A practical reference on cyclic heptapeptide: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2025-12-15 and is reviewed periodically as new material appears.
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.
Two structural changes distinguish the synthetic peptide from the natural hormone. A norleucine residue replaces methionine at one position, and a D-configured phenylalanine replaces the natural L-form at another. Both substitutions slow enzymatic breakdown, which extends the molecule's persistence relative to the parent hormone. The lactam bridge further constrains the backbone into a stable conformation. These features are standard design strategies in peptide chemistry and are not unique to this compound; they appear across many research peptides built for improved stability.
The compound was developed in the late 1980s and early 1990s by academic researchers investigating melanocortin signaling and pigmentation. Early work explored whether synthetic analogs could reproduce effects of the natural hormone under controlled conditions. The molecule never advanced through the full regulatory pathway required for approval as a medicine. From the mid-2000s onward it appeared in unregulated consumer markets, often distributed through informal channels. That gap between research origins and commercial availability shapes how the compound is discussed today.
| 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 |
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.
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.
The peptide acts as a non-selective agonist at melanocortin receptors, showing affinity for MC1R, MC3R, MC4R and MC5R. Activation of MC1R on melanocytes drives the conversion of tyrosine into melanin and shifts production toward the darker eumelanin form. MC4R signalling in the central nervous system is linked to appetite and energy balance, which helps explain why reduced food intake appeared in early human studies. Effects on MC4R and on vascular tone also account for the erectile responses recorded as unexpected findings in those same trials.
Melanotan-2 is frequently confused with afamelanotide, a linear analogue authorised in the European Union for erythropoietic protoporphyria. The two compounds differ in chain length, ring structure and receptor selectivity, so findings for one cannot be transferred directly to the other. Published controlled human data on melanotan-2 remain sparse, and much of what circulates online derives from small studies or unpublished reports. Questions about effect size, dose-response behaviour and long-term safety therefore remain unresolved.
In ancient times, one highly abrasive depilatory paste consisted of an admixture of slaked lime, water, wood-ash and yellow orpiment (arsenic trisulfide); In rural India and Iran, where this mixture is called vajibt, it is still commonly used to remove pubic hair. In other cultures, oil extracted from unripe olives (which had not reached one-third of their natural stage of ripeness) was used to remove body hair. During the medieval period, Catholic women were expected to let their hair grow long as a display of femininity, whilst keeping the hair concealed by wearing a wimple headdress in public places. The face was the only area where hair growth was considered unsightly; 14th-century ladies would also pick off hair from their foreheads to recede the hairline and give their face a more oval form. From the mid-16th century, it is said when Queen Elizabeth I came to power, she made eyebrow removal fashionable. By the 18th century, body hair removal was still considered a non-necessity by European and American women. But in 1760, when the first safety straight razor appeared for men to safely shave their beard and not inadvertently cut themselves, some women allegedly used this safety razor too. It was invented in Paris by the French master cutler Jean-Jacques Perret, author of La pogonotomie, ou L'art d'apprendre à se raser soi-même (Pogonotomy, or The Art of Learning to Shave). It was not until the late 19th century that women in Europe and America started to make hair removal a component of their personal care regime.
Antithrombin (AT) is a small glycoprotein that inactivates several enzymes of the coagulation system. It is a 464-amino-acid protein produced by the liver. It contains three disulfide bonds and a total of four possible glycosylation sites. α-Antithrombin is the dominant form of antithrombin found in blood plasma and has an oligosaccharide occupying each of its four glycosylation sites. A single glycosylation site remains consistently un-occupied in the minor form of antithrombin, β-antithrombin. Its activity is increased manyfold by the anticoagulant drug heparin, which enhances the binding of antithrombin to factor IIa (thrombin) and factor Xa.
== Clinical use == The most frequent use of aminoglycosides is empiric therapy for serious infections such as sepsis, complicated intra-abdominal infections, complicated urinary tract infections, and nosocomial respiratory tract infections. Usually, once cultures of the causal organism are grown and their susceptibilities tested, aminoglycosides are discontinued in favor of less toxic antibiotics. The recent emergence of infections due to Gram-negative bacterial strains with advanced patterns of antimicrobial resistance has prompted physicians to reevaluate the use of these antibacterial agents. This revived interest in the use of aminoglycosides has brought back to light the debate on the two major issues related to these compounds, namely the spectrum of antimicrobial susceptibility and toxicity. Current evidence shows that aminoglycosides do retain activity against the majority of Gram-negative clinical bacterial isolates in many parts of the world. Still, the relatively frequent occurrence of nephrotoxicity and ototoxicity during aminoglycoside treatment makes physicians reluctant to use these compounds in everyday practice. Recent advances in the understanding of the effect of various dosage schedules of aminoglycosides on toxicity have provided a partial solution to this problem, although more research still needs to be done in order to overcome this problem entirely.
