A practical reference on cyclic heptapeptide: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2025-08-26. Anything still debated is marked as such rather than presented as settled.
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-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone. Its sequence incorporates a lactam bridge that constrains the peptide into a ring, which increases resistance to enzymatic breakdown relative to the natural hormone. Researchers at the University of Arizona synthesised the compound in the late 1980s and early 1990s while studying pigmentation pathways. It has never received marketing approval from any national medicines regulator. In the scientific literature it is usually described as a laboratory research reagent rather than a therapeutic product.
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.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic cyclic heptapeptide | Analogue of alpha-melanocyte-stimulating hormone |
| Common synonyms | MT-II; melanotan 2 | No internationally accepted non-proprietary name |
| Typical presentation | Lyophilised powder in a sealed vial | Often supplied alongside a separate diluent |
| Regulatory status | Unapproved therapeutic substance | Customs seizure reported in several jurisdictions |
| Reported route in use | Subcutaneous injection | Self-administered outside clinical settings |
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.
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.
Similarly to other classic psychedelics, DET acts as a non-selective serotonin receptor agonist, including of the serotonin 5-HT2A, 5-HT2B, and 5-HT2C receptors. The drug has been shown to activate Gq-mediated signaling at the serotonin 5-HT2A receptor with Emax higher than 70% and to produce the head-twitch response in rodents which is a behavioral proxy of psychedelic-like effects. It is also a serotonin receptor agonist in the rat uterus and stomach strip, with slightly greater potency than dimethyltryptamine (DMT). DET is a very weak reversible monoamine oxidase inhibitor (MAOI), with IC50Tooltip half-maximal inhibitory concentration values of 59 μM for serotonin and 5,000 μM for tryptamine as substrates. Injections of 30 mg/kg to rats resulted in 67% reduction of brain MAO-A activity 15 minutes after administration. The substance may also act as a serotonin reuptake inhibitor, with low affinity but moderate potency. It shows no activity as a norepinephrine or dopamine reuptake inhibitor.
A birch is a thin-leaved deciduous hardwood tree of the genus Betula (), in the family Betulaceae, which also includes alders, hazels, and hornbeams. It is closely related to the beech-oak family Fagaceae. The genus Betula contains 30 to 60 known taxa of which 11 are on the IUCN 2011 Red List of Threatened Species. They are typically short-lived pioneer species and are widespread in the Northern Hemisphere, particularly in northern areas of temperate climates and in boreal climates. Birch wood is used for a wide range of purposes.
== Structure == Optimer ligands are composed of single-stranded DNA or RNA polymers. These nucleic acid molecules can exhibit cognate base-pairing to produce sections of double-stranded DNA or RNA within the Optimer molecules. Optimer ligands form secondary and tertiary structures with compatible internal base-pairing at specific portions of the ligand where possible according to the specific sequence. As not all of the bases in the Optimer sequence will be compatible for internal double-stranded pairing, single-stranded loop and bulge regions will remain in the secondary and tertiary structures, where hydrogen bond acceptor and donor groups are exposed and available to interact with the selected target for target engagement and target binding. The Optimer library that is screened for specific binders consists of 1014 sequences that will form different variable sequence-dependent structures. The wide diversity in this library enables target binding to a range of different molecules. Optimer molecules can bind crevices and exposed epitopes on protein and cellular targets and can wrap around small molecule targets. This enables an increased target range compared to traditional antibody technology that has limitations in accurately binding small molecule targets. As Optimer technology stems from aptamers, Optimer ligands have the ability to operate as reversible structural switches, changing their structure when binding their target molecule.
Sources: en.wikipedia.org
Using the money from her portraits, Jolene leaves and boards a bus west out of South Carolina. Jolene resorts to hitchhiking further west, supporting herself by prostitution. Jolene ends up in Arizona, working as a waitress at an outdoor diner. There, she meets Coco Leger, an aspiring musician and tattoo artist. A relationship blossoms between them and Jolene becomes a tattoo artist at Coco's parlor. After two weeks of dating, Jolene moves in with Coco and he convinces her to get married. After he passes out during sex, Coco is revealed to have a cocaine addiction, supporting his habit and the parlor by dealing cocaine. One evening, a young woman enters the parlor and declares herself to be his wife, Marin and introduces their son, Coco Jr. Coco returns and is confronted by both women before he walks out with Marin and the baby. Furious with Coco, Jolene destroys the parlor, dumps the cocaine on a table, steals the drug money and dumps her ring in the center of the cocaine before dialing 911 and fleeing the scene. Jolene later is in Las Vegas, working as an erotic dancer when she meets Sal Fontaine, a mobster. He takes a liking to her and invites her to quit dancing and move into his high rise condo. Jolene enjoys a life of luxury with Sal, going to fancy dinners and exploring her talent as an artist. One night, Sal demands that Jolene get dressed, go downstairs and wait for him. She falls asleep in the restaurant and quietly returns to the condo to find Sal dead and the mob looking for her. Jolene escapes and ends up hitchhiking on a truck to Tulsa.
