cyclic heptapeptide comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Last reviewed on 2026-03-03. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
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.
Melanotan II is a synthetic cyclic heptapeptide that acts as an agonist at melanocortin receptors. It was designed as a structural analogue of alpha-melanocyte-stimulating hormone, the endogenous peptide involved in pigment production. The analogue carries a lactam bridge that constrains the ring and slows enzymatic breakdown relative to the native hormone. In research literature it appears under several abbreviations, and naming conventions are not fully standardized. Published descriptions usually place it within the broader melanocortin agonist family.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C50H69N15O9 | Cyclic heptapeptide, C-terminally amidated |
| Approximate molecular mass | 1024 Da | Monoisotopic mass of the free peptide |
| Appearance | White to off-white powder | Typically supplied as a lyophilised solid |
| Solubility class | Soluble in water and polar solvents | Also dissolves in neutral aqueous buffer |
| Common synonyms | Melanotan II, MT-II, MT-2 | Described as a melanocortin agonist in early literature |
The compound emerged from research programs in the 1980s that examined analogues of alpha-melanocyte-stimulating hormone for pigmentation and photoprotection. Investigators modified the native sequence to extend activity duration and potency. A related analogue, afamelanotide, was developed within the same broad line of inquiry and eventually gained approval in certain jurisdictions for a rare light-sensitivity condition. Melanotan-2 itself did not progress through the same regulatory route and has no approved therapeutic indication.
Melanocortin receptors comprise five subtypes with distinct tissue distributions and functions. Melanotan-2 is described in the literature as a non-selective agonist that engages several of these subtypes, including MC1R, MC3R, MC4R, and MC5R. MC1R is the subtype most directly linked to melanin production in skin cells. Because the compound is not subtype-selective, its observed effects in experimental settings are generally attributed to activity across multiple receptor pathways rather than to a single target.
Published human data come mostly from small, short studies rather than large controlled trials. Reported outcomes include increased skin pigmentation and, in some reports, effects on appetite and libido, but sample sizes are small and follow-up is limited. Whether long-term use produces durable pigment changes or adverse effects is not established. Because products sold outside pharmacies are not standardized, the actual content of any given vial is often unknown. Independent testing of such material is uncommon.
Melanotan II is a synthetic cyclic heptapeptide analog derived from the core sequence of alpha-melanocyte-stimulating hormone. Researchers at the University of Arizona synthesized it during the 1980s while studying pigmentation and appetite signaling. The compound is not an approved medicine in any major jurisdiction and appears mainly in laboratory and research-chemical settings. Its structure incorporates a lactam bridge between side chains, which constrains the ring and slows enzymatic breakdown relative to the natural hormone.
Outside regulated medicine, melanotan II circulates through online vendors as a research chemical, often marketed for tanning. Products sold this way vary widely in purity, concentration, and labeling accuracy, and independent testing has documented discrepancies. Published reports describe both pigment effects and adverse reactions, including nausea, flushing, and darkening of existing moles. Long-term safety data are sparse, and no large controlled trial has established a risk profile. Questions about cumulative effects on melanocytes remain unresolved in the literature.
Melanotan II is a synthetic peptide analog modeled on alpha-melanocyte-stimulating hormone, a naturally occurring signaling peptide involved in pigmentation. Its structure is a cyclic heptapeptide containing two non-natural substitutions, norleucine at position four and D-phenylalanine at position seven. These modifications resist enzymatic breakdown and extend the molecule's activity relative to the native hormone. The compound binds melanocortin receptors and is studied mainly as a pharmacological tool rather than a therapeutic product. It has never received approval as a medicine in any major jurisdiction.
==== Factors that affect the typical range ==== The effect or race and gender on value of BNP and its utility in that context has been studied extensively. BNP is cleared by binding to natriuretic peptide receptors (NPRs) and neutral endopeptidase (NEP). Less than 5% of BNP is cleared renally. NT-proBNP is the inactive molecule resulting from cleavage of the prohormone Pro-BNP and is reliant solely on the kidney for excretion. The "Achilles' heel" of the NT-proBNP biomarker is the overlap in kidney disease in the heart failure patient population: kidney disease patients remove NT-proBNP slower than usual, making an elevated value hard to interpret. When interpreting an elevated BNP level, values may be elevated due to factors other than heart failure. Lower levels are often seen in obese patients. Higher levels are seen in those with renal disease, in the absence of heart failure.
