If you have been reading about cyclic peptide and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Updated 2026-08-01. Numbers and descriptions here follow the published literature rather than marketing material.
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controlled human data on melanotan-2 remain sparse, and much of what circulates online derives from small studies or unpublished reports.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.
Melanotan-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone. Its sequence incorporates a lactam bridge that constrains the peptide into a ring, which increases resistance to enzymatic breakdown relative to the natural hormone. Researchers at the University of Arizona synthesised the compound in the late 1980s and early 1990s while studying pigmentation pathways. It has never received marketing approval from any national medicines regulator. In the scientific literature it is usually described as a laboratory research reagent rather than a therapeutic product.
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.
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.
Regulatory treatment varies between countries. Several national medicines agencies have classified the peptide as unapproved, and customs authorities in some jurisdictions seize shipments on that basis. A few jurisdictions channel supply through prescription-only frameworks that do not list the substance by name. Because the material circulates mainly through online vendors, composition and purity are rarely verified before sale. Surveys of unapproved peptide products have reported labels that did not match measured content in a substantial fraction of samples.
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.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic cyclic heptapeptide | Alpha-MSH analogue with a lactam ring |
| Molecular formula | C50H69N15O9 | Commonly cited value for the neutral peptide |
| Molecular weight | 1024.18 g/mol | Calculated for the free molecule |
| Appearance | White to off-white powder | Typically supplied as a lyophilised solid |
| Solubility | Soluble in water, DMSO and ethanol | Dissolution in pure water is often slow |
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.
=== January 2004 === January 3: Marwan Hassoun and his cousin Zaydun Al-Samarrai are taken from their broken-down truck at about curfew time and forced to jump from the Tharthar dam into the Tigris River; the latter drowns. First Lt. Jack M. Saville and Sgt. 1st Class Tracy E. Perkins were charged on 2004 June 7 with manslaughter, assault, conspiracy, making false statements, and obstruction of justice. Sgt. Reggie Martinez was charged three weeks later with manslaughter and for making false statements, and Spec. Terry Bowman with assault and making false statements. Martinez' and Bowman's charges were dropped; Perkins got six months in jail. Saville was jailed (45 days) and fined $12,000 for assault but he remained on active duty until his military obligation was fulfilled.
== Awards and honours == 1998 Founders Award for Excellence from the Canadian College of Medical Geneticists. 1996 Honoured by Human Genome Organization at a special presentation in Heidelberg. 1996 Fellow of the American Association for the Advancement of Science. Fellow of the Canadian College of Medical Geneticists.
=== August === August 1 A mass shooting occurs at an In-N-Out in Twin Falls, Idaho, leaving four dead (including the perpetrator) and seven injured. The Marine Corps reports that an F-35B stealth warplane crashed in California, but the pilot bailed safely. Cyberwarfare during the Iran war: The New York Times reports, citing state and local officials, that evidence leads to Iran in a series of cyberattacks against water systems in at least seven US states, with Michigan being the second state to report the attacks publicly. August 2 – 2026 Iran war: Following Qatari diplomatic efforts to avert planned strikes and reopen the Strait of Hormuz, and concerns raised by Saudi Crown Prince Mohammed bin Salman over the proposed operation, Trump says that the United States and Israel have called off an attack on Iran after Tehran requested additional time to reach an agreement. Trump nevertheless stresses that the United States remains prepared to launch a large-scale bombing campaign against Iran. August 3 – The Supreme Court declines to halt a $655 million judgement against Palestinian authorities for attacks that killed and maimed Americans in Israel from 2002 to 2004. August 4 – The Women's National Basketball Association (WNBA) announces that the expansion team in Cleveland, Ohio, will be called the Sirens. The organization will debut in 2028. August 5 Drive-thru chain Salad and Go files for Chapter 11 bankruptcy and closes all 70 of its locations across Arizona and Nevada, citing the 2026 cyclosporiasis outbreak as part of the reason for declining business.
== Hydrogen-7 == 7H (atomic mass 7.05275(108) Da) has one proton and six neutrons. It was first synthesized in 2003 by a group of Russian, Japanese and French scientists at Riken's Radioactive Isotope Beam Factory by bombarding hydrogen with helium-8 atoms; all six of the helium-8's neutrons were donated to the hydrogen nucleus. The two remaining protons were detected by the "Riken telescope", a device made of several layers of sensors, positioned behind the target of the RI Beam cyclotron. 7H has a half-life of 652(558) ys (6.52(558)×10−22 s).
