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.
Updated 2025-08-24. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | Melanotan II; MT-II; N-acetyl-norleucyl-cyclo[Asp-His-D-Phe-Arg-Trp-Lys] amide | Naming follows peptide convention; the numeral distinguishes it from melanotan-1 |
| Molecular formula | C50H69N15O9 | Includes the lactam bridge; no counter-ion assumed |
| Monoisotopic mass | 1023.53 Da | Free base; salts and counter-ions shift the observed value |
| Appearance | White to off-white lyophilised powder | Batch-to-batch colour variation is not itself proof of impurity |
| Typical analytical method | RP-HPLC purity determination with ESI-MS identity confirmation | Retention time alone does not establish sequence identity |
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.
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 studies place melanotan-2 among non-selective melanocortin agonists, binding MC1R, MC3R, MC4R and MC5R rather than a single subtype. Activation of MC1R on cutaneous melanocytes raises tyrosinase activity and shifts pigment synthesis toward eumelanin, which is darker and more photostable than pheomelanin. Central receptors, particularly MC4R, are associated with appetite suppression and with reported effects on sexual function. Because subtype selectivity is low, the same molecule engages pigment, metabolic and vascular pathways at once, and this breadth is a common explanation offered for the range of adverse events described in user reports.
No regulatory authority has approved melanotan-2 for human use, and several countries classify it as a prescription-only or controlled substance, which restricts lawful supply. Material sold online is generally labelled as a research chemical and is not required to meet pharmaceutical standards of identity or purity. Published human data consist mainly of small uncontrolled studies, case reports and adverse-event notifications, so the evidence base is descriptive rather than confirmatory. Whether repeated melanocyte stimulation alters long-term naevus behaviour remains an open question that no completed trial has resolved.
However, he can't open the hatch by himself. The player must fight through the asylum and the local theater, which is now overrun with zombified soldiers, to meet him on the other side. The player and the deputy take off in a police helicopter. The game reaches its climax as the player and the deputy are forced to fight Dr. Franklin, who, after taking the full impact of the blast in episode 2, has been rebuilt into a half-zombie, half-machine cyborg. After the doctor's defeat, the player is pursued by Sheriff Rockwood in another helicopter with a mounted mini-gun. The player must defeat the sheriff and send him plummeting toward one of the great lakes before exploding. The game ends with the player and the deputy flying off into the sunrise while the game plays "You Are What I Eat" along with the end credits.
== Reactions == As a lactone, GBL is hydrolyzed under basic conditions, for example in a sodium hydroxide solution into sodium gamma-hydroxybutyrate, the sodium salt of gamma-hydroxybutyric acid. In acidic water, a mixture of the lactone and acid forms exists in an equilibrium. These compounds then may go on to form the polymer poly(4-hydroxybutyrate) as well as the dimer 1,6-Dioxecane-2,7-dione. When treated with a non-nucleophilic base, such as lithium diisopropylamide, GBL undergoes deprotonation of the alpha carbon atom to the carbonyl.
On 19 November, the communists—meeting in Mukachevo—issued a resolution requesting separation of Subcarpathian Ruthenia from Czechoslovakia and incorporation into the Ukrainian Soviet Socialist Republic. On 26 November, the Congress of National Committees unanimously accepted the resolution of the communists. The congress elected the National Council and instructed that a delegation be sent to Moscow to discuss union. The Czechoslovak delegation was asked to leave Subcarpathian Ruthenia. Negotiations between the Czechoslovak government and Moscow ensued. Both Czech and Slovak communists encouraged Beneš to cede Subcarpathian Ruthenia. The Soviet Union agreed to postpone annexation until the postwar period to avoid compromising Beneš's policy based on the pre-Munich frontiers. The treaty ceding Carpathian Ruthenia to the Soviet Union was signed in June 1945. Czechs and Slovaks living in Subcarpathian Ruthenia and Ruthenians (Rusyns) living in Czechoslovakia were given the choice of Czechoslovak or Soviet citizenship.
The list of minerals required for plants is similar to that for animals. Both use very similar enzymes, although differences exist. For example, legumes host molybdenum-containing nitrogenase, but animals do not. Many animals rely on hemoglobin (Fe) for oxygen transport, but plants do not. Fertilizers are often tailored to address mineral deficiencies in particular soils. Examples include molybdenum deficiency, manganese deficiency, zinc deficiency, and so on.
== Prognosis == As there is no known cure, the average life expectancy of people with progeria is 13 years, as of 2003. At least 90 percent of patients die from complications of atherosclerosis, such as heart attack or stroke. Mental development is not adversely affected; in fact, intelligence tends to be average to above average. With respect to the features of aging that progeria appears to manifest, the development of symptoms is comparable to aging at a rate eight to ten times faster than normal. With respect to those that progeria does not exhibit, patients show no neurodegeneration or cancer predisposition. They also do not develop conditions that are commonly associated with accumulation of damage, such as cataracts (caused by UV exposure) and osteoarthritis. Although there may not be any successful treatments for progeria itself, there are treatments for the problems it causes, such as arthritic, respiratory, and cardiovascular problems, and recent medicinal breakthroughs enabled one patient to live until age 28. People with progeria have normal reproductive development, and there are known cases of women with progeria who delivered healthy offspring.
