This is a working overview of cyclic heptapeptide, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-07-10 and is reviewed periodically as new material appears.
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.
Routine characterisation relies on reversed-phase high-performance liquid chromatography with ultraviolet detection near 214 nanometres, using a C18 column and a water-acetonitrile gradient containing trifluoroacetic acid. Electrospray ionisation mass spectrometry confirms the expected molecular mass and can reveal truncated or oxidised by-products that co-elute poorly. Sequence and stereochemistry require additional work, such as peptide mapping or amino acid analysis, because a chromatographic purity figure alone does not distinguish a diastereomer from the target peptide. Independent testing of research-grade material frequently shows measured content below the stated label, so a certificate of analysis is best read together with the method that produced it.
Melanotan-2 is handled in the laboratory as a lyophilised powder that dissolves readily in water, dimethyl sulfoxide and dimethylformamide, with limited solubility in ethanol. Stock solutions prepared in an organic solvent often precipitate when diluted into aqueous buffer, so gradual dilution with mixing is standard practice. The peptide carries a tryptophan residue and a histidine residue, both sensitive to oxidation and to alkaline conditions. Working solutions are therefore kept near neutral to slightly acidic pH, protected from light, and consumed within the same working session whenever that is practical.
Solid peptide kept dry at minus twenty degrees Celsius, shielded from light and moisture, is generally considered stable for extended periods. Solutions are divided into single-use aliquots and held at minus twenty or minus eighty degrees Celsius, because repeated freeze-thaw cycles promote aggregation and loss of material to container surfaces. Hydrolysis of the backbone and oxidation of tryptophan are the principal degradation routes in aqueous solution, and both accelerate at ambient temperature. Hygroscopic uptake after a vial is opened can also shift the actual mass weighed, which affects any concentration calculated from it.
| 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 |
Activity is attributed to agonism at melanocortin receptors, particularly MC1R and MC4R. Activation of MC1R on melanocytes increases melanin synthesis, which underlies the reported tanning effect. MC4R engagement in the central nervous system is linked to appetite suppression and to effects on sexual arousal reported in early clinical studies. Those studies were small and were not designed to establish efficacy or long-term safety. Receptor selectivity among the melanocortin subtypes is not absolute, which complicates attribution of any effect to a single pathway.
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.
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.
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.
== Further reading == Kadolph, Sara J. (2007). Textiles. Pearson Prentice Hall. ISBN 978-0-13-118769-6. Kohan, Melvin (1995). Nylon Plastics Handbook. Munich: Carl Hanser Verlag. ISBN 1569901899. "How Nylon Yarn is Made". Popular Science. December 1946. pp. 132–3.
=== Infectious disease applications === PCR allows for rapid and highly specific diagnosis of infectious diseases, including those caused by bacteria or viruses. PCR also permits identification of non-cultivatable or slow-growing microorganisms such as mycobacteria, anaerobic bacteria, or viruses from tissue culture assays and animal models. The basis for PCR diagnostic applications in microbiology is the detection of infectious agents and the discrimination of non-pathogenic from pathogenic strains by virtue of specific genes. Characterization and detection of infectious disease organisms have been revolutionized by PCR in the following ways:
=== 'Bronze Age' BioBlitz === On 2 August 2014, a BioBlitz organised by Vivacity found 190 species, including 53 lichens and the endangered European water vole and barn owl. The event also included a talk by the People's Trust for Endangered Species and used a wildlife trail to highlight species that would have been present 3,000 years ago, such as the grey wolf, brown bear and Eurasian beaver.
Dose dumping is a phenomenon of drug metabolism in which environmental factors can cause the premature and exaggerated release of a drug. This can greatly increase the concentration of a drug in the body and thereby produce adverse effects or even drug-induced toxicity. Dose dumping is most commonly seen in drugs taken by mouth and digested in the gastrointestinal tract. Around the same time patients take their medication, they can also ingest other substances like fatty meals or alcohol that increase drug delivery. The substances may act on the drug's capsule to speed up drug release, or they may stimulate the body's absorptive surfaces to increase the rate of drug uptake. Dose dumping is a disadvantage found in extended release dosage form. In general, drug companies try to avoid drugs with significant dose dumping effects. Such drugs are prone to problems and are often pulled from the market. Such was the case with the pain medication Palladone Once Daily formulation due to its dose-dumping effects when taken with alcohol.
=== January 2004 === January 3: Marwan Hassoun and his cousin Zaydun Al-Samarrai are taken from their broken-down truck at about curfew time and forced to jump from the Tharthar dam into the Tigris River; the latter drowns. First Lt. Jack M. Saville and Sgt. 1st Class Tracy E. Perkins were charged on 2004 June 7 with manslaughter, assault, conspiracy, making false statements, and obstruction of justice. Sgt. Reggie Martinez was charged three weeks later with manslaughter and for making false statements, and Spec. Terry Bowman with assault and making false statements. Martinez' and Bowman's charges were dropped; Perkins got six months in jail. Saville was jailed (45 days) and fined $12,000 for assault but he remained on active duty until his military obligation was fulfilled.
Sources: en.wikipedia.org
=== Complications === A potential complication that may occur in children that suffer acute anemia with a hemoglobin count below 5.5 g/dl is silent stroke A silent stroke is a type of stroke that does not have any outward symptoms (asymptomatic), and the patient is typically unaware they have suffered a stroke. Despite not causing identifiable symptoms a silent stroke still causes damage to the brain, and places the patient at increased risk for both transient ischemic attack and major stroke in the future.
== Role in hair growth/loss == In February 2008, researchers at the University of Bonn announced they have found the genetic basis of two distinct forms of inherited hair loss, opening a broad path to treatments for baldness. They found that mutations in the gene P2RY5 causes a rare, inherited form of hair loss called hypotrichosis simplex. It is the first receptor in humans known to play a role in hair growth. The fact that any receptor plays a specific role in hair growth was previously unknown to scientists, and with this new knowledge a focus on finding more of these genes may be able to lead to therapies for many different types of hair loss. In 2013, it was found that mutations in LPAR6 give rise to the Cornish Rex cat breed, which has a form of ectodermal dysplasia characterised by short woolly hair which is susceptible to loss.
As a tracer for cobalt in chemical reactions Sterilization of medical equipment. Radiation source for medical radiotherapy; specifically cobalt therapy, which uses beams of gamma rays from 60Co teletherapy machines. Radiation source for industrial radiography. Radiation source for leveling devices and thickness gauges. Radiation source for pest insect sterilization. As a radiation source for food irradiation and blood irradiation. As a primary standard for radiation dosimetry calibration. Cobalt has been discussed as a "salting" element to add to nuclear weapons, to produce a cobalt bomb, an extremely "dirty" weapon which would contaminate large areas with 60Co nuclear fallout, rendering them uninhabitable for a decade or more (multiple half-lives of cobalt-60) due to the gamma radiation field. In one design, the tamper of the weapon would be made of 59Co (natural cobalt). When the bomb explodes, neutrons from the nuclear fission would irradiate the cobalt and transmute it to 60Co. No country is known to have done any serious development of this type of weapon.
In the development of gliflozins, the distal ring contains a thiophene ring instead of an aromatic ring. However, the final chemical structures of the marketed gliflozins do not contain this thiophene ring.
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.
Purity is normally stated as an area percentage from high-performance liquid chromatography, for example ninety-five or ninety-eight percent. That figure describes the proportion of ultraviolet-absorbing material eluting as the main peak. It says nothing about water content, counterions, residual solvents or mass fraction of the peptide itself.