The short version of cyclic heptapeptide fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-04-22. Anything still debated is marked as such rather than presented as settled.
Melanotan-2 appears on the World Anti-Doping Agency prohibited list within the peptide hormone class, and several national regulators treat it as an unapproved prescription substance. Some countries restrict importation or sale for personal use. Because the compound is widely traded as a research chemical, the practical legal picture differs between jurisdictions and shifts over time. Human safety data covering long periods are limited, and whether repeated pigmentation changes carry any lasting risk to melanocytes remains an open question.
Freeze-dried melanotan-2 is normally kept as a desiccated powder at minus twenty degrees Celsius or lower, shielded from light and moisture. Peptides of this size degrade through hydrolysis, oxidation and deamidation, and each pathway accelerates as temperature and water activity rise. Repeated freeze-thaw cycles promote aggregation and loss of material, so aliquoting a stock solution before freezing is standard laboratory practice. Once dissolved, the solution is markedly less stable than the powder. In laboratory work, solutions are generally refrigerated and used within days rather than kept for months.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Typical storage temperature | -20 °C or below | For the lyophilised powder, desiccated |
| Storage form | Sealed vial, protected from light | Amber glass or foil-wrapped containers |
| Reconstituted stability | Short, refrigerate | Degradation accelerates in solution |
| Typical analytical method | Reversed-phase HPLC with mass spectrometry | Purity assessment plus identity confirmation |
| Common synonyms | Melanotan II, MT-II | Also written melanotan-2 |
Identification in laboratories relies on reversed-phase liquid chromatography coupled with tandem mass spectrometry, with product-ion spectra compared against a certified reference standard. High-resolution mass spectrometry supplies accurate mass confirmation, and peptide mapping after enzymatic digestion separates melanotan II from closely related analogues. Quantitation of seized material is complicated by unknown counter-ions and residual trifluoroacetate left from purification. Immunoassays raised against alpha-melanocyte-stimulating hormone can cross-react, so chromatographic confirmation is normally required. Urinary detection windows are short, and reported limits of detection differ substantially between laboratories.
Melanotan II holds no marketing authorisation from the Food and Drug Administration, the European Medicines Agency, the UK Medicines and Healthcare products Regulatory Agency or Australia's Therapeutic Goods Administration. Products sold under that name are treated as unapproved new drugs, and their sale or import is prohibited in several jurisdictions. Other countries classify the peptide as a prescription-only medicine or place it among controlled substances, so the legal position changes with the destination market. No pharmacopoeial monograph supplies an official specification, because the material is not a licensed pharmaceutical. Consequently, products offered online are not manufactured to a shared public standard.
The peer-reviewed record is dominated by small early-phase studies, case reports and pharmacovigilance summaries rather than large randomised trials. Papers typically examine tanning response, receptor selectivity or patterns of reported adverse events. Many note that participants obtained the peptide outside a clinical setting, which limits verification of composition and administered amount. Reported events vary widely, and causality is frequently unclear because the identity and purity of self-sourced material are unknown. Open questions include whether repeated melanocortin receptor stimulation produces cumulative effects, and how often label claims match actual content.
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.
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.
Identity and purity are assessed mainly by reversed-phase high-performance liquid chromatography with ultraviolet detection, often paired with mass spectrometry. Retention time supports identity, while the mass spectrum confirms the molecular weight of the intact peptide. Purity is frequently reported as a percentage of total peak area, a figure that depends on the wavelength, column and gradient used. Impurity profiling may also look for truncated sequences, oxidised forms and residual counterions. Amino acid analysis and peptide mapping provide orthogonal confirmation when required.
Regulatory status varies by jurisdiction, and the substance is frequently described as unapproved for therapeutic use. Some authorities classify it alongside prescription-only medicines or controlled categories, while others address it through general consumer protection rules. Analytical surveys have reported mismatches between label claims and measured content in products sold online, although the scope of such testing is limited. Whether these discrepancies are widespread remains an open question. Discussion in the literature therefore tends to combine chemistry, supply-chain observation and policy analysis.
The material is commonly handled as a lyophilized powder in sealed vials. The solid dissolves readily in water and in polar organic solvents, producing a clear solution after reconstitution. Light, heat and repeated freeze-thaw cycles are the concerns most often raised in handling guidance, because peptide bonds and the constrained ring can degrade. Working solutions are generally prepared fresh, and material left in solution is treated as less stable than the dry form. These properties shape how laboratories store and aliquot reference material.
