This is a working overview of melanocortin receptor, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-08-01 and is reviewed periodically as new material appears.
Independent verification is central to quality control because the compound is not produced under pharmaceutical manufacturing standards. Third-party laboratories can measure purity, identity, residual solvents, and microbial contamination, though the scope of testing varies between services. Reported analyses of vendor samples have shown batch-to-batch variation in peptide content and the presence of truncated or oxidized species. How much of this variation reflects synthesis conditions versus storage and shipping is not well characterized. No harmonized reference standard exists for the material as sold.
Handling guidance for melanotan II follows general practice for small synthetic peptides rather than a product-specific monograph. Lyophilized powder is typically kept at minus twenty degrees Celsius or colder, protected from light and moisture, because warmth and humidity accelerate degradation. Once reconstituted, solutions are usually refrigerated and used within a short window, as hydrolysis and microbial growth both become concerns. Repeated freeze-thaw cycles are generally avoided. These conventions come from laboratory peptide chemistry and not from formal stability studies on this specific compound.
Activity is attributed to agonism at melanocortin receptors, particularly MC1R and MC4R. Activation of MC1R on melanocytes increases melanin synthesis, which underlies the reported tanning effect. MC4R engagement in the central nervous system is linked to appetite suppression and to effects on sexual arousal reported in early clinical studies. Those studies were small and were not designed to establish efficacy or long-term safety. Receptor selectivity among the melanocortin subtypes is not absolute, which complicates attribution of any effect to a single pathway.
Regulatory treatment varies between countries. Several national medicines agencies have classified the peptide as unapproved, and customs authorities in some jurisdictions seize shipments on that basis. A few jurisdictions channel supply through prescription-only frameworks that do not list the substance by name. Because the material circulates mainly through online vendors, composition and purity are rarely verified before sale. Surveys of unapproved peptide products have reported labels that did not match measured content in a substantial fraction of samples.
Melanotan II is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone, a naturally occurring peptide involved in pigmentation signalling. Its structure substitutes a lactam bridge between side chains to increase stability relative to the native hormone. The compound is also known by the shorthand MT-II and by several non-proprietary synonyms used in research catalogues. It is not an approved therapeutic product in any major jurisdiction; material sold under this name is typically offered as a laboratory reagent rather than as a medicine.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white powder | Lyophilized form |
| Solubility | Freely soluble in water | Dissolves readily in aqueous buffer |
| Typical storage temperature | -20 °C or below | Protect from light and moisture |
| Typical analytical method | Reversed-phase HPLC and LC-MS | Purity estimate plus mass confirmation |
| Unit of measure | Milligram per vial | Content varies by vendor |
Regulatory treatment of this peptide varies by country. It holds no marketing authorization as a medicine in the United States, the European Union, or most other jurisdictions. Some countries classify products containing it as prescription-only or unlicensed medicines, which restricts lawful supply. Authorities have issued public notices warning that unregulated products may contain undeclared or incorrect ingredients. The molecule also appears on prohibited lists for competitive sport. These measures address supply oversight rather than any approved therapeutic role.
Published research on the compound remains limited. Much of the human data comes from small, early-stage studies rather than large controlled trials, and several questions about effects and variability between individuals remain open. Investigators have examined receptor activity, pigment pathways, and related physiological responses in laboratory and animal models. Findings from those models do not automatically translate to human outcomes. Reviews frequently note the scarcity of rigorous clinical evidence and call for better-characterized study 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.
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.
Quality assessment of research-grade peptide rests mainly on reversed-phase high-performance liquid chromatography for purity and on mass spectrometry for identity confirmation. A single main peak above a stated threshold, commonly ninety-eight percent by peak area, is the usual release criterion applied by suppliers. Independent analyses commissioned by laboratories and consumer organisations have repeatedly reported discrepancies between label claims and measured content, including truncated sequences, residual trifluoroacetate, and lower-than-declared peptide mass. Those findings do not establish that every supplier is unreliable, but they indicate that purity figures printed on a vial are claims requiring verification rather than settled facts.
Regulatory treatment varies by jurisdiction and has changed over time. In several countries the peptide is handled as an unapproved prescription medicine, and import or sale for human use is restricted, while elsewhere it falls under poisons or controlled-substance schedules. Enforcement activity against online vendors has been reported in Australia, New Zealand, the United Kingdom and the United States. Scholarly writing discusses melanotan-2 chiefly as an experimental tool and as a case study in unregulated peptide supply, and its precise legal position in any given country should be checked against current national schedules.
