Everything below concerns melanocortin receptor. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2026-02-18. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | Melanotan II; MT-II; N-acetyl-norleucyl-cyclo[Asp-His-D-Phe-Arg-Trp-Lys] amide | Naming follows peptide convention; the numeral distinguishes it from melanotan-1 |
| Molecular formula | C50H69N15O9 | Includes the lactam bridge; no counter-ion assumed |
| Monoisotopic mass | 1023.53 Da | Free base; salts and counter-ions shift the observed value |
| Appearance | White to off-white lyophilised powder | Batch-to-batch colour variation is not itself proof of impurity |
| Typical analytical method | RP-HPLC purity determination with ESI-MS identity confirmation | Retention time alone does not establish sequence identity |
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.
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.
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.
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.
=== Notable users === József Knoll, one of the developers of selegiline, began taking a low 1 mg daily dose of selegiline on January 1, 1989, at the age of 64. He reported in 2012 that this had continued for 22 years uninterrupted. Knoll stated that he had become so fascinated with the possible longevity-promoting effects of selegiline that he had decided to start taking it as a self-experiment. Knoll later died in 2018 at the age of 93. David Pearce, a British transhumanist philosopher, wrote his self-published book-length internet manifesto The Hedonistic Imperative six weeks after starting to take selegiline. Hamilton Morris, a psychoactive drug journalist and researcher, appears to have used selegiline. Sam Bankman-Fried, the founder and former CEO of the FTX cryptocurrency exchange, is known to have used selegiline for depression in the form of the Emsam patch for at least 5 to 10 years. He is also known to have simultaneously taken Adderall for treatment of attention deficit hyperactivity disorder (ADHD) and to have possessed non-pharmaceutical adrafinil, a prodrug of modafinil.
== Sources == Rupert, James (14 January 1992). "Christian Knights Claim Key Role in Georgia". The Washington Post. Bonner, Raymond (16 November 1993). "Georgian Fighter Wields Guns, Money and Charm". The New York Times. "Dzhaba Ioseliani, 76; Oft-Imprisoned Leader of Georgian Paramilitary Force". Associated Press. 5 March 2003 – via Los Angeles Times. Corley, Felix (25 March 2003). "Jaba Ioseliani: Violent warlord in post-Communist Georgia". The Independent. "Shevardnadze Is Wounded By Car Bomb In Georgia (Published 1995)". 1995-08-30. Archived from the original on 2024-04-23. Retrieved 2026-01-18. "Georgians Held in Failed Assassination of Shevardnadze". Los Angeles Times. 1995-09-19. Retrieved 2026-01-18. "IOSELIANI AND ACCOMPLICES SENTENCED. - Jamestown". jamestown.org. Retrieved 2026-01-18. "1997 Human Rights Report: Georgia". 1997-2001.state.gov. Retrieved 2026-01-18.
20 June – BBC One airs a Question Time election special featuring the leaders of the UK's four main political parties. Sunak says he is "incredibly angry" to learn of allegations that members of his party have betted on the date of the election, and that he will "boot out" anyone found to have broken the law. Scottish Parliament authorities have launched an investigation into the potential misuse of expenses to buy postage stamps by members of the SNP in order to send letters to voters. The Alliance Party launches its general election manifesto, with plans including reform of the devolved government at Stormont, and ringfencing funding for integrated eductation. 21 June – Nigel Farage tells the BBC that he believes the Russian invasion of Ukraine to have been precipitated by the West's eastward expansion of NATO and the European Union, but that the war itself is Vladimir Putin's fault. BBC Wales airs a televised election debate featuring Vaughan Gething (Labour), Jane Dodds (Liberal Democrat), Rhun ap Iorwerth (Plaid Cymru) and David TC Davies (Conservative). 22 June – BBC News publishes a list of eight Reform UK candidates who have made a wide range of offensive online posts about women between 2011 and 2023. Following criticism from other party leaders over his comments about Putin, Nigel Farage pens an op-ed in The Telegraph in which he says he has never been an "apologist or supporter" of Putin, but that "if you poke the Russian bear with a stick, don't be surprised if he responds".
K, is a factor dependent on the preferred probability level. Usually, it is set at 2.77, which reflects a 95% prediction interval, in which case there is less than 5% probability that a test result would become higher or lower than the critical difference by test-retest variability in the absence of other factors. CVa is the analytical variation CVi is the intra-individual variability For example, if a patient has a hemoglobin level of 100 g/L, the analytical variation (CVa) is 1.8% and the intra-individual variability CVi is 2.2%, then the critical difference is 8.1 g/L. Thus, for changes of less than 8 g/L since a previous test, the possibility that the change is completely caused by test-retest variability may need to be considered in addition to considering effects of, for example, diseases or treatments.
