The short version of cyclic heptapeptide fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-06-16. Anything still debated is marked as such rather than presented as settled.
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.
Melanotan-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone, a naturally occurring peptide involved in pigmentation signalling. Its sequence incorporates modified residues that increase potency and extend biological activity relative to the native hormone. The compound binds receptors of the melanocortin family and is examined mainly in laboratory research. It does not occur naturally and exists only as a manufactured chemical entity produced by solid-phase synthesis.
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.
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.
Melanotan-2 is a synthetic linear peptide built from seven amino acids arranged in a short chain. Its sequence is commonly written as Ac-Nle-Asp-His-D-Phe-Arg-Trp-Lys-NH2, which includes a modified N-terminus and an amidated C-terminus. The molecule belongs to the melanocortin family and acts as a receptor agonist. Structural features such as the D-phenylalanine residue and the Nle substitution are associated with increased stability against enzymatic degradation relative to the natural parent peptide.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C50H69N15O9 | Synthetic cyclic heptapeptide |
| Molecular mass | Approximately 1024 g/mol | Depends on counter-ion content |
| Appearance | White to off-white powder | Commonly supplied as a lyophilised solid |
| Solubility | Freely soluble in water | Also dissolves in common aqueous buffers |
| Typical storage | -20 degrees Celsius, desiccated | Protect from light and repeated freeze-thaw |
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 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.
== Clinical Evidence & Applications == Clinical and research studies suggest ZnC supports intestinal barrier function and may reduce inflammation in conditions like ulcerative colitis. Human and animal studies demonstrate mucosal protection against chemical injury and improved reparative responses. Reviews of clinical studies show benefit in oral and esophageal mucositis in cancer patients receiving chemoradiation, attributed to epithelial protection. Evidence supports the safety and efficacy of ZnC for the maintenance, prevention, and treatment of the mucosal lining and other epithelial tissues. The research supports its use for gastric ulcers and conditions of the upper GI and suggests other applications, particularly for oral mucositis.
== Background == Traditionally, most meat was shipped as primal cuts from the slaughterhouse to the butcher. Meat was then cut to commonly used cuts and packaged at the store or was custom cut for consumers. Case-ready meat is cut and packaged at central regional facilities and sent to retail stores ready for placement in refrigerated display cases. Local butchering, cutting, trimming, and overwrapping the meat at retail stores is greatly reduced. Advantages of the centralized master-packager preparation include: efficiency of centralized operations, tight quality control, close control of sanitization, specialized packaging, etc.
Further work was needed to develop a ration that did not require re-hydration (thus not requiring additional preparation time and water). Further effort, led by Dr. Rauno A. Lampi, Chief of Food Systems Equipment Division at the Natick Soldier Research, Development and Engineering Center, concentrated on the refinement of the retort pouch to contain a wet ration with a three-to-ten year shelf life that could be easily shipped, carried in the field, opened and consumed straight out of the package if necessary with no further heat or water. The resulting MRE went into special issue starting in 1981 and standard issue in 1986, using a limited menu of twelve entrées.
Insulin on board: This calculation is based on the size of a bolus, the time elapsed since the completion of the bolus, and a programmable metabolic rate. The pump software will estimate the insulin remaining in the bloodstream and relay it to the user. This supports the process of performing a new bolus before the effects of the last bolus are complete and, thereby, helps prevent the user from overcompensating for high blood sugar with unnecessary correction boluses. Bolus calculators: Pump software helps by calculating the dose for the next insulin bolus. The user enters the grams of carbohydrates to be consumed, and the bolus "wizard" calculates the units of insulin needed. It adjusts for the most recent blood glucose level and the insulin on board, and then suggests the best insulin dose to the user to approve and deliver. Custom alarms: The pump can monitor for activities during specific times of day and alarm the user if an expected activity did not occur. Examples include a missed meal bolus, a missed blood glucose test, a new blood glucose test 15 minutes after a low blood glucose test, etc. The alarms are customized for each user. Touch bolus: For persons with visual impairments, this button on the pump can be used to bolus for insulin without using the display. This works with a system of beeps or vibrations to confirm the bolus parameters to the pump user. This feature is described as 'touch', 'audio', or 'easy' bolus depending on brand. The feature was first introduced in the mid- to late 1990s.
