If you have been reading about reversed-phase HPLC and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Last reviewed on 2026-03-16. Where a claim depends on a specific study, the study is described rather than over-claimed.
Melanotan-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone. Its sequence incorporates a lactam bridge that constrains the peptide into a ring, which increases resistance to enzymatic breakdown relative to the natural hormone. Researchers at the University of Arizona synthesised the compound in the late 1980s and early 1990s while studying pigmentation pathways. It has never received marketing approval from any national medicines regulator. In the scientific literature it is usually described as a laboratory research reagent rather than a therapeutic product.
The peptide acts as a non-selective agonist at melanocortin receptors, showing affinity for MC1R, MC3R, MC4R and MC5R. Activation of MC1R on melanocytes drives the conversion of tyrosine into melanin and shifts production toward the darker eumelanin form. MC4R signalling in the central nervous system is linked to appetite and energy balance, which helps explain why reduced food intake appeared in early human studies. Effects on MC4R and on vascular tone also account for the erectile responses recorded as unexpected findings in those same trials.
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.
Reported observations after unregulated use include shifts in skin pigmentation and, in some accounts, unintended changes to moles and other lesions. Whether these outcomes are causally linked to the compound, and how often they occur, remain open questions because controlled data are scarce. The absence of standardised dosing and verified product purity complicates interpretation. Researchers have called for better surveillance and analytical characterisation of samples obtained outside regulated channels. Conclusions drawn from anecdotal evidence should be treated as provisional.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic cyclic heptapeptide | Alpha-MSH analogue with a lactam ring |
| Molecular formula | C50H69N15O9 | Commonly cited value for the neutral peptide |
| Molecular weight | 1024.18 g/mol | Calculated for the free molecule |
| Appearance | White to off-white powder | Typically supplied as a lyophilised solid |
| Solubility | Soluble in water, DMSO and ethanol | Dissolution in pure water is often slow |
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.
Receptor-binding studies classify melanotan II as a non-selective melanocortin agonist. It interacts with MC1R, MC3R, MC4R and MC5R, with reported affinities in the low nanomolar range and no strong subtype preference. Activation of MC1R on dermal melanocytes shifts pigment synthesis toward eumelanin, the dark polymer deposited in melanosomes and transferred to keratinocytes. Because the same peptide engages MC4R in the hypothalamus, it also appears in animal work on food intake and erectile response, which is why it is discussed in both pigment and metabolic research. Which receptor populations dominate after systemic exposure in humans is not fully established.
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.
Melanotan-2 is handled in the laboratory as a lyophilised powder that dissolves readily in water, dimethyl sulfoxide and dimethylformamide, with limited solubility in ethanol. Stock solutions prepared in an organic solvent often precipitate when diluted into aqueous buffer, so gradual dilution with mixing is standard practice. The peptide carries a tryptophan residue and a histidine residue, both sensitive to oxidation and to alkaline conditions. Working solutions are therefore kept near neutral to slightly acidic pH, protected from light, and consumed within the same working session whenever that is practical.
=== Criminalization and medical use === Non-clinical use of opium was criminalized in the United States by the Harrison Narcotics Tax Act of 1914, and by many other laws. The use of opioids was stigmatized, and it was seen as a dangerous substance, to be prescribed only as a last resort for dying patients. The Controlled Substances Act of 1970 eventually relaxed the harshness of the Harrison Act. In the United Kingdom the 1926 report of the Departmental Committee on Morphine and Heroin Addiction under the Chairmanship of the President of the Royal College of Physicians reasserted medical control and established the "British system" of control—which lasted until the 1960s. In the 1980s the World Health Organization published guidelines for prescribing drugs, including opioids, for different levels of pain. With little or no scientific evidence to support their claims, industry scientists and advocates suggested that people with chronic pain would be resistant to addiction. The release of OxyContin in 1996 was accompanied by an aggressive marketing campaign promoting the use of opioids for pain relief. Increasing prescription of opioids fueled a growing black market for heroin. Between 2000 and 2014 there was an "alarming increase in heroin use across the country and an epidemic of drug overdose deaths". As a result, health care organizations and public health groups, such as Physicians for Responsible Opioid Prescribing, have called for decreases in the prescription of opioids.
=== Motivational disorders === Selegiline has been found to produce pro-motivational effects and to reverse motivational deficits in rodents. In case reports and small clinical studies, selegiline has been reported to improve disorders of diminished motivation like apathy and abulia due to conditions such as traumatic brain injury. In accordance with the preceding findings, selegiline, along with other dopaminergic and activating agents, may be useful in the treatment of disorders of diminished motivation, including apathy, abulia, and akinetic mutism.
==== Consensus paper ==== In 2013 the E.S.PKU delegates launched a paper describing the needs for a better and equal treatment across Europe. This paper subsequently lead to the first European Guidelines for Phenylketonuria.
=== Planning and refining movements === When planning complex movements such as reaching or grooming, an animal must consider the current position and velocity of its limb and use that information to adjust dynamics to target a final position. If the animal's estimate of its limb's initial position is wrong, then a deficiency in the movement can result. Furthermore, proprioception is crucial in refining the movement if it deviates from the trajectory.
