The short version of MC1R fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-08-01. Anything still debated is marked as such rather than presented as settled.
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.
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.
The peptide was developed during the 1980s by researchers investigating melanocortin signalling and skin pigmentation pathways. Early work focused on analogues of alpha-melanocyte-stimulating hormone that would resist enzymatic breakdown more effectively than the parent molecule. Melanotan-2 emerged from that programme as a shortened, cyclised variant. Reports describing its synthesis and receptor activity later appeared in the scientific literature. Commercial availability grew through unregulated channels rather than through pharmaceutical approval.
Structurally, Melanotan-2 retains the core recognition motif of alpha-melanocyte-stimulating hormone while adding a lactam bridge that links two side chains and constrains the molecule into a ring. This modification lowers susceptibility to enzymatic degradation. The compound acts as an agonist at melanocortin receptors, particularly subtypes associated with melanin production. Because the same receptor family influences several physiological processes, researchers note that its activity is not confined to pigmentation alone. Receptor selectivity continues to be examined in published studies.
Melanotan-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone, a naturally occurring peptide involved in pigmentation signalling. Its sequence incorporates modified residues that increase potency and extend biological activity relative to the native hormone. The compound binds receptors of the melanocortin family and is examined mainly in laboratory research. It does not occur naturally and exists only as a manufactured chemical entity produced by solid-phase synthesis.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C50H69N15O9 | Free base; salt forms differ |
| Molecular weight | Approximately 1024 g/mol | Calculated for the free base |
| Appearance | White to off-white powder | Typically supplied as a lyophilised solid |
| Solubility | Soluble in water and polar solvents | Poorly soluble in non-polar solvents |
| Typical storage | -20 degrees Celsius, dry, protected from light | Refers to the solid form |
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 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.
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.
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-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.
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.
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.
== Historical introduction == The concept of chemical equilibrium was developed in 1803, after Berthollet found that some chemical reactions are reversible. For any reaction mixture to exist at equilibrium, the rates of the forward and backward (reverse) reactions must be equal. In the following chemical equation, arrows point both ways to indicate equilibrium. A and B are reactant chemical species, S and T are product species, and α, β, σ, and τ are the stoichiometric coefficients of the respective reactants and products:
1 March to 14 August Operation Kentucky Jumper was a clear and search operation conducted by the 101st Airborne Division, 9th Infantry Division and ARVN 3rd Regiment, 1st Division in Thừa Thiên Province. The operation resulted in 317 PAVN/VC killed for the loss of 61 U.S. killed.
A wide range of potential structures have been reported. These all feature the classical organophosphorus core (sometimes with the P=O replaced with P=S or P=Se), which is most commonly depicted as being a phosphoramidate or phosphonate, usually fluorinated (cf. monofluorophosphate). The organic groups are subject to more variety; however, a common substituent is phosgene oxime or analogues thereof. This is a potent chemical weapon in its own right, specifically as a nettle agent, and would be expected to increase the harm done by the Novichok agent. Many claimed structures from this group also contain cross-linking agent motifs which may covalently bind to the acetylcholinesterase enzyme's active site in several places, perhaps explaining the rapid denaturing of the enzyme that is claimed to be characteristic of the Novichok agents. Zoran Radić, a chemist at the University of California, San Diego, performed an in silico docking study with Mirzayanov's version of the A-232 structure against the active site of the acetylcholinesterase enzyme. The model predicted a tight fit with high binding affinity and formation of a covalent bond to a serine residue in the active site, with a similar binding mode to established nerve agents such as sarin and soman.
RaTG13 was sampled from bats in a mine in Mojiang County, Yunnan, located roughly 1,500 km (930 mi) away from Wuhan, and there are relatively few bat coronaviruses from Hubei province, where Wuhan is located.
Sources: en.wikipedia.org
== Donor selection == When grafts are taken from other animals, they are known as heterografts or xenografts. By definition, they are temporary biologic dressings which the body will reject within days to a few weeks. They are useful in reducing the bacterial concentration of an open wound, as well as reducing fluid loss. For more extensive tissue loss, a full-thickness skin graft, which includes the entire thickness of the skin, may be necessary. This is often performed for defects of the face and hand where contraction of the graft should be minimized. The general rule is that the thicker the graft, the less the contraction and deformity. Cell cultured epithelial autograft (CEA) procedures take skin cells from the person needing the graft to grow new skin cells in sheets in a laboratory; because the cells are taken from the person, that person's immune system will not reject them. However, because these sheets are very thin (only a few cell layers thick) they do not stand up to trauma, and the "take" is often less than 100%. Newer grafting procedures combine CEA with a dermal matrix for more support.Research is investigating the possibilities of combining CEA and a dermal matrix in one product. Experimental procedures are being tested for burn victims using stem cells in solution which are applied to the burned area using a skin cell gun. Recent advances have been successful in applying the cells without damage.
