The short version of cyclic heptapeptide fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-03-16. Anything still debated is marked as such rather than presented as settled.
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.
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.
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.
| 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 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.
No regulatory authority has approved melanotan-2 for human use, and several countries classify it as a prescription-only or controlled substance, which restricts lawful supply. Material sold online is generally labelled as a research chemical and is not required to meet pharmaceutical standards of identity or purity. Published human data consist mainly of small uncontrolled studies, case reports and adverse-event notifications, so the evidence base is descriptive rather than confirmatory. Whether repeated melanocyte stimulation alters long-term naevus behaviour remains an open question that no completed trial has resolved.
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.
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.
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.
Sensory neurons (afferent): Relay sensory information in the form of an action potential (nerve impulse) from the PNS to the CNS Motor neurons (efferent): Relay an action potential out of the CNS to the proper effector (muscles, glands) Interneurons: Cells that form connections between neurons and whose processes are limited to a single local area in the brain or spinal cord Structural classification:
specific heat capacity (cp) Also massic heat capacity. The heat capacity of a sample of a substance divided by the mass of the sample. Informally, it is the amount of heat that must be added to one unit of mass of the substance in order to cause an increase of one unit in temperature. The SI unit of specific heat capacity is joule per kelvin per kilogram (J/K/kg). Specific heat capacity often varies with temperature and with each state of matter.
== References == Aagaard et al.: "An inflammatory role for the mammalian carboxypeptidase inhibitor latexin: relationship to cystatins and the tumor suppressor TIG1." Structure 13(2), 309–317, 2005. Cho et al.: "Hypermethylation of CpG island loci and hypomethylation of LINE-1 and Alu repeats in prostate adenocarcinoma and their relationship to clinicopathological features." J Pathology 211(3), 269–277, 2007. Gautron et al.: "Ovacalyxin-32, a novel chicken eggshell matrix protein." J Biol Chem 276(42), 39243–39252, 2001. Jing et al.: "Tazarotene-Induced Gene 1 (TIG1) expression in prostate carcinomas and its relationship to tumorigenicity" J Natl Cancer Institute 94(7), 482–490, 2002. Liang et al.: "The quantitative trait gene latexin influences the size of the hematopoietic stem cell population in mice." Nature Genetics 39(2), 178–188, 2007. So et al.: "Multiple tumor suppressor genes are increasingly methylated with age in non-neoplastic gastric epithelia." Cancer Sci 97(11), 1155–1158, 2006.
where A is the signal (e.g. peak area) and the subscript i indicates the sample and the subscript st indicates the standard. The response factor of the standard is assigned an arbitrary factor, for example 1 or 100. Response factor of sample/Response factor of standard=RRF
==== Activity therapies ==== Activity therapies also called recreation therapy and occupational therapy, promote healing through active engagement. An example of occupational therapy would be promoting an activity that improves daily life, such as self-care or improving hobbies. Each of these therapies have proven to improve mental health and have resulted in healthier, happier individuals. In recent years, for example, coloring has been recognized as an activity that has been proven to significantly lower the levels of depressive symptoms and anxiety in many studies.
Sources: en.wikipedia.org
In the 1970s, Judi Sheppard Missett helped create the market for commercial aerobics with her Jazzercise program, at the same time as Jacki Sorensen was expanding her system of aerobic dancing. In the 1980s, Richard Simmons hosted an aerobic exercise show on television, and followed Jane Fonda's lead by releasing a series of exercise videos. In the 1990s, Billy Blanks's Tae Bo helped popularize cardio-boxing workouts that incorporated martial arts movements. Reebok shoes popularized step aerobics with their Reebok Step device and training program.
=== SARM1 === SARM1 is a Toll-like receptor protein and also functions as a intracellular NADase. Under normal circumstances NADase activity are inhibited in the presence of NAD+, where NAD+ binds to armadillo/heat motifs (ARMs), which inhibits the dimerization of the toll-like receptor domain that activates the NADase activity. If there are damages to the binding site of NAD+ or disruption that prevents the interaction between ARMs and the toll-like receptor domain, NADase activity will be turned on at a constitutive level. As a result SARM1 will have higher consumption of NAD+ and produce NADase products (ADP-ribose and nicotinamide) rather than the production of cADPR from ADP-ribosyl cyclase.
