A practical reference on melanocortin receptor: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2026-07-19 and is reviewed periodically as new material appears.
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.
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.
Reversed-phase high-performance liquid chromatography is the routine method for purity assessment. Peptides absorb near 214 nm because of the peptide bond, and a gradient of acetonitrile in water separates the intact peptide from deletion sequences, oxidised products, and earlier-eluting fragments at neutral pH. Electrospray ionisation mass spectrometry provides an orthogonal check: the measured mass must agree with the theoretical value. Amino acid analysis and peptide mapping confirm structure but are used less often. Reference standards remain scarce because the peptide is not described in any pharmacopoeia.
Regulatory treatment varies by country. In the United States the peptide is not approved as a medicine, and products offered for human use may be treated as unapproved new drugs; some states also restrict sale. Australia, the United Kingdom, and European Union member states apply comparable restrictions to unapproved peptide products. Border agencies have seized shipments labelled as research chemicals. Classification may change over time, and the legal position for personal importation is not clearly settled in most published guidance.
| 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 |
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 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.
Identity and purity are assessed mainly by reversed-phase high-performance liquid chromatography with ultraviolet detection, often paired with mass spectrometry. Retention time supports identity, while the mass spectrum confirms the molecular weight of the intact peptide. Purity is frequently reported as a percentage of total peak area, a figure that depends on the wavelength, column and gradient used. Impurity profiling may also look for truncated sequences, oxidised forms and residual counterions. Amino acid analysis and peptide mapping provide orthogonal confirmation when required.
Regulatory status varies by jurisdiction, and the substance is frequently described as unapproved for therapeutic use. Some authorities classify it alongside prescription-only medicines or controlled categories, while others address it through general consumer protection rules. Analytical surveys have reported mismatches between label claims and measured content in products sold online, although the scope of such testing is limited. Whether these discrepancies are widespread remains an open question. Discussion in the literature therefore tends to combine chemistry, supply-chain observation and policy analysis.
== Applications == The SDS-PAGE in combination with a protein stain is widely used in biochemistry for the quick and exact separation and subsequent analysis of proteins. It has comparatively low instrument and reagent costs and is an easy-to-use method. Because of its low scalability, it is mostly used for analytical purposes and less for preparative purposes, especially when larger amounts of a protein are to be isolated. Additionally, SDS-PAGE is used in combination with the western blot for the determination of the presence of a specific protein in a mixture of proteins - or for the analysis of post-translational modifications. Post-translational modifications of proteins can lead to a different relative mobility (i.e. a band shift) or to a change in the binding of a detection antibody used in the western blot (i.e. a band disappears or appears). In mass spectrometry of proteins, SDS-PAGE is a widely used method for sample preparation prior to spectrometry, mostly using in-gel digestion. In regards to determining the molecular mass of a protein, the SDS-PAGE is a bit more exact than an analytical ultracentrifugation, but less exact than a mass spectrometry or - ignoring post-translational modifications - a calculation of the protein molecular mass from the DNA sequence. In medical diagnostics, SDS-PAGE is used as part of the HIV test and to evaluate proteinuria. In the HIV test, HIV proteins are separated by SDS-PAGE and subsequently detected by Western Blot with HIV-specific antibodies of the patient, if they are present in his blood serum.
Crenarchaeol is mainly attributed to ammonium-oxidizing Nitrososphaerota and has four cyclopentane rings plus one cyclohexane ring, which distinguishes it from GDGT-4 and is unique to the Nitrososphaerota phylum. The evolution of the cyclohexane ring was likely to adjust the density of the membrane packing to more optimally function at the cooler ocean temperatures to which Nitrososphaerota adapted. Due to their structural similarities, crenarchaeol and GDGT-4 have similar GC/MS elution times. They are similar in prevalence to GDGT-0 and therefore are not included in the TEX86 paleothermometer because their abundance overwhelms the less abundant GDGT groups. A crenarchaeol regioisomer, however, is a part of the TEX86 paleothermometer. This isomer likely differs by having a cis configuration on the cyclopentane ring neighboring the additional cyclohexane ring. It is presumed to be also made by Nitrososphaerota.
She said that "This has nothing to do with tension or relations between Delcy Rodriguez and myself," and discussed that the "criminal structure" that has dominated Venezuela for years would eventually dismantle itself. A week later, Trump said he was considering involving Machado in his plans on Venezuela in some way, without specifying which role she would play. On 26 January, after a hearing on Venezuela on the US Senate, Marco Rubio met with Machado. She later said to reporters that a change in Venezuela was coming. Venezuelan TV network Venevisión broadcast Machado message after meeting with Rubio. According to the Venezuelan national press workers union, the state regulator later cut Venevision's access to some satellite TV providers. In an interview of NBC, Delcy Rodríguez said about Machado that "She will have to answer to Venezuela why she called upon a military intervention, why she called upon sanctions to Venezuela, and why she celebrated the actions that took place at the beginning of January." At Machado's request, she met for a second time with Donald Trump in the White House on 6 March to review plans for her trip to come back to Venezuela. In September 2026, Machado's reported about seven failed attempts to enter the country by air and sea, at least three while Delcy Rodríguez was away during a UN General Assembly.
