Everything below concerns melanocortin receptor. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2026-04-06. Numbers and descriptions here follow the published literature rather than marketing material.
Receptor studies place melanotan-2 among non-selective melanocortin agonists, binding MC1R, MC3R, MC4R and MC5R rather than a single subtype. Activation of MC1R on cutaneous melanocytes raises tyrosinase activity and shifts pigment synthesis toward eumelanin, which is darker and more photostable than pheomelanin. Central receptors, particularly MC4R, are associated with appetite suppression and with reported effects on sexual function. Because subtype selectivity is low, the same molecule engages pigment, metabolic and vascular pathways at once, and this breadth is a common explanation offered for the range of adverse events described in user reports.
No regulatory authority has approved melanotan-2 for human use, and several countries classify it as a prescription-only or controlled substance, which restricts lawful supply. Material sold online is generally labelled as a research chemical and is not required to meet pharmaceutical standards of identity or purity. Published human data consist mainly of small uncontrolled studies, case reports and adverse-event notifications, so the evidence base is descriptive rather than confirmatory. Whether repeated melanocyte stimulation alters long-term naevus behaviour remains an open question that no completed trial has resolved.
Handling guidance for melanotan II follows general practice for small synthetic peptides rather than a product-specific monograph. Lyophilized powder is typically kept at minus twenty degrees Celsius or colder, protected from light and moisture, because warmth and humidity accelerate degradation. Once reconstituted, solutions are usually refrigerated and used within a short window, as hydrolysis and microbial growth both become concerns. Repeated freeze-thaw cycles are generally avoided. These conventions come from laboratory peptide chemistry and not from formal stability studies on this specific compound.
Analytical confirmation of identity relies on mass spectrometry, most often coupled to liquid chromatography. Reversed-phase high-performance liquid chromatography separates the peptide from related impurities and provides a purity estimate based on peak area. Electrospray ionization mass spectrometry then confirms the expected molecular mass, while tandem mass spectrometry can map the fragment sequence. For research-grade material, these two techniques together form the standard minimum. Purity figures reported by vendors are frequently not traceable to an independent laboratory.
Independent verification is central to quality control because the compound is not produced under pharmaceutical manufacturing standards. Third-party laboratories can measure purity, identity, residual solvents, and microbial contamination, though the scope of testing varies between services. Reported analyses of vendor samples have shown batch-to-batch variation in peptide content and the presence of truncated or oxidized species. How much of this variation reflects synthesis conditions versus storage and shipping is not well characterized. No harmonized reference standard exists for the material as sold.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C50H69N15O9 | Free base; salt forms add to total mass |
| Molecular mass | About 1024 daltons | Calculated for the free base |
| Structural class | Cyclic heptapeptide | Contains D-phenylalanine and norleucine |
| Parent hormone | Alpha-melanocyte-stimulating hormone | Endogenous tridecapeptide of 13 residues |
| Receptor profile | Non-selective melanocortin agonist | Interacts with MC1R, MC3R, MC4R and MC5R |
Melanotan II is a synthetic cyclic heptapeptide analog derived from the core sequence of alpha-melanocyte-stimulating hormone. Researchers at the University of Arizona synthesized it during the 1980s while studying pigmentation and appetite signaling. The compound is not an approved medicine in any major jurisdiction and appears mainly in laboratory and research-chemical settings. Its structure incorporates a lactam bridge between side chains, which constrains the ring and slows enzymatic breakdown relative to the natural hormone.
Melanotan II binds several melanocortin receptor subtypes rather than a single target. MC1R on melanocytes drives melanin synthesis, while MC3R and MC4R participate in energy balance, appetite, and sexual response pathways. This lack of selectivity explains why reported effects extend beyond skin darkening. Substitutions at positions four and seven, including norleucine and D-phenylalanine, increase potency and resistance to peptidases. Understanding which receptor mediates which effect remains an active area of investigation.
