Everything below concerns analytical characterisation. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2025-10-10. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | Melanotan II; MT-II; N-acetyl-norleucyl-cyclo[Asp-His-D-Phe-Arg-Trp-Lys] amide | Naming follows peptide convention; the numeral distinguishes it from melanotan-1 |
| Molecular formula | C50H69N15O9 | Includes the lactam bridge; no counter-ion assumed |
| Monoisotopic mass | 1023.53 Da | Free base; salts and counter-ions shift the observed value |
| Appearance | White to off-white lyophilised powder | Batch-to-batch colour variation is not itself proof of impurity |
| Typical analytical method | RP-HPLC purity determination with ESI-MS identity confirmation | Retention time alone does not establish sequence identity |
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.
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.
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.
Solid peptide material is generally stable when kept cold and dry. Common practice is storage at -20 degrees Celsius or lower, with desiccant and protection from light. Repeated freeze-thaw cycles and exposure to moisture are associated with degradation, aggregation, or loss of material. Once dissolved, stability depends on solvent, concentration, and temperature, and solutions are usually treated as short-lived unless stability data support longer periods. Handling notes typically emphasise minimising time at ambient temperature.
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.
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.
Hong Kong is a special administrative region of China, with executive, legislative, and judicial powers devolved from the national government. The Sino-British Joint Declaration provided for economic and administrative continuity through the handover, resulting in an executive-led governing system largely inherited from the territory's history as a British colony. Under these terms and the "one country, two systems" principle, the Basic Law of Hong Kong is the regional constitution. The regional government is composed of three branches:
There are multiple reasons why isomerization is favored here. First, a bulky ligand set is usually used in these processes, such as phosphines, and it is highly unfavorable for them to adopt a cis orientation relative to each other, resulting in isomerization to the more favorable trans product. An alternative explanation for this phenomenon, dubbed antisymbiosis or transphobia, is by invocation of the sdn model. Under this theory, palladium is a hypervalent species. Hence R1 and the trans ligand, being trans to each other, will compete with one palladium orbital for bonding. This 4-electron 3-center bond is weakest when two strong donating groups are present, which heavily compete for the palladium orbital. Relative to any ligand normally used, the C-donor R1 ligand has a much higher trans effect. This trans influence is a measure of how competitive ligands trans to each other will compete for palladium's orbital. The usual ligand set, phosphines, and C-donors (R1) are both soft ligands, meaning that they will form strong bonds to palladium, and heavily compete with each other for bonding. Since halides or pseudohalides are significantly more electronegative, their bonding with palladium will be highly polarized, with most of the electron density on the X group, making them low trans effect ligands. Hence, it will be highly favorable for R1 to be trans to X, since the R1 group will be able to form a stronger bond to the palladium.
=== Delilah Fielding === Delilah Fielding McGee (Margo Harshman) is a Department of Defense analyst and McGee's girlfriend and later his wife. An agent with the Department of Defense, Delilah is first mentioned during the Season 10 finale "Damned If You Do" as a woman McGee has been flirting with who sends him some confidential information relating to a case. She first appears in the Season 11 premiere episode, "Whiskey Tango Foxtrot", during a coffee date with McGee and later becomes an ally, assisting the NCIS team in their hunt for terrorist Benham Parsa. In the Season 11 episodes "Kill Chain" and "Double Back", Delilah is left badly injured in a missile attack at a black-tie event she and McGee are attending. While McGee is not seriously injured, Delilah is left permanently paralyzed due to shrapnel embedded in her spine, and she thereafter uses a wheelchair. She soon recovers from the incident and continues to assist the NCIS team. In the episode "Page Not Found", McGee confides in Tony that he is planning to ask Delilah to move in with him; Delilah later reveals to Tony that she wants to take a job opening for a senior intelligence analyst, which would require her to move to Dubai for a year. Tony then separately tells the two about their other half's plans; McGee allows her to take the job, and they agree to continue their relationship long-distance. McGee also gives her a copy of his house key, which she accepts, reiterating her intent to move in with him after her assignment is over.
