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 2025-09-03 and is reviewed periodically as new material appears.
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.
The peptide was developed during the 1980s by researchers investigating melanocortin signalling and skin pigmentation pathways. Early work focused on analogues of alpha-melanocyte-stimulating hormone that would resist enzymatic breakdown more effectively than the parent molecule. Melanotan-2 emerged from that programme as a shortened, cyclised variant. Reports describing its synthesis and receptor activity later appeared in the scientific literature. Commercial availability grew through unregulated channels rather than through pharmaceutical approval.
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.
| Property | Value | Notes |
|---|---|---|
| Compound class | Synthetic cyclic heptapeptide | Alpha-MSH analogue containing a D-phenylalanine residue |
| Molecular formula | C50H69N15O9 | Average molecular mass approximately 1024.2 g/mol |
| Appearance | White to off-white lyophilised powder | Normally supplied as a freeze-dried solid in a sealed vial |
| Solubility | Freely soluble in water and polar solvents | Dissolves readily in aqueous buffers and in alcohol-water mixtures |
| Receptor targets | MC1R, MC3R, MC4R, MC5R | Acts as a non-selective melanocortin receptor agonist |
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.
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 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.
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.
Receptor binding at MC1R on melanocytes raises intracellular cyclic AMP and increases expression of tyrosinase and related enzymes. The downstream result is greater synthesis of eumelanin, the dark pigment, without ultraviolet exposure acting as the trigger. The compound is not selective, however, and also engages MC3R, MC4R and MC5R, which are expressed in the central nervous system and elsewhere. That lack of selectivity is the explanation usually offered for effects reported outside pigmentation, including appetite suppression and nausea. Selectivity remains a central theme in comparative studies of related peptides.
Human data remain limited and mostly short-term. Reports describe small trials and observational accounts rather than large controlled studies, so questions about dose-response relationships and long-term effects on melanocytes stay open. Whether repeated exposure alters naevus behaviour is not settled in the published record. Researchers also note that self-administered use outside clinical settings makes actual exposure difficult to quantify. Statements about efficacy and safety should therefore be read as preliminary rather than established.
Melanotan II is a synthetic cyclic heptapeptide that acts as an agonist at melanocortin receptors. It was designed as a structural analogue of alpha-melanocyte-stimulating hormone, the endogenous peptide involved in pigment production. The analogue carries a lactam bridge that constrains the ring and slows enzymatic breakdown relative to the native hormone. In research literature it appears under several abbreviations, and naming conventions are not fully standardized. Published descriptions usually place it within the broader melanocortin agonist family.
El Niño–Southern Oscillation (ENSO) is a global climate phenomenon that emerges from variation in winds and sea surface temperatures over the tropical Pacific Ocean. Those variations have an irregular pattern but do have some appearance of cycles. The occurrence of ENSO is not easily predictable. It affects the climate of much of the tropics and subtropics, and has links (teleconnections) to higher-latitude regions of the world. The warming phase of the sea surface temperature is known as "El Niño" and the cooling phase as "La Niña". The Southern Oscillation is the accompanying atmospheric oscillation, which is coupled with the sea temperature change. El Niño is associated with higher than normal sea level air pressure over Indonesia and Australia, and across the Indian Ocean to the Atlantic Ocean. La Niña has roughly the reverse pattern: high pressure over the central and eastern Pacific and lower pressure through much of the rest of the tropics and subtropics. The two phenomena typically last approximately one year each and typically occur every two to seven years with varying intensity, with neutral periods of lower intensity interspersed. El Niño events can be more intense, but La Niña events may repeat and last longer. A key mechanism of ENSO is the Bjerknes feedback (named after Jacob Bjerknes in 1969) in which the atmospheric changes alter the sea temperatures that, in turn, alter the atmospheric winds in a positive feedback. Weaker easterly trade winds result in a surge of warm surface waters to the east and reduced ocean upwelling on the equator.
== External links == Media related to Pyridoxine at Wikimedia Commons "Pyridoxine". Drug Information Portal. U.S. National Library of Medicine. Archived from the original on 23 January 2017. "Pyridoxine mass spectrum". Golm Metabolome Database.
Each lactoferrin molecule can reversibly bind two ions of iron, zinc, copper or other metals. The binding sites are localized in each of the two protein globules. There, each ion is bonded with six ligands: four from the polypeptide chain (two tyrosine residues, one histidine residue and one aspartic acid residue) and two from carbonate or bicarbonate ions. Lactoferrin forms a reddish complex with iron; its affinity for iron is 300 times higher than that of transferrin. The affinity increases in weakly acidic medium. This facilitates the transfer of iron from transferrin to lactoferrin during inflammations, when the pH of tissues decreases due to accumulation of lactic and other acids. The saturated iron concentration in lactoferrin in human milk is estimated as 10 to 30% (100% corresponds to all lactoferrin molecules containing 2 iron atoms). It is demonstrated that lactoferrin is involved not only in the transport of iron, zinc and copper, but also in the regulation of their intake. Presence of loose ions of zinc and copper does not affect the iron binding ability of lactoferrin, and might even increase it.
=== Venom-induced pathology === As a consequence of the numerous activities the enzyme participates in, it could be deduced that there is likely some enzymatic function regarding the complex network of venom toxin activities. Recent findings suggest a more defined role for LAAO in venom-induced tissue damage. One study demonstrated that LAAO from Bothrops atrox venom causes cell death in human keratinocytes via a sequence of autophagy, apoptosis, and necrosis, driven primarily by hydrogen peroxide production. In vivo, co-injection of the antioxidant N-acetyl cysteine (NAC) significantly reduced dermonecrosis in mice, implicating LAAO-generated oxidative stress in envenomation pathology.
