cyclic peptide raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
This page was last updated on 2025-11-05 and is reviewed periodically as new material appears.
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.
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.
Human data remain limited and mostly short-term. Reports describe small trials and observational accounts rather than large controlled studies, so questions about dose-response relationships and long-term effects on melanocytes stay open. Whether repeated exposure alters naevus behaviour is not settled in the published record. Researchers also note that self-administered use outside clinical settings makes actual exposure difficult to quantify. Statements about efficacy and safety should therefore be read as preliminary rather than established.
Melanotan II is a synthetic cyclic heptapeptide that acts as an agonist at melanocortin receptors. It was designed as a structural analogue of alpha-melanocyte-stimulating hormone, the endogenous peptide involved in pigment production. The analogue carries a lactam bridge that constrains the ring and slows enzymatic breakdown relative to the native hormone. In research literature it appears under several abbreviations, and naming conventions are not fully standardized. Published descriptions usually place it within the broader melanocortin agonist family.
| 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 |
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.
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.
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.
Lucilia spp. (green-bottle fly) Cochliomyia spp. (screw-worm fly) Phormia spp. (black-bottle fly) Calliphora spp. (blue-bottle fly) Sarcophaga spp. (flesh fly or sarcophagids) Flesh flies, or sarcophagids, members of the family Sarcophagidae, can cause intestinal myiasis in humans if the females deposit larvae on meat or fruit.
== Background == Yu was born in Beijing, China. She received a master's degree in ancient Chinese literature and a doctoral degree in film & TV studies from Beijing Normal University. She holds strategist/researcher positions in a roster of mass media groups such as China Television Artists Association, China Visual Association's Tertiary Arts committee, China Visual Association's Research Group, CCTV's Research Office, China News Research Group, China-Guangdong Research Institute, China-Guangdong Institute Legal Programs Committee, News Corp (Australia), etc. Yu is apparently a fan of pop music idols such as Jay Chou and Nan Quan Mama, a Chinese classic enthusiast and a Kunqu Opera performer. She is also unofficially known as "the chieftain of the fun-seeking club of the School of Media and Arts at Beijing Normal University."
=== Film === In the 1999 film, Notting Hill, Keziah, played by Emma Bernard is a vegetarian. In one scene, Keziah tells William "Will" Thacker (played by Hugh Grant), that she is a fruitarian. In the 2000 film, But I'm A Cheerleader, before Megan, one of the film's protagonists, is sent to a conversion therapy camp, her parents and others claim she is a lesbian because she is a vegetarian. Legally Blonde, a 2001 film, also featured a vegetarian—Elle Woods. When she introduces herself at Harvard Law School, she describes herself and her dog as "Gemini vegetarians". In the 2012 film, Life of Pi, Pi, played by Suraj Sharma, is a vegetarian based on his 3 religions: Hindu, Christian, and Muslim. And in the ship scene, one Taiwanese Sailor, played by Bo-Chieh Wang, is a vegetarian from his Buddhism religion to eat rice and the vegetarian gravy. In the 2018 Hollywood blockbuster, Black Panther, M'Baku (voiced by Winston Duke), the Jabari tribe leader who lives in the mountains of Wakanda, declares to a White CIA agent named Everett Ross (voiced by Martin Freeman), "if you say one more word, I'll feed you to my children!" After Everett is shaken by these words, he jokes, saying he is kidding because all those in his tribe, including himself, are vegetarians. Some praised this scene for challenging a stereotype of Black culture and the perception of what vegetarians look like. Duke later said that some Black outlets cooked vegan meals for him, and said that the scene is "kind of teaching kids that eating vegetables is cool," which is something he is for.