Sources: en.wikipedia.org
In November 1954, the U.S. decided to endorse the World Bank's proposed International Finance Corporation, which would raise funds from global capital markets to lend to the private sector in developing countries. The IFC was finally established in 1956. With Senator Mike Monroney playing a prominent role, Congress approved in July 1958 another new World Bank facility, the International Development Association (IDA). Funded by grants from industrialized countries, the IDA would make low-interest credits to developing countries for projects like public works. The IDA formally came into being in September 1960, with the U.S. contributing 42% of its initial resources. Also in 1958, the United States proposed doubling industrialized countries' contributions to the World Bank, raising the bank's capitalization from $10 billion to $21 billion in September 1959. While the U.S. supported expanded World Bank facilities, it did not support the proposal for a Special UN Fund for Economic Development (SUNFED). The UN did create a "Special Fund" in 1957, but it was limited to designing projects for the UN's technical assistance program, EPTA, and could not finance public works. The U.S. also adopted a regional initiative with Latin America. Through most of the 1950s, the U.S. concentrated on technical assistance in the region. Financial assistance sources were limited to the Eximbank and the World Bank, with the U.S. opposing proposals for a regional development bank.
=== Do–Du === George H. Dodd (c. 1942–2020). British biochemist who studied perfumes and pheromones. Edward Adelbert Doisy (1893–1986). American biochemist at St Louis University, known for discovering vitamin K. Nobel Prize in Physiology or Medicine (1943). Ford Doolittle (b. 1942). American biochemist at Dalhousie University, known for contributions to the study of cyanobacteria and of biochemical evolution in general. Member Natl. Acad. Sci. USA. Jonathan Dordick (b. 1959). American biochemical engineer at Rensselaer Polytechnic Institute, known for development of enzyme catalysis under extreme conditions. Ralph Dorfman (1911–1985). American biochemist at Stanford, known for treatments for cancer and rheumatoid arthritis Jennifer Doudna (b. 1964). American biochemist at UC Berkeley, known for CRISPR-mediated genome editing. Member Natl. Acad. Sci. USA. Nobel Prize in Chemistry, 2020. Alexander Dounce (1909–1997). American protein chemist at the University of Rochester, active in early work on the genetic code, one of the first to suggest that it was triplet-based. Gideon Dreyfuss (PhD 1978). American biochemist and biophysicist at the University of Pennsylvania, concerned with the function and biogenesis of non-coding RNA and the proteins that interact with RNA. Member Natl. Acad. Sci. USA. Jack Cecil Drummond FRS (1891–1952). British biochemist at University College London, known for the isolation of Vitamin A, and wartime advisor on nutrition. Murdered in France, with his wife and daughter. Vincent du Vigneaud (1901–1978).
The Furman is a unit of angular measure equal to 1⁄65,536 of a circle, or just under 20 arcseconds. It is named for Alan T. Furman, the American mathematician who adapted the CORDIC algorithm for 16-bit fixed-point arithmetic sometime around 1980. 16 bits give a resolution of 216 = 65,536 distinct angles. A related unit of angular measure equal to 1⁄256 of a circle, represented by 8 bits, has found some use in machinery control where fine precision is not required, most notably crankshaft and camshaft position in internal combustion engine controllers, and in video game programming. There is no consensus as to its name, but it has been called the 8-Bit Furman. These units are convenient because binary integer overflow resembles angular arithmetic: the value of an 8-bit integer overflows from 255 to 0 when a full circle has been traversed. This means binary addition and subtraction work as expected for angular arithmetic. Measures are often made using a Gray code, which is trivially converted into more conventional notation. Its value is equivalent to about 0.0245 radians or 1.41°.
The symptoms of myasthenia gravis developed within 6 days to 16 weeks (median time 4 weeks). Their medicine-induced myasthenia gravis symptoms were often severe with 29 people developing respiratory failure that required mechanical ventilation. Other studies have reported that these checkpoint inhibitors cause respiratory failure in 45% and death in 25–40% of people with myasthenia gravis. Statins: Statins are drugs that lower blood cholesterol levels in order to reduce the risk of developing a cardiovascular disease due to atherosclerosis. In a 2019 review of 169 people who were reported to develop myasthenia gravis or had worsened myasthenia gravis symptoms while taking a statin, 138 had developed generalized myasthenia gravis, 13 had developed ocular myasthenia gravis, and 18 had worsening of their myasthenia gravis. Following discontinuance of the statin and treatment of their myasthenia gravis, 63 people fully recovered, 27 people were recovering, 19 people had not yet recovered, 5 people recovered but had ongoing symptoms, 1 individual had died, and there was no follow-up data for 54 people. Among these cases, 56% were considered to be serious. A 2024 study evaluated 593 people who had myasthenia gravis and 790,399 people who did not have myasthenia gravis after being treated with a statin. The statin-treatment caused small but statistically significant increases in numbers of exacerbations of myasthenia gravis as well as new onsets of myasthenia gravis in people without the disorder.
