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 2025-08-28 and is reviewed periodically as new material appears.
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.
Published pharmacokinetic information is limited and comes mainly from small studies rather than registrational trials. Plasma half-life is usually described as short, on the order of tens of minutes, followed by rapid tissue distribution and clearance of the intact peptide. Metabolites and low concentrations of parent compound have been reported in urine, a detail relevant to anti-doping and forensic testing. Whether repeated exposure changes receptor sensitivity or clearance over time remains an open question. Values differ noticeably between analytical assays, so published numbers should be read as approximate rather than definitive.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C50H69N15O9 | Cyclic heptapeptide, C-terminally amidated |
| Approximate molecular mass | 1024 Da | Monoisotopic mass of the free peptide |
| Appearance | White to off-white powder | Typically supplied as a lyophilised solid |
| Solubility class | Soluble in water and polar solvents | Also dissolves in neutral aqueous buffer |
| Common synonyms | Melanotan II, MT-II, MT-2 | Described as a melanocortin agonist in early literature |
Proprotein convertases (PPCs) are a family of proteins that activate other proteins. Many proteins are inactive when they are first synthesized, because they contain chains of amino acids that block their activity. Proprotein convertases remove those chains and activate the protein. The prototypical proprotein convertase is furin. Proprotein convertases have medical significance, because they are involved in many important biological processes, such as cholesterol synthesis. Compounds called proprotein convertase inhibitors can block their action, and block the target proteins from becoming active. Many proprotein convertases, especially furin and PACE4, are involved in pathological processes such as viral infection, inflammation, hypercholesterolemia, and cancer, and have been postulated as therapeutic targets for some of these diseases.
=== Defunct === Liaison Committee for a Revolutionary Workers International, founded by former militants of the Argentinian MAS and PO Committee for a Workers' International (CWI), 1974–2019 – split into Committee for a Workers' International (Refounded) and International Socialist Alternative Coordinating Committee for the Refoundation of the Fourth International, CCRCI (2004-2020) International League for the Reconstruction of the Fourth International (ILRFI), 1976–1995 Workers International to Rebuild the Fourth International (WIRFI) International Revolutionary Marxist Tendency (TMRI), 1965–1992 Permanent Revolution Revolutionary Workers Ferment (Fomento Obrero Revolucionario, FOR) Trotskyist International Liaison Committee, 1979–1984 Tendencia Cuartainternacionalista Fourth International (ICR), also called FI (La Verité) or FI (International Secretariat) 1981–2015 Socialist Network (Post-Trotskyist, split from IMT) International Trotskyist Opposition] (ITO) 2022–2025 (Dissolved into LIS-ISL) League for the Fifth International (L5I), founded by expelled members of the IST. (1989-2025)
Staining is a technique used to enhance contrast in samples, generally at the microscopic level. Stains and dyes are frequently used in histology (microscopic study of biological tissues), in cytology (microscopic study of cells), and in the medical fields of histopathology, hematology, and cytopathology that focus on the study and diagnoses of diseases at the microscopic level. Stains may be used to define biological tissues (highlighting, for example, muscle fibers or connective tissue), cell populations (classifying different blood cells), or organelles within individual cells. In biochemistry, it involves adding a class-specific (DNA, proteins, lipids, carbohydrates) dye to a substrate to qualify or quantify the presence of a specific compound. Staining and fluorescent tagging can serve similar purposes. Biological staining is also used to mark cells in flow cytometry, and to flag proteins or nucleic acids in gel electrophoresis. Light microscopes are used for viewing stained samples at high magnification, typically using bright-field or epi-fluorescence illumination. Staining is not limited to only biological materials, since it can also be used to study the structure of other materials; for example, the lamellar structures of semi-crystalline polymers or the domain structures of block copolymers.
Inadequate nutritional intake: Alcoholics tend to take in less than the recommended amount of thiamine. Decreased uptake of thiamine from the GI tract: Active transport of thiamine into enterocytes is disturbed during acute alcohol exposure. Liver thiamine stores are reduced due to hepatic steatosis or fibrosis. Impaired thiamine utilization: Magnesium, which is required for the binding of thiamine to thiamine-using enzymes within the cell, is also deficient due to chronic alcohol consumption. The inefficient use of any thiamine that does reach the cells will further exacerbate the thiamine deficiency. Ethanol per se inhibits thiamine transport in the gastrointestinal system and blocks phosphorylation of thiamine to its cofactor form (ThDP). Following improved nutrition and the removal of alcohol consumption, some impairments linked with thiamine deficiency are reversed, in particular poor brain functionality, although in more severe cases, Wernicke–Korsakoff syndrome leaves permanent damage. (See delirium tremens.)
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Sources: en.wikipedia.org
An advocacy group that has taken a position against research on newborn blood screening data without parental consent is the Citizens' Council for Health Freedom, who take the position that newborn health screening for "a specific set of newborn genetic conditions" is a very different matter than storing the data or those DNA samples indefinitely to "use them for genetic research without parental knowledge or consent."
==== Pentavalent vaccine ==== Gavi spent 15 years (2005–2020) with a program for shaping the pentavalent vaccine market to be more stable and competitive. The vaccine price fell with increased competition, and price discrimination declined. Whether Gavi met quantitative goals will be assessed in 2020.
Also included are pouches of pickled vegetables (yellow radish, red cabbage, takana pickles, pickled hari-hari, or bamboo shoots) or salad (potato salad or tuna salad) and instant soup (miso, egg drop, wakame seaweed, or mushroom).
Pleasure promotes well-being as a positive feeling about what is attractive. Pain, by contrast, diminishes well-being as a negative feeling about what is aversive. Pleasure and pain are closely tied to the brain's reward system, influencing motivation and behavior by reinforcing beneficial actions and discouraging harmful ones. They shape how individuals perceive their lives and interact with their social and physical environments. Pleasure and pain are commonly seen as opposites that counterbalance each other. This view suggests that the negative value of experiencing intense pain can be compensated by the positive value of experiencing intense pleasure. A different perspective argues that their relation is more complex because they influence experience, motivation, and well-being in distinct ways that are not always symmetrical. Following this idea, one view holds that avoiding pain is more important than seeking pleasure. Pleasure and pain are often tied to emotions, which are temporary states of arousal, such as joy, hope, anger, and fear. Emotions include subjective experiences of pleasure and pain alongside other psychological phenomena, such as the evaluative assessment of a situation and a disposition to engage in certain types of behavior. For example, fear evaluates a situation as dangerous and is associated with a behavioral disposition to flee. Additionally, emotions are linked to physiological changes, like sweating, and bodily expressions that signal the emotional state to others.
Sources: en.wikipedia.org
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.
Afamelanotide is the linear analogue [Nle4-D-Phe7]-alpha-MSH, sometimes called melanotan I, while melanotan II is cyclic and carries three further substitutions. The two are distinct molecules and are not interchangeable in analytical testing.
Binding to the four melanocortin receptor subtypes is well documented in vitro. The relative contribution of each subtype to whole-body effects in humans is far less certain.
It is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone, containing seven amino acids with a lactam ring and a D-configured phenylalanine residue. It is supplied as a lyophilised powder for laboratory research.