Melanotan-2 is a synthetic cyclic heptapeptide designed as a structural analogue of alpha-melanocyte-stimulating hormone, the endogenous tridecapeptide that regulates pigment production. Two modifications distinguish it from the natural hormone: norleucine replaces methionine at the N-terminus, which limits oxidation, and a D-phenylalanine substitution raises receptor affinity. The ring is closed through an aspartate-lysine lactam bridge, giving the molecule a constrained conformation. The free base has a molecular mass near 1024 daltons, and commercial material is usually supplied as an acetate salt. It appears in the literature as a research peptide rather than an approved therapeutic agent.
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.
== Bibliography == Prentice, B. E., & Benell, D. (1992). "Determinants of empty returns by US refrigerated trucks: conjoint analysis approach". Canadian Journal of Agricultural Economics/Revue canadienne d'agroeconomie, 40(1), 109-127. doi:10.1111/j.1744-7976.1992.tb03680.x (abstract).
=== CSL Behring (Australia) === Albumex (serum albumin) Biostate (Factor VIII) Carimune, which is immunoglobulin for intravenous administration (IGIV) CMV Immunoglobulin-VF (cytomegalovirus immunoglobulin) Helixate, which is recombinant Antihemophilic Factor, a blood-clotting factor for the treatment of haemophilia Hepatitis B immunoglobulin human immunoglobulin – Intragam P, Normal, Rh(D) Immunoglobulin-VF, Sandoglobulin, MonoFIX-VF (Factor IX) Prothrombinex-HT (prothrombin complex) Rhophylac (Rh(D) immunoglobulin G) Tetanus Immunoglobulin-VF Thrombotrol-VF (antithrombin III) Vivaglobin, sub-cutaneous human immune globulin indicated for the treatment of primary immunodeficiency. This product gained FDA approval in January 2006. Von Willebrand factor Zoster Immunoglobulin-VF (varicella zoster immunoglobulin)
Sir John Christopher Willoughby was second in command and took command of the expedition when the two columns united northwest of Johannesburg on 30 December. Although Jameson's men had cut the telegraph wires to Cape Town, they had failed to cut the telegraph wires to Pretoria (cutting a fence by mistake). Accordingly, news of his incursion quickly reached Pretoria and Jameson's armed column was tracked by Transvaal forces from the moment that it crossed the border. The Jameson armed column first encountered resistance very early on 1 January when there was a very brief exchange of fire with a Boer outpost. Around noon the Jameson armed column was around twenty miles further on, at Krugersdorp, where a small force of Boer soldiers had blocked the road to Johannesburg and dug in and prepared defensive positions. Jameson's force spent some hours exchanging fire with the Boers, losing several men and many horses in the skirmish. Towards evening the Jameson armed column withdrew and turned south-east attempting to flank the Boer force. The Boers tracked the move overnight and on 2 January, as the light improved, a substantial Boer force with some artillery was waiting for Jameson at Doornkop. The tired raiders initially exchanged fire with the Boers, losing around thirty men before Jameson realized the position was hopeless and surrendered to Commandant Piet Cronjé. The raiders were taken to Pretoria and jailed.
polymerization The formation of a polymer from its constituent monomers; the chemical reaction or series of reactions by which monomeric subunits are covalently linked together into a polymeric chain or branching aggregate; e.g. the polymerization of a nucleic acid chain by linking consecutive nucleotides, a reaction catalyzed by a polymerase enzyme.
John Ronald Reuel Tolkien (; 3 January 1892 – 2 September 1973) was an English writer and academic philologist. He was the author of the high fantasy works The Hobbit (1937) and The Lord of the Rings (1954–1955). From 1925 to 1945 Tolkien was the Rawlinson and Bosworth Professor of Anglo-Saxon and a Fellow of Pembroke College, both at the University of Oxford. He then moved within the same university to become the Merton Professor of English Language and Literature and Fellow of Merton College, and held these positions from 1945 until his retirement in 1959. Tolkien was a devout Catholic and a close friend of C. S. Lewis, a co-member of the Inklings, an informal literary discussion group. He was appointed a Commander of the Order of the British Empire by Elizabeth II on 28 March 1972. After Tolkien's death, his son Christopher published a series of works based on his father's extensive notes and unpublished manuscripts, including The Silmarillion. These, together with The Hobbit and The Lord of the Rings, form a connected body of tales, poems, fictional histories, invented languages, and literary essays about a fantasy world called Arda and, within it, Middle-earth. Between 1951 and 1955 Tolkien applied the term legendarium to the larger part of these writings. While many other authors had published works of fantasy before Tolkien, the tremendous success of The Hobbit and The Lord of the Rings ignited a profound interest in the fantasy genre and ultimately precipitated an avalanche of new fantasy books and authors.
