cyclic peptide comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Last reviewed on 2025-09-26. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
Melanotan-2 is a synthetic peptide designed as an analog of alpha-melanocyte-stimulating hormone, a signaling molecule produced in the pituitary and skin. Its structure is a linear chain of seven amino acids that folds into a ring through an internal lactam bridge joining two side chains. The compound is sometimes written as MT-II or MEL-2 in informal and commercial contexts. It belongs to the melanocortin peptide family, a group of short signaling molecules that share a conserved core sequence recognized by melanocortin receptors.
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.
| 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 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.
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.
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.
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.
Voriconazole, sold under the brand name Vfend among others, is an antifungal medication used to treat a number of fungal infections. This includes aspergillosis, candidiasis, coccidioidomycosis, histoplasmosis, penicilliosis, and infections by Scedosporium or Fusarium. It can be taken by mouth or used by injection into a vein. Common side effects include vision problems, nausea, abdominal pain, rash, headache, and hallucinations. Use during pregnancy may result in harm to the fetus. It is in the triazole family of medications., and works by affecting fungal metabolism and fungal cell membranes. Voriconazole was patented in 1990 and approved for medical use in the United States in 2002. It is on the World Health Organization's List of Essential Medicines.
== Software and tools == Software tools for bioinformatics include simple command-line tools, more complex graphical programs, and standalone web-services. They are made by bioinformatics companies or by public institutions.
== After Liberation == Smolková-Keulemansová suffered from dysentery, jaundice, typhus and tuberculosis after liberation. She could not give an address to anyone she knew in Prague, so the International Red Cross did not allow her to return to her country of origin. To receive medical treatment, she was selected to go to Sweden for a six-month recovery stay with 6,000 other prisoners.
=== Iodine-131 tositumomab (Bexxar) and Zevalin (90Y-ibritumomab tiuxetan) for non-Hodgkin's lymphoma === Bexxar, a radioligand therapy using the radioisotope I-131+Tositumomab (a murine monoclonal antibody) and binding/targeting the ligand CD20 on human B-cells. CD20 is a membrane spanning protein found on B-cell lymphocytes that is a tumor marker as it is in higher concentration in cancer patients — specifically leukemias or lymphomas (like non-hodgkin's lymphoma).
Monitoring a person's health over time after treatment. This includes keeping track of the health of people who participate in a clinical study or clinical trial for a period of time, both during the study and after the study ends. (NCI) Food and Drug Administration (FDA)
Sources: en.wikipedia.org
In an interview, Taub commented that his visit was proof that "the people of Bradford [have] sent a clear message that George Galloway does not represent them." Galloway told a reporter from the BuzzFeed website: "As has just been proved, I cannot make Bradford an Israel-free zone, but I am certain that the Israeli ambassador was not welcome." Galloway accused the councillors who had invited the ambassador of fraternising with a "mouthpiece for murder". West Yorkshire Police investigated two complaints to determine if Galloway's words constituted hate speech (British law prohibits discrimination based on nationality). Galloway was questioned under caution by the police and the matter was referred to the Crown Prosecution Service. Galloway subsequently criticised the police investigation, describing it as "an absolute and despicable attempt to curb my freedom of speech". In October 2014, it emerged that Galloway would not be prosecuted for his comments on the grounds of "insufficient evidence", although West Yorkshire Police had "recorded this matter as a hate incident." On 29 August 2014, Galloway was assaulted in Notting Hill by Neil Masterson, a convert to Judaism, and suffered a bruised rib and severe bruising on his head and face and was hospitalised overnight. Masterson was charged with religiously aggravated assault and sentenced to 16 months in prison. Released from prison in September 2015, he soon returned to jail for a month after breaking a restraining order forbidding him from contacting Galloway. Masterson was also fined for harassment.
== Regulations and law enforcement == Chinese law states that industrial-grade animal fat is not allowed for use in food products because it does not meet basic hygiene standards and may contain high levels of potentially toxic contaminants. The national and local governments are researching ways to test and identify gutter oil but as of 2012 there were no nationwide standards in place to help with this process. The government is looking into methods that rely on technical equipment as well as on-site instant tests to screen suspect oil. There are five proposed tests for gutter oil but each has failed to accurately detect it. Due to China's vast industry of factories involved with legal waste oil processing to create products like plastics, rubbers, fuels, soaps, etc., there have been abundant rumors and allegations about unscrupulous middlemen selling gutter oil for cooking and frying. However, it remains difficult to prove and prosecute such profiteers. Food safety articles funded by PRC provincial science grants attribute continued difficulties in regulatory enforcement to the decentralized nature of the logistics chain, inadequate national infrastructure for disposal/recycling, and frequent innovations in visually and chemically disguising gutter oil. In August and September 2011, the Beijing city government passed two new sets of regulations. The first was "On Accelerating the City's Food Waste and Waste Oil Recycling Program". Its goals are to increase daily food waste processing to 2,200 tons by 2012 and to 2,900 tons by 2015.
