amino acid substitution is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Updated 2025-07-25. Numbers and descriptions here follow the published literature rather than marketing material.
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.
Solid peptide kept dry at minus twenty degrees Celsius, shielded from light and moisture, is generally considered stable for extended periods. Solutions are divided into single-use aliquots and held at minus twenty or minus eighty degrees Celsius, because repeated freeze-thaw cycles promote aggregation and loss of material to container surfaces. Hydrolysis of the backbone and oxidation of tryptophan are the principal degradation routes in aqueous solution, and both accelerate at ambient temperature. Hygroscopic uptake after a vial is opened can also shift the actual mass weighed, which affects any concentration calculated from it.
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.
| Property | Value | Notes |
|---|---|---|
| Compound class | Synthetic cyclic heptapeptide | Alpha-MSH analogue containing a D-phenylalanine residue |
| Molecular formula | C50H69N15O9 | Average molecular mass approximately 1024.2 g/mol |
| Appearance | White to off-white lyophilised powder | Normally supplied as a freeze-dried solid in a sealed vial |
| Solubility | Freely soluble in water and polar solvents | Dissolves readily in aqueous buffers and in alcohol-water mixtures |
| Receptor targets | MC1R, MC3R, MC4R, MC5R | Acts as a non-selective melanocortin receptor agonist |
The compound was developed in the late 1980s and early 1990s by academic researchers investigating melanocortin signaling and pigmentation. Early work explored whether synthetic analogs could reproduce effects of the natural hormone under controlled conditions. The molecule never advanced through the full regulatory pathway required for approval as a medicine. From the mid-2000s onward it appeared in unregulated consumer markets, often distributed through informal channels. That gap between research origins and commercial availability shapes how the compound is discussed today.
Melanotan-2 is a synthetic peptide designed as an analog of alpha-melanocyte-stimulating hormone, a signaling molecule produced in the pituitary and skin. Its structure is a linear chain of seven amino acids that folds into a ring through an internal lactam bridge joining two side chains. The compound is sometimes written as MT-II or MEL-2 in informal and commercial contexts. It belongs to the melanocortin peptide family, a group of short signaling molecules that share a conserved core sequence recognized by melanocortin receptors.
Two structural changes distinguish the synthetic peptide from the natural hormone. A norleucine residue replaces methionine at one position, and a D-configured phenylalanine replaces the natural L-form at another. Both substitutions slow enzymatic breakdown, which extends the molecule's persistence relative to the parent hormone. The lactam bridge further constrains the backbone into a stable conformation. These features are standard design strategies in peptide chemistry and are not unique to this compound; they appear across many research peptides built for improved stability.
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.
At anesthetic doses, 10–20% of adults and 1–2% of children experience adverse psychiatric reactions that occur during emergence from anesthesia, ranging from dreams and dysphoria to hallucinations and emergence delirium. Psychotomimetic effects decrease when adding lamotrigine and nimodipine and can be counteracted by pretreatment with a benzodiazepine or propofol. Ketamine anesthesia commonly causes tonic-clonic movements (greater than 10% of people) and rarely hypertonia. Vomiting can be expected in 5–15% of the patients; pretreatment with propofol mitigates it as well. Laryngospasm occurs only rarely with ketamine. Ketamine, generally, stimulates breathing; however, in the first 2–3 minutes of a high-dose rapid intravenous injection, it may cause a transient respiratory depression. At lower sub-anesthetic doses, psychiatric side effects are prominent. The most common psychiatric side effects are dissociation, visual distortions, and numbness. Also common (20–50%) are difficulty speaking, confusion, euphoria, drowsiness, and difficulty concentrating. Hallucinations are described by 6–10% of people. Dizziness, blurred vision, dry mouth, hypertension, nausea, increased or decreased body temperature, or flushing are the common (>10%) non-psychiatric side effects. All these adverse effects are most pronounced by the end of the injection, dramatically reduced 40 minutes afterward, and completely disappear within 4 hours after the injection.