Alpha-synuclein has been shown to interact with Dopamine transporter, Parkin (ligase), Phospholipase D1, SNCAIP, Tau protein. Beta amyloid Synuclein Contursi Terme - the village in Italy where a mutation in the α-synuclein gene led to a family history of Parkinson's disease Anti-α-synuclein drug Media related to Alpha-synuclein at Wikimedia Commons alpha-Synuclein at the U.S. National Library of Medicine Medical Subject Headings (MeSH) Human SNCA genome location and SNCA gene details page in the UCSC Genome Browser.
Tranexamic acid is a medication used to treat or prevent excessive blood loss from major trauma, postpartum bleeding, surgery, tooth removal, nosebleeds, and heavy menstruation. It is also used for hereditary angioedema. It is taken either by mouth, injection into a vein, or by intramuscular injection. Tranexamic acid is a synthetic analog of the amino acid lysine. It serves as an antifibrinolytic by reversibly binding four to five lysine receptor sites on plasminogen. This decreases the conversion of plasminogen to plasmin, preventing fibrin degradation and preserving the framework of fibrin's matrix structure. Tranexamic acid has roughly eight times the antifibrinolytic activity of an older analogue, ε-aminocaproic acid. Tranexamic acid also directly inhibits the activity of plasmin with weak potency (IC50 = 87 mM), and it can block the active-site of urokinase plasminogen activator (uPA) with high specificity (Ki = 2 mM), one of the highest among all the serine proteases. Side effects are rare; they include changes in color vision, seizures, blood clots, and allergic reactions. Tranexamic acid appears to be safe for use during pregnancy and breastfeeding. Tranexamic acid was first made in 1962 by Japanese researchers Shosuke and Utako Okamoto. It is on the World Health Organization's List of Essential Medicines. Tranexamic acid is available as a generic drug.
Sources: en.wikipedia.org
Currently, no over-the-counter weight-loss supplements have met criteria for recommended use by physicians. Dexatrim claims to provide a powerful benefit for weight loss despite the lack of scientific data to support their claims. Dexatrim further provides a disclaimer that no claims of efficacy and safety made by Dexatrim have been approved by the FDA. Although available OTC, the active ingredients in Dexatrim products carry risk of side effects, adverse reactions and adverse drug interactions, particularly if used at high-recommended or higher-than-recommended doses and/or for prolonged periods. The Dexatrim product itself carries a warning about the possible side effects of Dexatrim in patients with a history of high blood pressure, and also recommends the advice of a qualified physician before taking Dexatrim. In addition, the use of Dexatrim or other OTC weight-loss supplements presents a possible factor in establishing disruptive eating patterns, increases the risk that individuals will use these OTC supplements in lieu of seeking proper medical and nutritional consultation, and presents increased psychological risks associated with unsuccessful weight-loss attempts.
Amitriptyline, formerly sold under the brand name Elavil among others, is a tricyclic antidepressant primarily used to treat major depressive disorder, and a variety of pain syndromes such as neuropathic pain, fibromyalgia, migraine and tension headaches. Due to the frequency and prominence of side effects, amitriptyline is generally considered a second-line therapy for these indications. The most common side effects are dry mouth, drowsiness, dizziness, constipation, and weight gain. Glaucoma, liver toxicity and abnormal heart rhythms are rare but serious side effects. Blood levels of amitriptyline vary significantly from one person to another, and amitriptyline interacts with many other medications potentially aggravating its side effects. Amitriptyline was discovered in the late 1950s by scientists at Merck and approved by the US Food and Drug Administration (FDA) in 1961. It is on the World Health Organization's List of Essential Medicines. It is available as a generic medication. In 2023, it was the 90th most commonly prescribed medication in the United States, with more than 7 million prescriptions.
== Chemical structure == The chemical structure of sodium stibogluconate is somewhat ambiguous, and the structure shown above is idealized. Its solutions may contain multiple antimony compounds, although this heterogeneity may be unimportant. It has been speculated that the active species contains only a single antimony centre.
