If you have been reading about cyclic heptapeptide and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Updated 2025-09-13. Numbers and descriptions here follow the published literature rather than marketing material.
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.
The compound was developed in the late 1980s and early 1990s by academic researchers investigating melanocortin signaling and pigmentation. Early work explored whether synthetic analogs could reproduce effects of the natural hormone under controlled conditions. The molecule never advanced through the full regulatory pathway required for approval as a medicine. From the mid-2000s onward it appeared in unregulated consumer markets, often distributed through informal channels. That gap between research origins and commercial availability shapes how the compound is discussed today.
Melanotan-2 is a synthetic peptide designed as an analog of alpha-melanocyte-stimulating hormone, a signaling molecule produced in the pituitary and skin. Its structure is a linear chain of seven amino acids that folds into a ring through an internal lactam bridge joining two side chains. The compound is sometimes written as MT-II or MEL-2 in informal and commercial contexts. It belongs to the melanocortin peptide family, a group of short signaling molecules that share a conserved core sequence recognized by melanocortin receptors.
Two structural changes distinguish the synthetic peptide from the natural hormone. A norleucine residue replaces methionine at one position, and a D-configured phenylalanine replaces the natural L-form at another. Both substitutions slow enzymatic breakdown, which extends the molecule's persistence relative to the parent hormone. The lactam bridge further constrains the backbone into a stable conformation. These features are standard design strategies in peptide chemistry and are not unique to this compound; they appear across many research peptides built for improved stability.
| 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 |
The compound was developed in the late 1980s and 1990s by academic researchers investigating photoprotection. The rationale held that stimulating melanin production might reduce ultraviolet damage to skin and lower skin cancer risk. Early work examined receptor binding, pigment response, and short-term tolerability in small studies. That program did not produce an approved drug, and formal development stalled after early-phase trials. Whether induced pigmentation confers meaningful photoprotection remains an open question.
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.
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.
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.
=== Microscale thermophoresis === Microscale thermophoresis (MST) measures the size, charge and hydration entropy of molecules/substrates at equilibrium. The thermophoretic movement of a fluorescently labeled substrate changes significantly as it is modified by an enzyme. This enzymatic activity can be measured with high time resolution in real time. The material consumption of the all optical MST method is very low, only 5 μl sample volume and 10nM enzyme concentration are needed to measure the enzymatic rate constants for activity and inhibition. MST allows analysts to measure the modification of two different substrates at once (multiplexing) if both substrates are labeled with different fluorophores. Thus substrate competition experiments can be performed.
In August 2008, Helton was diagnosed with a degenerative back condition, putting his health and ability to continue play in question. On May 19, 2009, Helton got his 2,000th hit, a single, during an 8–1 road loss to the Atlanta Braves. On July 22, Helton hit his 500th career double in a 4–3 home victory over the Arizona Diamondbacks. He became the 50th player in MLB history to hit 500 career doubles and the fastest to do since 1954. Helton also joined Babe Ruth, Stan Musial, Lou Gehrig and Ted Williams as the only players in MLB history to have at least 500 doubles, 320 home runs and a .325 batting average for a career. On March 11, 2010, Helton signed a two-year, $9.9 million contract extension, which ran through the 2013 season. Helton's degenerative back condition sent him back to the disabled list in July. He returned from the DL in August and hit .256 with 8 home runs and 37 RBI for the season. After the season, Helton said he would return to the Rockies in 2011, dispelling rumors of a possible retirement. On February 15, 2011, Helton announced his intention to play baseball for three more years, preferably for the Rockies. On June 30 he played his 2,000th career game. In 2012, Helton continued to deal with what was by now a chronic health issue. On April 14, he drove a 2-run walk-off home run through heavy rain, the seventh walk-off of his career. On July 13, Helton was placed on the 15-day disabled list due to inflammation in his right hip. He had played 63 games to that point, and was batting .235.
Since its founding, the EU has operated among an increasing plurality of member state and globalising legal systems. This has meant both the European Court of Justice and the supreme courts of the states have had to develop principles to resolve conflicts of laws between different systems. Within the EU itself, the Court of Justice's view is that if Union law conflicts with a provision of State law, then Union law has primacy. In the first major case in 1964, Costa v ENEL, a Milanese lawyer, and former shareholder of an energy company, named Mr Costa refused to pay his electricity bill to Enel, as a protest against the Nationalization of the Italian energy corporations. He claimed the Italian nationalisation law conflicted with the Treaty of Rome, and requested a reference be made to both the Italian Constitutional Court and the Court of Justice under TFEU article 267. The Italian Constitutional Court gave an opinion that because the nationalisation law was from 1962, and the treaty was in force from 1958, Costa had no claim. By contrast, the Court of Justice held that ultimately the Treaty of Rome in no way prevented energy nationalisation, and in any case under the Treaty provisions only the commission could have brought a claim, not Mr Costa. However, in principle, Mr Costa was entitled to plead that the Treaty conflicted with national law, and the court would have a duty to consider his claim to make a reference if there would be no appeal against its decision.
