This is a working overview of melanocortin receptor, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2025-11-10. Anything still debated is marked as such rather than presented as settled.
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.
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-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.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic cyclic heptapeptide | Belongs to the melanocortin agonist family |
| Key substitutions | Nle4 and D-Phe7 | Improve resistance to enzymatic degradation |
| Molecular formula | C50H69N15O9 | Approximately 1024 g/mol |
| Regulatory status | Not approved as a medicine | Distributed as a research chemical |
| Common synonyms | Melanotan II, MT-II, MT-2 | Spelling varies across sources |
Melanotan-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone, the naturally occurring peptide involved in pigmentation signalling. Its sequence is conventionally written as Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, with a lactam bridge joining the aspartate side chain to the lysine side chain. The empirical formula is C50H69N15O9 and the monoisotopic mass lies near 1023.5 daltons. N-terminal acetylation and the D-configured phenylalanine both increase resistance to enzymatic breakdown compared with the parent hormone.
Pharmacologically, melanotan-2 behaves as a non-selective agonist across the melanocortin receptor family. Binding at MC1R on dermal melanocytes promotes eumelanin synthesis, which underlies the tanning response described in early human work. Activity at the centrally expressed MC4R receptor is associated with reported effects on appetite and erectile function. Because the peptide does not discriminate strongly among receptor subtypes, attributing any single observed effect to one receptor pathway is generally not possible without selective antagonists or receptor knockout models.
Research interest has centred on photoprotection and pigmentation, with a smaller body of work on appetite and sexual function. Published human data remain limited to small, frequently uncontrolled studies, and the compound has never received marketing approval from a national medicines regulator. Most laboratory work treats it as a pharmacological tool for probing melanocortin signalling in cell culture or animal models. Whether pigmentation changes observed in people translate into measurable protection against ultraviolet-induced DNA damage remains an open question.
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.
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.
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.
== Management == Initial therapy of the major rheumatological diseases is with analgesics, such as paracetamol and non-steroidal anti-inflammatory drugs (NSAIDs). Steroids, especially glucocorticoids, and stronger analgesics are often required for more severe cases.
=== Natural occurrence === Due to the short half-life of all isotopes of einsteinium, any primordial einsteinium—that is, einsteinium that could have been present on Earth at its formation—has long since decayed. Synthesis of einsteinium from naturally occurring uranium and thorium in the Earth's crust requires multiple neutron capture, an extremely unlikely event. Therefore, all einsteinium on Earth is produced in laboratories, high-power nuclear reactors, or nuclear testing, and exists only within a few years from the time of the synthesis. The transuranic elements up to fermium, including einsteinium, should have been present in the natural nuclear fission reactor at Oklo, but any quantities produced then would have long since decayed away. The absorption spectrum of einsteinium has been detected in Przybylski's Star, along with other actinide elements.
Each snake that has venom contains various haemorrhagins that cause the hemorrhage and damage of living tissues. Majority of snake venoms contain the zinc metalloproteinase like AaH I. These zinc metallproteinase have similar active sites to matrix metallproteimase which are responsible for degrading proteins of the extracellular matrix. Snake venom metallproteinase are able to work on collagen in connective tissues. Which means they are a part of the MMP super-family and help design drugs for anti-tumor and anti-arthritis. Because of this, they are great for learning more about the mechanisms of ligand-receptor interaction and cell-cell interaction. The agkistrodon acutus venom in particular contains a protein called ACTX-6 which can induce apoptosis. Apoptosis is forced cell death through morphological changes that lead to death. There are multiple ways that cells naturally die this way. Agkistrodon acutus venom can induce this cell death in cancer cells through the Fas pathway activation. Fas is a receptor for death in cells that when turned on will cause a caspase cascade. Which is a pathway made up of series of proteins called initiator and executioner caspases. Where initiator caspases help form apoptosis initiation factor that eventually activates executioner caspases. Executioner caspases procedure to eat the cell from the inside out by cleaving cytoskeleton filaments and DNA until the cell implodes.
Sources: en.wikipedia.org
Bicalutamide: A pure antiandrogen. It is effective similarly to flutamide but is much safer as well as better-tolerated. Birth control pills that consist of an estrogen, usually ethinylestradiol, and a progestin are supported by the evidence. They are functional antiandrogens. In addition, certain birth control pills contain a progestin that also has antiandrogenic activity. Examples include birth control pills containing cyproterone acetate, chlormadinone acetate, drospirenone, and dienogest. Cyproterone acetate: A dual antiandrogen and progestogen. In addition to single form, it is also available in some formulations of combined oral contraceptives at a low dosage (see below). It has a risk of liver damage. Eflornithine: Blocks putrescine that is necessary for the growth of hair follicles. Finasteride and dutasteride: 5α-Reductase inhibitors. They inhibit the production of the potent androgen DHT. A meta-analysis showed inconsistent results of finasteride in the treatment of hirsutism. Flutamide: A pure antiandrogen. It has been found to possess equivalent or greater effectiveness than spironolactone, cyproterone acetate, and finasteride in the treatment of hirsutism. However, it has a high risk of liver damage and hence is no longer recommended as a first- or second-line treatment. Flutamide is safe and effective. GnRH analogues: Suppress androgen production by the gonads and reduce androgen concentrations to castrate levels. Metformin: Insulin sensitizer.
Lenton Parr AM, founding dean, 1972–1975 William Kelly, 1975–1982 John Walker, 1982–1985 Gareth Sansom, 1986–1991 Norman Baggaley, 1991–1997 Mostyn Bramley-Moore, 1997–1999 Su Baker, 2000–2010 Barry Conyngham, 2010–2021 Marie Sierra, 2021–present
Motion of the cephalopods is usually backward as water is forced out anteriorly through the hyponome, but direction can be controlled somewhat by pointing it in different directions. Some cephalopods accompany this expulsion of water with a gunshot-like popping noise, thought to function to frighten away potential predators. Cephalopods employ a similar method of propulsion despite their increasing size (as they grow) changing the dynamics of the water in which they find themselves. Thus their paralarvae do not extensively use their fins (which are less efficient at low Reynolds numbers) and primarily use their jets to propel themselves upwards, whereas large adult cephalopods tend to swim less efficiently and with more reliance on their fins.
Sources: en.wikipedia.org
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.
No regulatory agency has approved it for any indication. It is encountered as a research chemical sold outside pharmaceutical supply chains. Products marketed this way are not subject to the manufacturing and labeling requirements that apply to approved drugs.
Reports describe increased skin pigmentation as well as side effects such as nausea, flushing, and changes to existing moles. Much of the evidence comes from small studies and case reports rather than large trials. The long-term safety profile is therefore uncertain.
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.