This is a working overview of MC1R, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-04-15. Anything still debated is marked as such rather than presented as settled.
Receptor studies place melanotan-2 among non-selective melanocortin agonists, binding MC1R, MC3R, MC4R and MC5R rather than a single subtype. Activation of MC1R on cutaneous melanocytes raises tyrosinase activity and shifts pigment synthesis toward eumelanin, which is darker and more photostable than pheomelanin. Central receptors, particularly MC4R, are associated with appetite suppression and with reported effects on sexual function. Because subtype selectivity is low, the same molecule engages pigment, metabolic and vascular pathways at once, and this breadth is a common explanation offered for the range of adverse events described in user reports.
No regulatory authority has approved melanotan-2 for human use, and several countries classify it as a prescription-only or controlled substance, which restricts lawful supply. Material sold online is generally labelled as a research chemical and is not required to meet pharmaceutical standards of identity or purity. Published human data consist mainly of small uncontrolled studies, case reports and adverse-event notifications, so the evidence base is descriptive rather than confirmatory. Whether repeated melanocyte stimulation alters long-term naevus behaviour remains an open question that no completed trial has resolved.
Melanotan-2 is a synthetic cyclic heptapeptide designed as a structural analogue of alpha-melanocyte-stimulating hormone, the endogenous tridecapeptide that regulates pigment production. Two modifications distinguish it from the natural hormone: norleucine replaces methionine at the N-terminus, which limits oxidation, and a D-phenylalanine substitution raises receptor affinity. The ring is closed through an aspartate-lysine lactam bridge, giving the molecule a constrained conformation. The free base has a molecular mass near 1024 daltons, and commercial material is usually supplied as an acetate salt. It appears in the literature as a research peptide rather than an approved therapeutic agent.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C50H69N15O9 | Free base; salt forms add to total mass |
| Molecular mass | About 1024 daltons | Calculated for the free base |
| Structural class | Cyclic heptapeptide | Contains D-phenylalanine and norleucine |
| Parent hormone | Alpha-melanocyte-stimulating hormone | Endogenous tridecapeptide of 13 residues |
| Receptor profile | Non-selective melanocortin agonist | Interacts with MC1R, MC3R, MC4R and MC5R |
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.
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 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.
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.
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.
While paramedics in the US have carried naloxone for decades, law enforcement officers in many states throughout the country carry naloxone to reverse the effects of heroin overdoses when reaching the location before paramedics. As of 12 July 2015, law enforcement departments in 28 US states are allowed to or required to carry naloxone to quickly respond to opioid overdoses. Programs training fire personnel in opioid overdose response using naloxone have also shown promise in the US, and efforts to integrate opioid fatality prevention into emergency response have grown due to the US overdose crisis. Following the use of the nasal spray device by police officers on Staten Island in New York, an additional 20,000 police officers began carrying naloxone in mid-2014. The state's Office of the Attorney General provided US$1.2 million to supply nearly 20,000 kits. Police Commissioner William Bratton said: "Naloxone gives individuals a second chance to get help". Emergency Medical Service Providers (EMS) routinely administer naloxone, except where basic Emergency Medical Technicians are prohibited by policy or by state law. In efforts to encourage citizens to seek help for possible opioid overdoses, many states have adopted Good Samaritan laws that provide immunity against certain criminal liabilities for anybody who, in good faith, seeks emergency medical care for either themselves or someone around them who may be experiencing an opioid overdose.
Because ODTs are soft in nature, the ability to successfully package an ODT in a bottle is difficult. However, CIMA Labs markets their Durasolv ODT as being able to be placed into bottle for commercial sale, while CIMA's Orasolv is marketed for blisters only. Zydis ODT tablets manufactured by Catalent Pharma Solutions and Lyophilized Freeze drying tablets manufactured by Galien-LPS are delivered in a blister pack. The differences between the two CIMA products are proprietary, however, the primary difference is expected to be the use of microcrystalline cellulose (MCC), such as Avicel PH101, in the Durasolv product. MCC serves multiple purposes in an ODT but in the case of CIMA's products, it acts as a binder, increasing the internal strength of the tablet and making it more robust for packaging in bottles.
