cyclic heptapeptide is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Last reviewed on 2026-07-22. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
Regulatory treatment varies by country. In the United States the peptide is not approved as a medicine, and products offered for human use may be treated as unapproved new drugs; some states also restrict sale. Australia, the United Kingdom, and European Union member states apply comparable restrictions to unapproved peptide products. Border agencies have seized shipments labelled as research chemicals. Classification may change over time, and the legal position for personal importation is not clearly settled in most published guidance.
Lyophilised melanotan-2 is supplied as a solid, which is more stable than a solution. The material is hygroscopic, so weighing is done quickly, in low humidity, with the container kept sealed. Reconstitution usually uses water for injection or bacteriostatic water, added down the wall of the vial to limit foaming. A reconstituted solution is held at 2 to 8 °C and kept away from light. Repeated freezing and thawing of the same vial is avoided because ice crystal formation and concentration effects degrade the peptide.
Reversed-phase high-performance liquid chromatography is the routine method for purity assessment. Peptides absorb near 214 nm because of the peptide bond, and a gradient of acetonitrile in water separates the intact peptide from deletion sequences, oxidised products, and earlier-eluting fragments at neutral pH. Electrospray ionisation mass spectrometry provides an orthogonal check: the measured mass must agree with the theoretical value. Amino acid analysis and peptide mapping confirm structure but are used less often. Reference standards remain scarce because the peptide is not described in any pharmacopoeia.
| 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 |
Melanotan II binds several melanocortin receptor subtypes rather than a single target. MC1R on melanocytes drives melanin synthesis, while MC3R and MC4R participate in energy balance, appetite, and sexual response pathways. This lack of selectivity explains why reported effects extend beyond skin darkening. Substitutions at positions four and seven, including norleucine and D-phenylalanine, increase potency and resistance to peptidases. Understanding which receptor mediates which effect remains an active area of investigation.
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.
Because the substance circulates mainly through informal markets, verification is a recurring theme in technical discussion. Independent analyses have found that labeled content and actual content can diverge, and that purity varies between samples. Analytical laboratories use reversed-phase chromatography to separate components and mass spectrometry to confirm identity. Isotope-labeled internal standards improve quantification in complex matrices. Such methods describe what a sample contains but say nothing about its sterility, lawful status, or suitability for any use. Open questions remain about how consistently testing is applied across the supply chain.
Regulatory treatment of this peptide varies by country. It holds no marketing authorization as a medicine in the United States, the European Union, or most other jurisdictions. Some countries classify products containing it as prescription-only or unlicensed medicines, which restricts lawful supply. Authorities have issued public notices warning that unregulated products may contain undeclared or incorrect ingredients. The molecule also appears on prohibited lists for competitive sport. These measures address supply oversight rather than any approved therapeutic role.
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.
=== Neural circuit mechanism with PGE2 action === PGE2 release comes from the arachidonic acid pathway. This pathway (as it relates to fever), is mediated by the enzymes phospholipase A2 (PLA2), cyclooxygenase-2 (COX-2), and prostaglandin E2 synthase. These enzymes ultimately mediate the synthesis and release of PGE2. PGE2 is the ultimate mediator of the febrile response. The setpoint temperature of the body will remain elevated until PGE2 is no longer present. PGE2 acts on neurons in the preoptic area (POA) through the prostaglandin E receptor 3 (EP3). EP3-expressing neurons in the POA innervate the dorsomedial hypothalamus (DMH), the rostral raphe pallidus nucleus in the medulla oblongata (rRPa), and the paraventricular nucleus (PVN) of the hypothalamus. Under normal conditions, EP3-expressing neurons in the POA are important thermoregulatory neurons, which provide continuous inhibitory signals with the transmitter GABA to control sympathetic output neurons in the DMH and rRPa, thereby performing bidirectional regulation of basal body temperature. During infection, PGE2 produced in the brain inhibits the activity of EP3-expressing neurons in the POA to attenuate the inhibition of sympathetic output, and thereby activates the sympathetic output system, which evokes non-shivering thermogenesis to produce body heat and skin vasoconstriction to decrease heat loss from the body surface, leading to fever.
Healing of a flap maintains the same process as healing of any wound. There are four stages: hemostasis, inflammation, proliferation, and remodeling, all of which can take up to a year to complete. Following flap surgery, the biggest risk in recovery is flap death. Flap failure is an uncommon occurrence but does happen. The reported flap failure rate in free flaps is less than 5%. This is most commonly caused by venous insufficiency; this accounts for of 54% of all failures. Venous insufficiency is commonly caused by a venous thrombus within the first 2 days following surgery. After the immediate postoperative risk, the flap will continue to heal, adhering to the stages of normal wound healing. It can take over 3 months for an incision to be at 80% tensile strength compared to normal tissue.
