Everything below concerns analytical characterisation. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2025-08-25. Numbers and descriptions here follow the published literature rather than marketing material.
Melanotan-2 has not received marketing authorisation from major regulatory agencies for any therapeutic indication. Several jurisdictions classify it as a prescription-only medicine or a controlled substance when supplied for human use. Because approved products do not exist, material sold online usually sits outside pharmaceutical supply chains and formal quality oversight. Regulators have issued public notices describing the compound as unapproved. Enforcement varies, and the legal position differs between countries, which complicates any single general statement about its status.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Regulatory status | Unapproved for therapeutic use | No marketing authorisation from major agencies |
| Legal classification | Varies by jurisdiction | Prescription-only or controlled in several countries |
| Common synonyms | Melanotan II; MT-II | Also referenced by catalogue codes |
| Typical analytical method | Reverse-phase HPLC | Often paired with mass spectrometry |
| Primary literature focus | Receptor pharmacology | Pigmentation and melanocortin signalling |
Identity and purity are assessed with chromatographic and mass spectrometric techniques. Reversed-phase high-performance liquid chromatography separates the target peptide from related impurities and degradation products, and the resulting retention time is compared against a reference standard. Mass spectrometry, often coupled to liquid chromatography, confirms molecular mass. Amino acid analysis or peptide mapping can provide additional sequence-level confirmation when required. Results are only as reliable as the reference materials used alongside them.
Regulatory treatment varies by country. In the United States, melanotan-2 is not approved for any indication, and products marketed for human use fall outside the approved drug framework. Some other jurisdictions have placed it under prescription controls or listed it as a prohibited or restricted substance. Online listings frequently describe the material as a research chemical, a category that does not carry the same manufacturing and labelling requirements as approved medicines.
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.
Human data remain limited and mostly short-term. Reports describe small trials and observational accounts rather than large controlled studies, so questions about dose-response relationships and long-term effects on melanocytes stay open. Whether repeated exposure alters naevus behaviour is not settled in the published record. Researchers also note that self-administered use outside clinical settings makes actual exposure difficult to quantify. Statements about efficacy and safety should therefore be read as preliminary rather than established.
Lyophilised peptide powder is comparatively stable when kept dry, cold and protected from light. Once dissolved, the molecule is exposed to hydrolysis, oxidation and microbial growth, and degradation accelerates at higher temperatures and in alkaline solution. Repeated freeze-thaw cycles concentrate solutes and promote aggregation. Handling guidance for research peptides commonly clusters around freezer temperatures for powder and short refrigerated use for reconstituted solutions, with pH control and sterile technique applied throughout.
Verification of a purchased sample requires documentation linking a batch to a certificate of analysis, and that document should be read for the methods used rather than the headline purity figure. A single chromatographic percentage does not establish identity. Independent laboratories can perform identity and content assays, but no such test establishes that a product is suitable for human use. Claims about efficacy rest largely on small, early studies rather than on replicated controlled trials, and that gap remains open.
Identity testing for a cyclic peptide of this size usually relies on reversed-phase high-performance liquid chromatography coupled to mass spectrometry. The mass spectrum confirms molecular weight, while the chromatographic trace indicates the proportion of related impurities. Tandem mass spectrometry can provide sequence-level information when fragmentation data are compared against a reference standard. Nuclear magnetic resonance is sometimes used to confirm the lactam bridge, although it requires more material and greater operator expertise than routine chromatographic methods.
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.
Bayesian inference of phylogeny combines the information in the prior and in the data likelihood to create the so-called posterior probability of trees, which is the probability that the tree is correct given the data, the prior and the likelihood model. Bayesian inference was introduced into molecular phylogenetics in the 1990s by three independent groups: Bruce Rannala and Ziheng Yang in Berkeley, Bob Mau in Madison, and Shuying Li in University of Iowa, the last two being PhD students at the time. The approach has become very popular since the release of the MrBayes software in 2001, and is now one of the most popular methods in molecular phylogenetics.