Physical presence may be required for women who are in relationships for the testosterone–partner interaction, where same-city partnered women have lower testosterone levels than long-distance partnered women.
Sources: en.wikipedia.org
THIQ is a drug used in scientific research, which is the first non-peptide agonist developed that is selective for the melanocortin receptor subtype MC4. In animal studies, THIQ stimulated sexual activity in rats, but with little effect on appetite or inflammation. This supports possible application of MC4 selective agonists for the treatment of sexual dysfunction in humans, although THIQ itself has poor oral bioavailability and a short duration of action so improved analogues will need to be developed.
==== Stability ==== According to Sassen (1997) the role of hydrates at chemosynthetic communities has been greatly underestimated. The biological alteration of frozen gas hydrates was first discovered during the MMS study entitled "Stability and Change in Gulf of Mexico Chemosynthetic Communities". It is hypothesized that the dynamics of hydrate alteration could play a major role as a mechanism for regulation of the release of hydrocarbon gases to fuel biogeochemical processes and could also play a substantial role in community stability. Recorded bottom-water temperature excursions of several degrees in some areas such as the Bush Hill site (4–5 °C at 500-metre (1,600-foot) depth) are believed to result in dissociation of hydrates, resulting in an increase in gas fluxes (MacDonald et al., 1994). Although not as destructive as the volcanism at vent sites of the mid-ocean ridges, the dynamics of shallow hydrate formation and movement will clearly affect sessile animals that form part of the seepage barrier. There is potential of a catastrophic event where an entire layer of shallow hydrate could break free of the bottom and considerably affect local communities of chemosynthetic fauna. At deeper depths (>1,000 metres (3,300 feet)), the bottom-water temperature is colder (by approximately 3 °C) and undergoes less fluctuation. The formation of more stable and probably-deeper hydrates influences the flux of light hydrocarbon gases to the sediment surface, thus influencing the surface morphology and characteristics of chemosynthetic communities.
I agreed emphatically with Henry Stimson. Once we had got ourselves into the business of bombing cities, we might as well do the job competently and get it over with. I felt better that morning than I had felt for years... Those fellows who had built the atomic bombs obviously knew their stuff... Later, much later, I would remember [the downside]. I am convinced that to avoid nuclear war it is not sufficient to be afraid of it. It is necessary to be afraid, but it is equally necessary to understand. And the first step in understanding is to recognize that the problem of nuclear war is basically not technical but human and historical. If we are to avoid destruction we must first of all understand the human and historical context out of which destruction arises. In 1967, in his capacity as a military adviser, Dyson wrote an influential paper on the issue of possible US use of tactical nuclear weapons in the Vietnam War. When a general said in a meeting, "I think it might be a good idea to throw in a nuke now and then, just to keep the other side guessing..." Dyson became alarmed and obtained permission to write a report on the pros and cons of using such weapons from a purely military point of view. (This report, Tactical Nuclear Weapons in Southeast Asia, published by the Institute for Defense Analyses, was obtained, with some redactions, by the Nautilus Institute for Security and Sustainability under the Freedom of Information act in 2002.) It was sufficiently objective that both sides of the debate based their arguments on it.
==== Isotopes related to nuclear weapons ==== The aforementioned processes can be measured using naturally occurring isotopes. Nevertheless, anthropogenic isotopes are also extremely useful for oceanographic measurements. Nuclear weapons tests released a plethora of uncommon isotopes into the world's oceans. 3H, 129I, and 137Cs can be found dissolved in seawater, while 241Am and 238Pu are attached to particles. The isotopes dissolved in water are particularly useful in studying global circulation. For example, differences in lateral isotopic ratios within an ocean can indicate strong water fronts or gyres. Conversely, the isotopes attached to particles can be used to study mass transport within water columns. For instance, high levels of Am or Pu can indicate downwelling when observed at great depths, or upwelling when observed at the surface.