Sources: en.wikipedia.org
=== Hypothyroidism === Hyperthyroidism due to certain types of thyroiditis can eventually lead to hypothyroidism (a lack of thyroid hormone), as the thyroid gland is damaged. Also, radioiodine treatment of Graves' disease often eventually leads to hypothyroidism. Such hypothyroidism may be diagnosed with thyroid hormone testing and treated by oral thyroid hormone supplementation.
The enzyme converts the precursor (6R)-2-acetyl-6-(3-acetyl-2,4,6-trihydroxy-5-methylphenyl)-3-hydroxy-6-methylcyclohexa-2,4-dien-1-one into (S)-usnic acid using oxidised nicotinamide adenine dinucleotide (NAD+) as cofactor and forming an ether bond. This enzyme belongs to the family of oxidoreductases, specifically those acting on the CH-OH group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is reduced-(S)-usnate:NAD+ oxidoreductase (ether-bond-forming). This enzyme is also called L-usnic acid dehydrogenase.
He convened researchers from the diverse fields converging on this newly recognized family of receptors and proposed a unifying nomenclature. Springer described the first sequence relationships among family members and was the first to use an αβ nomenclature in which α subunits were named after their receptor, such as αL for LFA-1 and αM for Mac-1. However, because the meeting was focused on fibronectin, the fibronectin receptor was designated α5β1, conferring the β1 designation on the subunit that pairs with more α subunits than any other β subunit in the family. The ones discovered by Springer on white blood cells became the β2 integrins. Contributions by Springer, Hynes, and Ruoslahti to the integrin field were recognized by the 2022 Lasker Basic Medical Research Award.
During its fourth year, Gearbox began working on its first independently owned game: Brothers in Arms: Road to Hill 30. Developed for PC and Microsoft's Xbox console, and built with the Unreal Engine 2, it was released in March 2005. The sequel, Brothers in Arms: Earned in Blood, followed seven months later. The series was published by Ubisoft, who supported both games with PlayStation 2 versions, and later worked with it to develop Brothers in Arms games for portable systems (mobile phones, PlayStation Portable and Nintendo DS) and the Wii home console. In 2005, Gearbox licensed the Unreal Engine 3 from Epic Games, to replace the Unreal Engine 2 technology used in previous games, and grew its internal development teams to handle the demands of next-generation technology and content. Brothers in Arms: Hell's Highway was the first new title to be announced, continuing the company's flagship franchise. Brothers in Arms: Hell's Highway was launched in September 2008. By 2008, the franchise also spun off a comic book series, a two-part television documentary, a line of action figures, and a novelization and non-fiction history book.
(CH2CH2)O + C2H5OH → HO–CH2CH2–OC2H5 2 (CH2CH2)O + C2H5OH → HO–CH2CH2–O–CH2CH2–OC2H5 Reactions with lower alcohols occur less actively than with water and require more severe conditions, such as heating to 160 °C (320 °F) and pressurizing to 3 MPa (440 psi) and adding an acid or alkali catalyst. Reactions of ethylene oxide with fatty alcohols proceed in the presence of sodium metal, sodium hydroxide, or boron trifluoride and are used for the synthesis of surfactants.
Sources: en.wikipedia.org
It is a synthetic cyclic heptapeptide modelled on alpha-melanocyte-stimulating hormone. A lactam bridge links two side chains, forming a ring that stabilises the molecule against proteolysis. It belongs to the broader melanocortin peptide family.
No national medicines agency has approved melanotan-2 for clinical use. Afamelanotide, a related but distinct peptide, holds a marketing authorisation in the European Union for a rare photosensitivity disorder. Melanotan-2 itself is handled as a laboratory chemical.
Its broad activity across melanocortin receptors makes it a tool for probing pigmentation, appetite and vascular signalling. Early trials recorded skin darkening and other effects that were not the original focus of the work. Those observations generated hypotheses that later studies have examined.
No. No major regulatory agency has granted a marketing authorisation for melanotan II as a medicine. Products sold under this name are generally presented as laboratory reagents and are not subject to the batch-release testing applied to approved drugs.