For separation, the denatured samples are loaded onto a gel of polyacrylamide, which is placed in an electrophoresis buffer with suitable electrolytes. Thereafter, a voltage (usually around 100 V, 10-20 V per cm gel length) is applied, which causes a migration of negatively charged molecules through the gel in the direction of the positively charged anode. The gel acts like a sieve. Small proteins migrate relatively easily through the mesh of the gel, while larger proteins are more likely to be retained and thereby migrate more slowly through the gel, thereby allowing proteins to be separated by molecular size. The electrophoresis lasts between half an hour to several hours depending on the voltage and length of gel used. The fastest-migrating proteins (with a molecular weight of less than 5 kDa) form the buffer front together with the anionic components of the electrophoresis buffer, which also migrate through the gel. The area of the buffer front is made visible by adding the comparatively small, anionic dye bromophenol blue to the sample buffer. Due to the relatively small molecule size of bromophenol blue, it migrates faster than proteins. By optical control of the migrating colored band, the electrophoresis can be stopped before the dye and also the samples have completely migrated through the gel and leave it. The most commonly used method is the discontinuous SDS-PAGE.
Eryngium planum, the blue eryngo or flat sea holly, is a species of flowering plant in the family Apiaceae, native to the area that includes central and southeastern Europe and Central Asia. It is a thistle-like herbaceous perennial growing to 50 cm (20 in) with branched silvery-blue stems, and numerous small blue conical flowerheads surrounded by spiky bracts in summer.
Sources: en.wikipedia.org
A tetrapeptide is a peptide, classified as an oligopeptide, since it only consists of four amino acids joined by peptide bonds. Many tetrapeptides are pharmacologically active, often showing affinity and specificity for a variety of receptors in protein-protein signaling. Present in nature are both linear and cyclic tetrapeptides (CTPs), the latter of which mimics protein reverse turns which are often present on the surface of proteins and druggable targets. Tetrapeptides may be cyclized by a fourth peptide bond or other covalent bonds. Examples of tetrapeptides are:
40 mg/day: India National Institute of Nutrition, Hyderabad 45 mg/day or 300 mg/week: the World Health Organization 80 mg/day: the European Commission Council on nutrition labeling 90 mg/day (males) and 75 mg/day (females): Health Canada 2007 90 mg/day (males) and 75 mg/day (females): United States National Academy of Sciences 100 mg/day: Japan National Institute of Health and Nutrition 110 mg/day (males) and 95 mg/day (females): European Food Safety Authority
Abrupt discontinuation of SSRIs, especially after prolonged therapy, causes a withdrawal syndrome, which may include symptoms such as nausea and vomiting, headache, dizziness, chills, body aches, paresthesias, insomnia, and brain zaps. Serotonin reuptake inhibitors should not be abruptly discontinued after extended therapy, and whenever possible, should be tapered over several weeks to minimize discontinuation-related symptoms. SSRI-associated withdrawal symptoms are not typically referred to as a dependence syndrome. However, commentators have noted that such symptoms meet the definition of a physical and psychological dependence syndrome. Paroxetine may produce discontinuation-related symptoms at a greater rate than other SSRIs, though qualitatively similar effects have been reported for all SSRIs. Discontinuation effects appear to be less for fluoxetine, perhaps owing to its long half-life and the natural tapering effect associated with its slow clearance from the body. One strategy for minimizing SSRI discontinuation symptoms is to switch the patient to fluoxetine and then taper and discontinue the fluoxetine.
== "The Genesis of the 'Final Solution’ from the Spirit of Science" == Peukert is perhaps best known for his 1989 essay “The Genesis of the 'Final Solution’ from the Spirit of Science” from his book Max Webers Diagnose der Moderne. Peukert began his essay with an attack on the conservative side in the Historikerstreit, stating that the obsession of Ernst Nolte with proving that Hitler had been somehow forced into committing genocide by the fear of the Soviet Union was an apologistic argument meant to diminish the horror of Auschwitz. Peukert further noted that on the origins of the Holocaust question that the internationalist argument that the "Final Solution to the Jewish Question" was all part of a master plan carried out by Hitler and a few of his followers is not longer accepted by most historians with the "Final Solution" being seen instead as the product of several processes coming together at the same time. Peukert wrote that the Shoah was not the result solely of anti-Semitism, but was instead the a product of the "cumulative radicalization" in which "numerous smaller currents" fed into the "broad current" that led to genocide. Peukert wrote the Holocaust was a product of:
=== Russia-Ukraine conflict === Following Russia's invasion of Ukraine in 2022, Teva Pharmaceuticals faced criticism for continuing its operations in Russia despite international sanctions. While the company committed to stopping new investments, its focus on ensuring an uninterrupted supply of medicines has raised ethical concerns, with critics arguing that Teva's presence weakens the impact of sanctions aimed at pressuring Russia economically.
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.
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.