Among Catholics, the positive rating decreased from 48% to 24%, and among evangelicals, from 30% to 21%. In the Northeast, traditionally a region of greater support for the president, approval fell from 49% to 33%. The survey was carried out between 10 and 11 February, with 2,007 voters from 113 cities, and has a margin of error of two percentage points. On 29 May, the study "Vida Digital de Lula", launched by the Ativaweb agency, identified that Lula lost one million followers on the social networks Instagram and Facebook. According to the study, the reasons would be the triggering of the INSS fraud scheme initiated in 2019 and the taxation of the Tax on Financial Operations (IOF). According to the portal O Antagonista, one of the reasons would be the embarrassments caused by first lady Janja. The AtlasIntel survey carried out on 30 May showed that disapproval rates of Lula's government reached the record level of 53.7%, according to the survey conducted in partnership with Bloomberg. This is the highest rate of dissatisfaction with the current administration since January 2024, due to the start of the investigations into the INSS fraud scheme. Approval of the PT government remained stable at 45.5% – in April, it was 46.1%, and in March, 44.9%. The Quaest survey released on 16 July indicated a recovery in the rating, according to the survey, because the difference between approval and disapproval was 17 points in June and 10 now. Disapproval, however, remained above approval, with 53% disapproval and 43% approval.
== Recent work on homing peptides and nanomedicine == Ruoslahti's research group has developed a novel class of tumor-homing peptides that can be used to enhance delivery of drugs and nanoparticles to tumors. These tumor-penetrating peptides selectively home to tumor vessels, where they activate a transport pathway that delivers the peptide, and along with it drugs and even nanoparticles, through the wall of tumor blood vessels and deep into tumor tissue. Having bound to tumor vessels the peptide is cleaved and an amino acid sequence motif named the C-end rule or CendR motif (pronounced "sender") is exposed at the C-terminus of the peptide. Subsequent binding of the peptide to neuropilin-1 activates the CendR transport pathway into and through tumor tissue. The prototype tumor-penetrating peptide, iRGD, is in clinical trials in solid tumor patients tested as an enhancer of cancer therapies. This peptide recognizes many different types of cancers, and it can be used for tumor delivery of various payloads that are either coupled to the peptide, or given together with it. iRGD has also been shown to effectively deliver drugs to the placenta, which could aid in the treatment of slow fetal growth. Recently, in vivo phage screening has been used to identify peptides that target hypertensive pulmonary arteries, atherosclerosis, and diseases of the brain.
Sources: en.wikipedia.org
"Whereas, for all time since the creation of mankind, no king whosoever had destroyed Armanum and Ebla, the god Nergal, by means of (his) weapons opened the way for Naram-Sin, the mighty, and gave him Armanum and Ebla. Further, he gave to him the Amanus, the Cedar Mountain, and the Upper Sea. By means of the weapons of the god Dagan, who magnifies his kingship, Naram-Sin, the mighty, conquered Armanum and Ebla."
== Chemical properties == Azidophenylalanine has the molecular formula C9H10N4O2 and a molecular weight of 206.20 g/mol. Its IUPAC name is (2S)-2-amino-3-(4-azidophenyl)propanoic acid. It appears as an off-white solid and is soluble in water, DMSO, and DMF. As with many other azides, the isolated compound exhibits explosive properties. It is light-sensitive and should be stored at -20 °C in the dark.
The human body's immune response to a surgically-implanted foreign object (prosthetic breast, cardiac pacemaker, orthopedic prosthesis) is to biologically isolate the foreign object with a capsule of tightly-woven collagen fibres. Afterwards, the capsular contracture occurs over time when the thickened, collagen-fibre capsule has compressed inwards, against the breast-implant with great mechanical pressure that deforms and breaks the implant, and so disfigures the breast; the causes of capsular contracture include bacterial contamination, shell-rupture of the medical device, leakage of the prosthetic filler-material, and hematoma. The prosthetic-breast implantation surgeries that have a low-rate of capsular contractures include surgical approaches that feature the submuscular emplacement of the breast-implant and the use of breast implants with a textured surface; limited handling of the breast implants before the surgery, limited contact with and handling of the skin of the implant-pocket, and irrigation of the surgical site with antibiotic solutions. To correct a capsular contraction, the plastic surgeon realises an open capsulotomy procedure to loosen and release the collagen-fibre capsule from the implant-pocket, for removal and replacement with a new model of prosthetic breast. Moreover, non-surgical therapies for treating collagen-fibre capsules include massage, external ultrasonic therapy, pharmaceutic therapy with leukotriene pathway inhibitor medications, and Diapulse therapy (Pulsed Electromagnetic Field Therapy, PEMFT).
== Dietary sources of energy == The typical human diet consists chiefly of carbohydrates, fats, proteins, water, ethanol, and indigestible components such as bones, seeds, and fibre (mostly cellulose). Carbohydrates, fats, and proteins typically comprise ninety percent of the dry weight of food. Ruminants can extract food energy from the respiration of cellulose because of bacteria in their rumens that decompose it into digestible carbohydrates. Other minor components of the human diet that contribute to its energy content are organic acids such as citric and tartaric, and polyols such as glycerol, xylitol, inositol, and sorbitol. Some nutrients have regulatory roles affected by cell signaling, in addition to providing energy for the body. For example, leucine plays an important role in the regulation of protein metabolism and suppresses an individual's appetite. Small amounts of essential fatty acids, constituents of some fats that cannot be synthesized by the human body, are used (and necessary) for other biochemical processes. The approximate food energy contents of various human diet components, to be used in package labeling according to the EU regulations and UK regulations, are:
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.
It is a synthetic seven-amino-acid peptide modeled on alpha-melanocyte-stimulating hormone. It carries two non-natural substitutions and a cyclic bridge that increase its stability relative to the natural hormone. It circulates as a research chemical and is not an approved medicine.