If you have been reading about melanocortin receptor and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Updated 2025-08-15. Numbers and descriptions here follow the published literature rather than marketing material.
Melanotan-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone. Its sequence incorporates a lactam bridge that constrains the peptide into a ring, which increases resistance to enzymatic breakdown relative to the natural hormone. Researchers at the University of Arizona synthesised the compound in the late 1980s and early 1990s while studying pigmentation pathways. It has never received marketing approval from any national medicines regulator. In the scientific literature it is usually described as a laboratory research reagent rather than a therapeutic product.
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.
Scientific discussion of Melanotan-2 spans pharmacology, dermatology, and public-health literature. Laboratory studies examine its receptor binding and cellular effects, while clinical reports describe outcomes observed after unregulated use. These two bodies of work differ in rigour and intent. Peer-reviewed trials of the compound as a medicine are limited, so much of the available information comes from case reports and surveillance data. Authors frequently note the gap between experimental findings and real-world use.
Reported observations after unregulated use include shifts in skin pigmentation and, in some accounts, unintended changes to moles and other lesions. Whether these outcomes are causally linked to the compound, and how often they occur, remain open questions because controlled data are scarce. The absence of standardised dosing and verified product purity complicates interpretation. Researchers have called for better surveillance and analytical characterisation of samples obtained outside regulated channels. Conclusions drawn from anecdotal evidence should be treated as provisional.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic cyclic heptapeptide | Alpha-MSH analogue with a lactam ring |
| Molecular formula | C50H69N15O9 | Commonly cited value for the neutral peptide |
| Molecular weight | 1024.18 g/mol | Calculated for the free molecule |
| Appearance | White to off-white powder | Typically supplied as a lyophilised solid |
| Solubility | Soluble in water, DMSO and ethanol | Dissolution in pure water is often slow |
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.
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.
Routine characterisation relies on reversed-phase high-performance liquid chromatography with ultraviolet detection near 214 nanometres, using a C18 column and a water-acetonitrile gradient containing trifluoroacetic acid. Electrospray ionisation mass spectrometry confirms the expected molecular mass and can reveal truncated or oxidised by-products that co-elute poorly. Sequence and stereochemistry require additional work, such as peptide mapping or amino acid analysis, because a chromatographic purity figure alone does not distinguish a diastereomer from the target peptide. Independent testing of research-grade material frequently shows measured content below the stated label, so a certificate of analysis is best read together with the method that produced it.
Melanotan-2 is handled in the laboratory as a lyophilised powder that dissolves readily in water, dimethyl sulfoxide and dimethylformamide, with limited solubility in ethanol. Stock solutions prepared in an organic solvent often precipitate when diluted into aqueous buffer, so gradual dilution with mixing is standard practice. The peptide carries a tryptophan residue and a histidine residue, both sensitive to oxidation and to alkaline conditions. Working solutions are therefore kept near neutral to slightly acidic pH, protected from light, and consumed within the same working session whenever that is practical.
13. Ir Med J. 2026 Sep 28;119(8):160. Non-Arteritic Anterior Ischaemic Optic Neuropathy Associated with Semaglutide use. Kearney M, Smyth NM, Hassan HSA, Khan MS. PRESENTATION: Non-arteritic ischaemic optic neuropathy (NAION) is a common cause of acute, painless monocular visual disturbance in older adults. This case discusses a woman in her 70s with vascular risk factors who presented with a three-day history of progressive left sided visual disturbance. Examination demonstrated a left relative afferent pupillary defect and inferior quadrantopia. DIAGNOSIS: Haematological investigations and neuroimaging were unremarkable. Formal ophthalmological assessment demonstrated superior optic disc swelling with an inferior visual field defect, consistent with NAION. TREATMENT: The patient had been taking semaglutide, as prescribed, for the six months prior to presentation. This was identified as a potential contributory agent and was discontinued. Visual acuity partially improved following cessation of semaglutide. DISCUSSION: This case seeks to highlight a possible association between semaglutide use and NAION. Although causality remains unproven, it underscores the importance of pharmacovigilance when manging patients presenting with ophthalmological symptoms.
The image of seedy underground, destitute smokers were often generated by anti-opium narratives and became a more accurate image of opium use following the effects of large scale opium prohibition in the 1880s.
