Everything below concerns reversed-phase HPLC. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2025-10-26. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
| 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 |
The peptide was developed during the 1980s by researchers investigating melanocortin signalling and skin pigmentation pathways. Early work focused on analogues of alpha-melanocyte-stimulating hormone that would resist enzymatic breakdown more effectively than the parent molecule. Melanotan-2 emerged from that programme as a shortened, cyclised variant. Reports describing its synthesis and receptor activity later appeared in the scientific literature. Commercial availability grew through unregulated channels rather than through pharmaceutical approval.
Structurally, Melanotan-2 retains the core recognition motif of alpha-melanocyte-stimulating hormone while adding a lactam bridge that links two side chains and constrains the molecule into a ring. This modification lowers susceptibility to enzymatic degradation. The compound acts as an agonist at melanocortin receptors, particularly subtypes associated with melanin production. Because the same receptor family influences several physiological processes, researchers note that its activity is not confined to pigmentation alone. Receptor selectivity continues to be examined in published studies.
Melanotan-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone, a naturally occurring peptide involved in pigmentation signalling. Its sequence incorporates modified residues that increase potency and extend biological activity relative to the native hormone. The compound binds receptors of the melanocortin family and is examined mainly in laboratory research. It does not occur naturally and exists only as a manufactured chemical entity produced by solid-phase synthesis.
Melanotan-2 appears on the World Anti-Doping Agency prohibited list within the peptide hormone class, and several national regulators treat it as an unapproved prescription substance. Some countries restrict importation or sale for personal use. Because the compound is widely traded as a research chemical, the practical legal picture differs between jurisdictions and shifts over time. Human safety data covering long periods are limited, and whether repeated pigmentation changes carry any lasting risk to melanocytes remains an open question.
Freeze-dried melanotan-2 is normally kept as a desiccated powder at minus twenty degrees Celsius or lower, shielded from light and moisture. Peptides of this size degrade through hydrolysis, oxidation and deamidation, and each pathway accelerates as temperature and water activity rise. Repeated freeze-thaw cycles promote aggregation and loss of material, so aliquoting a stock solution before freezing is standard laboratory practice. Once dissolved, the solution is markedly less stable than the powder. In laboratory work, solutions are generally refrigerated and used within days rather than kept for months.
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.
Reversed-phase high-performance liquid chromatography is the routine method for purity assessment. Peptides absorb near 214 nm because of the peptide bond, and a gradient of acetonitrile in water separates the intact peptide from deletion sequences, oxidised products, and earlier-eluting fragments at neutral pH. Electrospray ionisation mass spectrometry provides an orthogonal check: the measured mass must agree with the theoretical value. Amino acid analysis and peptide mapping confirm structure but are used less often. Reference standards remain scarce because the peptide is not described in any pharmacopoeia.
Regulatory treatment varies by country. In the United States the peptide is not approved as a medicine, and products offered for human use may be treated as unapproved new drugs; some states also restrict sale. Australia, the United Kingdom, and European Union member states apply comparable restrictions to unapproved peptide products. Border agencies have seized shipments labelled as research chemicals. Classification may change over time, and the legal position for personal importation is not clearly settled in most published guidance.
Lyophilised melanotan-2 is supplied as a solid, which is more stable than a solution. The material is hygroscopic, so weighing is done quickly, in low humidity, with the container kept sealed. Reconstitution usually uses water for injection or bacteriostatic water, added down the wall of the vial to limit foaming. A reconstituted solution is held at 2 to 8 °C and kept away from light. Repeated freezing and thawing of the same vial is avoided because ice crystal formation and concentration effects degrade the peptide.
== Treatment == In most cases, liver function will return to normal if the offending drug is stopped early. Additionally, the patient may require supportive treatment. In acetaminophen toxicity, however, the initial insult can be fatal. Fulminant hepatic failure from drug-induced hepatotoxicity may require liver transplantation. In the past, glucocorticoids in allergic features and ursodeoxycholic acid in cholestatic cases had been used, but there is no good evidence to support their effectiveness.
Disney films are usually co-directed and some directors have served on several winning teams: Wilfred Jackson, Hamilton Luske, Clyde Geronimi, David Hand, Ben Sharpsteen, Wolfgang Reitherman and Bill Roberts have all co-directed at least two films on the list. Only seven directors have topped the chart in consecutive years: McCarey (1944 and 1945), Nichols (1966 and 1967), Spielberg (1981 and 1982), Jackson (2002 and 2003), Verbinski (2006 and 2007) and the Russo brothers (2018 and 2019). Because of release schedules—especially in the case of films released towards the end of the year—and different release patterns across the world, many films can do business in two or more calendar years; therefore the grosses documented here are not confined to just the year of release. Grosses are not limited to original theatrical runs either, with many older films often being re-released periodically so the figures represent all the business a film has done since its original release; a film's first-run gross is included in brackets after the total if known. Because of incomplete data, it cannot be known for sure how much money some films have made and when they made it, but generally the chart chronicles the films from each year that went on to earn the most. In the cases where estimates conflict both films are recorded, and in cases where a film has moved into first place because of being re-released the previous record-holder is also retained.
