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 2025-12-22. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
Published research on the compound remains limited. Much of the human data comes from small, early-stage studies rather than large controlled trials, and several questions about effects and variability between individuals remain open. Investigators have examined receptor activity, pigment pathways, and related physiological responses in laboratory and animal models. Findings from those models do not automatically translate to human outcomes. Reviews frequently note the scarcity of rigorous clinical evidence and call for better-characterized study material.
Because the substance circulates mainly through informal markets, verification is a recurring theme in technical discussion. Independent analyses have found that labeled content and actual content can diverge, and that purity varies between samples. Analytical laboratories use reversed-phase chromatography to separate components and mass spectrometry to confirm identity. Isotope-labeled internal standards improve quantification in complex matrices. Such methods describe what a sample contains but say nothing about its sterility, lawful status, or suitability for any use. Open questions remain about how consistently testing is applied across the supply chain.
Regulatory treatment of this peptide varies by country. It holds no marketing authorization as a medicine in the United States, the European Union, or most other jurisdictions. Some countries classify products containing it as prescription-only or unlicensed medicines, which restricts lawful supply. Authorities have issued public notices warning that unregulated products may contain undeclared or incorrect ingredients. The molecule also appears on prohibited lists for competitive sport. These measures address supply oversight rather than any approved therapeutic role.
| 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 |
Regulatory treatment varies between countries. Several national medicines agencies have classified the peptide as unapproved, and customs authorities in some jurisdictions seize shipments on that basis. A few jurisdictions channel supply through prescription-only frameworks that do not list the substance by name. Because the material circulates mainly through online vendors, composition and purity are rarely verified before sale. Surveys of unapproved peptide products have reported labels that did not match measured content in a substantial fraction of samples.
Melanotan II is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone, a naturally occurring peptide involved in pigmentation signalling. Its structure substitutes a lactam bridge between side chains to increase stability relative to the native hormone. The compound is also known by the shorthand MT-II and by several non-proprietary synonyms used in research catalogues. It is not an approved therapeutic product in any major jurisdiction; material sold under this name is typically offered as a laboratory reagent rather than as a medicine.
Activity is attributed to agonism at melanocortin receptors, particularly MC1R and MC4R. Activation of MC1R on melanocytes increases melanin synthesis, which underlies the reported tanning effect. MC4R engagement in the central nervous system is linked to appetite suppression and to effects on sexual arousal reported in early clinical studies. Those studies were small and were not designed to establish efficacy or long-term safety. Receptor selectivity among the melanocortin subtypes is not absolute, which complicates attribution of any effect to a single pathway.
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.
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.
Lyophilized peptide powder is generally stored frozen, protected from light and moisture. Tryptophan residues are susceptible to oxidation, and the lactam bridge can hydrolyze under strongly acidic or basic conditions. Solutions prepared for laboratory work degrade faster than dry powder, and repeated freeze-thaw cycles accelerate loss. Common practice is to aliquot solutions before freezing and to avoid alkaline buffers. Reported stability windows vary with concentration, buffer, and temperature, so exact shelf lives are method-specific rather than universal.
Regulatory status differs by country, and in many places supplying the compound for human consumption is unlawful. Vendors frequently label material as intended for research use only, a designation that shifts stated purpose but does not create a legal pathway for personal use. Certificates of analysis accompanying such products vary widely in detail and provenance. Third-party testing exists but is voluntary, and results are rarely linked to a specific lot in a publicly verifiable way.
Identity testing for a synthetic peptide relies on several complementary methods. Reversed-phase high-performance liquid chromatography separates the target from related impurities and reports purity as a percentage of total peak area. Mass spectrometry confirms molecular mass and can reveal deletions or truncations. Amino acid analysis and peptide mapping provide sequence-level confirmation, while counter-ion content and residual solvents are measured separately. A purity figure alone does not establish identity, so a complete dataset combines chromatographic and spectrometric evidence.
