A practical reference on melanocortin receptor: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2026-05-05. Anything still debated is marked as such rather than presented as settled.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular class | Synthetic cyclic heptapeptide | Analog of alpha-MSH with an internal lactam bridge |
| Molecular weight | Approximately 1024 daltons | Free base value; salt forms differ |
| Appearance | White to off-white powder | Usually supplied as a lyophilized solid |
| Solubility | Freely soluble in water | Poorly soluble in nonpolar solvents |
| Typical storage | −20 °C, dry, protected from light | Repeated freeze-thaw cycles degrade peptides |
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.
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.
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.
== Contraindications == Allergy to sulfonylureas or sulfonamides Diabetes mellitus type 1 Diabetic ketoacidosis Patients that underwent removal of the pancreas Acute porphyria Severe liver disease accompanying with liver insufficiency Several conditions (e.g., infectious diseases or major surgical intervention), when insulin administration is required Pregnancy or breastfeeding
== Evolution == When a synonymous or silent mutation occurs, the change is often assumed to be neutral, meaning that it does not affect the fitness of the individual carrying the new gene to survive and reproduce. Synonymous changes may not be neutral because certain codons are translated more efficiently (faster and/or more accurately) than others. For example, when a handful of synonymous changes in the fruit fly alcohol dehydrogenase gene were introduced, changing several codons to sub-optimal synonyms, production of the encoded enzyme was reduced and the adult flies showed lower ethanol tolerance. Many organisms, from bacteria through animals, display biased use of certain synonymous codons. Such codon usage bias may arise for different reasons, some selective, and some neutral. In Saccharomyces cerevisiae synonymous codon usage has been shown to influence mRNA folding stability, with mRNA encoding different protein secondary structure preferring different codons. Another reason why synonymous changes are not always neutral is the fact that exon sequences close to exon-intron borders function as RNA splicing signals. When the splicing signal is destroyed by a synonymous mutation, the exon does not appear in the final protein. This results in a truncated protein. One study found that about a quarter of synonymous variations affecting exon 12 of the cystic fibrosis transmembrane conductance regulator gene result in that exon being skipped.
In plants, light-dependent reactions occur in the thylakoid membranes of the chloroplasts where they drive the synthesis of ATP and NADPH. The light-dependent reactions are of two forms: cyclic and non-cyclic. In the non-cyclic reaction, the photons are captured in the light-harvesting antenna complexes of photosystem II by chlorophyll and other accessory pigments (see diagram "Z-scheme"). The absorption of a photon by the antenna complex loosens an electron by a process called photoinduced charge separation. The antenna system is at the core of the chlorophyll molecule of the photosystem II reaction center. That loosened electron is taken up by the primary electron-acceptor molecule, pheophytin. As the electrons are shuttled through an electron transport chain (the so-called Z-scheme shown in the diagram), a chemiosmotic potential is generated by pumping proton cations (H+) across the membrane and into the thylakoid space. An ATP synthase enzyme uses that chemiosmotic potential to make ATP during photophosphorylation, whereas NADPH is a product of the terminal redox reaction in the Z-scheme. The electron enters a chlorophyll molecule in Photosystem I. There it is further excited by the light absorbed by that photosystem. The electron is then passed along a chain of electron acceptors to which it transfers some of its energy. The energy delivered to the electron acceptors is used to move hydrogen ions across the thylakoid membrane into the lumen.
This section has also been interpreted by some doctors, most notably the authors of a commentary article published in the Journal of the American Medical Association in 2005, as meaning that prescribing HGH off-label may be considered illegal. And some articles in the popular press, such as those criticizing the pharmaceutical industry for marketing drugs for off-label use (with concern of ethics violations) have made strong statements about whether doctors can prescribe HGH off-label: "Unlike other prescription drugs, HGH may be prescribed only for specific uses. U.S. sales are limited by law to treat a rare growth defect in children and a handful of uncommon conditions like short bowel syndrome or Prader-Willi syndrome, a congenital disease that causes reduced muscle tone and a lack of hormones in sex glands." At the same time, anti-aging clinics where doctors prescribe, administer, and sell HGH to people are big business. In a 2012 article in Vanity Fair, when asked how HGH prescriptions far exceed the number of adult patients estimated to have HGH-deficiency, Dragos Roman, who leads a team at the FDA that reviews drugs in endocrinology, said "The F.D.A. doesn't regulate off-label uses of H.G.H. Sometimes it's used appropriately. Sometimes it's not."