==== Medication use ==== Most medications are compatible with continued breastfeeding. Many medicines pass into breastmilk in small amounts; however, very few medications actually reach the infant and are absorbed in a way that would actually impact the infant. Several characteristics of medications, including size and pH of the medication molecule and how well the medication is absorbed in the GI tract, influence how much of a medication may reach, and may ultimately be absorbed, by the infant. In addition to the effects on the infant, many medications are known to significantly suppress milk production, including pseudoephedrine, diuretics, and contraceptives that contain estrogen. There are several resources to assist medical professionals in determining which medications are safe for pregnancy and breastfeeding. While patients can use these resources, they are targeted toward medical professionals. Patients should be encouraged to consult a lactation specialist or a medical provider trained in breastfeeding medicine if any concerns arise. Two helpful resources are listed below.
Sources: en.wikipedia.org
== Economy == Bophuthatswana was the richest of the TBVC-states as it had platinum mines, which accounted for two-thirds of the total platinum production in the Western world. It was also rich in asbestos, granite, vanadium, chromium and manganese. Additional revenues came from the Sun City casino, which was a day trip from Johannesburg and Pretoria, where gambling was illegal under the National Party government, as it was throughout all of South Africa. Bophuthatswana had a relatively capitalist free market economy, as seen by the government's drive for infrastructure development, foreign direct investments and virtually no regulatory barriers to starting and running a business. Initially, its economy was driven by agriculture then later by mining, hospitality and banking. Bophuthatswana also issued bearer development bonds. The so-called "Bop Bonds" were redeemed by the government of the North West province from 1995 to 1997, and are now worthless as financial instruments. However, bonds in excellent condition are considered collectible. Bonds issued in 1988 and 1989, in R10 and R20 denominations, currently trade at 10–25% of original face value.
Invega Sustenna is supplied as a white to off-white aqueous extended-release suspension for intramuscular injection in single-dose prefilled syringes. In addition to the active ingredient, paliperidone palmitate, the formulation contains the following inactive ingredients: polysorbate 20, polyethylene glycol 4000, citric acid monohydrate, disodium hydrogen phosphate anhydrous, sodium dihydrogen phosphate monohydrate, sodium hydroxide, and water for injection.
The deal was to constitute a reverse merger, whereby Allergan acquired Pfizer, with the new company then changing its name to "Pfizer, plc". On April 6, 2016, Pfizer and Allergan terminated the merger agreement after the Obama administration and the United States Department of the Treasury introduced new laws intended to limit corporate inversions (the extent to which companies could move their headquarters overseas in order to reduce the amount of taxes they pay). In June 2016, the company acquired Anacor Pharmaceuticals for $5.2 billion, expanding its portfolio in both inflammation and immunology drugs areas. In August 2016, the company made a $40 million bid for the assets of BIND Therapeutics, which was in bankruptcy. The same month, the company acquired Bamboo Therapeutics for $645 million, expanding its gene therapy offerings. In September 2016, the company acquired cancer drug-maker Medivation for $14 billion. In October 2016, the company licensed the anti-CTLA4 monoclonal antibody, ONC-392, from OncoImmune. In November 2016, Pfizer funded a $3,435,600 study with the CDC Foundation to research "screen-and-treat" strategies for cryptococcal disease in Botswana. In December 2016, Pfizer acquired AstraZeneca's small-molecule antibiotics business for $1.575 billion. In January 2018, Pfizer announced that it would end its work on research into treatments for Alzheimer's disease and Parkinsonism (a symptom of Parkinson's disease and other conditions). The company said about 300 researchers would lose their jobs.
The two major inactive metabolites are the N-dealkylation products (the carboxylic acid ID-20219 and the piperazine ID-11614), and a norbornane hydroxylated derivative of ID-20219 (ID-20220). Of lurasidone and its metabolites circulating in the blood, the native drug makes up 11%, the main active metabolite 4%, and the inactive carboxylic acids 24% and 11%, respectively. Several dozen metabolites have been identified altogether.:59–61 Biological half-life is given as 18 hours or 20 to 40 hours in different sources. 80% or 67% of a radiolabelled dose was recovered from the feces, and 9% or 19% from the urine.