Proteins consist of chains of amino acids which spontaneously fold to form the three dimensional (3-D) structures of the proteins. The 3-D structure is necessary to understanding the biological function of the protein. Protein structures can be determined experimentally through techniques such as X-ray crystallography, cryo-electron microscopy and nuclear magnetic resonance (NMR), which are all expensive and time-consuming. Such efforts, using the experimental methods, have identified the structures of about 170,000 proteins over the last 60 years, while there are over 200 million known proteins across all life forms. Over the years, researchers have applied numerous computational methods to predict the 3D structures of proteins from their amino acid sequences, accuracy of such methods in best possible scenario is close to experimental techniques (NMR) by the use of homology modeling based on molecular evolution. CASP, which was launched in 1994 to challenge the scientific community to produce their best protein structure predictions, found that GDT scores of only about 40 out of 100 can be achieved for the most difficult proteins by 2016. AlphaFold started competing in the 2018 CASP using an artificial intelligence (AI) deep learning technique.
The NUBPL gene encodes a protein that is a member of the Mrp/NBP35 ATP-binding family. This protein is required for the assembly of the mitochondrial membrane respiratory chain NADH dehydrogenase (Complex I), the first oligomeric enzymatic complex of the mitochondrial respiratory chain located in the inner mitochondrial membrane. Its role in assembly is the delivery of one or more iron–sulfur (Fe-S) clusters to complex I subunits in anaerobic conditions in vitro. The dysfunction of NUBPL results in an irregular assembly of the peripheral arm of complex I, which may lead to a decrease in activity. Knockdown of the protein also causes abnormal mitochondrial ultrastructure characterized by respiratory supercomplex remodeling, christa membrane loss, and abnormally high lactate levels.
Archives of Biochemistry and Biophysics is a biweekly peer-reviewed scientific journal that covers research in biochemistry and biophysics. It is published by Elsevier. As of 2012, the editors-in-chief were Paul Fitzpatrick (University of Texas Health Science Center at San Antonio), Helmut Sies (University of Düsseldorf), Jian-Ping Jin (Wayne State University School of Medicine), and Henry Jay Forman (University of Southern California). The journal was established in 1942 by Academic Press as the Archives of Biochemistry, obtaining its current name in 1952. It absorbed the journal Molecular Cell Biology Research Communications (formerly section B of Biochemical and Biophysical Research Communications), which was published from 1999 to 2001. An index to authors for the first 75 volumes, covering the period from 1943 to 1958, was published in October 1959.
Translocation: The receptor is, along with the part of the membrane it is embedded in, brought to the inside of the cell, where it is dephosphorylated within the acidic vesicular environment and then brought back. This mechanism is used to regulate long-term exposure, for example, to a hormone, by allowing resensitisation to follow desensitisation. Alternatively, the receptor may undergo lysosomal degradation, or remain internalised, where it is thought to participate in the initiation of signalling events, the nature of which depending on the internalised vesicle's subcellular localisation. Arrestin linking: The phosphorylated receptor can be linked to arrestin molecules that prevent it from binding (and activating) G proteins, in effect switching it off for a short period of time. This mechanism is used, for example, with rhodopsin in retina cells to compensate for exposure to bright light. In many cases, arrestin's binding to the receptor is a prerequisite for translocation. For example, beta-arrestin bound to β2-adrenoreceptors acts as an adaptor for binding with clathrin, and with the beta-subunit of AP2 (clathrin adaptor molecules); thus, the arrestin here acts as a scaffold assembling the components needed for clathrin-mediated endocytosis of β2-adrenoreceptors.
Sources: en.wikipedia.org
Pituitary prolactin is controlled by the Pit-1 transcription factor, which binds to the gene at several sites including a proximal promoter. This promoter is inhibited by dopamine and stimulated by estrogens, neuropeptides, and growth factors. Estrogens can also suppress dopamine. Interaction with neuropeptides is still a matter of active research: no specific prolactin-releasing hormone has been identified. It is known that mice react to both VIP and TRH, but humans seem to only react to TRH. There are prolactin-releasing peptides that work in vitro, but whether they deserve their name has been questioned. Oxytocin does not play a large role. Mice without a posterior pituitary do not raise their prolactin levels even with suckling and oxytocin injection, but scientists have yet to identify which specific hormone produced by this region is responsible. In birds (turkeys), VIP is a powerful prolactin-releasing factor, while peptide histidine isoleucine has almost no effect.