Few foods naturally contain vitamin D. Cod liver oil as a dietary supplement contains 450 IU/teaspoon. Fatty fish (but not lean fish such as tuna) are the best natural food sources of vitamin D3. Beef liver, eggs, and cheese have modest amounts. Mushrooms provide variable amounts of vitamin D2, as mushrooms can be treated with UV light to greatly increase their content. In certain countries, breakfast cereals, dairy milk and plant milk products are fortified. Infant formulas are fortified with 400 to 1000 IU per liter, a normal volume for a full-term infant after the first month. Cooking only minimally decreases vitamin content.
In 2018, Trump signed into law the First Step Act which, among other federal prison reforms, made the 2010 Fair Sentencing Act retroactive. A US Supreme Court decision in 2021 determined that retroactivity applied to cases where mandatory minimum penalties had been imposed. In 2020, both the ACLU and The New York Times reported that Republicans and Democrats were in agreement that it was time to end the war on drugs. During his presidential campaign, President Joe Biden (2021–2025) stated that he would take the steps to alleviate the war on drugs and end the opioid epidemic. On December 4, 2020, during the Trump administration, the House of Representatives passed the Marijuana Opportunity Reinvestment and Expungement Act (MORE Act), which would decriminalize cannabis at the federal level by removing it from the list of scheduled substances, expunge past convictions and arrests, and tax cannabis to "reinvest in communities targeted by the war on drugs". The MORE Act was received in the Senate in December 2020 where it remained. In April 2022, the act was again passed by the House, and awaits Senate action. Over time, states in the US have approached drug liberalization at a varying pace. Initially, in the 1930s, the states were ahead of the federal government in prohibiting cannabis; in recent decades, the trend has reversed. Beginning with cannabis for medical use in California in 1996, states began to legalize cannabis.
== See also == Renin-angiotensin system: When the blood flow through the juxtaglomerular apparatus decreases, blood pressure is considered low, and the adrenal cortex secretes aldosterone to increase sodium reabsorption in the collecting duct, thereby increasing blood pressure. Bainbridge reflex: In response to stretching of the right atrium wall, heart rate increases, lowering venous blood pressure. Baroreflex: When the stretch receptors in the aortic arch and carotid sinus increase, the blood pressure is considered to be elevated and the heart rate decreases to lower blood pressure. Antidiuretic hormone: The hypothalamus detects the extracellular fluid hyperosmolality and the posterior pituitary gland secretes antidiuretic hormone to increase water reabsorption in the collecting duct.
Sources: en.wikipedia.org
== Causes == The syndrome is thought to arise from a mutation of several collagen genes during fetal development. It is a sex independent autosomal dominant trait meaning a person with the syndrome has a 50% chance of passing it on to each child. There are three variants of Stickler syndrome identified, each associated with a collagen biosynthesis gene. A metabolic defect concerning the hyaluronic acid and the collagen of the 2-d type is assumed to be the cause of this syndrome.
I have been frequently asked why I invented the name "Penicillin". I simply followed perfectly orthodox lines and coined a word which explained that the substance penicillin was derived from a plant of the genus Penicillium just as many years ago the word "Digitalin" was invented for a substance derived from the plant Digitalis. In modern usage penicillin is used more broadly to refer to any β-lactam antimicrobial that contains a thiazolidine ring fused to the β-lactam core and may or may not be a natural product. Like most natural products, penicillin is present in Penicillium moulds as a mixture of active constituents (gentamicin is another example of a natural product that is an ill-defined mixture of active components). The principal active components of Penicillium are listed in the following table:
=== February === 3 February – Prime Minister Keir Starmer rejects an allegation that he broke COVID-19 regulations by having a voice coach present at a press conference where he responded to a Brexit deal negotiated by Boris Johnson. For the first time, Reform UK have led an opinion poll, after coming top with 25% in a YouGov poll for Sky News. Labour are second on 24%, with the Conservatives on 21%. Northern Ireland's Economy Minister, Conor Murphy steps down from the post and announces he will leave Stormont after being elected to the Irish Seanad. Caoimhe Archibald is appointed to replace him as Economy Minister. 4 February – BBC News reports that Jack Lopresti, the former Conservative MP for Filton and Bradley Stoke who lost the seat at the last general election has joined the Ukrainian military. Welsh Conservatives leader Darren Millar and his colleague Russell George miss a Senedd vote on the Eluned Morgan government's budget for 2025–26 because they have travelled to the United States for the annual National Prayer Breakfast. 5 February – Deputy Prime Minister Angela Rayner confirms that local elections in East Sussex, West Sussex, Essex, Thurrock, Hampshire, the Isle of Wight, Norfolk, Suffolk and Surrey will be delayed for a year to allow major local government reorganisations to take place. Four of the seven MPs suspended from the Labour Party for voting against the child benefit cap are readmitted to the party; they are Richard Burgon, Ian Byrne, Imran Hussain and Rebecca Long-Bailey.