18 July A survey of more than 3,000 experts finds that the extinction crisis could be worse than previously thought, and estimates that roughly 30% of species "have been globally threatened or driven extinct since the year 1500." The first "dormant" black hole (meaning it does not emit high levels of X-ray radiation) is identified outside the Milky Way. The object, with nine solar masses, orbits a rare O-type star in a system called VFTS 243 within the Large Magellanic Cloud. A study shows that climate change-related exceptional marine heatwaves in the Mediterranean Sea during 2015–2019 resulted in widespread mass sealife die-offs in five consecutive years. 20 July – Scientists report that SARS-CoV-2 builds tunneling nanotubes from nose cells to gain access to the brain. 21 July A potential gene therapy cure for haemophilia B, which corrects the genetic defect associated with the condition is announced with trial results by doctors. It caused a sustained increase in factor IX activity in 9 of 10 patients in the small trial. Sunspot AR3060 explodes early in the morning. It releases a C-5 class solar flare, and a "solar tsunami". The NOAA predicts that a geomagnetic storm from this event will strike the Earth on 23 July, between 0000 UTC and 0400 UTC, as a G2 class storm, with a slight chance of a G3 storm. Aurorae could be visible as far south as 50° N latitude. Researchers report the development of deep learning software that can design proteins that contain prespecified functional sites.
Sources: en.wikipedia.org
== Synthesis in nonhuman organisms == Leucine is an essential amino acid in the diet of animals because they lack the complete enzyme pathway to synthesize it de novo from potential precursor compounds. Consequently, they must ingest it, usually as a component of proteins. Plants and microorganisms synthesize leucine from pyruvic acid with a series of enzymes:
==== MeSH D13.695.667 – purine nucleotides ==== MeSH D13.695.667.138 – adenine nucleotides MeSH D13.695.667.138.124 – adenosine diphosphate MeSH D13.695.667.138.124.070 – adenosine diphosphate sugars MeSH D13.695.667.138.124.070.075 – adenosine diphosphate glucose MeSH D13.695.667.138.124.070.125 – adenosine diphosphate ribose MeSH D13.695.667.138.124.070.125.040 – o-acetyl-adp-ribose MeSH D13.695.667.138.124.070.125.195 – cyclic adp-ribose MeSH D13.695.667.138.180 – adenosine monophosphate MeSH D13.695.667.138.180.080 – adenosine phosphosulfate MeSH D13.695.667.138.236 – adenosine triphosphate MeSH D13.695.667.138.236.050 – adenylyl imidodiphosphate MeSH D13.695.667.138.236.250 – ethenoadenosine triphosphate MeSH D13.695.667.138.382 – coenzyme a MeSH D13.695.667.138.382.300 – acyl coenzyme a MeSH D13.695.667.138.382.300.020 – acetyl coenzyme a MeSH D13.695.667.138.382.300.500 – malonyl coenzyme a MeSH D13.695.667.138.382.300.700 – palmitoyl coenzyme a MeSH D13.695.667.138.395 – cyclic amp MeSH D13.695.667.138.395.225 – 8-bromo cyclic adenosine monophosphate MeSH D13.695.667.138.395.250 – bucladesine MeSH D13.695.667.138.410 – deoxyadenine nucleotides MeSH D13.695.667.138.506 – flavin-adenine dinucleotide MeSH D13.695.667.138.694 – nad MeSH D13.695.667.138.749 – nadp MeSH D13.695.667.138.850 – phosphoadenosine phosphosulfate MeSH D13.695.667.138.925 – vidarabine phosphate MeSH D13.695.667.454 – guanine nucleotides MeSH D13.695.667.454.160 – cyclic gmp MeSH D13.695.667.454.160.325 – dibutyryl cyclic gmp MeSH D13.695.667.454.200 – deoxyguanine nucleotides MeSH D13.695.667.454.340 – guanosine diphosphate MeSH D13.695.667.454.340.350 – guanosine diphosphate sugars MeSH D13.695.667.454.340.350.400 – guanosine diphosphate fucose MeSH D13.695.667.454.340.350.500 – guanosine diphosphate mannose MeSH D13.695.667.454.440 – guanosine pentaphosphate MeSH D13.695.667.454.480 – guanosine tetraphosphate MeSH D13.695.667.454.504 – guanosine triphosphate MeSH D13.695.667.454.504.380 – guanosine 5'-o-(3-thiotriphosphate) MeSH D13.695.667.454.504.400 – guanylyl imidodiphosphate MeSH D13.695.667.454.525 – 5'-guanylic acid MeSH D13.695.667.454.700 – rna caps MeSH D13.695.667.454.700.710 – rna cap analogs MeSH D13.695.667.616 – inosine nucleotides MeSH D13.695.667.616.300 – cyclic imp MeSH D13.695.667.616.400 – inosine diphosphate MeSH D13.695.667.616.500 – inosine monophosphate MeSH D13.695.667.616.800 – inosine triphosphate