As an integral component of the Barshop Institute's comprehensive research training portfolio, UT-MSTAR complements the Institute's graduate and postdoctoral training programs while expanding opportunities for early-career investigators to enter the field of aging research.
Convergent evolution—the repeated evolution of similar traits in multiple lineages which all ancestrally lack the trait—is rife in nature, as illustrated by the examples below. The ultimate cause of convergence is usually a similar evolutionary biome, as similar environments will select for similar traits in any species occupying the same ecological niche, even if those species are only distantly related. In the case of cryptic species, it can create species which are only distinguishable by analysing their genetics. Distantly related organisms often develop analogous structures by adapting to similar environments.
Sources: en.wikipedia.org
Deborah Kay Dunn-Walters FMedSci (born September 1963) is a British immunologist who is Professor of Immunology and Associate Dean for Research and Innovation at the University of Surrey. Her research considers B-cell development in healthy ageing and in disease, particularly from the viewpoint of antibody repertoires. During the COVID-19 pandemic, Dunn-Walters focussed on mapping responses to SARS-CoV-2 infection and the development of single cell analyses of the immunological responses to a COVID-19 vaccine. She was a member of the Scientific Advisory Group for Emergencies, and provided the government with scientific advice during the pandemic.
== Honours and awards == Fellow of the Royal Society of Canada, 1925 Fellow of the Royal Society, 1933 Honorary Doctorate D.Sc, Harvard University, 1936 Cameron Prize for Therapeutics of the University of Edinburgh, 1937 Commander of the Order of the British Empire, 1943 Honorary Doctorate D.Sc., University of Oxford, 1946 Honorary Doctorate, University of Alberta, 1946 Medal of Freedom with Silver Palm (US), 1947 Banting Medal of the American Diabetes Association, 1960 Honorary Doctorate D.Sc. from the University of Western Ontario, 30 May 1964
Lawrencium is a synthetic chemical element; it has symbol Lr (formerly Lw) and atomic number 103. It is named after Ernest Lawrence, inventor of the cyclotron, a device used to discover many artificial radioactive elements. A radioactive metal, lawrencium is the eleventh transuranium element, the third transfermium, and the last member of the actinide series. Like all elements with atomic numbers over 100, lawrencium can only be produced in particle accelerators by bombarding lighter elements with charged particles. Fourteen isotopes of lawrencium are known; the most stable is 266Lr with half-life 11 hours, but the shorter-lived 260Lr (half-life 2.7 minutes) is most commonly used in chemistry because it can be produced on a larger scale. Chemistry experiments confirm that lawrencium behaves as a heavier homolog to lutetium in the periodic table, and is trivalent. It could thus also be classified as the first of the 7th-period transition metals. Its electron configuration is anomalous for its position in the periodic table, having an s2p configuration instead of the s2d configuration of its homolog lutetium. However, this does not appear to affect lawrencium's chemistry. In the 1950s, 1960s, and 1970s, many claims of synthesis of element 103 of varying quality were made by laboratories in the Soviet Union and the United States. The priority of the discovery and therefore the name of the element was disputed between Soviet and American scientists.
Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus). The parent nucleus transforms or "decays" into a daughter product, with a mass number that is reduced by four and an atomic number that is reduced by two. An alpha particle is identical to the nucleus of a helium-4 atom, which consists of two protons and two neutrons. For example, uranium-238 undergoes alpha decay to form thorium-234. While alpha particles have a charge +2 e, this is not usually shown because a nuclear equation describes a nuclear reaction without considering the electrons – a convention that does not imply that the nuclei necessarily occur in neutral atoms. Except for beryllium-8 (which decays to two alpha particles), alpha decay typically occurs in the heaviest nuclides. Theoretically, it can occur only in nuclei somewhat heavier than nickel (element 28), where the overall binding energy per nucleon is no longer a maximum and the nuclides are therefore unstable toward spontaneous fission-type processes. In practice, this mode of decay has only been observed in nuclides considerably heavier than nickel, with the lightest known alpha emitter (other than beryllium-8) being the second lightest isotope of antimony, 104Sb. Alpha decay is by far the most common form of cluster decay, where the parent atom ejects a defined daughter collection of nucleons, leaving another defined product behind. It is the most common form because of the combined extremely high nuclear binding energy and relatively small mass of the alpha particle.
