This is a working overview of cyclic heptapeptide, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-07-24. Anything still debated is marked as such rather than presented as settled.
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.
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.
Verification of a purchased sample requires documentation linking a batch to a certificate of analysis, and that document should be read for the methods used rather than the headline purity figure. A single chromatographic percentage does not establish identity. Independent laboratories can perform identity and content assays, but no such test establishes that a product is suitable for human use. Claims about efficacy rest largely on small, early studies rather than on replicated controlled trials, and that gap remains open.
Identity testing for a cyclic peptide of this size usually relies on reversed-phase high-performance liquid chromatography coupled to mass spectrometry. The mass spectrum confirms molecular weight, while the chromatographic trace indicates the proportion of related impurities. Tandem mass spectrometry can provide sequence-level information when fragmentation data are compared against a reference standard. Nuclear magnetic resonance is sometimes used to confirm the lactam bridge, although it requires more material and greater operator expertise than routine chromatographic methods.
| 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 |
Receptor binding at MC1R on melanocytes raises intracellular cyclic AMP and increases expression of tyrosinase and related enzymes. The downstream result is greater synthesis of eumelanin, the dark pigment, without ultraviolet exposure acting as the trigger. The compound is not selective, however, and also engages MC3R, MC4R and MC5R, which are expressed in the central nervous system and elsewhere. That lack of selectivity is the explanation usually offered for effects reported outside pigmentation, including appetite suppression and nausea. Selectivity remains a central theme in comparative studies of related peptides.
Human data remain limited and mostly short-term. Reports describe small trials and observational accounts rather than large controlled studies, so questions about dose-response relationships and long-term effects on melanocytes stay open. Whether repeated exposure alters naevus behaviour is not settled in the published record. Researchers also note that self-administered use outside clinical settings makes actual exposure difficult to quantify. Statements about efficacy and safety should therefore be read as preliminary rather than established.
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.
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.
Early published reports described melanotan-2 as a tanning agent without sun protection, which means darkening is not the same as protection against ultraviolet radiation. Later studies explored the peptide in erectile dysfunction, hemorrhagic shock, and some skin conditions. No regulator in the United States or Europe has approved it for clinical use. Many products labelled melanotan-2 are sold without approval and their identity and purity are unverified. Its long-term safety in humans remains an open question.
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.
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.
==== United States ==== In 2026, Apotex received a tentative approval from the United States Food and Drug Administration to produce generic semaglutide. The tentative approval means that a scientific assessment of the generic drug was completed successfully, and that contracts and supply chains can be established, but that selling the drug would depend on intellectual property constraints. Semaglutide is expected to become patent-free in the United States no earlier than December 2031.
==== Kinetics of antibody response ==== Humoral responses after a single DNA injection can be much longer-lived than after a single injection with a recombinant protein. Antibody responses against hepatitis B virus (HBV) envelope protein (HBsAg) have been sustained for up to 74 weeks without boost, while lifelong maintenance of protective response to influenza haemagglutinin was demonstrated in mice after gene gun delivery. Antibody-secreting cells (ASC) migrate to the bone marrow and spleen for long-term antibody production, and generally localise there after one year. Comparisons of antibody responses generated by natural (viral) infection, immunization with recombinant protein and immunization with pDNA are summarised in Table 4. DNA-raised antibody responses rise much more slowly than when natural infection or recombinant protein immunization occurs. As many as 12 weeks may be required to reach peak titres in mice, although boosting can decrease the interval. This response is probably due to the low levels of antigen expressed over several weeks, which supports both primary and secondary phases of antibody response. DNA vaccine expressing HBV small and middle envelope protein was injected into adults with chronic hepatitis. The vaccine resulted in specific interferon gamma cell production. Also specific T-cells for middle envelop proteins antigens were developed. The immune response of the patients was not robust enough to control HBV infection
Tapentadol is a novel opioid that displays high affinity and selectivity for the μ-opioid receptor; In a human liability pharmacology study conducted by the sponsor, it was found that tapentadol displays a high abuse potential similar to hydromorphone, a controlled substance with a similar risk of abuse, misuse and diversion; and Based on a human abuse liability study, 50 mg of tapentadol produces comparable opioid effects to that of 4 mg of hydromorphone. Since 2009 the drug has been categorized in the US as a Schedule II Controlled Substance with ACSCN 9780; in 2014 it was allocated a 17,500 kg aggregate manufacturing quota. In 2010, Australia made tapentadol a S8 controlled drug. The following year, tapentadol was classified as a Class A controlled drug in the United Kingdom, and was also placed under national control in Cyprus, Estonia, Finland, Greece, Latvia and Spain. More recently, Canada made the opioid a Schedule I controlled drug, putting it in the same class as other prescription opioids such as morphine, fentanyl, tramadol, and heroin. In India (except the state of Punjab), multiple brands of tapentadol remain available over the counter. Recent reports have suggested increasing tapentadol abuse and dependence in India, where users have improvised injections with 50 and 100 mg tablets. Furthermore, a large number of listings for tapentadol sourced from India can be found internationally on illicit marketplaces on the dark web.