Sources: en.wikipedia.org
The breast augmentation procedures realised by way of IMF augmentation (through the inframammary fold), of the TABA augmentation via the armpit (trans-axillary breast augmentation), and of the TUBA augmentation via the navel (trans-umbilical breast augmentation) avoid the nipple-areola complex in order to preserve the tactile sensitivity of the areola and the breastfeeding functions. Moreover, two conditions most affect and interfere with the functioning of the lactiferous ducts: (i) the subglandular implantation of the prosthetic breast, and (ii) the implantation of oversized prosthetic-breasts. Therefore, the implantation of small prosthetic breasts and a submuscular implant-pocket are the breast-augmentation surgeries that least thwart the breastfeeding function.
As a result of population growth in African-Caribbean regions of overseas France and immigration from North and sub-Saharan Africa to mainland France, sickle cell disease has become a major health problem in France. Sickle cell disease has become the most common genetic disease in the country, with an overall birth prevalence of one in 2,415 in mainland France, ahead of phenylketonuria (one in 10,862), congenital hypothyroidism (one in 3,132), congenital adrenal hyperplasia (one in 19,008) and cystic fibrosis (one in 5,014) for the same reference period.
The N-terminus (also known as the amino-terminus, NH2-terminus, N-terminal end or amine-terminus) is the start of a protein or polypeptide, referring to the free amine group (-NH2) located at the end of a polypeptide. Within a peptide, the amine group is bonded to the carboxylic group of another amino acid, making it a chain. That leaves a free carboxylic group at one end of the peptide, called the C-terminus, and a free amine group on the other end called the N-terminus. By convention, peptide sequences are written N-terminus to C-terminus, left to right (in LTR writing systems). This correlates the translation direction to the text direction, because when a protein is translated from messenger RNA, it is created from the N-terminus to the C-terminus, as amino acids are added to the carboxyl end of the protein.
Any object, totally or partially immersed in a fluid or liquid, is buoyed up by a force equal to the weight of the fluid displaced by the object. Archimedes' principle allows the buoyancy of any floating object partially or fully immersed in a fluid to be calculated. The downward force on the object is simply its weight. The upward, or buoyant, force on the object is that stated by Archimedes' principle above. Thus, the net force on the object is the difference between the magnitudes of the buoyant force and its weight. If this net force is positive, the object rises; if negative, the object sinks; and if zero, the object is neutrally buoyant—that is, it remains in place without either rising or sinking. In simple words, Archimedes' principle states that, when a body is partially or completely immersed in a fluid, it experiences an apparent loss in weight that is equal to the weight of the fluid displaced by the immersed part of the body(s).
=== Pituitary gland === The pituitary gland is formed within the rostral neural plate. The Rathke's pouch, a cavity of ectodermal cells of the oropharynx, forms between the fourth and fifth week of gestation and upon full development, it gives rise to the anterior pituitary gland. By seven weeks of gestation, the anterior pituitary vascular system begins to develop. During the first 12 weeks of gestation, the anterior pituitary undergoes cellular differentiation. At 20 weeks of gestation, the hypophyseal portal system has developed. The Rathke's pouch grows towards the third ventricle and fuses with the diverticulum. This eliminates the lumen and the structure becomes Rathke's cleft. The posterior pituitary lobe is formed from the diverticulum. Portions of the pituitary tissue may remain in the nasopharyngeal midline. In rare cases this results in functioning ectopic hormone-secreting tumors in the nasopharynx. The functional development of the anterior pituitary involves spatiotemporal regulation of transcription factors expressed in pituitary stem cells and dynamic gradients of local soluble factors. The coordination of the dorsal gradient of pituitary morphogenesis is dependent on neuroectodermal signals from the infundibular bone morphogenetic protein 4 (BMP4). This protein is responsible for the development of the initial invagination of the Rathke's pouch. Other essential proteins necessary for pituitary cell proliferation are Fibroblast growth factor 8 (FGF8), Wnt4, and Wnt5.
Sources: en.wikipedia.org
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.
The natural hormone is a linear tridecapeptide that is rapidly degraded in circulation. Melanotan-2 is shortened, cyclised, N-terminally acetylated, and carries a D-amino acid substitution, all of which slow enzymatic breakdown.
No national medicines regulator has approved melanotan-2 for therapeutic or cosmetic use. In several jurisdictions it is treated as an unapproved prescription medicine, and its legal classification differs from country to country.
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.