Antibody diversification typically occurs through somatic hypermutation, class switching, and affinity maturation targeting the BCR gene loci, but on occasion more unconventional forms of diversification have been documented. For example, in the case of malaria caused by Plasmodium falciparum, some antibodies from those who had been infected demonstrated an insertion from chromosome 19 containing a 98-amino acid stretch from leukocyte-associated immunoglobulin-like receptor 1, LAIR1, in the elbow joint. This represents a form of interchromosomal transposition. LAIR1 normally binds collagen, but can recognize repetitive interspersed families of polypeptides (RIFIN) family members that are highly expressed on the surface of P. falciparum-infected red blood cells. In fact, these antibodies underwent affinity maturation that enhanced affinity for RIFIN but abolished affinity for collagen. These "LAIR1-containing" antibodies have been found in 5–10% of donors from Tanzania and Mali, though not in European donors. European donors did show 100–1000 nucleotide stretches inside the elbow joints as well, however. This particular phenomenon may be specific to malaria, as infection is known to induce genomic instability.
Sources: en.wikipedia.org
Gestational trophoblastic disease like hydatidiform moles ("molar pregnancy") or choriocarcinoma may produce high levels of βhCG due to the presence of syncytiotrophoblasts, part of the villi that make up the placenta, and despite the absence of an embryo. This, as well as several other conditions, can lead to elevated hCG readings in the absence of pregnancy. hCG levels are also a component of the triple test, a screening test for certain fetal chromosomal abnormalities/birth defects. High hCG levels in the maternal serum could suggest Down syndrome, potentially due to continued hCG production by the placenta beyond the first trimester. A study of 32 normal pregnancies came to the result that a gestational sac of 1–3 mm was detected at a mean hCG level of 1150 IU/L (range 800–1500), a yolk sac was detected at a mean level of 6000 IU/L (range 4500–7500) and fetal heartbeat was visible at a mean hCG level of 10,000 IU/L (range 8650–12,200).
=== Pharmacokinetics === Escitalopram is a substrate of P-glycoprotein and hence P-glycoprotein inhibitors such as verapamil and quinidine may improve its blood-brain barrier penetrability. In a preclinical study in rats combining escitalopram with a P-glycoprotein inhibitor, its antidepressant-like effects were enhanced.
== Drug interactions == The additional or sequential use of other nephrotoxic drugs like aminoglycosides, amphotericin B, capreomycin, colistin, polymyxin B, vancomycin, foscarnet, or cisplatin should be closely monitored, or whenever possible completely avoided.
Chile's self-perception is characterized by attributions of: civilization, economic development, political order, successful national project and ethnic homogeneity with a predominance of white-western. On the contrary, the perception of Peru-Bolivia includes the attributions of barbarism, economic underdevelopment, political chaos, failed national projects, predominance of the indigenous and ethnic heterogeneity. This would imply in Chile an ethnocentric and unfavorable attitude towards the outgroup made up of Peru and Bolivia. Examples of this would be the historical narratives of the Chilean politician and orator, Benjamín Vicuña Mackenna, who spread the civilizing discourse that tried to justify the violence committed in the War of the Pacific and contaminated with anti-Peruvian sentiment. It is also known that there has been a tendency among Chilean essayists and historians to condemn the pro-Peruvian Americanists in the Spanish-South American War, accused of having been naive politicians who they were detrimental to national interests, when a pragmatic attitude should have been taken and not meddle in the Peruvian conflict of the Chincha islands due to an unrequited idealism by all the American nations (which would even isolate Chile, like the countries of the Triple Alliance). An example of this anti-Peruvian current with this historical episode is the work of Francisco Antonio Encina in his book Historia de Chile (1938–52), which has been seriously criticized by historians in the academic environment for a lack of scientific rigor.
Sources: en.wikipedia.org
The proposal also "include[d] offers to negotiate an oil agreement with the United States 'satisfactory to both nations' national security interests,' develop a joint plan 'to alleviate Iraq's economical and financial problems' and 'jointly work on the stability of the gulf.'" On 29 November 1990, the Security Council passed Resolution 678, which gave Iraq until 15 January 1991 to withdraw from Kuwait, and empowered states to use "all necessary means" to force Iraq out of Kuwait after the deadline.