Sources: en.wikipedia.org
Pepscan is a procedure for mapping and characterizing epitopes involving the synthesis of overlapping peptides and analysis of the peptides in enzyme-linked immunosorbent assays (ELISAs). The method is based on combinatorial chemistry and was pioneered by Mario Geysen and coworkers. Rob Meloen was one of Geysen's co-workers. He also played an important role in the development of numerous other new technologies, including vaccine and diagnostic product development for several viral diseases. From 1994 to 2010, Meloen was Professor of Special Appointment (Chair: Biomolecular Recognition) at Utrecht University. He was one of the co-founders of the company Pepscan (Lelystad, the Netherlands) and became Scientific Director (CSO). Pepscan is now part of the Biosynth Group. Twenty-five years later, the Pepscan methodology, evolved and modernized with the latest insights, is still an important part of Pepscan’s epitope mapping platform, which is instrumental in therapeutic antibody development.
Dihydrocodeine products which can be purchased over the counter in many European and Pacific Rim countries generally contain from 2 to 20 mg of dihydrocodeine per dosing unit combined with one or more other active ingredients such as paracetamol (acetaminophen), aspirin, ibuprofen, antihistamines, decongestants, vitamins, medicinal herb preparations, and other such ingredients. In a subset of these countries and foreign possessions, 30 mg tablets and 60 mg controlled-release tablets are available over the counter and chemists may very well be able to dispense the 90 and 120 mg strengths at their discretion. In the United States, the most common analgesic brands with dihydrocodeine are: DHC Plus (16 and 32 mg), Panlor SS (32 mg), ZerLor (32 mg), Panlor DC (16 mg) and Synalgos DC (16 mg). These combination products also include paracetamol (acetaminophen) and caffeine. Aspirin is used in the case of Synalgos DC. Dihydrocodeine is sometimes marketed in combination preparations with paracetamol as co-dydramol (BAN) to provide greater pain relief than either agent used singly (see Synergy § Drug synergy). In the UK and other countries, 30 mg tablets containing only dihydrocodeine as the active ingredient are available, also a 40 mg Dihydrocodeine tablet is available in the UK as DF-118 Forte. The original dihydrocodeine product, Paracodin, is an elixir of dihydrocodeine hydroiodide also available as a Tussionex-style suspension in many European countries.
These reviews suggest that lisdexamfetamine is persistently effective at treating BED and is associated with significant reductions in the number of binge eating days and binge eating episodes per week. Furthermore, a meta-analytic systematic review highlighted an open-label, 12-month extension safety and tolerability study that reported lisdexamfetamine remained effective at reducing the number of binge eating days for the duration of the study. In addition, both a review and a meta-analytic systematic review found lisdexamfetamine to be superior to placebo in several secondary outcome measures, including persistent binge eating cessation, reduction of obsessive-compulsive related binge eating symptoms, reduction of body-weight, and reduction of triglycerides. Lisdexamfetamine, like all pharmaceutical amphetamines, has direct appetite suppressant effects that may be therapeutically useful in both BED and its comorbidities. Based on reviews of neuroimaging studies involving BED-diagnosed participants, therapeutic neuroplasticity in dopaminergic and noradrenergic pathways from long-term use of lisdexamfetamine may be implicated in lasting improvements in the regulation of eating behaviors that are observed.
The association between nucleotide excision repair capability and longevity is strengthened by the evidence that defects in nucleotide excision repair proteins in humans and rodents cause features of premature aging, as reviewed by Diderich. Further support for the theory that DNA damage is the primary cause of aging comes from study of Poly ADP ribose polymerases (PARPs). PARPs are enzymes that are activated by DNA strand breaks and play a role in DNA base excision repair. Burkle et al. reviewed evidence that PARPs, and especially PARP-1, are involved in maintaining mammalian longevity. The life span of 13 mammalian species correlated with poly(ADP ribosyl)ation capability measured in mononuclear cells. Furthermore, lymphoblastoid cell lines from peripheral blood lymphocytes of humans over age 100 had a significantly higher poly(ADP-ribosyl)ation capability than control cell lines from younger individuals.
According to Analayo, each of the twelve nidanas "re-quires all five aggregates to be in existence concurrently." Furthermore:The teaching on dependent arising does not posit the existence of any of the links in the abstract, but instead show how a particular link, as an aspect of the continuity of the five aggregates, has a conditioning influence on another link. It does not imply that any of these links exist apart from the five aggregates.
Sources: en.wikipedia.org
==== Damage-associated molecular patterns ==== Extracellular heat-shock proteins can be sensed by the immune system as damage-associated molecular patterns (DAMPs). They are able to interact with pattern recognition receptors like TLR2 or TLR4 and activate antigen presenting cells by upregulation of co-stimulation molecules (CD80, CD86, CD40), MHC molecules and pro-inflammatory and Th1 cytokines. HSP70 was shown to react to DAMP release, causing an influx of HSP70-positive T-EVs (tumor cells) that initiate anti-tumor immune signaling cascades. Heat-shock proteins can signal also through scavenger receptors, which can either associate with TLRs, or activate pro-inflammatory intracellular pathways like MAPK or NF-kB. With the exception of SRA, which down-regulates immune response.