Tyrannosaurus is the most widely known dinosaur in popular culture. Science writer Riley Black states, "In all of prehistory, there is no animal that commands our attention quite like Tyrannosaurus rex... Since the time this dinosaur was officially named in 1905, the enormous carnivore has stood as the ultimate dinosaur." Paleontologist David Hone notes the popularity of Tyrannosaurus models and skeletal displays in museums and writes that films like Jurassic Park and King Kong "would not have been the same without it." T. rex is the only dinosaur that is commonly known to the general public by its full scientific name (binomial name) and the scientific abbreviation T. rex has also come into wide usage.
=== EC 7.4 Catalysing the translocation of amino acids and peptides === Subclasses are based on the reaction processes that provide the driving force for the translocation. At present there is only one subclass: EC 7.4.2 Translocation of amino acids and peptides linked to the hydrolysis of a nucleoside triphosphate.
He plants several bombs on Earth and challenges S.P.D.'s Earth unit to find them as part of a game he played on previous planets before he destroyed them while using his tiny size to hide. After Ban finds him disguised as a walkie-talkie, Byz Goa retaliates by piloting a Kaijuki called Cannon Gladiator 2 (キャノングラディエーター2, Kyanon Guradiētā Tsū), only to be deleted by Dekaranger Robo. Byz Goa is voiced by Tomokazu Seki (関 智一, Seki Tomokazu). Dradian Goldom (ドラド星人ゴルドム, Dorado Seijin Gorudomu): A criminal from Planet Drad who kidnaps Attika Alpachi's son to force him into taking a city block hostage while Goldom robs a nearby bank in the confusion, only for the Dekarangers to realize the truth. Goldom attempts to escape in his Kaijuki, Terrible Terror 2 (テリブルテーラー2, Teriburu Tērā Tsū), but is deleted by Deka Bike Robo. Goldom is voiced by Takaya Kuroda (黒田 崇矢, Kuroda Takaya). Amoreian Baachiyo (アモーレ星人バーチョ, Amōre Seijin Bacho): A hermaphroditic spider-themed criminal and stalker from Planet Amore who possesses four tendrils capable of firing spider silk-like threads to restrain targets and whose people earned a reputation for being overly passionate and "too in love". Following a brief encounter with Tetsu while the officer was working undercover as a woman, falling in love with "her", and eventually metamorphosing from his powerless immature form to his stronger adult form, Baachiyo stalks Swan Shiratori with the belief that she was the person he fell in love with.
According to data from app analytics group Sensor Tower, advertising on TikTok in the US grew by 11% in March 2023, with companies including Pepsi, DoorDash, Amazon, and Apple among the top spenders. According to estimates from research group Insider Intelligence, TikTok is projected to generate $14.15 billion in revenue in 2023, up from $9.89 billion in 2022. In March 2024, The Wall Street Journal reported that TikTok's growth in the US had stagnated.
Sources: en.wikipedia.org
=== Injections and implants === In 1933 or 1934, Schering introduced progesterone in oil solution as a medication by intramuscular injection under the brand name Proluton. This was the first pharmaceutical formulation of progesterone to be marketed for medical use. It was initially a corpus luteum extract, becoming pure synthesized progesterone only subsequently. A clinical study of the formulation was published in 1933. Multiple formulations of progesterone in oil solution for intramuscular injection, under the brand names Proluton, Progestin, and Gestone, were available by 1936. A parenteral route was used because oral progesterone had very low activity and was thought to be inactive. Progesterone was initially very expensive due to the large doses required. However, with the start of steroid manufacturing from diosgenin in the 1940s, costs greatly decreased. Subcutaneous pellet implants of progesterone were first studied in women in the late 1930s. They were the first long-acting progestogen formulation. Pellets were reported to be extruded out of the skin within a few weeks at high rates, even when implanted beneath the deep fascia, and also produced frequent inflammatory reactions at the site of implantation. In addition, they were absorbed too slowly and achieved unsatisfactorily low progesterone levels. Consequently, they were soon abandoned, in favor of other preparations such as aqueous suspensions.