=== Emerging technologies === Many different forms of human enhancing technologies are either on the way or are currently being tested and trialed. A few of these emerging technologies include human genetic engineering (gene therapy), neurotechnology (neural implants and brain–computer interfaces), cyberware, strategies for engineered negligible senescence, nanomedicine, and 3D bioprinting. Variants of human genetic engineering with so far limited usage include the artificial creation of human-animal hybrids (where each cell has partly human and partly animal genetic contents) and human-animal chimeras (where some cells are human and some cells are animal in origin).
An analysis of Global Burden of Disease Study data estimated that about 163 million people worldwide were living with a substance use disorder in 2021, comprising roughly 111 million cases of alcohol use disorder and about 53 million of drug use disorders. Although these totals rose as the world population grew, the age-standardized prevalence rate fell by about 17% between 1990 and 2021. Prevalence peaks in young adults, at roughly 25 to 29 years, and is consistently higher among males. Age-standardized prevalence was highest in high-income North America and lowest in western sub-Saharan Africa and in north Africa and the Middle East; rates fell in most regions, but drug use disorders rose in several high-income settings. Measured as a risk factor rather than as a disorder, alcohol use was responsible for an estimated 2.6 million deaths worldwide in 2019, or 4.7% of all deaths, and psychoactive drug use for a further 0.6 million; about 2 million of the alcohol-attributable and 0.4 million of the drug-attributable deaths were among men. Alcohol-attributable burden was heaviest in countries with a low Socio-demographic Index, whereas drug-attributable burden increased with higher socio-demographic development. Between 2010 and 2023, drug use was one of only three risk factors worldwide whose age-standardized attributable DALY rate rose.
Sources: en.wikipedia.org
== History == Thiotepa and its synthesis were patented in 1952 by the American Cyanamid company. It was made for use in the textile industry and in the production process of plastics. However, thiotepa entered human trials in 1953 and was found to be effective against acute myeloid leukemia, chronic myelogenous leukemia, and Hodgkin's lymphoma. The first clinical trial noted a "reasonable margin for safety" between the apparent dose and undesired bone marrow suppression In January 2007, the European Medicines Agency (EMA) designated thiotepa as an orphan drug. In April 2007, the United States FDA designated thiotepa as a conditioning treatment for use prior to hematopoietic stem cell transplantation. In June 2024, the FDA approved a ready-to-dilute liquid formulation of thiotepa to treat breast and ovarian cancer.
In late August 2025, the United States began a naval buildup in the southern Caribbean with the stated goal of combating drug trafficking. US president Donald Trump directed the United States Armed Forces to begin using military force against certain Latin American drug cartels, characterizing the smugglers as narcoterrorists. The first major increase came with the deployment of the USS Iwo Jima and its amphibious ready group in August. The arrival of the USS Gerald R. Ford carrier strike group in November marked the second increase. A sharper escalation came in mid-December, when the US began intercepting and seizing crude oil tankers, imposed a naval quarantine on sanctioned vessels transporting oil to or from Venezuela, and announced plans to designate the Venezuelan government a Foreign Terrorist Organization. The first operation of the campaign was the strike and sinking of a vessel—coming from Venezuela and purportedly involving Tren de Aragua gang members carrying illegal drugs—in September that killed 11 people. As the US continued the buildup of military assets to Puerto Rico and El Salvador, subsequent airstrikes destroyed other alleged drug-smuggling vessels, including those allegedly connected to the Colombian National Liberation Army. The Dominican Navy engaged to recover drugs from one of the destroyed vessels, and Trinidad and Tobago backed the US. By early November, the deployment of assets to the Caribbean region had become the largest in decades.
