If you have been reading about melanocortin receptor 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 2025-12-16. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
Receptor-binding studies classify melanotan II as a non-selective melanocortin agonist. It interacts with MC1R, MC3R, MC4R and MC5R, with reported affinities in the low nanomolar range and no strong subtype preference. Activation of MC1R on dermal melanocytes shifts pigment synthesis toward eumelanin, the dark polymer deposited in melanosomes and transferred to keratinocytes. Because the same peptide engages MC4R in the hypothalamus, it also appears in animal work on food intake and erectile response, which is why it is discussed in both pigment and metabolic research. Which receptor populations dominate after systemic exposure in humans is not fully established.
Published pharmacokinetic information is limited and comes mainly from small studies rather than registrational trials. Plasma half-life is usually described as short, on the order of tens of minutes, followed by rapid tissue distribution and clearance of the intact peptide. Metabolites and low concentrations of parent compound have been reported in urine, a detail relevant to anti-doping and forensic testing. Whether repeated exposure changes receptor sensitivity or clearance over time remains an open question. Values differ noticeably between analytical assays, so published numbers should be read as approximate rather than definitive.
Melanotan II is a synthetic cyclic heptapeptide with the sequence Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, corresponding to a molecular formula of C50H69N15O9 and a monoisotopic mass near 1024 daltons. It was designed as a structural analogue of alpha-melanocyte-stimulating hormone, a peptide hormone produced by cleavage of proopiomelanocortin. A lactam bridge between the aspartate and lysine side chains closes the ring, and the C-terminal amide removes a free carboxyl group. Both modifications increase resistance to enzymatic degradation compared with the linear parent hormone. Four substitutions distinguish it from afamelanotide, the linear analogue studied under the name melanotan I.
| Property | Value | Notes |
|---|---|---|
| Compound class | Synthetic cyclic heptapeptide | Alpha-MSH analogue containing a D-phenylalanine residue |
| Molecular formula | C50H69N15O9 | Average molecular mass approximately 1024.2 g/mol |
| Appearance | White to off-white lyophilised powder | Normally supplied as a freeze-dried solid in a sealed vial |
| Solubility | Freely soluble in water and polar solvents | Dissolves readily in aqueous buffers and in alcohol-water mixtures |
| Receptor targets | MC1R, MC3R, MC4R, MC5R | Acts as a non-selective melanocortin receptor agonist |
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.
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.
== Casualties == In total, Georgia suffered three combat fatalities (all in 2008) and at least 19 servicemen were injured in Iraq. In addition, one Georgian serviceman died in a car accident and one committed suicide, both in 2007.
(2026) study the evolution of amphibious hearing in pinnipeds on the basis of data from extant and extinct representatives of the group and their relatives, link its evolution to the evolution of cavernous tissue in pinniped ear canal and middle ear, and report evidence of presence of amphibious hearing in the last common ancestor of "enaliarctines" and modern pinnipeds but not in more basal members of the pinniped stem group. The first pinniped fossil from Taiwan (a femur of a member of the genus Zalophus from the Pleistocene strata from the bottom of the Taiwan Strait) is described by Sun et al. (2026). Dewaele et al. (2026) study the long bone variability of extant earless seals, finding no evidence of consistently clear genus- or species-specific shapes, and note the need for reevaluation of validity of fossil taxa described on the basis of isolated long bones. Postcranial earless seal bones with distinctive morphology are reported from the Miocene strata from Hrytsiv (Ukraine; the type locality of Planopusa semenovi) by Otriazhyi et al. (2026). Dewaele (2026) revises the fossil record of earless seals from the Miocene strata of the Chesapeake Group (Maryland and Virginia, United States), reporting evidence of presence of three seal morphotypes in the studied fossil material.