The water normally used to quench steel will also be in short supply, and require strong agitation. Casting steel can be a difficult process in microgravity, requiring special heating and injection processes, or spin forming. Heating can be performed using sunlight combined with electrical heaters. The casting process would also need to be managed to avoid the formation of voids as the steel cools and shrinks. Various metal-working techniques can be used to shape the metal into the desired form. The standard methods are casting, drawing, forging, machining, rolling, and welding. Both rolling and drawing metals require heating and subsequent cooling. Forging and extrusion can require powered presses, as gravity is not available. Electron beam welding has already been demonstrated on board the Skylab, and will probably be the method of choice in space. Machining operations can require precision tools which will need to be imported from the Earth for some duration. New space manufacturing technologies are being studied at places such as Marshall's National Center for Advanced Manufacturing. The methods being investigated include coatings that can be sprayed on surfaces in space using a combination of heat and kinetic energy, and electron beam free form fabrication of parts. Approaches such as these, as well as examination of material properties that can be investigated in an orbiting laboratory, will be studied on the International Space Station by NASA and Made In Space, Inc.
Robert Joseph Wittman (born February 3, 1959) is an American politician and environmental health specialist serving as the U.S. representative for Virginia's 1st congressional district since 2007. A member of the Republican Party, his district contains portions of the Richmond suburbs and Hampton Roads area, as well as the Northern Neck and Middle Peninsula.
Sources: en.wikipedia.org
Mescaline, also known in chemical terms as 3,4,5-trimethoxyphenethylamine, is a naturally occurring psychedelic drug and alkaloid of the phenethylamine and scaline families found in certain cacti like peyote (Lophophora williamsii) and the San Pedro cactus (Echinopsis pachanoi, others). The drug is used recreationally, spiritually, and medically, with psychedelic effects occurring at doses of 100 to 800 mg (as its hydrochloride salt) orally and it can be used in pure form or in the form of mescaline-containing cacti. Mescaline induces a psychedelic experience characterized by visual changes, altered perception of time, space, and self, synesthesia, and spiritual experiences, with an onset of 30 to 60 minutes, a time to peak of 2 to 4 hours, and a duration that increases with dose and ranges from 6 to 14 hours. Mescaline primarily acts as a partial agonist at serotonin 5-HT2A receptors, with varying affinity and efficacy across multiple other receptors and targets. The serotonin 5-HT2A receptor antagonist ketanserin blocks mescaline's psychoactive effects. Mescaline is a relatively hydrophilic compound structurally related to dopamine, first synthesized in 1919, with numerous synthetic methods and potent analogues developed since. It occurs naturally in various cacti species, with concentrations varying widely, and is biosynthesized in plants from amino acids like phenylalanine and tyrosine. The practice of humans consuming mescaline-containing cacti dates back over 6,000 years.
Leslie Hicks is an American full professor of analytical chemistry at the University of North Carolina at Chapel Hill. Her work primarily focuses on the study of proteomics and protein post-translational modifications using mass spectrometry, and identifying biologically active peptides in plants.
== Adverse effects == As a "non-sedating" antihistamine, loratadine causes less (but still significant, in some cases) sedation and psychomotor retardation than the older antihistamines, because it penetrates the blood/brain barrier less. Headache is also a possible side effect. Unlike earlier-generation antihistamines, loratadine is considered largely free of antimuscarinic effects (urinary retention, dry mouth, blurred vision).
25 Jan&1 Sep) mimicking neurons' communication, is reported. 9 November IBM unveils its 433-qubit 'Osprey' quantum processor, the successor to its Eagle system. A study shows that 50+ aged users of the dietary program SNAP "had about 2 fewer years of cognitive aging over a 10-year period compared with non-users" despite it having nearly no conditions for the sustainability and healthiness of the food products purchased with the coupons (or coupon-credits). 10 November A study describes how one may eventually be able to detect (distinguish) wormholes, suggesting they may have never been observed because they appear very similar to black holes. Notable software developments: After domain seizures of Z-Library by copyright law enforcement and moves toward dark web and IPFS technologies by its content providers, the open source shadow library UI Anna's Archive – which also provides access to a full copy of Z-Library content and scientific articles – is established by a team of archivists, essentially providing the largest human book and literature library. News outlets report about the development of a post-editing model using GPT-3 that improves machine translations after identification of current translation problems (8 Nov/25 Oct). The largest global inventory and interactive map of greenhouse gas emission sources is released by Climate TRACE (9 Nov).
Additionally, models accounting for the simultaneous effect of pH, micelle and organic concentration have been suggested. These models allow for further enhancement of the optimization of the separation of weak acids and bases. One research group, Rukhadze, et al. derived a first order linear relationship describing the influence of micelle and organic concentration, and pH on the selectivity and resolution of seven barbiturates. The researchers discovered that a second order mathematical equation would more precisely fit the data. The derivations and experimental details are beyond the scope of this discussion. The model was successful in predicting the experimental conditions necessary to achieve a separation for compounds which are traditionally difficult to resolve. Jandera, Fischer, and Effenberger approached the modeling problem in yet another way. The model used was based on lipophilicity and polarity indices of solutes. The lipophilicity index relates a given solute to a hypothetical number of carbon atoms in an alkyl chain. It is based and depends on a given calibration series determined experimentally. The lipophilicity index should be independent of the stationary phase and organic modifier concentration. The polarity index is a measure of the polarity of the solute-solvent interactions. It depends strongly on the organic solvent, and somewhat on the polar groups present in the stationary phase. 23 compounds were analyzed with varying mobile phases and compared to the lipophilicity and polarity indices.
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 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.