Sources: en.wikipedia.org
=== Imaging === After determination using biomarkers, a variety of imaging studies may be used to differentiate between intrahepatic or extrahepatic cholestasis. Ultrasound is often used to identify the location of the obstruction but, is often insufficient in determining the level of biliary obstruction or its cause because it can pick up bowel gas that may interfere with readings. CT scans are not impacted by bowel gas and may also be more suitable for overweight patients. Typically, the cause of cholestasis and magnitude of obstruction is better diagnosed with CT compared to ultrasound. MRI scans provide similar information to CT scans but are more prone to interference from breathing or other bodily functions. Although CT, ultrasound, and MRI may help differentiate intrahepatic and extrahepatic cholestasis, the cause and extent of obstruction is best determined by cholangiography. Potential causes of extrahepatic cholestasis include obstructions outside the wall of the lumen, those outside the duct, and obstructions found in the duct lumen. Endoscopic retrograde cholangiography may be useful to visualize the extrahepatic biliary ducts. In case of anatomical anomalies, or if endoscopic retrograde cholangiography is unsuccessful, percutaneous transhepatic cholangiography may be used. CT or MRI-based cholangiography may also be useful, particularly in cases where additional interventions are not anticipated.
Recent changes in Moscow's regional climate are often cited by climate scientists as evidence of global warming, since the city is in the middle latitudes of the Northern Hemisphere; however, by definition, climate change is global, not regional. During the summer, very high temperatures are often recorded in the city (in 2001, 2002, 2003, 2010, 2011, and 2021). Along with the southern part of Central Russia, after recent years of hot summer seasons, Moscow's climate shows hot-summer classification trends. Winter has also become significantly milder: for example, the average January temperature in the early 1900s was −12.0 °C (10.4 °F), while it is currently about −7.0 °C (19.4 °F). The end of January–February is often colder, with frosts reaching −30.0 °C (−22.0 °F) a few nights per year (in 2006, 2010, 2011, 2012, and 2013). As of 2024, the most recent decade was the warmest in the history of meteorological observations of Moscow. Temperature changes in the city are shown in the table below:
The atomic radii of the alkali metals increase going down the group. Because of the shielding effect, when an atom has more than one electron shell, each electron feels electric repulsion from the other electrons as well as electric attraction from the nucleus. In the alkali metals, the outermost electron only feels a net charge of +1, as some of the nuclear charge (which is equal to the atomic number) is cancelled by the inner electrons; the number of inner electrons of an alkali metal is always one less than the nuclear charge. Therefore, the only factor which affects the atomic radius of the alkali metals is the number of electron shells. Since this number increases down the group, the atomic radius must also increase down the group. The ionic radii of the alkali metals are much smaller than their atomic radii. This is because the outermost electron of the alkali metals is in a different electron shell than the inner electrons, and thus when it is removed the resulting atom has one fewer electron shell and is smaller. Additionally, the effective nuclear charge has increased, and thus the electrons are attracted more strongly towards the nucleus and the ionic radius decreases.
Sources: en.wikipedia.org
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.
Much of the evidence comes from case reports and accounts of unregulated use rather than controlled trials. Differences in product purity and dosing add further variability.
Laboratory work focuses on receptor binding and cellular signalling. Observational reports document outcomes after use, and analytical chemists examine samples to assess content and purity.
No. It is a laboratory-made peptide, while the natural hormone is alpha-melanocyte-stimulating hormone, a longer peptide produced by the pituitary gland and by skin cells. Melanotan-2 mimics only a short active region of that hormone and contains non-natural residues such as D-phenylalanine.