Published human data come mostly from small, short studies rather than large controlled trials. Reported outcomes include increased skin pigmentation and, in some reports, effects on appetite and libido, but sample sizes are small and follow-up is limited. Whether long-term use produces durable pigment changes or adverse effects is not established. Because products sold outside pharmacies are not standardized, the actual content of any given vial is often unknown. Independent testing of such material is uncommon.
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.
Closer Roberto Osuna converted his 25th consecutive save on May 24, breaking a club record. The streak had started the previous August 18, surpassing Brad Lidge (24 consecutive from June 21–September 28, 2005). Osuna's feat remained the franchise longest until Josh Hader converted 29 consecutive from April 7 to August 29, 2024. On May 28, A. J. Hinch obtained his 500th win as manager, as the Astros toppled the Chicago Cubs, 9–6. Chicago blasted five home runs, but Houston answered with five doubles—two by Jake Marisnick (8)—and two home runs by Alex Bregman (17). Bregman collected three RBI, and Michael Brantley had two hits and two RBI as Houston scored four times in the bottom of the fourth. Josh James (2–0) picked up the victory in relief while surrendering three runs over 2+1⁄3 frames. With injuries stacking up, on May 29 shortstop Carlos Correa sustained a bruised rib during a massage session. He was forced to join fellow All-Stars Springer and Jose Altuve on the injured list (IL) and expected to miss four to six weeks.
In Mexico, the Directorate General of Civil Aviation (DGAC) investigates aviation accidents. In the Netherlands, the Dutch Safety Board (Onderzoeksraad voor Veiligheid) is responsible for the investigation of incidents and accidents, including air accidents. Its aim is the improvement of safety in the Netherlands. Its main focus is on those situations in which civilians are dependent on the government, companies or organizations for their safety. The Board solely investigates when incidents or accidents occur and aims to draw lessons from the results of these investigations. The Safety Board is objective, impartial and independent in its judgment. The Board will always be critical towards all parties concerned.
On March 28, 2013, a team of bioengineers from Stanford University led by Drew Endy announced that they had created the biological equivalent of a transistor, which they named a "transcriptor". That is, they created a three-terminal device with a logic system that can control other components. The transcriptor regulates the flow of RNA polymerase across a strand of DNA using special combinations of enzymes to control movement. According to project member Jerome Bonnet, "The choice of enzymes is important. We have been careful to select enzymes that function in bacteria, fungi, plants and animals, so that bio-computers can be engineered within a variety of organisms." Transcriptors can replicate traditional AND, OR, NOR, NAND, XOR, and XNOR gates with equivalents, which Endy dubbed "Boolean Integrase Logic (BIL) gates", in a single-layer process (i.e., without requiring multiple instances of the simpler gates to build up more complex ones). Like a traditional transistor, a transcriptor can amplify an input signal. A group of transcriptors can do almost any type of computing, including counting and comparison.
Sources: en.wikipedia.org
The Senate consisted of 90 senators, ten nominated by each of the nine provinces. It was chaired by a President of the Senate elected by the senators from among themselves. The National Assembly consists of 400 members, elected by voters on a proportional representation/party list system. There are no electoral districts, and each party is allocated a number of seats proportionate to the percentage of the votes it receives across the country. It is chaired by a Speaker elected by the MPs from among themselves. In 1997, the current Constitution of South Africa came into force, in which the Senate was replaced by a 90-member National Council of Provinces (NCOP), made up of a 10-member delegation from each province (six delegates elected by the provincial legislature, the Premier and three other members of the provincial legislature). The NCOP is chaired by a Chairperson elected by the members from among themselves. The parliamentary system uses proportional representation, with voters voting for political parties rather than for candidates. Proportional representation allows for smaller parties to have a chance of acquiring seats in parliament, although these parties often combine in order to have a stronger voice within the political system, especially against the ANC. The Electoral Commission of South Africa is charged with keeping elections fair, regular, and equal. Parties submit closed lists of candidates to the IEC, and the IEC fills the seats allotted to individual parties using the candidate lists after election results come in.
