cyclic heptapeptide raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2026-06-04. Anything still debated is marked as such rather than presented as settled.
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.
Regulatory treatment varies between countries. Several national medicines agencies have classified the peptide as unapproved, and customs authorities in some jurisdictions seize shipments on that basis. A few jurisdictions channel supply through prescription-only frameworks that do not list the substance by name. Because the material circulates mainly through online vendors, composition and purity are rarely verified before sale. Surveys of unapproved peptide products have reported labels that did not match measured content in a substantial fraction of samples.
Melanotan II is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone, a naturally occurring peptide involved in pigmentation signalling. Its structure substitutes a lactam bridge between side chains to increase stability relative to the native hormone. The compound is also known by the shorthand MT-II and by several non-proprietary synonyms used in research catalogues. It is not an approved therapeutic product in any major jurisdiction; material sold under this name is typically offered as a laboratory reagent rather than as a medicine.
| 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.
Melanotan-2 is a synthetic linear peptide built from seven amino acids arranged in a short chain. Its sequence is commonly written as Ac-Nle-Asp-His-D-Phe-Arg-Trp-Lys-NH2, which includes a modified N-terminus and an amidated C-terminus. The molecule belongs to the melanocortin family and acts as a receptor agonist. Structural features such as the D-phenylalanine residue and the Nle substitution are associated with increased stability against enzymatic degradation relative to the natural parent peptide.
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.
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.
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.
Melanotan-2 is frequently confused with afamelanotide, a linear analogue authorised in the European Union for erythropoietic protoporphyria. The two compounds differ in chain length, ring structure and receptor selectivity, so findings for one cannot be transferred directly to the other. Published controlled human data on melanotan-2 remain sparse, and much of what circulates online derives from small studies or unpublished reports. Questions about effect size, dose-response behaviour and long-term safety therefore remain unresolved.
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.
== External links == Prof. Matthias Tschöp (16 May 2012). Medicine: Prof. Matthias Tschöp. Alexander von Humboldt Foundation. Prof. Matthias Tschöp, Chair of Metabolic Diseases, TUM School of Medicine
The MTHFR nucleotide at position 677 in the gene has two possibilities: C (cytosine) or T (thymine). C at position 677 (leading to an alanine at amino acid 222) is the reference allele. The 677T allele (leading to a valine substitution at amino acid 222) encodes a thermolabile alternative enzyme variant with reduced activity. Both reference and alternative genotypes are common, with the alternative allele frequency at 10-35%, depending on ancestry. Individuals with two copies of 677C (677CC) have the most common genotype. 677TT individuals (homozygous) have lower MTHFR activity than CC or CT (heterozygous) individuals. About ten percent of the North American population are T-homozygous for this polymorphism. There is ethnic variability in the frequency of the T allele – frequency in Mediterranean/Hispanics is greater than the frequency in Caucasians which, in turn, is greater than in Africans/African-Americans. The degree of enzyme thermolability (assessed as residual activity after heat inactivation) is much greater in 677TT individuals (18–22%) compared with 677CT (56%) and 677CC (66–67%). Individuals of 677TT are predisposed to mild hyperhomocysteinemia (high blood homocysteine levels), because they have less active MTHFR available to produce 5-methyltetrahydrofolate (which is used to decrease homocysteine). Low dietary intake of the vitamin folate can also cause mild hyperhomocysteinemia. Low folate intake affects individuals with the 677TT genotype to a greater extent than those with the 677CC/CT genotypes.
=== Pharmacodynamics === Ephenidine and related diarylethylamines have been studied in vitro as treatments for neurotoxic injuries, and are antagonists of the NMDA receptor (Ki = 66.4 nM for ephenidine). Ephenidine also possesses weaker affinity for dopamine and norepinephrine transporters (379 nM and 841 nM, respectively) as well as σ1R (629 nM) and σ2R (722 nM) binding sites.
Announced in July 2021, the Steam Deck is a hybrid game console similar to the Nintendo Switch. It is primarily a handheld device that supports playing of Steam games, but through a separate dock unit, the console can output to an external monitor and use external power, networking, and USB accessories connected to the dock. The hardware is based on customized AMD Zen 2 and RDNA 2 chipsets. Units started shipping in February 2022. An OLED version of the Steam Deck was released in November 2023; besides the improved display, the OLED modeling includes increased battery life, improved audio, and more storage compared to the original model.
=== TSI slant === The triple sugar iron (TSI) test is a differential media used to tell whether an organism can ferment glucose, sucrose, and/or lactose and whether an organism can produce hydrogen sulfide gas.
Sources: en.wikipedia.org
== Mechanism == Uniporters work to transport molecules or ions by passive transport across a cell membrane down its concentration gradient. Upon binding and recognition of a specific substrate molecule on one side of the uniporter membrane, a conformational change is triggered in the transporter protein. This causes the transporter protein to change its three-dimensional shape, which ensures the substrate molecule is captured within the transporter proteins structure. The conformational change leads to the translocation of the substrate across the membrane onto the other side. On the other side of the membrane, the uniporter undergoes another conformational change in the release of the substrate molecule. The uniporter returns to its original conformation to bind another molecule for transport. Unlike symporters and antiporters, uniporters transport one molecule/ion in a single direction based on the concentration gradient. The entire process depends on the substrate's concentration difference across the membrane to be the driving force for the transport by uniporters. Cellular energy in the form of ATP is not required for this process.