Sources: en.wikipedia.org
All public universities in Belgium were operated under the legislation of the national government until higher education was moved to the control of the three communities in 1990. Consequently, the Flemish, the French, and the German communities determine which institutes of higher education organize and issue diplomas. Until the 1970s, Belgium had two state universities: the University of Liège (ULiège) and the Ghent University (UGent), both founded in 1817. These are often referred to as the two historic state universities. In 1965, small specialized single-faculty public institutions were recognized as universities, including the Faculty of Veterinary Medicine and the Gembloux Agro-Bio Tech; both are now part of the University of Liège. The Belgian state created smaller public universities that have since merged with larger institutions, including the public university at Mons in 1965 which became part of the University of Mons in 2009. The state-created university founded in Antwerp in 1971 is now part of University of Antwerp. Hasselt University started as a state-created public institution managed by the Province of Limburg. Similarly, the Province of Luxembourg managed the state-created public university in Arlon which became part of ULiège in 2004. Since 1891, private universities have gradually become state-recognized and funded. Some private, mostly Catholic, organizations are called free institutions, as in administratively free from the state despite being state-funded.
== External links == Cofactors lecture Archived 2016-10-05 at the Wayback Machine (Powerpoint file) Enzyme+cofactors at the U.S. National Library of Medicine Medical Subject Headings (MeSH) The CoFactor Database
== Structure of the peptide bond == In 1937, Huggins analyzed the β-sheet models of William Astbury and realized that the hydrogen bonding could not work as described since the bond geometry of the amide nitrogen (then presumed to be tetrahedral) would deflect the hydrogen away from the carbonyl oxygen. He further suggested that resonance might play a role in changing the geometry of the peptide bond to make the hydrogen bonds more linear. However, he did not state explicitly that the peptide bond was planar, as emphasized by Pauling in a nearly simultaneous paper.
Several species sometimes suffer from a wasting condition caused by Vibrio bacteria. A more widespread sea star wasting disease sporadically causes mass mortalities. The results of a 2025 study of starfish off the coast of central British Columbia suggest that those living in the fjords can better survive outbreaks of the disease due to the lower temperatures and higher salinity of their environment. The protozoan Orchitophrya stellarum is known to infect and damage the gonads of starfish. Starfish are vulnerable to high temperatures. Experiments have shown that the feeding and growth rates of Pisaster ochraceus reduce greatly when their body temperatures rise above 23 °C (73 °F) and that they die when their temperature rises to 30 °C (86 °F). This species has a unique ability to absorb seawater to keep itself cool when it is exposed to sunlight by a receding tide. It also appears to rely on its arms to absorb heat, so as to protect the central disc and vital organs. Starfish and other echinoderms can be vulnerable to marine pollution. The common starfish is considered to be a bioindicator species for marine ecosystems. A 2009 study found that P. ochraceus is unlikely to be affected by ocean acidification as severely as other marine animals with calcareous skeletons. In other groups, structures made of calcium carbonate are vulnerable to dissolution when the pH is lowered. Researchers found that when P. ochraceus were exposed to 21 °C (70 °F) and 770 parts per million of carbon dioxide (beyond rises expected in the next century), they were relatively unaffected.
== Biological significance and applications == Imidazole is incorporated into many important biological compounds. The most pervasive is the amino acid histidine, which has an imidazole side-chain. Histidine is present in many proteins and enzymes, e.g. by binding metal cofactors, as seen in hemoglobin. Imidazole-based histidine compounds play an important role in intracellular buffering. Histidine can be decarboxylated to histamine. Histamine can cause urticaria (hives) when it is produced during allergic reaction.