Recent economic growth has led to a considerable increase of new millionaires, including the new entrepreneurs, Colombians with a net worth exceeding US$1 billion. In 2017, however, the National Administrative Department of Statistics (DANE) reported that 26.9% of the population were living below the poverty line, of which 7.4% were in "extreme poverty". The multidimensional poverty rate stands at 17.0 percent of the population. The Government has also been developing a process of financial inclusion within the country's most vulnerable population. The contribution of tourism to GDP was US$5,880.3bn (2.0% of total GDP) in 2016. Tourism generated 556,135 jobs (2.5% of total employment) in 2016. Foreign tourist visits were predicted to have risen from 0.6 million in 2007 to 4 million in 2017.
Israel airstrikes struck Khiam, Zebqin, Yater, Shebaa, Nabatieh, Bir Kalb, Kfar Kila, Aalma ech Chaab, and Mays al-Jabal, killing a Hezbollah militant and a Amal Movement militant. Another three people were wounded, namely a Hezbollah militant and a Syrian national. An Israeli Navy officer was killed by a malfunctioning missile launched by the Iron Dome on a Dvora-class fast patrol boat off the coast of Nahariya, northern Israel and two others were injured. An Israel drone strike struck Zawtar El Charkiyeh. The Amal movement said one of its fighters from Khiam was killed. Hezbollah confirmed the death of six militants. Departures and arrivals were canceled at Ben Gurion Airport until 10 a.m.; two El Al flights were diverted. The Golan Regional Council instructed residents of the Golan Heights to remain in their shelters. Yoav Gallant declared an "emergency situation" for two days. Representatives of the United States were monitoring the situation. On 8 September, special forces from the Shaldag Unit raided and destroyed an Iranian rocket manufacturing facility beneath a branch of the Syrian Scientific Studies and Research Center in Masyaf, which was used to supply Hezbollah with precision rockets. On 16 September, the Security Cabinet of Israel approved a new war aim of returning evacuated residents to the north of Israel, adding to the goals of destroying Hamas and liberating the hostages.
A few days before Mr. Jardine’s departure from Canton, the entire foreign community entertained him at a dinner in the dining room of the East India Company’s Factory. About eighty persons of all nationalities, including India, were present, and they did not separate until several hours after midnight. It was an event frequently referred to afterwards amongst the residents, and to this day there are a few of us who still speak of it.
Sources: en.wikipedia.org
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.
The natural hormone is a linear tridecapeptide that is rapidly degraded in circulation. Melanotan-2 is shortened, cyclised, N-terminally acetylated, and carries a D-amino acid substitution, all of which slow enzymatic breakdown.
No national medicines regulator has approved melanotan-2 for therapeutic or cosmetic use. In several jurisdictions it is treated as an unapproved prescription medicine, and its legal classification differs from country to country.
Mass spectrometry combined with liquid chromatography provides both molecular weight confirmation and a measure of related impurities. Tandem mass spectrometry adds sequence information. A purity percentage reported without a mass measurement does not confirm what the material is.