As the nascent polypeptide elongates during proteosynthesis, it passes through the ribosomal tunnel, interacting with the tunnel walls, thus regulating the rate at which it passes through the tunnel. This in turn affect the rate of partial folding, which may already occur at this stage. Short stretches of alpha-helix may form in the inner part of the tunnel and tertiary structure may start forming in the wider tunnel vestibule. As the N-terminus reaches the tunnel exit and is processed by the ribosome-associated protein biogenesis factors, the tertiary structure formed in the tunnel may partially refold. The folding is then completed when the C-terminus is released from the PTC and the protein escapes the tunnel.
==== Sodium ==== Cortisol promotes sodium absorption through the small intestine of mammals. Sodium depletion, however, does not affect cortisol levels so cortisol cannot be used to regulate serum sodium. Cortisol's original purpose may have been sodium transport. This hypothesis is supported by the fact that freshwater fish use cortisol to stimulate sodium inward, while saltwater fish have a cortisol-based system for expelling excess sodium.
Sources: en.wikipedia.org
It performs antimicrobial functions in microorganisms like algae, fungi, bacteria, and gram-positive bacteria of different yeast species. Chitosan composite for tissue engineering: Chitosan powder blended with alginate is used to form functional wound dressings. These dressings create a moist, biocompatible environment which aids in the healing process. This wound dressing is also biodegradable and has porous structures that allows cells to grow into the dressing. Furthermore, thiolated chitosans (see thiomers) are used for tissue engineering and wound healing, as these biopolymers are able to crosslink via disulfide bonds forming stable three-dimensional networks.
=== Natural processes === There are over 30 collagens in nature that are similar in chemical composition but differ in terms of crystal structure. By far, collagen I and II are the most abundant. They initiatively form fibrils in vitro, while fibronectin, fibronectin-binding, collagen-binding integrins and collagen V are essential for collagen I forming and collagen XI for collagen II forming. Therefore, cellular mechanisms play key role in the protein self-assembly process.
Flyorov is also known for the discovery of spontaneous fission with Konstantin Petrzhak. IUPAC approved the name in May, 2012 and the naming ceremony for flerovium and livermorium was held on 24 October 2012 in Moscow. Other proposals included atlantisium (An, a reference via Atlantis to the island of stability), lazarevium (Lz, in honor of Yuri Lazarev), and oganessium (Og, in honor of Yuri Oganessian). In a 2015 interview with Oganessian, the host, in preparation to ask a question, said, "You said you had dreamed to name [an element] after your teacher Georgy Flyorov." Without letting the host finish, Oganessian repeatedly said, "I did."
ATC code A Alimentary tract and metabolism is a section of the Anatomical Therapeutic Chemical Classification System, a system of alphanumeric codes developed by the World Health Organization (WHO) for the classification of drugs and other medical products. Codes for veterinary use (ATCvet codes) can be created by placing the letter Q in front of the human ATC code: for example, QA. National versions of the ATC classification may include additional codes not present in this list, which follows the WHO version.
As a sign of the expanding commercial ties between the two regions (and Han and Tibetan peoples in particular), a special exhibition was held in Chengdu, so that Sichuanese may see and come into contact with Xikang products. In order to levy taxes from the region, Liu also established a Finance Ministry. Historians and analysts have debated over the effectiveness of these measures. Yang Zhonghua, writing in 1941, praised them as a relatively proactive policy; however, it has been argued by Xie Benzao that Liu's plans, though ambitious on paper, were limited by the realities of war and mostly for the purpose of resource extraction. Another road-building project of Liu Wenhui, constructed in the late 1920s from Yazhou to Chengdu, was known by locals mainly for the ruthlessness of its methods. Despite these projects, Xikang was mostly seen as a rear location distant from the conflicts in Sichuan. Liu encouraged students from Sichuan to take part in "border construction" in Xikang. In September 1929, he set up a newsletter, Bianzheng (邊政), dedicated to frontier administration. The issues of the Bianzheng promoted Sun Yat-sen's Three Principles and advertised Xikang as an attractive region for Chinese settlement, teeming with resources but nonetheless coveted by British imperialists. Propaganda plays published in the newsletter, which can be seen as the official policy of Liu Wenhui's government, exhorted youths to settle and develop the Xikang frontier, despite hardships, and thwart the imperialist plans of Tibet and Britain.
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.
Mass spectrometry combined with liquid chromatography provides both molecular weight confirmation and a measure of related impurities. Tandem mass spectrometry adds sequence information. A purity percentage reported without a mass measurement does not confirm what the material is.