Sources: en.wikipedia.org
=== DNA microarray === DNA microarrays are a useful analytical application of oligonucleotides. Compared to standard cDNA microarrays, oligonucleotide based microarrays have more controlled specificity over hybridization, and the ability to measure the presence and prevalence of alternatively spliced or polyadenylated sequences. One subtype of DNA microarrays can be described as substrates (nylon, glass, etc.) to which oligonucleotides have been bound at high density. There are a number of applications of DNA microarrays within the life sciences.
=== Neurodegenerative diseases === AEP is activated during brain ischemia or brain acidosis and epilepsia seizure. It digests SET protein, which is an inhibitor of DNase, leading to DNA damage and causing damage of the brain. Increased activity of AEP in brain is also observed in patients with Alzheimer's disease and Parkinson's disease (PD). AEP cleaves tau protein and amyloid precursor protein. In patients with PD, alpha synuclein is cut by AEP into toxic chunks., which are hypothesized to possibly play a role in the initiation or pathogenesis of PD
George Walker Bush (born July 6, 1946) is an American former politician, businessman, and Air Force veteran who served as the 43rd president of the United States from 2001 to 2009. A member of the Republican Party, he served as the 46th governor of Texas from 1995 to 2000. He is the eldest son of George H. W. Bush, the 41st president of the United States. Born into the prominent Bush family in New Haven, Connecticut, Bush flew warplanes in the Texas Air National Guard in his twenties. After graduating from Harvard Business School in 1975, he worked in the oil industry. He later co-owned the Major League Baseball team Texas Rangers before being elected governor of Texas in 1994. As governor, Bush successfully sponsored legislation for tort reform, increased education funding, set higher standards for schools, and reformed the criminal justice system. He also helped make Texas the leading producer of wind-generated electricity in the United States. In the 2000 presidential election, he defeated Democratic incumbent vice president Al Gore while losing the popular vote after a narrow and contested United States Electoral College win, which involved the Supreme Court decision Bush v. Gore to stop a recount in Florida. In his first term, Bush signed a major tax-cut program and an education-reform bill, the No Child Left Behind Act. He pushed for socially conservative efforts such as the Partial-Birth Abortion Ban Act, restrictions on same-sex marriage, and faith-based initiatives.
=== Procedure in Vietnam === Prior to 2013, shooting was the primary method of execution in Vietnam. The use of lethal injection method was approved by the government in 2010, adopted in 2011, and then started being used in 2013. Urges to adopt other methods than lethal injection to replace the shooting execution began earlier, in 2006, after concerns of the mental state of the firing squad members after executions. The drugs used consist of sodium thiopental (anesthetic), pancuronium bromide (paralytic), and potassium chloride (cardiotoxin). The production of these substances, however, is low in Vietnam. This led to drug shortages and to considering using other domestic poisons or the readoption of shootings. The first prisoner in Vietnam to be executed by lethal injection, on August 6, 2013, was 27-year-old Nguyen Anh Tuan, arrested for murder and robbery. Between 2013 and 2016, 429 prisoners were executed by this method in the country.
=== Continued employment by the Astros === As part of a personal services contract Bagwell signed with the Astros, he served as a coach in spring training of 2007. On July 11, 2010, the Astros hired Bagwell to be their hitting coach, replacing Sean Berry. At the time of the switch, the Astros had the second-worst average (.237) in the majors and the worst OBP (.295). At the end of the season, the team marginally improved, but was still last in the league in OBP (.303) and SLG (.362) and Bagwell announced he would not return as hitting coach. After a five-year gap in contact with the Astros organization, Bagwell accepted a formal invitation from manager A. J. Hinch to be a guest instructor in spring training of 2015. He is currently a special advisor to team owner Jim Crane.
Sources: en.wikipedia.org
The lyophilised solid is best kept cold, dry and dark, typically at minus twenty degrees Celsius. Moisture and repeated warming cycles are the main causes of degradation. Solutions prepared from the powder are less stable and are normally used quickly.
Reversed-phase liquid chromatography assesses purity, while mass spectrometry confirms molecular mass and detects sequence errors. Amino acid analysis and peptide mapping add structural detail. These techniques are complementary rather than interchangeable.
It is listed as a prohibited peptide hormone by the World Anti-Doping Agency. No medicines regulator has approved it for human use. Import and sale rules vary by country.
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.