The transformation of the Jardin ('Garden') from the medicinal garden of the king to a national public museum of natural history required the creation of twelve chaired positions. Over the ensuing years the number of Chairs and their subject areas evolved, some being subdivided into two positions and others removed. The list of Chairs of the MNHN includes major figures in the history of the Natural sciences. Early chaired positions were held by Jean-Baptiste Lamarck, René Desfontaines, and Georges Cuvier, and later occupied by Paul Rivet, Léon Vaillant, and others.
In April 1943, Enrico Fermi suggested to Robert Oppenheimer the possibility of using the radioactive byproducts from enrichment to contaminate the German food supply. The background was fear that the German atomic bomb project was already at an advanced stage, and Fermi was also skeptical at the time that an atomic bomb could be developed quickly enough. Oppenheimer discussed the proposal with Edward Teller, who suggested the use of 90Sr. James Bryant Conant and Leslie R. Groves were also briefed, but Oppenheimer wanted to proceed with the plan only if enough food could be contaminated with the weapon to kill half a million people.
=== Regulatory elements === To build and develop biological systems, regulating components including regulators, ribosome-binding sites (RBSs), and terminators are crucial. Despite years of study, there are many various varieties and numbers of promoters and terminators for Escherichia coli, but also for the well-researched model organism Saccharomyces cerevisiae, as well as for other organisms of interest, these tools are quite scarce. Numerous techniques have been invented for the finding and identification of promoters and terminators in order to overcome this constraint, including genome mining, random mutagenesis, hybrid engineering, biophysical modelling, combinatorial design, and rational design.
Sources: en.wikipedia.org
In addition, there were hundreds of thousands of part-time employees and informers in various Syrian intelligence departments. According to estimates, there was one member of various branches of the Ba'athist secret police for every 158 citizens, which was said to be one of the largest ratios in the world. The general intelligence, political security, and military intelligence divisions of the Ba'athist secret police had several branches in all governorates controlled by the Assad regime, where they were all headquartered in Damascus. With state impunity granted by the Assad regime, officers of the Mukhabarat wielded pervasive influence over local bodies, civil associations and bureaucracy, where they played a major role in shaping Ba'athist administrative decisions. Additionally, intense factional rivalries and power struggles existed among various branches of the secret police. Several academics have described the military, bureaucratic, and secret police apparatus of the Ba'athist state as constituting a pyramidal socio-political structure with an Orwellian surveillance system designed to neutralize independent civic activities and political dissent from its very onset. During Ba'athist rule, Syria was one of the five countries listed on Reporters Without Borders' list of "State Enemies of the Internet" in March 2013, which was a list of countries ruled by governments that perpetrate pervasive surveillance of news providers that resulted in harsh restrictions on access to information and personal lives.
Liver function tests (LFTs or LFs), also referred to as a hepatic panel or liver panel, are groups of blood tests that provide information about the state of a patient's liver. These tests include prothrombin time (PT/INR), activated partial thromboplastin time (aPTT), albumin, bilirubin (direct and indirect), and others. The liver transaminases aspartate transaminase (AST or SGOT) and alanine transaminase (ALT or SGPT) are useful biomarkers of liver injury in a patient with some degree of intact liver function. Most liver diseases cause only mild symptoms initially, but these diseases must be detected early. Hepatic (liver) involvement in some diseases can be of crucial importance. This testing is performed on a patient's blood sample. Some tests are associated with functionality (e.g., albumin), some with cellular integrity (e.g., transaminase), and some with conditions linked to the biliary tract (gamma-glutamyl transferase and alkaline phosphatase). Because some of these tests do not measure function, it is more accurate to call these liver chemistries or liver tests rather than liver function tests. Several biochemical tests are useful in the evaluation and management of patients with hepatic dysfunction. These tests can be used to detect the presence of liver disease. They can help distinguish among different types of liver disorders, gauge the extent of known liver damage, and monitor the response to treatment.
Native Chemical Ligation (NCL) is an important extension of the chemical ligation concept for constructing a larger polypeptide chain by the covalent condensation of two or more unprotected peptides segments. Native chemical ligation is the most effective method for synthesizing native or modified proteins of typical size (i.e., proteins< ~300 AA).
== Medical uses == Olanzapine/fluoxetine was approved by the U.S. Food and Drug Administration (FDA) to treat the depressive episodes of bipolar I disorder in 2003. In 2009, it was granted approval for the treatment of treatment-resistant depression. Olanzapine/fluoxetine, or other antidepressant/antipsychotic combinations, are sometimes prescribed off-label for anxiety disorders, eating disorders, obsessive–compulsive disorder (OCD), and posttraumatic stress disorder (PTSD).
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.
Low temperature slows hydrolysis and oxidation, the two main routes by which the peptide backbone and side chains are modified. A lyophilised powder stored at −20 °C is more stable than one kept at room temperature, and once the material is dissolved the degradation rate rises, making refrigeration more important.