=== European Union === Hitchens was a supporter of the European Union. In an appearance on C-SPAN in 1993, Hitchens said, "As of 1992, there is a now a Euro passport that makes you free to travel within the boundaries of... member countries, and I've always liked the idea of European unity, and so I held out for a Euro passport. So I travel as a European." Speaking at the launch of his brother Peter Hitchens' book, The Abolition of Britain at Conway Hall in London, Hitchens denounced the so-called Eurosceptic movement, describing it as "the British version of fascism". He went on to say, "Scepticism is a title of honour. These people are not sceptical. They're fanatical. They're dogmatic".
Sources: en.wikipedia.org
This was elegantly restated in 1963 in a plaque unveiled at Johns Hopkins to commemorate the major contribution (of McLean) to the discovery of heparin in 1916 in collaboration with Professor William Henry Howell. In the 1930s, several researchers were investigating heparin. Erik Jorpes at Karolinska Institutet published his research on the structure of heparin in 1935, which made it possible for the Swedish company Vitrum AB to launch the first heparin product for intravenous use in 1936. Between 1933 and 1936, Connaught Medical Research Laboratories, then a part of the University of Toronto, perfected a technique for producing safe, nontoxic heparin that could be administered to patients, in a saline solution. The first human trials of heparin began in May 1935, and, by 1937, it was clear that Connaught's heparin was safe, easily available, and effective as a blood anticoagulant. Before 1933, heparin was available in small amounts, was extremely expensive and toxic, and, as a consequence, of no medical value. Heparin production experienced a break in the 1990s. Until then, heparin was mainly obtained from cattle tissue, which was a by-product of the meat industry, especially in North America. With the rapid spread of BSE, more and more manufacturers abandoned this source of supply. As a result, global heparin production became increasingly concentrated in China, where the substance was now procured from the expanding industry of breeding and slaughtering hogs.
Unit I – Bonthapally: The primary manufacturing hub situated in Bonthapally village, Medak District, Telangana, with multiple production blocks including kilo labs and quality assurance laboratories. It holds approvals from major regulatory agencies and supports commercial API production. Unit II – Pashamylaram: A large-scale manufacturing facility comprising multiple production blocks, an engineering workshop, and warehouses. Unit III – Gaddapotharam: A multi-product facility designed for advanced intermediates and APIs, with analytical development and pilot plant capabilities. R&D Centre – Bonthapally: Research and development centre with a team of approximately 360 scientists, pilot labs, and analytical capabilities to catalyze process development and technology transfer.
=== Tolerance, dependence and withdrawal === Prolonged use of bromazepam can cause tolerance and may lead to both physical and psychological dependence on the drug, and as a result, it is a medication which is controlled by international law. It is nonetheless important to note that dependence, long-term use and misuse occur in a minority of cases and are not representative of most patients' experience with this type of medication. It shares with other benzodiazepines the risk of abuse, misuse, psychological dependence or physical dependence. A withdrawal study demonstrated both psychological dependence and physical dependence on bromazepam including marked rebound anxiety after 4 weeks chronic use. Those whose dose was gradually reduced experienced no withdrawal. Patients treated with bromazepam for generalised anxiety disorder were found to experience withdrawal symptoms such as a worsening of anxiety, as well as the development of physical withdrawal symptoms when abruptly withdrawn bromazepam. Abrupt or over rapid withdrawal from bromazepam after chronic use even at therapeutic prescribed doses can lead to a severe withdrawal syndrome including status epilepticus and a condition resembling delerium tremens. Animal studies have shown that chronic administration of diazepam (or bromazepam) causes a decrease in spontaneous locomotor activity, decreased turnover of noradrenaline and dopamine and serotonin, increased activity of tyrosine hydroxylase and increased levels of the catecholamines.
They also extend into, but are not destined to supplant, systems biology models of metabolic pathways. They are also parallel to physiome models, but do not aim at modelling physiological functions beyond fluid circulation in detail. In fact the above four types of models can reinforce each other when integrated.
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 seven-amino-acid peptide modeled on alpha-melanocyte-stimulating hormone. It carries two non-natural substitutions and a cyclic bridge that increase its stability relative to the natural hormone. It circulates as a research chemical and is not an approved medicine.