Sources: en.wikipedia.org
Extraradical hyphae extend outward from the mantle into the soil, compensating for the suppression of root hairs by increasing the effective surface area of the colonized root. These hyphae can spread out singly, or in an aggregate arrangement known as a rhizomorph. These composite hyphal organs can have a wide range of structures. Some rhizomorphs are simply parallel, linear collections of hyphae. Others have more complex organization, for example the central hyphae may be larger in diameter than other hyphae, or the hyphae may grow continuously at the tip, penetrating into new areas in a way that superficially resembles meristematic activity. This part of the ectomycorrhiza, which is called the extraradical or extramatrical mycelium, functions largely as a transport structure. They often spread considerable distances, maintaining a large contact area with the soil. Some studies have shown a relationship between nutrient transport rates and the degree of rhizomorph organization. The rhizomorphs of different EcM types often have different organization types and exploration strategies, observed as different structure and growth within the soil. These differences also help identify the symbiotic fungus. The hyphae extending outward into the soil from an ectomycorrhiza can infect other nearby plants. Experiments and field studies show that this can lead to the formation of common mycorrhizal networks (CMNs) that allow sharing of carbon and nutrients among the connected host plants.
Blue Shift was announced in the second quarter of 2000 as part of an upcoming Dreamcast port of Half-Life. While the port was developed by Captivation Digital Laboratories, Blue Shift was developed by Gearbox Software, who also developed the first Half-Life expansion, Opposing Force. The game had the working title Half-Life: Guard Duty; publisher Sierra Entertainment announced the name Blue Shift on August 30, 2000. As with Opposing Force, the title has a double meaning, referring to both the blue shift light phenomenon and the name of Barney's shift. The Dreamcast port would include higher detail models and textures that were double the polygon count of Valve's original Half-Life models. At the European Computer Trade Show in September 2000, information about Blue Shift's story and development direction was revealed, along with a release date of November 1, 2000, for the Dreamcast version of Half-Life. The port was delayed by Sierra to ensure the "high expectations of consumers" were met, anticipating release by the end of the year. On March 29, 2001, Sierra announced that Blue Shift would also be released for Windows as a standalone game that would not require the original Half-Life to run. The new models developed for the Dreamcast version would also be included in the PC version as the Half-Life High Definition pack, and could be applied to Half-Life and Opposing Force. At the E3 2001, Gearbox announced that Blue Shift was complete and exhibited a playable version. It was released on June 12, 2001, in North America, and on June 15 in Europe.
== Lifespan == Gastric pit cells are replaced every 2–4 days. This high rate of turnover is a protective mechanism designed to protect the epithelial lining of the stomach from both the proteolytic action of pepsin and the acid produced by parietal cells. Gastric chief cells are much longer lived and are believed to differentiate from stem cells located higher in the gastric unit in the isthmus. These stem cells differentiate into mucous neck cells in the isthmus and transition into chief cells as they migrate towards the base. Since the mucus neck cells do not divide as it becomes a chief cell this process is known as transdifferentiation. The gene Mist1 has been shown to regulate mucus neck cell to chief cell transdifferentiation and plays a role in the normal development of the chief cell organelles and structures.
Sources: en.wikipedia.org
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.
It is shorter than the native hormone and carries a cyclic constraint that improves stability. These changes raise receptor potency and slow breakdown relative to the naturally occurring peptide.
Published accounts date its development to the 1980s, when researchers were generating analogues of melanocyte-stimulating hormone. That work aimed to produce more stable compounds for studying pigmentation biology.
No. Melanotan-2 is manufactured synthetically. The naturally occurring peptide in the same family is alpha-melanocyte-stimulating hormone, which the body produces as part of normal endocrine and neural signalling.