=== Photobiont === The photobiont partner of Parmotrema perlatum is from Trebouxia, a green algal genus belonging to the order Trebouxiales (order Chlorophyta). It has been identified as an undescribed species within a clade containing Trebouxia arboricola. A study compared the desiccation tolerance and physiological responses of lichenised Trebouxia to isolated cultures of the same alga. Both forms can survive extended desiccation, but with differing responses to photo-oxidative stress. Lichenisation enhances the photoprotective mechanisms of Trebouxia, improving quenching of excess light energy, particularly under high relative humidity, and controlling reactive oxygen species production under light exposure. However, isolated cultures showed better photosynthetic performance after desiccation recovery. This research demonstrates the mutual benefits of the lichen-photobiont partnership, where the alga gains a sheltered environment boosting its resilience to environmental stressors. Further studies on Parmotrema perlatum revealed specific antioxidant mechanisms supporting its photobiont under stress. The lichen shows high levels of reactive oxygen species scavenging enzymes such as superoxide dismutase and ascorbate peroxidase, protecting the photobiont from oxidative damage during dehydration and rehydration cycles. This enhanced antioxidant system provides not only physical shelter but also biochemical protection, increasing the photobiont's resilience to environmental fluctuations.
Sources: en.wikipedia.org
27 May – First Minister Humza Yousaf accuses the UK government of sabotaging a pilot recycling scheme, the Deposit Return Scheme, by excluding glass from the project, glass having been a key part of Scottish proposals for the scheme. 31 May Thomas Henderson, who along with his co-accused, murdered a man during a botched robbery at the deceased man's Dundee flat, is sentenced to life prison ent th a minimum of 18 years. A huge wildfire covering 30 square miles (80 km2), possibly the largest ever seen in the UK, is brought under control by the Scottish Fire and Rescue Service at Cannich in the Highlands.
=== Branched polymers === A monomer with functionality of 3 or more will introduce branching in a polymer and will ultimately form a cross-linked macrostructure or network even at low fractional conversion. The point at which a tree-like topology transits to a network is known as the gel point because it is signalled by an abrupt change in viscosity. One of the earliest so-called thermosets is known as Bakelite. It is not always water that is released in step-growth polymerization: in acyclic diene metathesis or ADMET, dienes polymerize with loss of ethene.
Apollo 11 left lunar orbit and returned to Earth, landing safely in the Pacific Ocean on July 24, 1969. When the spacecraft splashed down, 2,982 days had passed since Kennedy's commitment to landing a man on the Moon and returning him safely to the Earth before the end of the decade; the mission was completed with 161 days to spare. With the safe completion of the Apollo 11 mission, the Americans won the race to the Moon. Armstrong and his crew became worldwide celebrities, feted with ticker-tape parades on August 13 in New York City and Chicago, attended by an estimated six million. That evening in Los Angeles they were honored at an official state dinner attended by members of Congress, 44 governors, the Chief Justice of the United States, and ambassadors from 83 nations. The President and Vice president presented each astronaut with the Presidential Medal of Freedom. The astronauts spoke before a joint session of Congress on September 16, 1969. This began a 38-day world tour to 22 foreign countries and included visits with the leaders of many countries. The public's reaction in the Soviet Union was mixed. The Soviet government limited the release of information about the lunar landing, which affected the reaction. A portion of the populace did not give it any attention, and another portion was angered by it. The first landing was followed by another, precision landing on Apollo 12 in November 1969, within walking distance of the Surveyor 3 spacecraft which landed on April 20, 1967.
Pakistan was ranked 99th in the Global Innovation Index by 2025. The 1960s marked the rise of Pakistan's space program, led by SUPARCO, yielding advancements in rocketry, electronics, and aeronomy. Notably, Pakistan launched its first rocket into space, pioneering South Asia's space exploration. In 1990, it successfully launched its first satellite, becoming the first Muslim nation and second in South Asia to achieve this milestone.
=== Emerging fields === Photopharmacology is an emerging approach in medicine in which drugs are activated and deactivated with light. The energy of light is used to change for shape and chemical properties of the drug, resulting in different biological activity. This is done to ultimately achieve control when and where drugs are active in a reversible manner, to prevent side effects and pollution of drugs into the environment. Epigenetic therapy may offer an alternative 'master switch' to gene therapy to introduce persistent changes to the phenotype. Aging is well-known to be measurable through epigenetic clock. Drugs may induce persistent changes. When they cause drugs to lose efficacy, it is called drug tolerance. On the other hand, they may introduce benign changes to the body. Psychoplastogen produce profound effects by regulating neuroplasticity. Psychostimulants prevent grey matter loss in ADHD patients, at therapeutic doses.
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.
Low temperature slows hydrolysis and oxidation, the two main routes by which the peptide backbone and side chains are modified. A lyophilised powder stored at −20 °C is more stable than one kept at room temperature, and once the material is dissolved the degradation rate rises, making refrigeration more important.