Sources: en.wikipedia.org
The appropriate term for describing a person of particularly short stature (or with the genetic condition achondroplasia) has developed euphemistically. The noun dwarf stems from Old English: dweorg, originally referring to a being from Germanic mythology—a dwarf—that dwells in mountains and in the earth, and is associated with wisdom, smithing, mining, and crafting. The etymology of the word dwarf is contested, and scholars have proposed varying theories about the origins of the being, including that dwarfs may have originated as nature spirits or as beings associated with death, or as a mixture of concepts. Competing etymologies include a basis in the Indo-European root *dheur- (meaning 'damage'), the Indo-European root *dhreugh (whence modern Dutch droom 'dream' and bedrog 'deception'), and comparisons have been made with the Old Indian dhvaras (a type of demonic being). The being may not have gained associations with small stature until a later period. The terms "little person", "LP" and "person of short stature" are the preferred terms of many of those with this disorder, and while some are uncomfortable with "dwarf" it remains a common term in some areas. However, the plural "dwarfs" as opposed to "dwarves" is generally preferred in the medical context, possibly because the plural "dwarves" was popularized by author J. R. R. Tolkien, describing a race of characters in his The Lord of the Rings books resembling Norse dwarfs.
== Awards == Hunt has been awarded several honors including the Distinguished Contribution Award from the American Society for Mass Spectrometry in 1994; the Christian B. Anfinsen Award from the Protein Society; the Chemical Instrumentation Award and Field and Franklin Award from the American Chemical Society; the Thomson Medal from the International Mass Spectrometry Society; the Human Proteome Organization's Distinguished Achievement Award in Proteomics, and the Association of Biomolecular Resource Facilities 2007 Award. In addition, he also received the Charles H. Stone Award (American Chemical Society) and the Pehr Edman Award for outstanding achievements in the application of mass spectrometry. He received the Chemical Instrumentation Award sponsored by the American Chemical Society in 1997.
On November 16, 2004, Valve released Half-Life 2. The game had a six-year development cycle, which saw several delays and the leak of the game's source code in October, 2003. Half-Life 2 returns the player to the role of Gordon Freeman. Set twenty years after the original game, Earth has been occupied by the Combine, a transdimensional race that exploited the events of the first game to invade. The G-Man inserts Freeman into City 17 in Eastern Europe to combat the Combine occupation. Considered one of the greatest video games of all time, Half-Life 2 was praised for its advances in computer animation, sound, narration, computer graphics, artificial intelligence and physics, and won more than 35 Game of the Year awards. Half-Life 2 was the first game to use Valve's Steam content delivery system, a system that eventually led to Valve falling out with publisher Sierra Entertainment.
) as a crystal and powder. The signal observed, called the Pake doublet, was from the magnetically active hydrogens in water. Pake then calculated the proton-proton bond length. NMR measurements were further revolutionized when commercial machines became available in the 1960s. Before this, NMR experiments involved constructing massive projects, locating large magnets, and hand wiring miles of copper coil. Proton NMR remained the most popular technique throughout advancements in following decades, but 2H and 3H were used in other flavors of NMR spectroscopy. 2H has a different magnetic moment and spin than 1H, but generally a much smaller signal. Historically, deuterium NMR is a poor alternative to proton NMR, but has been used to study the behavior of lipids on cell membranes. A variant of 2H NMR called 2H-SNIF has shown potential for understating position-specific isotope compositions and comprehending biosynthetic pathways. Tritium is also used in NMR, as it is the only nucleus more sensitive than 1H, generating very large signals. However, tritium's radioactivity discouraged many studies of 3H-NMR. While tritium's radioactivity discourages use in spectroscopy, tritium is essential for nuclear weapons. Scientists began understanding nuclear energy as early as the 1800s, but large advancements were made in studies of the atomic bomb in the early 1940s. Wartime research, especially the Manhattan Project, greatly advanced the understanding of radioactivity. 3H is a byproduct in reactors, a result of hitting lithium-6 with neutrons, producing almost 5 MeV of energy.
== History == The term "food drunk" has sometimes been used to describe the supposed state of a person after overeating. In October 1905, Thomas Edison (then 58 years old) declared that "the country is food drunk.... the people eat too much and sleep too much, and don't work enough". The phrase was echoed by Dr J E Rullfson of Toledo after fasting for sixty days from January 5, 1907. He held that the entire human race is food drunk, saying "the dinner eaten by Napoleon just before the Battle of Leipzig proved so indigestible that the monarch's brain was clouded and as a result the battle was lost and a pie which King Philip failed to digest caused the revolt of the Netherlands."
Sources: en.wikipedia.org
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.
No approved regulatory indication exists in major markets. An approval exists for a different peptide, afamelanotide, which is used for a rare photosensitivity disorder called erythropoietic protoporphyria. Melanotan-2 itself remains a research compound with no cleared clinical role.
Melanocortin-1 receptors on melanocytes are the receptor most closely linked to pigment production. The peptide is not selective, however, and also activates melanocortin-3, melanocortin-4, and melanocortin-5 receptors. That lack of selectivity is the usual explanation offered for both its range of observed effects and its off-target effects.
It is a synthetic cyclic heptapeptide and an analogue of alpha-melanocyte-stimulating hormone. The molecule is produced by chemical synthesis rather than extracted from a biological source.