Amphetamine was first synthesized in 1887 in Germany by Romanian chemist Lazăr Edeleanu who named it phenylisopropylamine; its stimulant effects remained unknown until 1927, when it was independently resynthesized by Gordon Alles and reported to have sympathomimetic properties. Amphetamine had no medical use until late 1933, when Smith, Kline and French began selling it as an inhaler under the brand name Benzedrine as a decongestant. Benzedrine sulfate was introduced 3 years later and was used to treat a wide variety of medical conditions, including narcolepsy, obesity, low blood pressure, low libido, and chronic pain, among others. During World War II, amphetamine and methamphetamine were used extensively by both the Allied and Axis forces for their stimulant and performance-enhancing effects. As the addictive properties of the drug became known, governments began to place strict controls on the sale of amphetamine. For example, during the early 1970s in the United States, amphetamine became a schedule II controlled substance under the Controlled Substances Act. In spite of strict government controls, amphetamine has been used legally or illicitly by people from a variety of backgrounds, including authors, musicians, mathematicians, and athletes. Amphetamine is illegally synthesized in clandestine labs and sold on the black market, primarily in European countries. Among European Union (EU) member states in 2018, 11.9 million adults of ages 15–64 have used amphetamine or methamphetamine at least once in their lives and 1.7 million have used either in the last year.
VFFAEDVGSNKGAIIGLMVGGVVIAT In relation to the secondary structure of p3 peptide, it is thought that after the cleavage by the α- and γ- secretases and extraction from the membrane it would convert quickly from the α-helix conformation it has when it is part of APPsα sequence to a β-hairpin structure. Then, this highly hydrophobic monomer would rapidly evolve into fibrils with no soluble intermediate forms, the ones related to amyloid’s structure. The main reason why p3 does not aggregate in amyloidogenic forms while Aβ does, is that the N-terminal domain Aβ1–16, which is present in Aβ’s sequence but not in p3's one, is known to protect the hydrophobic core of the oligomers from being dissolved by the watered medium. So, p3 peptide oligomers would likely expose hydrophobic residues to water and would be less stable. As a consequence, p3 peptide structural determinants can assemble into fibrils, but no oligomeric forms have been identified. That is why p3 peptide represents the benign form of amyloid.
== Defects and disease == There is evidence to believe that certain defects of any components of the elastic matrix may impair and alter the structural appearance of elastic and collagen fibers. Cutis laxa and Williams syndrome have elastic matrix defects that have been directly associated with alterations in the elastin gene. Alpha-1 antitrypsin deficiency is a genetic disorder where elastin is excessively degraded by elastase, a degrading protein released by neutrophils during the inflammatory response. This leads most often to emphysema and liver disease in affected individuals. Buschke–Ollendorff syndrome, Menkes disease, pseudoxanthoma elasticum, and Marfan's syndrome have been associated with defects in copper metabolism and lysyl oxidase or defects in the microfibril (defects in fibrillin, or fibullin for example). Hurler disease, a lysosomal storage disease, is associated with an altered elastic matrix. Hypertension and some congenital heart defects are associated with alterations in the great arteries, arteries, and arterioles with alterations in the elastic matrix.
=== Liver === Bridging fibrosis – an advanced stage of liver fibrosis, seen in the progressive form of chronic liver diseases. The term bridging refers to the formation of a "bridge" by a band of mature and thick fibrous tissue from the portal area to the central vein. This form of fibrosis leads to the formation of pseudolobules. Long-term exposure to hepatotoxins, such as thioacetamide, carbon tetrachloride, and diethylnitrosamine, has been shown to cause bridging fibrosis in experimental animal models. Senescence of hepatic stellate cells could prevent progression of liver fibrosis, although has not yet been implemented as a therapy due to risks associated with hepatic dysfunction.
Sources: en.wikipedia.org
For 2026 and subsequent years, qualified overtime compensation must be reported on Form W-2, box 12, code TT. Employers must report all qualified overtime compensation without regard to the tax limit of $12,500 ($25,000 if married filing jointly). An employee who is actively engaged in the management of their employer and owns at least a 20-percent equity interest in it is not eligible to take the tax deduction. Overtime compensation is not excluded or exempt from gross income. Employers continue to be required to withhold income taxes, social security taxes, and Medicare taxes from workers' overtime pay. An employee is allowed, however, to give their employer an updated Form W-4 that includes their acticipated tax deduction for qualified overtime compensation in Step 4(b).
