Everything below concerns melanocortin receptor. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2025-12-17. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
Melanotan II is a synthetic cyclic heptapeptide analog derived from the core sequence of alpha-melanocyte-stimulating hormone. Researchers at the University of Arizona synthesized it during the 1980s while studying pigmentation and appetite signaling. The compound is not an approved medicine in any major jurisdiction and appears mainly in laboratory and research-chemical settings. Its structure incorporates a lactam bridge between side chains, which constrains the ring and slows enzymatic breakdown relative to the natural hormone.
Melanotan II binds several melanocortin receptor subtypes rather than a single target. MC1R on melanocytes drives melanin synthesis, while MC3R and MC4R participate in energy balance, appetite, and sexual response pathways. This lack of selectivity explains why reported effects extend beyond skin darkening. Substitutions at positions four and seven, including norleucine and D-phenylalanine, increase potency and resistance to peptidases. Understanding which receptor mediates which effect remains an active area of investigation.
| 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, 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.
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.
== Clinical significance == Sinus node dysfunction also known as sick sinus syndrome is a group of irregular heartbeat conditions caused by faulty electrical signals of the heart. When the heart's sinoatrial node is defective, the heart's rhythms become abnormal—typically too slow or exhibiting pauses in its function or a combination, and very rarely faster than normal. Blockage of the arterial blood supply to the SA node (most commonly due to a myocardial infarction or progressive coronary artery disease) can therefore cause ischemia and cell death in the SA node. This can disrupt the electrical pacemaker function of the SA node, and can result in sinus node dysfunction. If the SA node does not function or the impulse generated in the SA node is blocked before it travels down the electrical conduction system, a group of cells further down the heart will become its pacemaker.
==== Entrapment of catalytically active noble metal nanoparticles ==== The entrapment of catalytically active noble metals can be accomplished by grafting on functional groups to the unsaturated metal site on MOFs. Ethylenediamine (ED) has been shown to be grafted on the Cr metal sites and can be further modified to encapsulate noble metals such as Pd. The entrapped Pd has similar catalytic activity as Pd/C in the Heck reaction. Ruthenium nanoparticles have catalytic activity in a number of reactions when entrapped in the MOF-5 framework. This Ru-encapsulated MOF catalyzes oxidation of benzyl alcohol to benzaldehyde, although degradation of the MOF occurs. The same catalyst was used in the hydrogenation of benzene to cyclohexane. In another example, Pd nanoparticles embedded within defective HKUST-1 framework enable the generation of tunable Lewis basic sites. Therefore, this multifunctional Pd/MOF composite is able to perform stepwise benzyl alcohol oxidation and Knoevenagel condensation.
Casamino acid is the mixture of amino acids produced from acid hydrolysis of casein, a family of phosphoproteins found in mammalian milk. In comparison, tryptone describes casein that has undergone enzymatic degradation by the protease trypsin, leaving many smaller peptide chains alongside the free amino acids. Casamino acid is used as a component of microbiological growth medium to support protein synthesis. However, tryptophan, an essential amino acid, is lost while digesting the casein with strong acids. Providing this abundant source of nitrogen can alter the phenotype of microorganisms, such as bacterial species recognizing nutrient-rich media and reducing their motility, as compared to their typical environmental behaviors.
Sources: en.wikipedia.org
=== Phosphoenolpyruvate carboxykinase (PEPC-K) === Glyceroneogenesis can be regulated at two reaction pathways. First, it can be held at the decarboxylation of oxaloacetate to phosphoenolpyruvate. Secondly, the TCA cycle can affect glyceroneogenesis when the glutamate or substrates in the TCA cycle are being used as a precursor. Decarboxylation of oxaloacetate to phosphoenolpyruvate is catalyzed by PEPC-K, the essential enzyme which regulates glyceroneogenesis. Increases in PEPC-K levels or overexpression of the gene that codes for PEPC-K will increase glyceroneogenesis. Also, oxaloacetate can be decarboxylated to phosphoenolpyruvate when more PEPC-K can catalyze the reaction. Gene expression of PEPC-K can be suppressed by norepinephrine, glucocorticoids, and insulin. Norepinephrine is a neurotransmitter which decreases the activity of PEPC-K when the cell is in a cold environment. Glucocorticoids are steroid hormones involved in the reciprocal regulation of glyceroneogenesis in the liver and adipose tissues. Through a poorly-understood mechanism, they induce transcription of PEPC-K in the liver while decreasing transcription in adipose tissues. Insulin is a peptide hormone that causes cells to take in glucose. Through glyceroneogenesis, insulin down-regulates the expression of PEPC-K in both liver and adipose tissues.
