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 2026-07-19. Where a claim depends on a specific study, the study is described rather than over-claimed.
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 analog derived from the core sequence of alpha-melanocyte-stimulating hormone. Researchers at the University of Arizona synthesized it during the 1980s while studying pigmentation and appetite signaling. The compound is not an approved medicine in any major jurisdiction and appears mainly in laboratory and research-chemical settings. Its structure incorporates a lactam bridge between side chains, which constrains the ring and slows enzymatic breakdown relative to the natural hormone.
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.
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 |
|---|---|---|
| Chemical class | Synthetic cyclic heptapeptide | Analog of alpha-melanocyte-stimulating hormone |
| Primary receptor family | Melanocortin receptors MC1R through MC5R | Binding is not subtype-selective |
| Development period | 1980s | Synthesized during pigmentation and appetite research |
| Regulatory status | Not an approved medicine | No major regulator has authorized human use |
| Related compound | Afamelanotide | Linear analog studied for photoprotection |
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.
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.
Identify viral infection of a cell (viral protein expression). Determine an individual's susceptibility to cancer (oncogene expression). Find if a bacterium is resistant to penicillin (beta-lactamase expression). Gene expression profiling evaluates a panel of genes to help understand the fundamental mechanism of a cell. This is increasingly used in cancer therapy to target specific chemotherapy. (See RNA-Seq and DNA microarray for details.) Similarly, the analysis of the location of protein expression is a powerful tool, and this can be done on an organismal or cellular scale. Investigation of localization is particularly important for the study of development in multicellular organisms and as an indicator of protein function in single cells. Ideally, measurement of expression is done by detecting the final gene product (for many genes, this is the protein); however, it is often easier to detect one of the precursors, typically mRNA and to infer gene-expression levels from these measurements.
A post hoc analysis from a randomized, placebo-controlled, multi-centre study carried out at 11 secondary care centres, as well as a longitudinal single-centre study on pregnant women in Norway, also determined that metformin had no effect on maternal androgens in pregnancies occurring in the setting of PMOS. One systemic review suggested that polymorphisms in the vitamin D receptor gene are associated with the prognosis of polyendocrine metabolic ovarian syndrome, though this is based on small sample sizes and is debated. Studies have shown benefits for vitamin D supplementation in women with vitamin D deficiency and PMOS. Hyperinsulinemia can increase the production of androgens in the ovaries. One context in which this occurs is HAIR-AN syndrome, a rare subtype of PMOS.
== External links == "État civil de Paris en ligne" [Paris civil status online] (in French). Archived from the original on January 5, 2020. "Commission de reconstitution de l'état civil parisien (1875-1897)" [Commission for the reconstitution of Parisian civil status (1875-1897)] (PDF) (in French). Archived from the original (PDF) on January 1, 2022. "Inventaire des registres de catholicité de baptêmes, mariages et sépultures des églises parisiennes de 1792 à 1909 conservés aux archives de Paris (collection de l'archevêché) et dans les paroisses" [Inventory of Catholic registers of baptisms, marriages and burials in Paris churches from 1792 to 1909 held by the Archives de Paris (archbishop's collection) and parishes.] (PDF) (in French). Archived from the original (PDF) on February 21, 2024. "Diocèse de Paris, formulaire de recherche pour trouver la paroisse dont dépend une adresse parisienne" [Diocese of Paris, search form to find the parish of a Paris address] (in French). Archived from the original on March 9, 2014. "Registre de relevés d'actes de baptêmes, mariages et sépultures de l'église Saint-Sulpice de Paris pour la période 1537-1748" [Register of records of baptisms, marriages and burials from the Saint-Sulpice church in Paris for the period 1537-1748] (in French). Archived from the original on December 4, 2013. "Archives numérisées de l'AP-HP Assistance Publique Hôpitaux de Paris" [Digital archives of AP-HP Assistance Publique Hôpitaux de Paris] (in French). Archived from the original on October 22, 2013.