Artesunate is a medication used to treat malaria. The intravenous form is preferred to quinine for severe malaria. Often it is used as part of combination therapy, such as artesunate plus mefloquine. It is not used for the prevention of malaria. Artesunate can be given by injection into a vein, injection into a muscle, by mouth, and by rectum. The most common side effects include kidney failure requiring dialysis, hemoglobinuria (the presence of hemoglobin in urine) and jaundice. Artesunate is generally well tolerated. Side effects may include a slow heartbeat, allergic reaction, dizziness, and low white blood cell levels. During pregnancy it appears to be a safer option, even though animal studies have found harm to the baby. Use is likely fine during breastfeeding. It is in the artemisinin class of medication. Artesunate was developed by Liu Xu in 1977. It is on the World Health Organization's List of Essential Medicines. It was approved for medical use in the United States in May 2020. It is in the class of medications known as artemisinins, which are derivatives from "qinghao", or sweet wormwood plant (Artemisia annua).
Here, the resulting dimer has a stoichiometry different from the initial pair of monomers. Disaccharides need not be composed of the same monosaccharides to be considered dimers. An example is sucrose, a dimer of fructose and glucose, which follows the same reaction equation as presented above. Amino acids can also form dimers, which are called dipeptides. An example is glycylglycine, consisting of two glycine molecules joined by a peptide bond. Other examples include aspartame and carnosine.
Sources: en.wikipedia.org
==== Circulation ==== Circulation within local systems, such as bays, estuaries, and groundwater, may be examined with radium isotopes. 223Ra has a half-life of 11 days and can occur naturally at specific locations in rivers and groundwater sources. The isotopic ratio of radium will then decrease as the water from the source river enters a bay or estuary. By measuring the amount of 223Ra at a number of different locations, a circulation pattern can be deciphered. This same exact process can also be used to study the movement and discharge of groundwater. Various isotopes of lead can be used to study circulation on a global scale. Different oceans (i.e. the Atlantic, Pacific, Indian, etc.) have different isotopic signatures. This results from differences in isotopic ratios of sediments and rocks within the different oceans. Because the different isotopes of lead have half-lives of 50–200 years, there is not enough time for the isotopic ratios to be homogenized throughout the whole ocean. Therefore, precise analysis of Pb isotopic ratios can be used to study the circulation of the different oceans.
Two conserved cysteines coordinate one Fe ion while the other Fe ion is coordinated by two conserved histidines. The 2Fe-2S cluster is bound in the highly conserved C-terminal region of the Rieske subunit.
Xylazine binds at a ratio of 160:0, the lowest of all α2-adrenergic receptor agonists and 1/10th of that of medetomidine and dexmedotimidine. Xylazine is less selective than the other α2-Adrenergic receptor agonists. The analgesic effect of xylazine comes from binding to receptors at the substantia gelatinosa and locus coeruleus.
Sources: en.wikipedia.org
No regulatory agency has authorised melanotan-2 as a medicine for any indication. It circulates mainly as a research chemical or through unregulated channels. As a result, identity, purity and content are not independently guaranteed.
Melanotan-1, also called afamelanotide, is a linear analogue with greater selectivity for MC1R and has received approval in some jurisdictions for a specific photosensitivity disorder. Melanotan-2 is cyclic, less selective, and reaches central receptors more readily. The two are often confused in online discussion despite different pharmacology and regulatory status.
Alpha-MSH is an endogenous tridecapeptide derived from pro-opiomelanocortin. Melanotan-2 reproduces its core receptor-binding sequence inside a shortened, stabilised ring. The result is a molecule with a longer effective half-life and higher potency than the parent hormone.
The lyophilized powder is generally held at minus twenty degrees Celsius or below, away from light and moisture. Reconstituted solutions are typically refrigerated and used quickly. These practices derive from general peptide handling rather than a formal stability study.