Nycomed, a Swiss drug company which manufactures Actovegin, claims it can be used for circulation and nutrition disturbances, skin grafting, burns, and wound-healing impairment. Actovegin has also been used as a performance enhancer. It has been investigated for use in treatment of polyneuropathy in diabetes, and for stroke. One study found that when tissues suffer from hypoxia caused circulation abnormalities, Actovegin helps capillaries improve circulation by enhancing the neogenic mechanism in blood vessels. Anaphylactic shock has been observed in at least one patient treated with actovegin. There are reports suggesting that Actovegin have ergogenic ability, however one small trial found no apparent benefit from short-term use. Two studies certified Actovegin to have an anti-inflammatory effect. One of the two studies certified Actovegin to reduce Progressive muscular atrophy-induced inflammation in human cells. Another study certified Actovegin to have a positive impact on the growth of muscle cells.
Five amino acids possess a charge at neutral pH. Often these side chains appear at the surfaces on proteins to enable their solubility in water, and side chains with opposite charges form important electrostatic contacts called salt bridges that maintain structures within a single protein or between interfacing proteins. Many proteins bind metal into their structures specifically, and these interactions are commonly mediated by charged side chains such as aspartate, glutamate and histidine. Under certain conditions, each ion-forming group can be charged, forming double salts. The two negatively charged amino acids at neutral pH are aspartate (Asp, D) and glutamate (Glu, E). The anionic carboxylate groups behave as Brønsted bases in most circumstances. Enzymes in very low pH environments, like the aspartic protease pepsin in mammalian stomachs, may have catalytic aspartate or glutamate residues that act as Brønsted acids.
Sources: en.wikipedia.org
Moroder studied chemistry at the University of Padova, where he graduated 1965 in chemistry with the doctoral thesis on synthesis of S-peptide of ribonuclease A in the laboratory of Ernesto Scoffone at the Institute of Organic Chemistry. In 1968 he joined Klaus H. Hofmann's Group at the University of Pittsburgh to work on chemical synthesis of the peptidic adrenocorticotropic hormone and its derivatives. Moroder habilitated in 1971 at the University of Padova in Chemistry of Natural Products. 1975 he became a senior research fellow in the Department of Peptide Chemistry at the Max Planck Institute for Biochemistry (MPIB) in Martinsried headed by Erich Wünsch. Between 1991 and 2008 he was the head of the Laboratory of Bioorganic chemistry at the MPIB. Since 1994 he was an adjunct professor at the Technical University of Munich.
The Journal of Biological Chemistry publishes research in any area of biochemistry or molecular biology in one online-only issue per week. Molecular & Cellular Proteomics is a monthly online only publication. Articles appearing in MCP "...describe the structural and functional properties of proteins and their expression, particularly with respect to the developmental time courses of the organism of which they are a part." The journal also publishes other content such as "HUPO views" (reports from the Human Proteome Organization), proceedings from HUPO meetings, and the proceedings of the International Symposium On Mass Spectrometry In The Life Sciences. The Journal of Lipid Research covers "...the science of lipids in health and disease. The Journal emphasizes lipid function and the biochemical and genetic regulation of lipid metabolism. In addition, JLR publishes manuscripts on patient-oriented and epidemiological research relating to altered lipid metabolism, including modification of dietary lipids." ASBMB Today is the society's monthly news magazine. It contains extensive coverage of awards, meetings, research highlights, job placement advertising and human interest articles. All ASBMB members receive a complimentary subscription to ASBMB Today. The online version of the magazine features daily publishing.
To address specific nutritional needs of individual patients, several providers of IDPN therapy developed formulations that take clinical variables into account in order to best fit the patient's individual needs and condition. Specific formulations address distinct differences between nutritional needs of those patients who exhibit protein malnutrition and those patients who exhibit calorie malnutrition. Nutrition Clinical nutrition
Sources: en.wikipedia.org
The lyophilized powder is generally held at minus twenty degrees Celsius or below, away from light and moisture. Reconstituted solutions are typically refrigerated and used quickly. These practices derive from general peptide handling rather than a formal stability study.
Reversed-phase liquid chromatography estimates purity, and mass spectrometry confirms molecular mass. Together they distinguish the intended peptide from truncated or modified forms. Sequence-level confirmation may use tandem mass spectrometry or amino acid analysis.
Because it is not made under pharmaceutical standards, purity and content can vary between vendors and batches. Independent testing has documented labeling discrepancies. A certificate of analysis from an accredited laboratory offers more assurance than a vendor's own claim.
No. No major regulatory agency has granted a marketing authorisation for melanotan II as a medicine. Products sold under this name are generally presented as laboratory reagents and are not subject to the batch-release testing applied to approved drugs.