After its expulsion from Malaysia, Singapore became independent as the "Republic of Singapore" on 9 August 1965, with Lee Kuan Yew and Yusof bin Ishak as the first prime minister and president respectively. In 1967, the country co-founded the Association of Southeast Asian Nations (ASEAN). Race riots erupted again in 1969 as a spillover from the 13 May incident in Malaysia. On this occasion, the unrest was more firmly contained. Lee's emphasis on rapid economic growth, racial integration, promotion of business entrepreneurship and curbs on democratic freedoms by governing with extensive legal powers shaped Singapore's policies for the next half century. Economic growth continued throughout the 1980s, with the unemployment rate falling to 3% and real GDP growth averaging at about 8% up until 1999. During the 1980s, Singapore began to shift towards high-tech industries, such as the wafer fabrication sector, in order to remain competitive as neighbouring countries began manufacturing with cheaper labour. Singapore Airlines was formed in 1972 and Changi Airport was opened in 1981, replacing the international airport at Paya Lebar. Lee's government capitalised on Singapore's favourable geographical position to develop the Port of Singapore into one of the world's busiest ports, while the service and tourism industries also expanded significantly during this period. The PAP has remained in power since 1959.
Felines, especially domestic cats, are well known for having penile spines. Upon withdrawal of a cat's penis, the spines rake the walls of the female's vagina, which may serve as a trigger for ovulation. Many other felid species have penile spines, but they are relatively small in jaguars and pumas, and do not occur in margays. Penile spines in chimpanzees and mice are small surface projections made by the piling up of keratinized cell layers in the outermost skin surface. They occur in wombats, koalas, spotted hyenas, fossas, echidnas, primates, bats, and several rodent species. Penile spines are often found in primate species that form copulatory plugs after mating. In galagos, penile spines may form a "genital lock" during copulation.
=== Pharmacology research === Pharmacological studies on synephrine date back to the late 1920s, when it was observed that injected synephrine raised blood pressure, constricted peripheral blood vessels, dilated pupils, stimulated the uterus, and relaxed the intestines in experimental animals. Representative of this early work is the paper by Tainter and Seidenfeld, who were the first researchers to systematically compare the different effects of the two synephrine enantiomers, d- and l- synephrine, as well as of the racemate, d,l-synephrine, in various animal assays. In experiments on anesthetized cats, Tainter and Seidenfeld confirmed earlier reports of the increase in blood pressure produced by intravenous doses of synephrine, showing that the median pressor doses for the isomers were: l-synephrine: 0.5 mg/kg; d,l-synephrine: 1.0 mg/kg; and d-synephrine: 2–20 mg/kg. These effects lasted 2–3 minutes, peaking at ~30 seconds after administration. l-Synephrine was thus the more potent enantiomer, with about 1/60x the potency of the standard pressor l-epinephrine in the same assay. A later study, by Lands and Grant, showed that a dose of ~0.6 mg/kg of racemic synephrine, given intravenously to anesthetized dogs, produced a rise in blood pressure of 34 mmHg lasting 5–10 minutes, and estimated that this pressor activity was about 1/300x that of epinephrine. Using cats and dogs, Tainter and Seidenfeld observed that neither d- nor l-synephrine caused any changes in the tone of normal bronchi, in situ, even at "maximum" doses.
=== Independent Grand Lodge of Colon === At the insistence of Albert Pike (after he had been allowed to return from exile to the United States), in 1867, the Grand Lodge of Colon under the leadership of Grand Master Andrés Puente, established its own constitution. Even though they recognized the sovereignty of the Supreme Council, their new constitution established that the Grand Lodge of Colon held the exclusive authority to enact its own bylaws, issue charters, and regulate its own Lodges. Albert Pike gave his staunch support and approval in the new autonomy of the Grand Lodge. The Supreme Council of the Scottish Rite in Cuba, however, outright refused to recognize any independent authority of the Grand Lodge of Colon. They dissolved the Grand Lodge and assumed all of its orders. On September 20, 1867, the Grand Lodge of Colon agreed to suspend their constitution until a joint meeting of the Supreme Council and the Grand Lodge could occur, where the parties were scheduled to discuss the situation. That meeting was scheduled to happen on November 25, 1868. That meeting never took place, due to the outbreak of the Ten Years' War.
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.
Only a small number of early-stage human studies have been reported, and most were limited in size and duration. No large late-stage program has established a general efficacy or safety profile. The evidence base is therefore thin compared with approved medicines.