=== Aerobic regeneration of NAD+ and further catabolism of pyruvate === In aerobic eukaryotes, a complex mechanism has developed to use the oxygen in air as the final electron acceptor, in a process called oxidative phosphorylation. Aerobic prokaryotes, which lack mitochondria, use a variety of simpler mechanisms.
Sources: en.wikipedia.org
==== On the culture of secrecy ==== David Bandurski, journalist and researcher at China Media Project, criticised the state's control of the media for suppressing "information critical to the well-being of ordinary Chinese". He asserted that increased press freedom needs to be a component of any strategy to deal with this and other future food-security lapses in China. Bandurski cited warnings on 9 October 2008 issues of Nanfang Daily and the Information Times for consumers to be aware of that problematic dairy stock (that produced before 14 September) have reappeared in some stores under cover of aggressive promotions. Former senior party official Bao Tong said "the more dark secrets are exposed, the better. You can't cure the disease, or save the Chinese people, until you get to the root of the problem." "If the Chinese government tries to play down this incident, there will be no social stability in China, let alone harmony ... It will mean that this government has lost the most basic level of trust."
== Catabolism and excretion == Steroids are primarily oxidized by cytochrome P450 oxidase enzymes, such as CYP3A4. These reactions introduce oxygen into the steroid ring, allowing the cholesterol to be broken up by other enzymes into bile acids. These acids can then be eliminated by secretion from the liver in bile. The expression of the oxidase gene can be upregulated by the steroid sensor PXR when there is a high blood concentration of steroids. Steroid hormones, lacking the side chain of cholesterol and bile acids, are typically hydroxylated at various ring positions or oxidized at the 17 position, conjugated with sulfate or glucuronic acid and excreted in the urine.
This would be the driving force behind Morpheus' descent into fanatical terrorism against the system in an attempt to force the machines to reveal Neo's fate; ultimately leading to his assassination. The subject of Neo then fell to the side lines for other struggles; until the arrival of the Oligarchs in Chapter 9. The original intruder, Halborn, was notably intrigued by the life of the One and was personally shocked about the implications of Neo's ability to affect Machines outside of the simulation had on his search for what he called the "Biological Interface Program". After Halborn's removal in Chapter 10, little more was questioned until the revelation of the Trinity project, originally headed by the Oracle, in Chapter 12. It was revealed that both Neo and Trinity were actually the culmination of decades of machine research into translating human DNA perfectly into machine code; allowing them to interface directly with technology without the need for simulated interfaces.
Sources: en.wikipedia.org
== Protein turnover in the exercise science == Four weeks of aerobic exercise has been shown to increase skeletal muscle protein turnover in previously unfit individuals. A diet high in protein increases whole body turnover in endurance athletes. Some bodybuilding supplements claim to reduce the protein breakdown by reducing or blocking the number of catabolic hormones within the body. This is believed to increase anabolism. However, if protein breakdown falls too low then the body would not be able to remove muscle cells that have been damaged during workouts which would in turn prevent the growth of new muscle cells.
Traditional balance of power theory … fails to explain state behavior in the post-Cold War era. Since the end of the Cold War, the United States has been expanding its economic and political power. More recently, it has begun to engage in increasingly unilateralist military policy… [Y]et despite these growing material capabilities, major powers such as China, France, Germany, India, and Russia have not responded with significant increases in their defense spending. Nor have they formed military coalitions to countervail US power, as the traditional balance of power theory would predict.