== Languages == The name international unit is often capitalized in English and other languages, although major English-language dictionaries treat it as a common noun and thus use lower case. The name has several accepted abbreviations. It is usually abbreviated as IU in English, and UI in Romance languages (for example Spanish unidad internacional, Portuguese unidade internacional, French unité internationale, Italian unità internazionale, Romanian unitate internațională), IE in several Germanic languages (for example German internationale Einheit, Dutch internationale eenheid) or as other forms (for example Russian МЕ, международная единица [mezhdunarodnaya yedinitsa], or ЕД, единица действия [yedinitsa deystviya] 'activity unit', Hungarian NE, nemzetközi egység). In order to remove the possibility of having the letter "I" confused with the digit "1", some hospitals have it as a stated policy omit the "I", that is, to only use U or E when talking and writing about dosages, while other hospitals require the word "units" (or words "international units") to be written out entirely. (For example, "three international units per litre" may be abbreviated "3 U/L". The "liter" sign (L) is less affected, as less confusing written forms are used.)
One benefit of open-source AI is the increased transparency it offers compared to closed-source alternatives. The open-sourced aspects of models allow those algorithms and code to be inspected, which promotes accountability and helps developers understand how a model reaches its conclusions. Additionally, open-weight models, such as Llama and Stable Diffusion, allow developers to directly access model parameters, potentially facilitating the reduced bias and increased fairness in their applications. This transparency can help create systems with human-readable outputs, or "explainable AI", which is a growingly key concern, especially in high-stakes applications such as healthcare, criminal justice, and finance, where the consequences of decisions made by AI systems can be significant.
Sources: pubmed.ncbi.nlm.nih.gov
=== Comparative Experiments === A comparative NAIL-MS experiment is quite similar to a SILAC experiment but for RNA instead of proteins. First, two populations of the respective cells are cultivated. One of the cell populations is fed with growth medium containing unlabeled nutrients, whereas the second population is fed with growth medium containing stable isotope labeled nutrients. The cells then incorporate the respective isotopologues into their RNA molecules. One of the cell populations serves as a control group whereas the other is subject to the associated research (e.g. KO strain, stress). Upon harvesting of the two cell populations they are mixed and co-processed together to exclude purification-bias. Due to the distinct masses of incorporated nutrients into the nucleosides a differentiation of the two cell populations is possible by mass spectrometry.
A think tank or public policy institute is an organization that performs research and advocacy concerning topics such as social policy, political strategy, economics, military, technology, and culture. Most think tanks are non-governmental organizations, but some are semi-autonomous agencies within a government, and some are associated with particular political parties, businesses, or the military. Think tanks are often funded by individual donations, with many also accepting government grants. Think tanks publish articles and studies, and sometimes draft legislation on particular matters of policy or society. This information is then used by governments, businesses, media organizations, social movements, or other interest groups. Think tanks range from those associated with highly academic or scholarly activities to those that are overtly ideological and pushing for particular policies, with a wide range among them in terms of the quality of their research. Later generations of think tanks have tended to be more ideologically oriented.
In September 2019, Colombia's President Iván Duque Márquez launched a new military crackdown against FARC, which declared the resumption of the armed struggle due to the government's failure to abide by the 2016 peace deal.
== History == Mid-1990s: Oracle Clinical is introduced as part of Oracle’s life-sciences applications portfolio (first documentation references appear in 1996). Adoption in large sponsors (late 1990s–2000s): Deployment at major companies; for example, Boehringer Ingelheim reported selecting Oracle Clinical/RDC as its EDC to integrate with existing clinical databases and scale to most trials. RDC Classic → RDC Onsite (2000s): A web-based interface (RDC Onsite) supersedes the legacy client, enabling browser-based site entry and monitoring documented by sponsors and public research networks. Acquisition era (2009–2012): Oracle expands the health-sciences portfolio with acquisitions of Relsys (Argus Safety, 2009), Phase Forward (2010), and ClearTrial (2012), shaping the broader eClinical suite around OC/RDC. Cloud transition (2020s): Oracle introduces Clinical One Data Collection as a cloud-native path for trial data capture, positioned alongside or as a successor for on-premises OC/RDC deployments.