== V == vaccine - vacuole - valence - valine - van der Waals force - van der Waals radius - vapor pressure - vapour pressure - vasoactive intestinal peptide - vasoactive intestinal peptide receptor - vasopressin - vasopressin receptor - venom - vertebrate photoreceptor - vesicle - vestibular system - vimentin - viral envelope protein - viral oncogene protein - viral protein - virology - virus (biology) - vitamin - vitamin D-dependent calcium-binding protein - vitellogenin - vitronectin - von Willebrand factor
=== Pharmacodynamics === Oxprenolol is a beta blocker. In addition, it has been found to act as an antagonist of the serotonin 5-HT1A and 5-HT1B receptors with respective Ki values of 94.2 nM and 642 nM in rat brain tissue.
Axelopran is an oral PAMORA which is under development by Theravane Biopharma. It has completed phase II in clinical trials in more than 400 patients with OIC. Axelopran has a different chemical structure from other PAMORAs but with a similar mechanism of action. It acts as an antagonist for MOR, KOR and DOR, but with higher affinity for MOR and KOR than for DOR. Like other PAMORAs, the main goal is the treatment of OIC. Axelopran is also being investigated in fixed-dose combination (FDC) with oxycodone. It is done by using spray coating technology to create an FDC of axelopran and controlled-release oxycodone. There is a demand for optimization of the receptor selectivity and affinity accompanied by an exploration of candidate compounds regarding their route of administration. These are the main objectives and future strategies for drug discovery and the development of PAMORAs. Predominantly, the MORs exhibit functionally selective agonism. Therefore, future possible candidate compounds that target OIC are PAMORAs with optimized selectivity and affinity.
Sources: en.wikipedia.org
Metabolic dysfunction–associated steatotic liver disease (MASLD), previously known as non-alcoholic fatty liver disease (NAFLD), is a type of chronic liver disease. This condition is diagnosed when there is excessive fat build-up in the liver (hepatic steatosis), and at least one metabolic risk factor. When there is also increased alcohol intake, the term MetALD, or metabolic dysfunction and alcohol associated/related liver disease is used, and differentiated from alcohol-related liver disease (ALD) where alcohol is the predominant cause of the steatotic liver disease. The terms non-alcoholic fatty liver (NAFL) and non-alcoholic steatohepatitis (NASH, now known as metabolic dysfunction associated steatohepatitis, MASH) have been used to describe different severities, the latter indicating the presence of further liver inflammation. MASLD may progress to MASH, with the risk of progression estimated as 7–35% per year. MASH may also regress to MASLD, especially with a healthy diet, exercise, and medications. Both MASLD and MASH have liver related complications such as cirrhosis, liver cancer, liver failure, as well as liver independent complications such as cardiovascular disease. These complications are much more common with MASH. Obesity and type 2 diabetes are strong risk factors for MASLD. Other risks include being overweight, metabolic syndrome (defined as at least three of the five following medical conditions: abdominal obesity, high blood pressure, high blood sugar, high serum triglycerides, and low serum HDL cholesterol), a diet high in fructose, and older age.
=== Systemicity and translocation === Insecticides may be systemic or non-systemic (contact insecticides). Systemic insecticides penetrate into the plant and move (translocate) inside the plant. Translocation may be upward in the xylem, or downward in the phloem or both. Systemicity is a prerequisite for the pesticide to be used as a seed-treatment. Contact insecticides (non-systemic insecticides) remain on the leaf surface and act through direct contact with the insect. Insects feed from various compartments in the plant. Most of the major pests are either chewing insects or sucking insects. Chewing insects, such as caterpillars, eat whole pieces of leaf. Sucking insects use feeding tubes to feed from phloem (e.g. aphids, leafhoppers, scales and whiteflies), or to suck cell contents (e.g. thrips and mites). An insecticide is more effective if it is in the compartment the insect feeds from. The physicochemical properties of the insecticide determine how it is distributed throughout the plant.
The Nationalist Republican Party (Portuguese: Partido Republicano Nacionalista, PRN, usually called Nationalists) was a right-wing republican party during the First Portuguese Republic. It was founded as a merger of the Republican Liberal Party, the Reconstitution Party and some elements of the old National Republican Party of Sidónio Pais. Initially with moderate conservative orientation, it drifted increasingly to the right, making concessions to Catholic constituencies towards the end of the First Republic.
==== Lungs ==== Inhaled acetylcysteine is also used post-operatively, as a diagnostic aid, and in tracheotomy care. It may be considered ineffective in cystic fibrosis. A 2013 Cochrane review in cystic fibrosis found no evidence of benefit. Acetylcysteine is used in the treatment of obstructive lung disease as an adjuvant treatment.
