogenolysis necessary to maintain normal blood sugar levels. Glucagon is a common treatment for this type of hypoglycemia. Various inborn errors of carbohydrate metabolism are caused by deficiencies of enzymes or transport proteins necessary for glycogen synthesis or breakdown. These are collectively referred to as glycogen storage diseases.
== Occurrence == Dimethyl trisulfide has been found in volatiles emitted from cooked onion, leek and other Allium species, from broccoli and cabbage, as well as from Limburger cheese, and is involved in the unpalatable aroma of aged beer and stale Japanese sake. It is a product of bacterial decomposition, including the early stages of human decomposition, and is a major attractant for blowflies looking for hosts. Dimethyl trisulfide along with dimethyl sulfide and dimethyl disulfide have been confirmed as volatile compounds given off by the fly-attracting plant known as dead-horse arum (Helicodiceros muscivorus). These flies are attracted to the odor of fetid meat and help pollinate this plant. DMTS contributes to the foul odor given off by the fungus Phallus impudicus, also known as the common stinkhorn. DMTS causes the characteristic malodorous smell of a fungating lesion, e.g., from cancer wounds, and contributes to the odor of human feces. DMTS can be synthesized by the reaction of methanethiol with hydrogen sulfide (in the presence of copper (II)) and with sulfur dichloride, among other methods:
In Western societies, the contexts for depictions of the human body include information, art and pornography. Information includes both science and education, such as anatomical drawings. Any ambiguous image not easily fitting into one of these categories may be misinterpreted, leading to disputes. The most contentious disputes are between fine art and erotic images, which define the legal distinction of which images are permitted or prohibited.
Viola arvensis is a species of violet known by the common name field pansy. It is native to Europe, western Asia, and North Africa, and it is known on other continents as an introduced species and a weed of disturbed and cultivated areas. Viola arvensis was shown to contain cyclotides, a class of peptides found in plants. The peptide cycloviolacin O2 in particular has shown to possess cytotoxic activity against human cancer cells and is therefore looked at as a potential drug lead.
Sources: en.wikipedia.org
== Function == Corin converts the atrial natriuretic peptide (ANP) precursor, pro-ANP, to mature ANP, a cardiac hormone that regulates salt-water balance and blood pressure. In mice, corin deficiency prevents pro-ANP processing and causes salt-sensitive hypertension. Corin may also function as a pro-brain-type natriuretic peptide convertase. Corin-mediated ANP production in the pregnant uterus promotes spiral artery remodeling and trophoblast invasion. CORIN mutations have been reported in patients with preeclampsia. In mice, corin functions in the dermal papilla to regulate coat color in an Agouti-dependent pathway.
=== Current === There are currently 67 territorial authorities. Before the Auckland Council "super merge" in November 2010, there were 73 territorial authorities. Before the Banks Peninsula District Council merged with the Christchurch City Council in 2006, there were 74 territorial authorities.
== History == KNX-100 was first described in the scientific literature by 2012. It was originated at the University of Sydney by Iain McGregor and Michael Bowen and colleagues and is under development by Kinoxis Therapeutics in partnership with Boehringer Ingelheim. In 2018, it was reported that KNX-100 had been under development for more than a decade. The drug was identified via a phenotypic screen of compounds derived from a fragment-based drug discovery system targeting the oxytocin system. In January 2026, it was disclosed that KNX-100's mechanism of action is inhibition of the enzyme arachidonate 15-lipoxygenase (ALOX15).
Sources: en.wikipedia.org
It is a synthetic cyclic heptapeptide and an analogue of alpha-melanocyte-stimulating hormone. The molecule is produced by chemical synthesis rather than extracted from a biological source.
It is shorter than the native hormone and carries a cyclic constraint that improves stability. These changes raise receptor potency and slow breakdown relative to the naturally occurring peptide.
Published accounts date its development to the 1980s, when researchers were generating analogues of melanocyte-stimulating hormone. That work aimed to produce more stable compounds for studying pigmentation biology.
It is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone, containing seven amino acids with a lactam ring and a D-configured phenylalanine residue. It is supplied as a lyophilised powder for laboratory research.