=== Governors (1947–1958) === Gaston Mourgues (6 September 1947 – 29 April 1948), acting Albert Mouragues (29 April 1948 – 23 February 1953) Salvador Jean Étcheber (23 February 1953 – 3 November 1956) Yvon Bourges (3 November 1956 – 15 July 1958) Max Berthet (15 July 1958 – 11 December 1958), acting
Some archaeons such as Methanocaldococcus jannaschii do not have a cysteine—tRNA ligase. Instead they probably make cystyl-rRNA in through seryl-tRNA and phosphoseryl-tRNA, analogous to the Sec-tRNA production route in eukarya and archaea. Some bacteria with the Sec machinery also have a noncanonical tRNACysGCA or tRNACysUCA. They are recognized by the usual Cysteine—tRNA ligase, but needs the help of SelB to work. The tRNACysUCA type, also called tRNAReC, can cause Cys to be inserted instead of Sec at UGA. This might help the bacterium cope with a lack of selenium. Some versions of tRNAReC have further mutated to be recognized by the seryl-tRNA synthase and SelA, making them a second kind of tRNASec. This is proposed to be called tRNAReU. ReU is not as efficient as the standard tRNASec. Some bacteria also have so-caleed allo-tRNAs, which have an acceptor domain similar to tRNASec. They appear to cause some other amino acid to be replaced by serine. There are also lab-modified versions of the tRNA-SelAB system.
Sources: en.wikipedia.org
== Biography == In 1964 Bernd Michael Rode graduated from high school (“Akademisches Gymnasium Innsbruck”) and commenced studies in chemistry at the University of Innsbruck. In 1973 he received his Ph.D. degree in chemistry with sub auspiciis praesidentis from the University of Innsbruck. In 1973 Prof. Rode started his career as an assistant professor at the Institute of Inorganic and Analytical Chemistry of the University of Innsbruck. After research stays in Germany (University of Stuttgart and University of Karlsruhe) he became an associate professor in Innsbruck in the year 1976. After spending a 1-year research stay at the University of Tokyo, Prof. Rode started his professorship at the Institute of Inorganic and Theoretical Chemistry at the University of Innsbruck. From 2006 to 2011 he was head of the Department of Theoretical Chemistry and head of the Institute for General Inorganic and Theoretical Chemistry. One of Prof. Rode’s largest achievements was the foundation of the University Network ASEA-UNINET (Austrian South East Asian University Partnership Network) in 1994. The foundations for this network were laid by informal contacts between the University of Innsbruck and Thai Universities that date back to the 1970s. In the 1980s partnerships between the University of Innsbruck, the University of Vienna, the University of Agricultural Sciences Vienna, the Chulalongkorn University, the Mahidol University, the Kasetsart University and the Chiang Mai University were concluded.
== External links == Type 1 diabetes at the American Diabetes Association Type 1 diabetes at the Mayo Clinic Natural History of Type 1 Diabetes: Academic article chronicling type 1 diabetes through history
=== Alternative lists in other Nikayas === The Kalahavivāda Sutta of the Sutta Nipāta (Sn. 862-872) has the following chain of causes (as summarized by Doug Smith):name-and-form conditions contact, contact conditions feeling, feeling conditions desire, desire conditions clinging, and clinging conditions quarrels, disputes, lamentations, and grief. Dīgha Nikāya Sutta 1, the Brahmajala Sutta, verse 3.71 describes six nidānas:
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 regulator in a major market has approved it for human use. It appears in research settings and in products marketed outside pharmacy channels. Legal status for personal possession varies by country.