Sources: en.wikipedia.org
==== Surgical ==== There are many surgical options available for the treatment of uterine prolapse, which may be performed through a vaginal procedure or through the abdomen. Generally, vaginal procedures are considered to be less invasive, offer a quicker recovery, and have a shorter operative time compared to abdominal procedures, but abdominal procedures offer longer-term results and potentially reduce risk of postoperative vaginal pain with intercourse. Laparoscopic and robotic approaches to abdominal procedures in prolapse surgery have become more common as they require smaller incision sites, result in less blood loss, and have shorter hospital stays. If a hysterectomy is performed, a vaginal vault suspension (known as colpopexy), in which the upper portion of the vagina is surgically connected to another structure in the pelvis, is commonly performed to prevent vaginal vault prolapse in the future. Forms of colpopexy include sacrocolpopexy, in which the vaginal vault is attached to the sacrum using a surgical mesh; sacrospinous ligament fixation, in which the upper vagina is attached to the sacrospinous ligaments using sutures; and uterosacral ligament vaginal vault suspension, in which the upper vagina is attached to the uterosacral ligaments using sutures. Colpopexy can be performed with or without a hysterectomy. If performed without a hysterectomy, the procedure is known as a hysteropexy. Hysteropexy procedures include sacrohysteropexy and sacrospinous hysteropexy.
== Lemna farming == High yields of Lemna with a high protein content for use in human nutrition, animal and fish feed can be achieved by careful control of growth conditions. Although Lemna can tolerate temperatures ranging from 6 °C (43 °F) to 33 °C (91 °F), the optimal growth range is 20 °C (68 °F) to 28 °C (82 °F)}. The acceptable pH range is 5 to 9, but better growth is obtained in the pH range of 6.5 to 7.5}. A minimum water depth of 1 foot (30 cm) is desirable to prevent excessive temperature swings. High nitrogen levels, for example 20 mM urea, have provided a protein content in the range of 45% by dry weight.
=== Bibliography === Wiseman A (1993). "Designer enzyme and cell applications in industry and in environmental monitoring". J Chem Technol Biotechnol. 56 (1): 3–13. Bibcode:1993JCTB...56....3W. doi:10.1002/jctb.280560103. PMID 7763363. Diekmann S, Weston J, Anders E, et al. (April 2002). "Metal-mediated reactions modeled after nature". J. Biotechnol. 90 (2): 73–94. doi:10.1016/s1389-0352(01)00067-8. PMID 12069195.
The French Wars of Religion in the 16th century and the French Revolution in the 18th successively destroyed much of what existed in the way of the architectural and artistic remnant of this Norman creativity. The former, with their violence, caused the wanton destruction of many Norman edifices; the latter, with its assault on religion, caused the purposeful destruction of religious objects of any type, and its destabilisation of society resulted in rampant pillaging. By far the most famous work of Norman art is the Bayeux Tapestry, which is not a tapestry but a work of embroidery. It was commissioned by Odo, the Bishop of Bayeux and first Earl of Kent, employing natives from Kent who were learned in the Nordic traditions imported in the previous half century by the Danish Vikings. In Britain, Norman art primarily survives as stonework or metalwork, such as capitals and baptismal fonts. In southern Italy, however, Norman artwork survives plentifully in forms strongly influenced by its Greek, Lombard, and Arab forebears. Of the royal regalia preserved in Palermo, the crown is Germanic and Byzantine in style and the coronation cloak is of Arab craftsmanship with Arabic inscriptions. Many churches preserve sculptured fonts, capitals, and more importantly mosaics, which were common in Norman Italy and drew heavily on the Greek heritage. Lombard Salerno was a centre of ivorywork in the 11th century and this continued under Norman domination.
=== Covalent catalysis === Many enzymes including serine protease, cysteine protease, protein kinase and phosphatase evolved to form transient covalent bonds between them and their substrates to lower the activation energy and allow the reaction to occur. This process can be divided into 2 steps: formation and breakdown. The former step is rate-limit step while the later step is needed to regenerate intact enzyme. Nucleophilic catalysis: This process involves the donation of electrons from the enzyme's nucleophile to a substrate to form a covalent bond between them during the transition state. The strength of this interaction depends on two aspects.: the ability of the nucleophilic group to donate electrons and the electrophile to accept them. The former one is mainly affected by the basicity(the ability to donate electron pairs) of the species while the later one is in regard to its pKa. Both groups are also affected by their chemical properties such as polarizability, electronegativity and ionization potential. Amino acids that can form nucleophile including serine, cysteine, aspartate and glutamine. Electrophilic catalysis: The mechanism behind this process is exactly same as nucleophilic catalysis except that now amino acids in active site act as electrophile while substrates are nucleophiles. This reaction usually requires cofactors as the amino acid side chains are not strong enough in attracting electrons.
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.
Laboratory confirmation typically combines retention time matching on a chromatographic system with mass measurement. A reference standard of known identity is needed for a meaningful comparison. Sequence-level techniques can add further confirmation.