Sources: en.wikipedia.org
It could also reflect steric and chemical properties that had another effect on the codon during its evolution. Amino acids with similar physical properties also tend to have similar codons, reducing the problems caused by point mutations and mistranslations. Three main hypotheses address the origin of the genetic code. Many models belong to one of them or to a hybrid:
In early July 1990, Iraq complained about Kuwait's behavior, such as not respecting their quota, and openly threatened to take military action. On the 23rd, the CIA reported that Iraq had moved 30,000 troops to the Iraq–Kuwait border, and the US naval fleet in the Persian Gulf was placed on alert. Saddam believed an anti-Iraq conspiracy was developing – Kuwait had begun talks with Iran, and Iraq's rival Syria had arranged a visit to Egypt. On 15 July 1990, Saddam's government laid out its combined objections to the Arab League, including that policy moves were costing Iraq $1 billion a year, that Kuwait was still using the Rumaila oil field, and that loans made by the UAE and Kuwait could not be considered debts to its "Arab brothers". He threatened force against Kuwait and the UAE, saying: "The policies of some Arab rulers are American ... They are inspired by America to undermine Arab interests and security." The US sent aerial refuelling planes and combat ships to the Persian Gulf in response to these threats. Discussions in Jeddah, Saudi Arabia, mediated on the Arab League's behalf by Egyptian president Hosni Mubarak, were held on 31 July and led Mubarak to believe that a peaceful course could be established.
=== Biosimilar drugs === Biosimilar drugs are biological products that are highly similar to an already approved biologic drug, with few or no clinically meaningful differences in terms of safety, purity, and potency. These drugs are developed to be equivalent to the reference biologic, often at a lower cost, providing alternative treatment options. In the context of ankylosing spondylitis, biosimilars are typically used as alternatives to the original biologic drugs. Biosimilars for ankylosing spondylitis may include versions of tumor necrosis factor inhibitors or other biologics commonly used in the treatment of the condition. When possible, physicians are recommended to use the original drugs over the biosimilar versions. Even biosimilars with perfect replication of the quality, composition, and other properties of the original drug are susceptible to nocebo effects.
Psilocybe cubensis grows naturally in tropical and subtropical conditions, often near cattle due to the ideal conditions they provide for the growth of the fungus. The cow usually consumes grains or grass covered with the spores of P. cubensis and the fungus will begin to germinate within the dung. Mushrooms such as Psilocybe cubensis are relatively easy to cultivate indoors. First, spores are inoculated within sterilized jars or bags, colloquially known as grainspawn, containing a form of carbohydrate nutrient such as rye or milo gains. After approximately one month, the spores fully colonize the grain spawn forming dense mycelium, which is then mixed within a bulk substrate such as a coconut husk fiber and vermiculite mixture. Given proper humidity, temperature, and fresh air exchange, the substrate will produce fruiting Psilocybe cubensis bodies within a month of planting. To preserve potency after harvesting, growers often dehydrate the fruit and store them in air-tight containers in cool environments. A study conducted in 2009 showed that mushrooms grown in the dark had higher levels of psilocybin and psilocin compared to the mushrooms grown in bright, indirect light, which had minimum levels. Studies were conducted where an environmentally controlled wind tunnel and a computer program were used to determine the influence of humidity on the individual basidiocarps of P. cubensis which aided in mapping their growth and development.
=== Medication === Overall, pharmaceuticals have limited benefit for treating anorexia. However, olanzapine, an antipsychotic, has been shown to result in a modest but statistically significant increase in body weight in AN patients, in addition to a decrease in obsessive thoughts. While the effectiveness of antidepressants in treating anorexia has not been well established, fluoxetine, an SSRI, can also be used during treatment. Metreleptin is undergoing research for its potential benefit in the treatment of anorexia nervosa. It is hypothesized that the gradual loss of body fat mass, and the ensuing low leptin levels, influence the psychological components of the disorder. It was shown that short-term metreleptin treatment of patients with anorexia nervosa had rapid on-set of beneficial cognitive, emotional, and behavioral effects. Among other things, depression, drive for activity, repetitive thoughts of food, inner restlessness, and weight phobia decreased rapidly. Whether metreleptin (or another leptin analogue) is a suitable treatment for anorexia nervosa remains to be seen.
Sources: en.wikipedia.org
It is a synthetic cyclic heptapeptide modelled on alpha-melanocyte-stimulating hormone. A lactam bridge links two side chains, forming a ring that stabilises the molecule against proteolysis. It belongs to the broader melanocortin peptide family.
No national medicines agency has approved melanotan-2 for clinical use. Afamelanotide, a related but distinct peptide, holds a marketing authorisation in the European Union for a rare photosensitivity disorder. Melanotan-2 itself is handled as a laboratory chemical.
Its broad activity across melanocortin receptors makes it a tool for probing pigmentation, appetite and vascular signalling. Early trials recorded skin darkening and other effects that were not the original focus of the work. Those observations generated hypotheses that later studies have examined.
Major regulatory agencies have not approved it for any indication. Some countries permit it only under prescription frameworks, while others classify it as a controlled substance.