=== No development reported === AB-1224 – microbiome modulator AGX-201 (histamine dihydrochloride salt) – histamine H1 receptor antagonist and histamine H3 receptor agonist Aminolevulinic acid/sodium ferrous citrate (5-ALA-SFC, 5-ALA/SFX; sodium ferrous citrate/aminolevulinic acid; SPP-003) – erythropoiesis stimulant and photosensitizer Aripiprazole transdermal (AQS-1301; transdermal aripiprazole) – dopamine D2 and D3 receptor partial agonist, serotonin 5-HT1A and 5-HT7 receptor partial agonist, serotonin 5-HT2A and 5-HT2B receptor antagonist or inverse agonist, and atypical antipsychotic BAER-101 (AZ-7325; AZD-7325) – selective GABAA α2 and α3 subunit-containing receptor positive allosteric modulator BBP-472 – phosphatidylinositol 3 kinase β (PI3Kβ) inhibitor Fasoracetam co-crystallised (co-crystallised fasoracetam; AEVI-004) – various actions and racetam Guanfacine once-daily (Guanfacine Carrier Wave; SPD-547) – α2-adrenergic receptor agonist KBLP-010 – bacteria replacement and microbiome modulator Oxytocin intranasal (OPN-300; OptiNose oxytocin) – oxytocin receptor agonist Research programme: allosteric modulators - Addex Therapeutics (various) – various actions Research programme: antisense oligonucleotide therapeutics - RogCon U.R (RCUR-313, RCUR-SMP) – voltage-gated sodium channel Nav1.2 expression stimulants Research programme: autism and obesity therapeutics - Berand Neuropharmacology – histone deacetylase inhibitors Research programme: brain development disorder therapeutics - Seaside Therapeutics (STX-110) – metabotropic glutamate mGlu5 receptor antagonists and muscarinic acetylcholine M1 receptor antagonists Research programme: cannabinoid receptor modulators - GW Pharmaceuticals (cannabigerol; CBG) – cannabinoid receptor modulators Research programme: cannabis extract therapeutics - Cannabis Science (CBIS compounds) – cannabinoid receptor modulators Research programme: central nervous system therapeutics - AbbVie/Rugen – undefined mechanism of action Research programme: CNS disorder therapeutics - Promentis Pharmaceuticals – antioxidants, glutamate receptor modulators, SLC7A11 modulators Research programme: CNS disorders therapeutics - Sage Therapeutics (SAGE-105; SGE-202; SGE-301; SGE-516) – GABAA receptor modulators and ionotropic glutamate NMDA receptor modulators Research programme: G protein-coupled receptor modulating small molecules - Omeros Corporation – G protein-coupled receptor modulator and neuromedin U receptor modulator Research programme: GPCR modulators - Nxera Pharma – various actions Research programme: immunomodulating bacteria-based therapeutics - 4D Pharma – bacteria replacements Research programme: metabotropic glutamate receptor 5 antagonists - Roche/Seaside Therapeutics – metabotropic glutamate mGlu5 receptor antagonists Research programme: oxytocin intranasal - Pastorus Pharma – neurotransmitter modulators/oxytocin receptor agonists Research programme: therapeutic autoantibodies - Sengenics – undefined mechanism of action RG-7713 (RG7713) – vasopressin V1A receptor antagonist Tideglusib (AMO-02, NP-031112, NP-12; Nypta, Zentylor) – glycogen synthase kinase 3β (GSK-3β) inhibitor Vafidemstat (ORY-2001) – dual lysine specific demethylase 1 (LSD1) inhibitor and monoamine oxidase B (MAO-B) inhibitor Xenon (NBTX-001) – ionotropic glutamate NMDA receptor antagonist
Sources: en.wikipedia.org
No regulatory agency has authorised melanotan-2 as a medicine for any indication. It circulates mainly as a research chemical or through unregulated channels. As a result, identity, purity and content are not independently guaranteed.
Melanotan-1, also called afamelanotide, is a linear analogue with greater selectivity for MC1R and has received approval in some jurisdictions for a specific photosensitivity disorder. Melanotan-2 is cyclic, less selective, and reaches central receptors more readily. The two are often confused in online discussion despite different pharmacology and regulatory status.
Alpha-MSH is an endogenous tridecapeptide derived from pro-opiomelanocortin. Melanotan-2 reproduces its core receptor-binding sequence inside a shortened, stabilised ring. The result is a molecule with a longer effective half-life and higher potency than the parent hormone.
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.