I wish that all nations may recover and retain their independence; that those which are overgrown may not advance beyond safe measure of power, that a salutary balance may ever be maintained among nations and that our peace, commerce, and friendship, may be sought and cultivated by all.... Not in our day, but at no distant one, we may shake a rod over the heads of all, which may make the stoutest of them tremble. In 1942, Robert Strausz-Hupé found that it "is in the interests of the United States no less than that of humanity" that the United States should be the only one "geographical power nucleus" from which a "balancing and stabilizing" power of arbiter be exercised. This "will pave the way for a new and universal order." Writing the same year in Life magazine, Joseph Thorndike tells about "many observers" seeking "preponderant power in the postwar world" to replace balance of power:
== Efficacy == The COVID-19 mRNA vaccines from Moderna and Pfizer–BioNTech had short-term efficacy rates of over 90 percent against the original SARS-CoV-2 virus. Prior to mRNA, drug trials on pathogens other than COVID-19 were not effective and had to be abandoned in the early phases of trials. The reason for the efficacy of the new mRNA vaccines is not clear. Physician-scientist Margaret Liu stated that the efficacy of the new COVID-19 mRNA vaccines could be due to the "sheer volume of resources" that went into development, or that the vaccines might be "triggering a nonspecific inflammatory response to the mRNA that could be heightening its specific immune response, given that the modified nucleoside technique reduced inflammation but hasn't eliminated it completely", and that "this may also explain the intense reactions such as aches and fevers reported in some recipients of the mRNA SARS-CoV-2 vaccines". These reactions though severe were transient and another view is that they were believed to be a reaction to the lipid drug delivery molecules. In June 2021, the US Food and Drug Administration added a warning about the possibility of increased risk of myocarditis and pericarditis for some people.
Sources: en.wikipedia.org
By far the most widely used compound in this field is 2-cyanoacrylic acid ethyl ester, while 2-cyanoacrylic acid methyl ester and allyl cyanoacrylate are used to a lesser extent. Cyanoacrylate adhesives are also applied in medicine for wound closure as an alternative to suturing. However, short-chain alkyl esters (e.g., methyl cyanoacrylate) frequently cause adverse effects, particularly inflammation; therefore, different compounds are employed in medical applications than in technical uses. In particular, butyl cyanoacrylate and 2-octyl cyanoacrylate are predominantly used. Nitriles are used as electrolyte additives in lithium batterys. For example, the addition of 1,3,6-hexanetricarbonitrile leads to a significant performance improvement compared with a corresponding battery without such an additive. The mechanism of action of nitrile additives has not yet been fully elucidated.
Creatine phosphate (CP), like ATP, is stored in muscle cells. When it is broken down, a considerable amount of energy is released. The energy released is coupled to the energy requirement necessary for the resynthesis of ATP. The total muscular stores of both ATP and CP are small. Thus, the amount of energy obtainable through this system is limited. The phosphagen stored in the working muscles is typically exhausted in seconds of vigorous activity. However, the usefulness of the ATP-CP system lies in the rapid availability of energy rather than quantity. This is important with respect to the kinds of physical activities that humans are capable of performing. The phosphagen system (ATP-PCr) occurs in the cytosol (a gel-like substance) of the sarcoplasm of skeletal muscle, and in the myocyte's cytosolic compartment of the cytoplasm of cardiac and smooth muscle. During muscle contraction:
=== KwaZulu Bantustan === KwaZulu was a bantustan in South Africa, intended by the apartheid government as a semi-independent homeland for the Zulu people. The capital was moved from Nongoma to Ulundi in 1980. It was led until its abolition in 1994 by Chief Mangosuthu Buthelezi of the Zulu royal family and head of the Inkatha Freedom Party (IFP). It was merged with the surrounding South African province of Natal to form the new province of KwaZulu-Natal. The name KwaZulu translates roughly as Place of Zulus, or more formally Zululand.
== Preparations by size == Plasmid preparation can be divided into five main categories based on the scale of the preparation: minipreparation, midipreparation, maxipreparation, megapreparation, and gigapreparation. The choice of which method to use will depend on the amount of plasmid DNA required, as well as the specific application for which it will be used. Kits are available from varying manufacturers to purify plasmid DNA, which are named by size of bacterial culture and corresponding plasmid yield. In increasing order they are: miniprep, midiprep, maxiprep, megaprep, and gigaprep. The plasmid DNA yield will vary depending on the plasmid copy number, type and size, the bacterial strain, the growth conditions, and the kit.
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 heptapeptide and a non-selective melanocortin receptor agonist. Structurally it is modelled on alpha-melanocyte-stimulating hormone, a peptide that occurs naturally in the body.