== Sources == Bushkovitch, Paul (5 December 2011). A Concise History of Russia. Cambridge University Press. ISBN 978-1-139-50444-7. Crummey, Robert O. (6 June 2014). The Formation of Muscovy 1300 - 1613. Routledge. ISBN 978-1-317-87200-9. Fennell, John (15 November 2023). The Emergence of Moscow, 1304–1359. Univ of California Press. ISBN 978-0-520-34759-5. Kuchkin, Vladimir A. (2013). "Московское великое княжество" [Grand Principality of Moscow]. In Kravets, S. L. (ed.). Большая российская энциклопедия. Том 21: Монголы — Наноматериалы (in Russian). Большая российская энциклопедия. pp. 308–310. ISBN 978-5-85270-355-2. Archived from the original on 20 May 2026. Riasanovsky, Nicholas V.; Steinberg, Mark D. (2019). A history of Russia (Ninth ed.). New York: Oxford University Press. ISBN 978-0-19-064558-8. Smirnova, E. S. (2013). "Московская школа" [Moscow school]. In Kravets, S. L. (ed.). Большая Российская энциклопедия. Том 21: Монголы — Наноматериалы (in Russian). Большая Российская энциклопедия. pp. 273–274. ISBN 978-5-85270-355-2.
Lithium, the lightest of the alkali metals, is the only alkali metal which reacts with nitrogen at standard conditions, and its nitride is the only stable alkali metal nitride. Nitrogen is an unreactive gas because breaking the strong triple bond in the dinitrogen molecule (N2) requires a lot of energy. The formation of an alkali metal nitride would consume the ionisation energy of the alkali metal (forming M+ ions), the energy required to break the triple bond in N2 and the formation of N3− ions, and all the energy released from the formation of an alkali metal nitride is from the lattice energy of the alkali metal nitride. The lattice energy is maximised with small, highly charged ions; the alkali metals do not form highly charged ions, only forming ions with a charge of +1, so only lithium, the smallest alkali metal, can release enough lattice energy to make the reaction with nitrogen exothermic, forming lithium nitride. The reactions of the other alkali metals with nitrogen would not release enough lattice energy and would thus be endothermic, so they do not form nitrides at standard conditions. Sodium nitride (Na3N) and potassium nitride (K3N), while existing, are extremely unstable, being prone to decomposing back into their constituent elements, and cannot be produced by reacting the elements with each other at standard conditions. Steric hindrance forbids the existence of rubidium or caesium nitride.
Optimal health ranges (or "target ranges") are between 120 and 360 μmol/L or equivalently 2 to 6 mg/dL. This is optimally achieved during at least the first 10 years, to allow the brain to develop normally. The diet requires restricting or eliminating foods high in phenylalanine (Phe), particularly high-protein foods such as meat, fish, eggs, dairy products, legumes, nuts, and soy-based products. Specialized low-phenylalanine medical foods are typically used to meet nutritional requirements. Starchy foods, such as potatoes and corn are generally acceptable in controlled amounts, but the quantity of Phe consumed from these foods must be monitored. A corn-free diet may be prescribed in some cases. A food diary is usually kept to record the amount of Phe consumed with each meal, snack, or drink. An "exchange" system can be used to calculate the amount of Phe in a portion of food from the protein content identified on a nutritional information label. Lower-protein "medical food" substitutes are often used in place of regular bread, pasta, and other grain-based foods, which contain a significant amount of Phe. Many fruits and vegetables are lower in Phe and can be eaten in larger quantities. Infants may still be breastfed to receive all of the benefits of breastmilk, but the quantity must also be monitored, and supplementation with missing nutrients will be required. The sweetener aspartame, present in many diet foods and soft drinks, must also be avoided, as aspartame contains phenylalanine.
Sources: en.wikipedia.org
No. It is a synthetic analogue carrying four amino acid changes, a lactam ring and an amidated C-terminus. The natural hormone is a linear thirteen-amino-acid peptide processed from proopiomelanocortin.
Afamelanotide is the linear analogue [Nle4-D-Phe7]-alpha-MSH, sometimes called melanotan I, while melanotan II is cyclic and carries three further substitutions. The two are distinct molecules and are not interchangeable in analytical testing.
Binding to the four melanocortin receptor subtypes is well documented in vitro. The relative contribution of each subtype to whole-body effects in humans is far less certain.
It is a synthetic cyclic heptapeptide and a non-selective melanocortin receptor agonist. Structurally it is modelled on alpha-melanocyte-stimulating hormone, a peptide that occurs naturally in the body.