=== Vertebrates === The size of the heart varies among the different animal groups, with hearts in vertebrates ranging from those of the smallest mice (12 mg) to the blue whale (600 kg). In vertebrates, the heart lies in the middle of the ventral part of the body, surrounded by a pericardium. which in some fish may be connected to the peritoneum. In all vertebrates, the heart has an asymmetric orientation, almost always on the left side. According to one theory, this is caused by a developmental axial twist in the early embryo. The sinoatrial node is found in all amniotes but not in more primitive vertebrates. In these animals, the muscles of the heart are relatively continuous, and the sinus venosus coordinates the beat, which passes in a wave through the remaining chambers. Since the sinus venosus is incorporated into the right atrium in amniotes, it is likely homologous with the SA node. In teleosts, with their vestigial sinus venosus, the main centre of coordination is, instead, in the atrium. The rate of heartbeat varies enormously between different species, ranging from around 20 beats per minute in codfish to around 600 in hummingbirds and up to 1,200 bpm in the ruby-throated hummingbird.
=== From titration curves === From the titration of protonatable group, one can read the so-called pKa1⁄2 which is equal to the pH value where the group is half-protonated (i.e. when 50% such groups would be protonated). The pKa1⁄2 is equal to the Henderson–Hasselbalch pKa (pKHHa) if the titration curve follows the Henderson–Hasselbalch equation. Most pKa calculation methods silently assume that all titration curves are Henderson–Hasselbalch shaped, and pKa values in pKa calculation programs are therefore often determined in this way. In the general case of multiple interacting protonatable sites, the pKa1⁄2 value is not thermodynamically meaningful. In contrast, the Henderson–Hasselbalch pKa value can be computed from the protonation free energy via
Sources: en.wikipedia.org
== Nervous control == The mechanical states of catch connective tissue are under nervous control and thus we can regard this tissue as one of neurally controlled mechano-effectors such as muscles. It is found in the sea-urchin spine joints that the stiffness of catch connective tissue changes in the coordinated manner with the muscle contractions. One of the characteristic cells found in catch connective tissue is juxtaligamental cells containing secretory granules. These cells are supposed to contain proteins controlling stiffness of extracellular materials. When stained with the antibody specific to echinoderm nerves sea-cucumber body wall is supplied with immunoreactive fine fibers running among the collagen fibrils. Pharmacological experiments suggested the presence of two types of cholinergic systems, one is the nicotinic one involved in the dermal stiffening and the other is the muscarinic one involved in softening. Cholinergic nerves seem to control the secretory activities of juxtaligamental cells. The presence of the cholinergic system was supported by the neuropeptide stichopin that inhibits the action of stiffening cholinergic systems. Stichopin is one of four new peptides in the dermis of sea cucumbers. Other ones are the neuropeptide NGIWYamide that stiffens the dermis and two holokinins that soften the dermis. The nerves containing these neuropeptides possibly control the secretory activities of juxtaligamental cells.
== Uses == Ceramides may be found as ingredients of some topical skin medications used to complement treatment for skin conditions such as eczema. They are also used in cosmetic products such as some soaps, shampoos, skin creams, and sunscreens. Additionally, ceramides are being explored as a potential therapeutic in treating cancer.
== Diagnosis == While Sjögren's disease is one of the most common autoimmune diseases, it has no specific and non-invasive diagnostic tests. Diagnosing Sjögren's disease is complicated by the range of symptoms that a patient may manifest, and the similarity between symptoms of Sjögren's disease and those of other conditions. Also, patients with Sjögren’s symptoms approach different specialities for treatment, which can make diagnosis difficult. Since dry eyes and dry mouth are very common symptoms, and frequently occur in people over 40, affected people may believe the symptoms are age-related. Therefore, they often ignore them. Some medications can cause symptoms similar to those of Sjögren's disease.
