This is a working overview of cyclic heptapeptide, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-07-21. Anything still debated is marked as such rather than presented as settled.
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.
Receptor binding at MC1R on melanocytes raises intracellular cyclic AMP and increases expression of tyrosinase and related enzymes. The downstream result is greater synthesis of eumelanin, the dark pigment, without ultraviolet exposure acting as the trigger. The compound is not selective, however, and also engages MC3R, MC4R and MC5R, which are expressed in the central nervous system and elsewhere. That lack of selectivity is the explanation usually offered for effects reported outside pigmentation, including appetite suppression and nausea. Selectivity remains a central theme in comparative studies of related peptides.
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 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 |
|---|---|---|
| Chemical class | Synthetic cyclic heptapeptide | Melanocortin receptor agonist |
| Molecular formula | C50H69N15O9 | Neutral form, mass near 1024.2 g/mol |
| Primary targets | MC1R, MC3R, MC4R, MC5R | Binding is non-selective across subtypes |
| Related compounds | Alpha-MSH, melanotan I, afamelanotide | Structurally or functionally related peptides |
| Common abbreviations | MT-II, MT-2 | Naming in the literature is not uniform |
Melanotan II is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone, a naturally occurring peptide involved in pigmentation signalling. Its structure substitutes a lactam bridge between side chains to increase stability relative to the native hormone. The compound is also known by the shorthand MT-II and by several non-proprietary synonyms used in research catalogues. It is not an approved therapeutic product in any major jurisdiction; material sold under this name is typically offered as a laboratory reagent rather than as a medicine.
Activity is attributed to agonism at melanocortin receptors, particularly MC1R and MC4R. Activation of MC1R on melanocytes increases melanin synthesis, which underlies the reported tanning effect. MC4R engagement in the central nervous system is linked to appetite suppression and to effects on sexual arousal reported in early clinical studies. Those studies were small and were not designed to establish efficacy or long-term safety. Receptor selectivity among the melanocortin subtypes is not absolute, which complicates attribution of any effect to a single pathway.
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.
=== Leaderless initiation === A number of bacterial mRNAs have no 5'UTR whatsoever, or a very short one. The complete 70S ribosome, with the help of IF2 (recruiting fMet-tRNA), can simply start translating such a "leaderless" mRNA. A number of factors modify the efficiency of leaderless initiation. A 5' phosphate group attached to the start codon seems near-essential. AUG is strongly preferred in E. coli, but not necessarily in other species. IF3 inhibits leaderless initiation. A longer 5'UTR or one with significant secondary structure also inhibits leaderless initiation.
=== International === By March 2014, Dunkin' Donuts' largest international market was South Korea, representing nearly 40 percent of all international sales. With over 900 outlets in the country, it had three times as many as McDonald's and about a third more than Starbucks. South Korea is home to Dunkin' Donuts' only coffee roasting plant outside the U.S. The company still sees China and its vastly larger population as the more lucrative opportunity. In 2008, Dunkin' Donuts opened its first restaurant in Shanghai, representing the first step in its China expansion strategy. By March 2014, it had about 50 stores in the country and an agreement to open 100 more over the next five years. The operation in China is under a franchise agreement with Jollibee Foods Cooperation, but only seven stores were opened in Beijing, opposed to the planned 100. In 2022, Jollibee announced that it will end the Dunkin Donuts franchise in China to allow expansions into other markets in other regions. Since then, stores started to close and as of 2025, there are no Dunkin stores in mainland China. In Australia, Dunkin' Donuts opened in the 1980s, but by the late 2000s, they had left the Australian market. In 2014, Dunkin' Brands global chairman Nigel Travis said there were no plans in the short term to return the brand to the Australian market. Baskin-Robbins, a subsidiary of Dunkin' Brands, continues to exist in the country. In Brazil, Dunkin' Donuts opened its first building in 1980. In 2013, it planned to open 25 franchises in the country.
== Use in humidity control == There is net evaporation from a solution with a water activity greater than the relative humidity of its surroundings. There is net absorption of water by a solution with a water activity less than the relative humidity of its surroundings. Therefore, in an enclosed space, an aqueous solution can be used to regulate humidity.
Sources: en.wikipedia.org
Bluebottle fly adults feed on nectar, and they are pollinators of flowers. They are especially attracted to flowers that have strong odors, such as those that have adapted to smell like rotting meat. Plants pollinated by the fly include the skunk cabbage (Symplocarpus foetidus), American pawpaw (Asimina triloba), dead horse arum (Helicodiceros muscivorus), goldenrod and some species of the carrot family. These insects tend to fly in packs in order to detect possible food sources more efficiently. If one fly detects food, it disperses a pheromone, which will alert the others to the meal.
== Education == Tack received his Bachelor of Arts degree in physical chemistry from Princeton University in 1961 and his PhD from the University of California, Berkeley in 1965 for spectroscopic studies of photosynthesis.
The Melbourne, Australia inner-city suburbs of Richmond and Abbotsford are locations in which the use and dealing of heroin has been concentrated for a protracted time period. Research organisation the Burnet Institute completed the 2013 'North Richmond Public Injecting Impact Study' in collaboration with the Yarra Drug and Health Forum, City of Yarra and North Richmond Community Health Centre and recommended 24-hour access to sterile injecting equipment due to the ongoing "widespread, frequent and highly visible" nature of illicit drug use in the areas. During the period between 2010 and 2012 a four-fold increase in the levels of inappropriately discarded injecting equipment was documented for the two suburbs. In the local government area the City of Yarra, of which Richmond and Abbotsford are parts of, 1550 syringes were collected each month from public syringe disposal bins in 2012. Furthermore, ambulance callouts for heroin overdoses were 1.5 times higher than for other Melbourne areas in the period between 2011 and 2012 (a total of 336 overdoses), and drug-related arrests in North Richmond were also three times higher than the state average. The Burnet Institute's researchers interviewed health workers, residents and local traders, in addition to observing the drug scene in the most frequented North Richmond public injecting locations.
Sources: en.wikipedia.org
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.
Activation of MC1R increases pigment synthesis independently of ultraviolet exposure, which is the mechanism usually cited for darkening without sun exposure. Ultraviolet light still influences skin response through separate biological pathways.
Because the peptide binds several melanocortin receptor subtypes, its effects are not confined to pigmentation. This complicates interpretation of both intended and unintended outcomes reported in studies.
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.