== External links == Histology image: 77_04 at the University of Oklahoma Health Sciences Center – "Slide 77 skeletal muscle" Anatomy Atlases – Microscopic Anatomy, plate 05.83 – "Smooth Muscle" Diagram at kctcs.edu
Muscular dystrophies may be X-linked recessive, autosomal recessive, or autosomal dominant. Diagnosis often involves blood tests and genetic testing. There is no cure for any disorder from the muscular dystrophy group. Several drugs designed to address the root cause are currently available including gene therapy (Elevidys), and antisense drugs (Ataluren, Eteplirsen etc.). Other medications used include glucocorticoids (Deflazacort, Vamorolone); calcium channel blockers (Diltiazem); to slow skeletal and cardiac muscle degeneration, anticonvulsants to control seizures and some muscle activity, and Histone deacetylase inhibitors (Givinostat) to delay damage to dying muscle cells. Physical therapy, braces, and corrective surgery may help with some symptoms while assisted ventilation may be required in those with weakness of breathing muscles. Outcomes depend on the specific type of disorder. Many affected people will eventually become unable to walk and Duchenne muscular dystrophy in particular is associated with shortened life expectancy. Muscular dystrophy was first described in the 1830s by Charles Bell. The word "dystrophy" comes from the Greek dys, meaning "no, un-" and troph- meaning "nourish".
Sources: en.wikipedia.org
== History == Fosfomycin (originally known as phosphonomycin) was discovered in a joint effort of Merck and Co. and Spain's Compañía Española de Penicilina y Antibióticos (CEPA). It was first isolated by screening broth cultures of Streptomyces fradiae isolated from soil samples for the ability to cause formation of spheroplasts by growing bacteria. The discovery was described in a series of papers published in 1969. CEPA began producing fosfomycin on an industrial scale in 1971 at its Aranjuez facility.
=== Clinical trials and early approvals for diabetes === In June 2008, a phase II clinical trial began studying semaglutide, a once-weekly diabetes therapy as a longer-acting alternative to liraglutide. It was given the brand name Ozempic. Clinical trials started in January 2016 and ended in May 2017. The US Food and Drug Administration (FDA) approved semaglutide based on evidence from seven clinical trials of 4087 participants with type 2 diabetes. The trials were conducted at 536 sites in 33 countries, including Canada, Mexico, Russia, Ukraine, Turkey, India, South Africa, Japan, Hong Kong, multiple European countries, Argentina, and the United States. In two of these trials (NCT02054897 and NCT02305381), participants were randomly assigned to receive either semaglutide or placebo injection weekly. Neither the participant nor the health care provider knew which treatment was being given until after the trials were completed. Treatment was given for 30 weeks. In the other five trials (NCT01930188, NCT01885208, NCT02128932, NCT02207374, and NCT02254291), participants were randomly assigned to receive either semaglutide or another anti-diabetic medication, and the participant and provider knew which medication was being given in four trials. Treatment was given for 30 weeks or 56 weeks. In each trial, HbA1c was measured from the start of the trial to the end of the trial and compared between the semaglutide group and the other groups.
Isotope analysis is the determination of isotopic signature, the relative abundances of isotopes of a given element in a particular sample. Isotope analysis is frequently done by isotope ratio mass spectrometry. For biogenic substances in particular, significant variations of isotopes of C, N, and O can occur. Analysis of such variations has a wide range of applications, such as the detection of adulteration in food products or the geographic origins of products using isoscapes. The identification of certain meteorites as having originated on Mars is based in part upon the isotopic signature of trace gases contained in them. Isotopic substitution can be used to determine the mechanism of a chemical reaction via the kinetic isotope effect. Another common application is isotopic labeling, the use of unusual isotopes as tracers or markers in chemical reactions. Normally, atoms of a given element are indistinguishable from each other. However, by using isotopes of different masses, even different nonradioactive stable isotopes can be distinguished by mass spectrometry or infrared spectroscopy. For example, in 'stable isotope labeling with amino acids in cell culture (SILAC)' stable isotopes are used to quantify proteins. If radioactive isotopes are used, they can be detected by the radiation they emit (this is called radioisotopic labeling).
Cyproheptadine, sold under the brand name Periactin among others, is a first-generation antihistamine which is used to treat allergies. In addition, it has a number of off-label uses, such as treatment of serotonin syndrome, insomnia, and use as an appetite stimulant. The drug is taken orally. It is an antihistamine and hence acts as a histamine H1 receptor antagonist. In addition to its antihistamine activity, cyproheptadine has anticholinergic, antiserotonergic, antidopaminergic, and local anesthetic properties. These activities make cyproheptadine useful for various additional uses besides antihistamine indications. As a first-generation antihistamine, cyproheptadine crosses the blood–brain barrier and can produce sedation. The drug can also produce significant central anticholinergic effects at clinically used doses. Cyproheptadine was patented in 1959 and came into medical use in 1961. In 2023, it was the 234th most commonly prescribed medication in the United States, with more than 1 million prescriptions.