Urinary tract infection Skin infection Respiratory tract infection Odontogenic infection (an infection that originates within a tooth or in the closely surrounding tissues) Vaginal infections Intra-amniotic infection In addition, locations of inflammation where infection is the most common cause include pneumonia, meningitis and salpingitis.
==== Iraq War ==== Hitchens employed the term "Islamofascist" and supported the Iraq War, causing his critics to consider him a "neoconservative". Hitchens, however, refused to embrace this designation, insisting, "I'm not any kind of conservative". In 2004, Hitchens stated that neoconservative support for US intervention in Iraq convinced him that he was "on the same side as the neo-conservatives" when it came to contemporary foreign policy issues, and characterized himself as an unqualified "supporter of Paul Wolfowitz." He referred to his associations as "temporary neocon allies". In this period he opined that "the Bush administration [...] has redefined the lazy term 'conservative' to mean someone who is impatient with the status quo." In the years after the fatwa issued against Salman Rushdie in response to his novel The Satanic Verses, Hitchens became increasingly critical of what he called "excuse making" on the left. At the same time, he was attracted to the foreign policy ideas of some on the Republican-right that promoted pro-liberalism intervention, especially the neoconservative group that included Paul Wolfowitz. Around this time, he befriended the Iraqi dissident and businessman Ahmed Chalabi. Hitchens argued the case for the Iraq War in a 2003 collection of essays entitled A Long Short War: The Postponed Liberation of Iraq, and participated in public debates on the topic with George Galloway, Scott Ritter, and his brother Peter Hitchens.
=== Use in alternative medicine === Practitioners of alternative medicine have advocated the use of hydrogen peroxide for various conditions, including emphysema, influenza, AIDS, and in particular cancer. Medical authorities and regulatory agencies warn that such uses are unsupported by scientific evidence and can be dangerous. Ingesting or injecting hydrogen peroxide, even in so-called “food-grade” concentrations, has led to serious adverse effects and fatalities. Both the effectiveness and safety of hydrogen peroxide therapy is scientifically questionable. Hydrogen peroxide is produced by the immune system, but in a carefully controlled manner. Cells called phagocytes engulf pathogens and then use hydrogen peroxide to destroy them. The peroxide is toxic to both the cell and the pathogen and so is kept within a special compartment, called a phagosome. Free hydrogen peroxide will damage any tissue it encounters via oxidative stress, a process that also has been proposed as a cause of cancer. Claims that hydrogen peroxide therapy increases cellular levels of oxygen have not been supported. The quantities administered would be expected to provide very little additional oxygen compared to that available from normal respiration. It is also difficult to raise the level of oxygen around cancer cells within a tumour, as the blood supply tends to be poor, a situation known as tumor hypoxia. Large oral doses of hydrogen peroxide at a 3% concentration may cause irritation and blistering to the mouth, throat, and abdomen as well as abdominal pain, vomiting, and diarrhea.
In the Post-Vulgate cycle and Thomas Malory's Le Morte d'Arthur, the wound of the Maimed King, Pellehan (Pellam in Malory) was given to him by Balin in the "Dolorous Stroke", when Balin grabs a spear and stabs Pellam in self-defense. However, the spear is the Spear of Longinus, the lance that pierced Christ's side, and Pellam and his land must suffer for its misuse until the coming of Galahad. The Dolorous Stroke is typically represented as divine vengeance for a sin on the part of its recipient. The nature of Pellam's sin is not stated explicitly, though he at least tolerates his murderous brother Garlon, who slays knights while under cover of invisibility, apparently at random. King Pelles is one of a line of Grail keepers established by Joseph, and the father of Eliazer and Elaine (the mother of Galahad). He resides in the castle of Corbenic in Listenois. In the Vulgate, Pelles is the son of Pellehan, but the Post-Vulgate is less clear about their relationship. It is even murkier in Malory's work: one passage explicitly identifies them (book XIII, chapter 5), though this is contradicted elsewhere. In all, there are four characters (some of whom can probably be identified with each other) who fill the role of Fisher King or Wounded King in Malory's Le Morte d'Arthur.
Sources: en.wikipedia.org
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.
Melanotan-1, also called afamelanotide, is a shorter linear analog with a different amino acid sequence and no lactam ring. It has been evaluated in formal clinical programs, while melanotan-2 has not. The two are distinct molecules and are not interchangeable.
No. Bremelanotide is a related but distinct cyclic peptide that reached approved status for one specific clinical indication. Melanotan-2 is a separate molecule with its own sequence and properties. Shared ancestry in the melanocortin family does not make them the same substance.
No. Melanotan-2 is manufactured synthetically. The naturally occurring peptide in the same family is alpha-melanocyte-stimulating hormone, which the body produces as part of normal endocrine and neural signalling.