In July 2015, Allergan agreed to sell its generic drug business (Actavis Generics) to Teva for $40.5 billion ($33.75 billion in cash and $6.75 billion worth of shares). As a result, Teva dropped its pursuit of Mylan. In order for the deal to gain regulatory approval, Teva sold off a number of assets, including a portfolio of five generic drugs to Sagent Pharmaceuticals for $40 million, as well as a further eight medicines to Dr. Reddy's in a $350 million deal. Teva also sold a further 15 marketed generics, as well as three others that were close to market, for $586 million to Impax Laboratories. In July, Teva sold off a further 42 products to Australian generics company, Mayne Pharma, for $652 million; the deal moved Mayne up 50 spots, into the top-25 companies of US generic companies. As part of the deal Teva will seek to raise $20 to $25 billion through a bond sale. After completing the $39 billion acquisition of Actavis Generics, Teva announced another, smaller, deal with Allergan, agreeing to acquire its generic distribution business Anda for $500 million.
=== Treatment of corneal thinning === Keratoconus is the most common form of corneal ectasia, a progressive thinning of the cornea. The condition is treated by corneal collagen cross-linking, which increases corneal stiffness. Cross-linking is achieved by applying a topical riboflavin solution to the cornea, which is then exposed to ultraviolet A light.
Sources: en.wikipedia.org
=== Non-inhibitory roles === Non-inhibitory extracellular serpins also perform a wide array of important roles. Thyroxine-binding globulin and transcortin transport the hormones thyroxine and cortisol, respectively. The non-inhibitory serpin ovalbumin is the most abundant protein in egg white. Its exact function is unknown, but it is thought to be a storage protein for the developing foetus. Heat shock serpin 47 is a chaperone, essential for proper folding of collagen. It acts by stabilising collagen's triple helix whilst it is being processed in the endoplasmic reticulum. Some serpins are both protease inhibitors and perform additional roles. For example, the nuclear cysteine protease inhibitor MENT, in birds also acts as a chromatin remodelling molecule in a bird's red blood cells.
Adriaens, D. and Verraes, W. (1997). Ontogeny of the maxillary barbel muscles in Clarias gariepinus (Siluroidei: Clariidae), with some notes on the palatine-maxillary mechanism. Journal of Zoology (London) 241, 117–133. Bailey, D.M. , Wagner, H.J., Jamieson, A.J., Ross, M.F. and Priede, I.G. (2007) A taste of the deep-sea: The roles of gustatory and tactile searching behaviour in the grenadier fish Coryphaenoides armatus. Deep-Sea Research Part I: Oceanographic Research Papers, 54(1), pp. 99–108. (doi:10.1016/j.dsr.2006.10.005) de Freitas Barros Neto, L., Frigo, R. G., Gavilan, S. A., de Moura, S. A. B., & Lima, S. M. Q. (2020). Barbel development associated to aquatic surface respiration in Triportheus signatus (Characiformes: Triportheidae) from the semiarid Caatinga rivers. Environmental Biology of Fishes, 103(1), 89–98. https://doi.org/10.1007/s10641-019-00935-x Eakin, R. R., Eastman, J. T. and Vacchi, M. (2006). Sexual dimorphism and mental barbel structure in the South Georgia plunderfish Artedidraco mirus (Perciformes : Notothenioidei : Artedidraconidae). Polar Biology 30, 45–52. Fadaee, B., Pourkazemi, M., Tavakoli, M., Joushideh, H., Khoshghalb, M. R. B., Hosseini, M. R. and Abdulhay, H. (2006). Tagging and tracking juvenile sturgeons in shallow waters of the Caspian Sea (less than 10 m depth) using CWT (Coded Wire Tags) and barbel incision. Journal of Applied Ichthyology 22, 160–165. Fox, H. (1999). Barbels and barbel-like tentacular structures in sub-mammalian vertebrates: A review. Hydrobiologia 403, 153–193. Grover-Johnson, N. and Farbman, A. (1976).