== In popular culture == In Monty Python's Life of Brian (1979), some people mishear parts of the Sermon on the Mount's beatitudes, including "Blessed are the cheesemakers" rather than "Blessed are the peacemakers" (Matthew 5:9). Cheesemaking has served as the theme of several fictional works and games. This includes Fromage, a 2024 strategy board game.
Sources: en.wikipedia.org
=== Supercritical fluid decomposition === Supercritical water can be used to decompose biomass via supercritical water gasification of biomass. This type of biomass gasification can be used to produce hydrocarbon fuels for use in an efficient combustion device or to produce hydrogen for use in a fuel cell. In the latter case, hydrogen yield can be much higher than the hydrogen content of the biomass due to steam reforming where water is a hydrogen-providing participant in the overall reaction.
=== Non-cardiac conditions === The distinction between cardiac and non-cardiac conditions is somewhat artificial; the conditions listed below are not primary heart diseases, but they exert indirect effects on the heart muscle. Other conditions that directly or indirectly lead to heart muscle damage and death can also increase troponin levels, such as kidney failure. Cardiac troponins are increased in around 40% of patients with critical illnesses such as sepsis. There is an increased risk of mortality and length of stay in the intensive-care unit in these patients. In severe gastrointestinal bleeding, there can also be a mismatch between oxygen demand and supply of the myocardium.
==== Wounded child, no surviving family ==== One of the most difficult aspects of the medical crisis in Gaza is “wounded child, no surviving family” (WCNSF). As of February 2025, the United Nations has reported roughly 25,000 such cases in Gaza; with no relatives left, clinicians become the children's sole caregivers and advocates, which complicates treatment decisions and long-term care planning. For children lacking any family support, the confusion and distress that accompany serious injuries are magnified many times over. Disrupted access to healthcare also triggers cascading physical, psychological, and social harms that demand responses beyond routine medical practice. Providers must address immediate needs as well as rehabilitation, mental-health support, and coordination with social services without family involvement. These challenges differ markedly from typical adult care.
== Other == Apical foramen, the hole at the tip of the root of a tooth Foramen ovale (heart), a hole between the venous and arterial sides of the fetal heart Transverse foramen, one of a pair of openings in each cervical vertebra, in which the vertebral artery travels Greater sciatic foramen, a major foramen of the pelvis Interventricular foramina, channels connecting ventricles in the brain Lesser sciatic foramen, an opening between the pelvis and the posterior thigh Obturator foramen, the hole created by the ischium and pubis bones of the pelvis Omental foramen, the connecting opening between the greater sac and the lesser sac in the abdominal cavity Sacral foramina, which perforate the vertebral canal from the Sacrum (sacral bone), and through which the sacral nerves pass Vertebral foramen, the foramen formed by the anterior segment (the body), and the posterior part, the vertebral arch Foramen of Panizza, a hole connecting two aortas just after they leave the heart in crocodiles
Sources: en.wikipedia.org
No. It is a laboratory-made peptide, while the natural hormone is alpha-melanocyte-stimulating hormone, a longer peptide produced by the pituitary gland and by skin cells. Melanotan-2 mimics only a short active region of that hormone and contains non-natural residues such as D-phenylalanine.
No approved regulatory indication exists in major markets. An approval exists for a different peptide, afamelanotide, which is used for a rare photosensitivity disorder called erythropoietic protoporphyria. Melanotan-2 itself remains a research compound with no cleared clinical role.
Melanocortin-1 receptors on melanocytes are the receptor most closely linked to pigment production. The peptide is not selective, however, and also activates melanocortin-3, melanocortin-4, and melanocortin-5 receptors. That lack of selectivity is the usual explanation offered for both its range of observed effects and its off-target effects.
No. It is a synthetic analogue carrying four amino acid changes, a lactam ring and an amidated C-terminus. The natural hormone is a linear thirteen-amino-acid peptide processed from proopiomelanocortin.