=== COVID-19 pandemic === During the COVID-19 pandemic in Missouri, Schmitt filed lawsuits to prevent St. Louis County from implementing public health restrictions (such as restrictions on indoor dining, mask mandates and limits on gatherings) to reduce COVID-19's spread. He opposed the release from jail of some inmates charged with violent felonies during the pandemic, a measure that had been proposed to reduce COVID-19 spread in detention facilities. Schmitt was involved in efforts to combat scammers and price gougers attempting to profiteer from COVID-19. In March 2020, he sued televangelist Jim Bakker and Morningside Church Productions, Inc. for falsely claiming that "Silver Solution" (colloidal silver) was an effective COVID-19 treatment. In April 2020, on behalf of the State of Missouri, Schmitt sued the Chinese government, Chinese Communist Party, and other Chinese officials and institutions in the U.S. District Court for the Eastern District of Missouri, alleging that their actions to suppress information, arrest whistleblowers, and deny COVID-19's contagious nature led to loss of life and severe economic consequences in Missouri. Missouri is the first state to sue China over the pandemic. Schmitt described the lawsuit as a historic accountability measure, but legal experts called it a public relations stunt. The nine defendants were not served for more than a year after the complaint's filing, and the state spent $12,000 to translate the complaint into Chinese. In July 2022, U.S. District Judge Stephen N. Limbaugh Jr.
Mephedrone is one of hundreds of designer drugs or legal highs that have been reported in recent years, including artificial chemicals such as synthetic cannabis and semisynthetic substances such as methylhexanamine. These drugs are primarily developed to avoid being controlled by laws against illegal drugs, thus giving them the label of designer drugs. According to the European Monitoring Centre for Drugs and Drug Addiction, the synthesis of mephedrone was first reported in 1929 by Saem de Burnaga Sanchez in the Bulletin de la Société Chimique de France, under the name "toluyl-alpha-monomethylaminoethylcetone", but the compound remained an obscure product of academia until 2003, when it was "re-discovered" and publicised by an underground chemist on The Hive website, registered to a Portuguese IP working under the pseudonym "Kinetic". Kinetic posted on the site, "I've been bored over the last couple of days and had a few fun reagents lying around, so I thought I'd try and make some 1-(4-methylphenyl)-2-methylaminopropanone hydrochloride, or 4-methylmethcathinone." before going on to describe that after consuming it, the user had a "fantastic sense of well-being that I haven't got from any drug before except my beloved Ecstasy." After the initial description of mephedrone's qualitative effects by Kinetic, the drug was commercially introduced in Israel by a mathematician named Ezekiel Golan or "Dr. Z". A drug similar to mephedrone, containing cathinone, was sold legally in Israel from around 2004, under the name hagigat.
== Protactinium-233 == Protactinium-233 is also part of the thorium fuel cycle. It is an intermediate beta decay product between thorium-233 (produced from natural thorium-232 by neutron capture) and uranium-233 (the fissile fuel of the thorium cycle). Some thorium-cycle reactor designs try to protect 233Pa from further neutron capture producing 234Pa and 234U, which are not useful as fuel.
As of 2025, Biden was the oldest sitting president in U.S. history. His cognitive health was perceived to have declined by Republicans and some media figures, and privately by some Democrats. Members of Biden's family and White House staffers insulated Biden from scrutiny of his advanced aging and decline in acuity. The media widely covered public concern about Biden's mental acuity after a weak performance in a June 2024 presidential debate, but gave it limited coverage beforehand, in part due to harsh pushback from White House officials. Biden initially deemed himself fit to serve two terms as president, but after the 2024 election said that he may have been too old to serve a second term. As part of the investigation into Biden's handling of classified documents, special counsel Robert Hur said that Biden did not remember when he was vice president ("if it was 2013—when did I stop being vice president?") or when his son Beau died. Hur wrote that his memory "appeared to have significant limitations". On July 21, 2022, Biden tested positive for COVID-19 with reportedly mild symptoms. According to the White House, he was treated with Paxlovid. He worked in isolation in the White House for five days and returned to isolation when he tested positive again on July 30. On July 17, 2024, Biden again tested positive for COVID-19.
Sources: en.wikipedia.org
It is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone, containing seven amino acids with a lactam ring and a D-configured phenylalanine residue. It is supplied as a lyophilised powder for laboratory research.
The natural hormone is a linear tridecapeptide that is rapidly degraded in circulation. Melanotan-2 is shortened, cyclised, N-terminally acetylated, and carries a D-amino acid substitution, all of which slow enzymatic breakdown.
No national medicines regulator has approved melanotan-2 for therapeutic or cosmetic use. In several jurisdictions it is treated as an unapproved prescription medicine, and its legal classification differs from country to country.
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.