Direct interaction with DNA is the simplest and the most direct method by which a protein changes transcription levels. Genes often have several protein binding sites around the coding region with the specific function of regulating transcription. There are many classes of regulatory DNA binding sites known as enhancers, insulators and silencers. The mechanisms for regulating transcription are varied, from blocking key binding sites on the DNA for RNA polymerase to acting as an activator and promoting transcription by assisting RNA polymerase binding. The activity of transcription factors is further modulated by intracellular signals causing protein post-translational modification including phosphorylation, acetylation, or glycosylation. These changes influence a transcription factor's ability to bind, directly or indirectly, to promoter DNA, to recruit RNA polymerase, or to favor elongation of a newly synthesized RNA molecule. The nuclear membrane in eukaryotes allows further regulation of transcription factors by the duration of their presence in the nucleus, which is regulated by reversible changes in their structure and by binding of other proteins. Environmental stimuli or endocrine signals may cause modification of regulatory proteins eliciting cascades of intracellular signals, which result in regulation of gene expression. It has become apparent that there is a significant influence of non-DNA-sequence specific effects on transcription.
Prominent Romanian painters include: Nicolae Grigorescu, Ștefan Luchian, Ion Andreescu Nicolae Tonitza, and Theodor Aman. Notable Romanian classical composers of the 19th and 20th centuries include: Ciprian Porumbescu, Anton Pann, Eduard Caudella, Mihail Jora, Dinu Lipatti, and especially George Enescu. The annual George Enescu Festival is held in Bucharest in honour of the 20th-century composer. Contemporary musicians like Angela Gheorghiu, Gheorghe Zamfir, Inna, Alexandra Stan, and many others have achieved various levels of international acclaim. From the late 2000s through the early 2010s, the Romanian popcorn music style had established itself in the international mainstream. At the Eurovision Song Contest Romanian singers achieved third place in 2005 and 2010. In cinema, several movies of the Romanian New Wave have achieved international acclaim. At the Cannes Film Festival, The Death of Mr. Lazarescu by Cristi Puiu won the Prix Un Certain Regard in 2005, while 4 Months, 3 Weeks and 2 Days by Cristian Mungiu won the festival's top prize, the Palme d'Or, in 2007. At the Berlin International Film Festival, Child's Pose by Călin Peter Netzer won the Golden Bear in 2013. The list of World Heritage Sites includes six cultural sites located within Romania, including eight painted churches of northern Moldavia, eight wooden churches of Maramureș, seven villages with fortified churches in Transylvania, the Horezu Monastery, and the Historic Centre of Sighișoara.
Sources: en.wikipedia.org
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.
No approved regulatory indication exists in major markets. An approval exists for a different peptide, afamelanotide, which is used for a rare photosensitivity disorder called erythropoietic protoporphyria. Melanotan-2 itself remains a research compound with no cleared clinical role.
Melanocortin-1 receptors on melanocytes are the receptor most closely linked to pigment production. The peptide is not selective, however, and also activates melanocortin-3, melanocortin-4, and melanocortin-5 receptors. That lack of selectivity is the usual explanation offered for both its range of observed effects and its off-target effects.
Purity is normally stated as an area percentage from high-performance liquid chromatography, for example ninety-five or ninety-eight percent. That figure describes the proportion of ultraviolet-absorbing material eluting as the main peak. It says nothing about water content, counterions, residual solvents or mass fraction of the peptide itself.