The plantar fascia contributes to support of the arch of the foot by acting as a tie-rod, where it undergoes tension when the foot bears weight. One biomechanical model estimated it carries as much as 14% of the total load of the foot. In an experiment using cadavers, it was found that failure of the plantar fascia averaged at loads of 118±244 newtons (12 ± 25 kilograms-force; 27 ± 55 pounds-force). Failure most often occurred at the proximal attachment to the calcaneus, which is consistent with the usual location of symptoms (i.e., in plantar fasciitis). Complete rupture or surgical release of the plantar fascia leads to a decrease in arch stiffness and a significant collapse of the longitudinal arch of the foot. By modeling it was predicted such conditions would result in a 17% increase in vertical displacement and a 15% increase in horizontal elongation of the foot when it was loaded at 683 newtons (70 kgf; 154 lbf). Surgical release also significantly increases both stress in the plantar ligaments and plantar pressures under the metatarsal heads. Although most of the figures mentioned above are from either cadaver studies or investigations using models, they highlight the relatively large load the plantar fascia is subjected to while contributing to the structural integrity of the foot.
Sources: en.wikipedia.org
It was later revealed that Fripp had attempted to replace himself with McDonald and Steve Hackett of Genesis, but this was rejected by the managers. Following the band's disbandment, the live album USA was released in May 1975, formed of recordings from their 1974 North American tour. It received some positive reviews, including being deemed "a must" for fans of the band and "insanity you're better off having". Issues with the tapes rendered some of Cross's playing inaudible, so Eddie Jobson of Roxy Music was hired to perform violin and keyboard overdubs; further edits were also made to allow the music to fit on a single LP. More live recordings from the 1972–1974 era would be issued as The Night Watch in 1997, and as part of the box sets The Great Deceiver (1992), Larks' Tongues in Aspic (1972–1973) (2012), The Road to Red (1974), and Starless (1973–1974) (both 2014). After short stints with Roxy Music and Uriah Heep, Wetton went on to co-form U.K. with Bruford in 1977, and Asia in 1981; Bruford, in addition to U.K., formed the jazz fusion band Bruford. From 1975 to 1980, King Crimson were completely inactive.
=== Effects of climate change === The effects of climate change on tea crops have been widely investigated and include yield losses, negative effects on regional economies, and changes in tea taste, aroma, texture, colour that affect market prices, and consumer demand. Climate change affects the quantity of tea farmers are able to grow by influencing precipitation levels, increasing temperatures, encouraging insect pests, and shifting the timing of growing seasons. This happens differently in different regions. China and India—two of the largest producers—are both experiencing shorter growing seasons, heatwaves, and exposure of crops to hot spells. To reduce the effects of climate change, tea famers are turning to agroforestry, soil enrichment through the incorporation of legumes, growing tea plants from seed, soil conservation methods, and new varieties of tea that have adaptations. Additional research is needed to explore the synergistic effects of multiple climate stressors on tea and in underrepresented regions such as Africa and Southeast Asia. To further the research agenda, scholars note the importance of emerging molecular technologies and information tools for modelling and simulation. Agroforestry and modern technologies for soil management "can improve nitrogen use efficiency, reduce greenhouse gas emissions, and support sustainable tea cultivation" alongside socioeconomic research to ensure farmers can access such technologies and remain economically viable.
The oldest confirmed record of a "modern" biological community related with a vent is the Figueroa Sulfide, from the Early Jurassic of California. The ecosystem so formed is reliant upon the continued existence of the hydrothermal vent field as the primary source of energy, which differs from most surface life on Earth, which is based on solar energy. However, although it is often said that these communities exist independently of the sun, some of the organisms are actually dependent upon oxygen produced by photosynthetic organisms, while others are anaerobic.
Sources: en.wikipedia.org
No regulator in a major market has approved it for human use. It appears in research settings and in products marketed outside pharmacy channels. Legal status for personal possession varies by country.
Afamelanotide is a linear analog that has received approval in some jurisdictions for a specific photoprotection indication. Melanotan II is cyclic and less selective across melanocortin receptors. The two are related but are not interchangeable in regulatory or clinical terms.
A compound that activates several receptor subtypes may produce effects beyond pigmentation. Selectivity influences which tissues respond and shapes the side-effect profile described in reports. Designing subtype-selective analogs is a stated goal of melanocortin research.
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.