Alkanes with more than three carbon atoms can be arranged in various ways, forming structural isomers. The simplest isomer of an alkane is the one in which the carbon atoms are arranged in a single chain with no branches. This isomer is sometimes called the n-isomer (n for "normal", although it is not necessarily the most common). However, the chain of carbon atoms may also be branched at one or more points. The number of possible isomers increases rapidly with the number of carbon atoms. For example, for acyclic alkanes:
Sources: en.wikipedia.org
=== Blood pressure control === Modulating and ameliorating diabetic complications may improve the overall quality of life for diabetic patients. For example, a 2008 study concluded that when elevated blood pressure was tightly controlled, diabetic related deaths were reduced by 32% compared to those with less controlled blood pressure.
==== Feed additives ==== Enzymes are often added to animal feed to improve the health and growth of farmed animals, particularly chickens and pigs. The feed is typically treated with high pressure steam to kill bacteria such as Salmonella. Therefore the added enzymes (e.g. phytase and xylanase) must be able to withstand this thermal challenge without being irreversibly inactivated.
Although most species of psilocybin-containing mushrooms bruise blue when handled or damaged due to the oxidization of phenolic compounds, this reaction is not a definitive method of identification or determining a mushroom's potency.
== General description == C chondrites contain a relatively high proportion of carbon (up to 3%), which is in the form of graphite, carbonates, and organic compounds, including amino acids. In addition, they contain water and minerals that have been modified by the influence of water. The carbonaceous chondrites were not exposed to higher temperatures, so that they are hardly changed by thermal processes. Some carbonaceous chondrites, such as the Allende meteorite, contain calcium-aluminum-rich inclusions (CAIs). These are compounds that emerged early from the primeval solar nebula, condensed out and represent the oldest minerals formed in the Solar System. Some primitive carbonaceous chondrites, such as the CM chondrite Murchison, contain presolar minerals, including moissanite (natural silicon carbide) and tiny nanometer-sized diamonds that apparently were not formed in the Solar System. These presolar minerals were probably formed during the explosion of a nearby supernova or in the vicinity of a pulsating red giant (more precisely: a so-called AGB star) before they got into the cloud of matter from which the Solar System was formed. Such star explosions release pressure waves that can condense clouds of matter in their surroundings, leading to the formation of new ones, stars and planetary systems. Another carbonaceous chondrite, the Flensburg meteorite (2019), provides evidence of the earliest known occurrence of liquid water in the young Solar System to date.
{\displaystyle {\begin{aligned}u(y,z)&={\frac {G}{2\mu }}(y+z)(\pi -y)-{\frac {G}{\pi \mu }}\sum _{n=1}^{\infty }{\frac {1}{\beta _{n}^{3}\sinh(2\pi \beta _{n})}}\left\{\sinh[\beta _{n}(2\pi -y+z)]\sin[\beta _{n}(y+z)]-\sinh[\beta _{n}(y+z)]\sin[\beta _{n}(y-z)]\right\},\quad \beta _{n}=n+{\tfrac {1}{2}},\\[6pt]Q&={\frac {G\pi ^{4}}{12\mu }}-{\frac {G}{2\pi \mu }}\sum _{n=1}^{\infty }{\frac {1}{\beta _{n}^{5}}}\left[\coth(2\pi \beta _{n})+\csc(2\pi \beta _{n})\right].\end{aligned}}}
Sources: en.wikipedia.org
It is a synthetic cyclic heptapeptide modelled on alpha-melanocyte-stimulating hormone. A lactam bridge links two side chains, forming a ring that stabilises the molecule against proteolysis. It belongs to the broader melanocortin peptide family.
No national medicines agency has approved melanotan-2 for clinical use. Afamelanotide, a related but distinct peptide, holds a marketing authorisation in the European Union for a rare photosensitivity disorder. Melanotan-2 itself is handled as a laboratory chemical.
Its broad activity across melanocortin receptors makes it a tool for probing pigmentation, appetite and vascular signalling. Early trials recorded skin darkening and other effects that were not the original focus of the work. Those observations generated hypotheses that later studies have examined.
Major regulatory agencies have not approved it for any indication. Some countries permit it only under prescription frameworks, while others classify it as a controlled substance.