Nicotinamide, as a part of the cofactor nicotinamide adenine dinucleotide (NADH / NAD+), is crucial to life. In cells, nicotinamide is incorporated into NAD+ and nicotinamide adenine dinucleotide phosphate (NADP+). NAD+ and NADP+ are cofactors in a wide variety of enzymatic oxidation-reduction reactions, most notably glycolysis, the citric acid cycle, and the electron transport chain. If humans ingest nicotinamide, it will likely undergo a series of reactions that transform it into NAD, which can then undergo a transformation to form NADP+. This method of creation of NAD+ is called a salvage pathway. However, the human body can produce NAD+ from the amino acid tryptophan and niacin without ingestion of nicotinamide. NAD+ acts as an electron carrier that mediates the interconversion of energy between nutrients and the cell's energy currency, adenosine triphosphate (ATP). In oxidation-reduction reactions, the active part of the cofactor is the nicotinamide. In NAD+, the nitrogen in the aromatic nicotinamide ring is covalently bonded to adenine dinucleotide. The shared electrons of the other carbon atoms in the aromatic ring stabilize the formal charge on the nitrogen. When a hydride atom is added onto NAD+ to form NADH, the molecule loses its aromaticity and therefore a good amount of stability. This higher-energy product later releases its energy by donating a hydride, and in the case of the electron transport chain, it assists in forming adenosine triphosphate. When one mole of NADH is oxidized, it releases 158.2 kJ of energy.
Cohen and the McCartneys agreed on the condition that Lisa remain a vegetarian, with both satisfied with how the episode turned out. In the episode, Lisa decides to stop eating meat after bonding with a lamb at a petting zoo. Her schoolmates and family members ridicule her for her beliefs, but with the help of Apu as well as Paul and Linda McCartney, she commits to vegetarianism. The staff promised that she would remain a vegetarian, resulting in one of the few permanent character changes made in the show. In an August 2020 interview, McCartney said that he and his wife were worried that Lisa "would be a vegetarian for a week, then Homer would persuade her to eat a hot dog," but were assured by the producers that she would remain that way, and he was delighted that they "kept their word." In September 1998, the King of the Hill episode "And They Call It Bobby Love" aired on FOX. In the episode, "Bobby has a relationship with a vegetarian named Marie. She later dumps him after he eats a steak in front of her." In the March 2002 South Park episode "Fun with Veal", Stan Marsh becomes a vegetarian after he learns that veal is made of baby cows, which Cartman makes fun of. The episode ends with the boys, including Stan, getting grounded, but not before going out with their parents for burgers, meaning that Stan is no longer a vegetarian. In the DVD commentary, the creators said they wanted to balance their message of not eating baby animals, by at the same time not advocating people abstain from meat consumption altogether.
== National variants == Similar meat and pastry recipes include the Czech klobásník, the Belgian worstenbroodje, the Dutch saucijzenbroodje, the German Münsterländer Wurstbrötchen and sausage bread in the United States. Hong Kong has developed its own style of sausage roll. Instead of having sausage meat wrapped in puff pastry like the traditional Western style, the Hong Kong style "sausage bun" (Chinese: 腸仔包) consists of a sausage wrapped inside a soft milk bread style bun.
=== Antibody-directed enzyme prodrug therapy === Antibody-directed enzyme prodrug therapy (ADEPT) involves the application of cancer-associated monoclonal antibodies that are linked to a drug-activating enzyme. Systemic administration of a non-toxic agent results in the antibody's conversion to a toxic drug, resulting in a cytotoxic effect that can be targeted at malignant cells. The clinical success of ADEPT treatments is limited.
Sources: en.wikipedia.org
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.
Both are synthetic analogues derived from the same parent hormone. Reference descriptions usually characterise afamelanotide as more selective for the MC1R subtype, whereas melanotan-2 is reported to interact with a wider range of melanocortin receptors.
Early studies explored melanocortin signalling and pigmentation, which later led to informal use of the label tanning peptide. That label is not a regulatory category and does not imply approved status for any purpose.
It is a synthetic cyclic heptapeptide and an analogue of alpha-melanocyte-stimulating hormone. The molecule is produced by chemical synthesis rather than extracted from a biological source.