Monumental and Historic Architecture Landscape and rural heritage Research, Restoration of Architectural Heritage and Outreach Urban Analysis Engineering applied to Heritage Color Research on Heritage Documentation, Critical Analysis and Promotion of Heritage Museum
=== Oliver and Schäfer (1894) === British physician George Oliver and physiologist Edward Albert Schäfer, professor at University College London, collaborated on the physiological effects of adrenal extracts. They first published their findings in two reports in 1894, a full publication followed in 1895. Though frequently falsely attributed to secretin, found in 1902 by Bayliss and Starling, Oliver and Schäfer's adrenal extract containing adrenaline, the substance causing the physiological changes, was the first hormone to be discovered. The term hormone would later be coined by Starling.
=== Midlife isolation === After the break between Jung and Freud in 1913, Jung went through a pivotal psychological transformation, and, after the Munich congress, he was on the verge of a psychosis.This was exacerbated by the outbreak of the First World War in August 1914. Jung described the experience as a horrible "confrontation with the unconscious". He saw visions and heard voices. He worried at times that he was "menaced by a psychosis" or was "doing a schizophrenia". These experiences precipitated his writing of his Red Book, his seven-volume personal diaries that were only published partially and posthumously in 2009. In his crisis, Jung gave up his lectureship at the University of Zürich, although he continued his private practice in Küstnacht until his death in 1961. Jung spoke at meetings of the Psycho-Medical Society in London in 1913 and 1914. His travels were soon interrupted by the war, but his ideas continued to receive attention in England primarily through the efforts of Constance Long, who translated and published the first English volume of his collected writings. As well as his eventual break from Freud, Jung's publication of Psychology of the Unconscious in 1913 resulted in many of Jung's friends and colleagues dropping away and declaring him a mystic. This book was Jung's first publication, which represented his individual point of view and declared the difference between psychoanalysis and analytic psychology.
Sources: en.wikipedia.org
=== Economic and social developments of the early communist era === In 1944, large agricultural holdings and former German property in Poland started to be redistributed through land reform, and industry started to be nationalized. Communist restructuring and the imposition of work-space rules encountered active worker opposition already in the years 1945–1947. The moderate Three-Year Plan of 1947–1949 continued with the rebuilding, socialization and socialist restructuring of the economy. It was followed by the Six-Year Plan of 1950–1955 for heavy industry. The rejection of the Marshall Plan in 1947 made aspirations for catching up with West European standards of living unrealistic. The government's highest economic priority was the development of heavy industry useful to the military. State-run or controlled institutions common in all the socialist countries of eastern Europe were imposed on Poland, including collective farms and worker cooperatives. The latter were dismantled in the late 1940s as not socialist enough, although they were later re-established; even small-scale private enterprises were eradicated. Stalinism introduced heavy political and ideological propaganda and indoctrination in social life, culture and education.
The predominance of the balance of power in the practice of statesmen for three centuries … should not obscure the fact that throughout world history periods dominated by the balance-of-power policies have not been the rule. The balance of power scarcely existed anywhere as a conscious principle of international politics before 1500… Evoking examples of the ancient Chinese and Roman civilizations, Quincy Wright added:
Official governmental portal Archived 17 April 2024 at the Wayback Machine Official website for tourism and holiday in Lower Saxony Archived 5 May 2018 at the Wayback Machine Map with tourist highlights, notepad and personal guide Archived 26 March 2009 at the Wayback Machine (in German) Geographic data related to Lower Saxony at OpenStreetMap
In pharmacology, relative bioavailability measures the bioavailability (estimated as the AUC) of a formulation (A) of a certain drug when compared with another formulation (B) of the same drug, usually an established standard, or through administration via a different route. When the standard consists of intravenously administered drug, this is known as absolute bioavailability (see above). F r e l = 100 ⋅ A U C A ⋅ D B A U C B ⋅ D A {\displaystyle F_{\mathrm {rel} }=100\cdot {\frac {AUC_{\mathrm {A} }\cdot D_{\mathrm {B} }}{AUC_{\mathrm {B} }\cdot D_{\mathrm {A} }}}}
The Magnetic Levitation Method (MLM) is a technique for growing 3D cell cultures. In this approach, cells are treated with magnetic nanoparticles and exposed to spatially varying magnetic fields produced by neodymium magnetic drivers. The process causes cells to levitate to the air-liquid interface within a standard petri dish. The magnetic nanoparticle assemblies consist of magnetic iron oxide nanoparticles, gold nanoparticles, and cell-adhesive peptide sequences. This method can be applied to cultures with five hundred to millions of cells and is adaptable for use in single-dish systems as well as high-throughput, low-volume systems. Magnetized cells can also be used as building blocks for magnetic 3D bioprinting.
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.
No. No major regulatory agency has granted a marketing authorisation for melanotan II as a medicine. Products sold under this name are generally presented as laboratory reagents and are not subject to the batch-release testing applied to approved drugs.