=== Venom system morphology === Little is known about the venom and the venom apparatus of centipedes. Studies on venom gland described it as the cuticle and epidermis being turned inside out. The venom gland consists of many epithelial secretory units, each with its own excretory system that is shaped like valves. Centipedes of the order Scolopendromorpha have interspersed radial striated muscles between the secretory units, where one end connects to the lumen of the venom gland and the other end connects to peripheral muscles. These muscles may be used for the contraction and constriction of anthe gland during venom ejection. The venom glands of Scolopendridae species are elongated cylindrical shape, with the lumen spanning almost the entire length of the gland. The long span of the lumen likely allows greater control over the secretion of different venom components. The venom glands span along the outer curvature of trochanteroprefemur of each forcipule.
== History == During the Soyuz 6 mission of 1969, Russian cosmonauts performed the first welding experiments in space. Three different welding processes were tested using a hardware unit called Vulkan. The tests included welding aluminum, titanium, and stainless steel. The Skylab mission, launched in May 1973, served as a laboratory to perform various space manufacturing experiments. The station was equipped with a materials processing facility that included a multi-purpose electric furnace, a crystal growth chamber, and an electron beam gun. Among the experiments to be performed was research on molten metal processing; photographing the behavior of ignited materials in zero-gravity; crystal growth; processing of immiscible alloys; brazing of stainless steel tubes, electron beam welding, and the formation of spheres from molten metal. The crew spent a total of 32 man-hours on materials science and space manufacturing investigation during the mission. The Space Studies Institute began hosting a bi-annual Space Manufacturing Conference in 1977 . Microgravity research in materials processing continued in 1983 using the Spacelab facility. This module has been carried into orbit 26 times aboard the Space Shuttle, as of 2002. In this role the shuttle served as an interim, short-duration research platform before the completion of the International Space Station.
Sources: en.wikipedia.org
==== Lithium ==== Lithium has been used to augment antidepressant therapy in those who have failed to respond to antidepressants alone. As an augmentation agent for major depression, lithium is much more effective than placebo. Lithium augmentation has proven efficacy in treating major depressive disorder in multiple randomized controlled trials. For treatment-resistant depression, lithium augmentation reduces the odds of remaining ill by 56-95%. In the STAR-D study, for patients who had not achieved remission with two previous treatment trials, an additional 15.9% achieved remission. A disadvantage of lithium versus other augmentation agents is the need for occasional blood tests to monitor lithium levels. Lithium dramatically decreases the suicide risk in recurrent major depression by 88.5%. In addition to its effects on suicide, lithium also decreases mortality from all causes in people with mood disorders.
== Early life and research == Atul Malhotra is a US citizen born in Edmonton, Alberta, Canada. He attended the University of Alberta in Canada, obtaining a bachelor's degree in Chemistry and a Medical degree in chemistry from the same university. He completed his internal medicine residency at the Mayo Clinic in Rochester, Minnesota. Malhotra does research in the domains of pulmonary medicine, intensive care unit (ICU), obstructive sleep apnea (OSA), and other respiratory biology disciplines. He studies the biology underlying the consequences of sleep apnea as well as its causation. His group uses computational modelling, cell culture techniques, rodent models, epidemiology, and clinical trials in addition to its primary focus on human physiology. Finding new therapeutic targets for sleep apnea is the main goal of his lab to meet a critical public health need. He was global principal investigator for the SURMOUNT-OSA study which led to the FDA approval of tirzepatide for treatment of moderate to severe sleep apnea in people with obesity.
=== Medications === The antifibrotics pirfenidone and nintedanib have been shown to slow the decline in lung function (as measured by forced vital capacity [FVC]) in those with ILD compared to placebo. Pirfenidone was associated with a 45% less decline in FVC at 52 weeks compared to placebo in a trial involving people with idiopathic pulmonary fibrosis, and was associated with a slower FVC decline in those with progressive pulmonary fibrosis. Nintedanib was also associated with a slower FVC decline and increased mean survival in people with ILD. The immunomodulator tocilizumab has a benefit in scleroderma associated ILD by helping to preserve lung function (as measured by FVC) at 48 weeks. The immunomodulators cyclophosphamide, mycophenolate mofetil and rituximab all showed improved lung function (as measured by % predicted FVC) compared to placebo in systemic sclerosis or scleroderma associated ILD. The inhaled vasodilator treprostinil (a synthetic prostacyclin which acts as a prostaglandin I2 analogue) is indicated in the treatment of pulmonary hypertension secondary to interstitial lung disease and is associated with improved exercise capacity as measured by a 6-minute walk test.
This is a list of the fastest animals in the world, by types of animal. The peregrine falcon is the fastest bird, and the fastest member of the animal kingdom, with a diving speed of over 300 km/h (190 mph). The fastest land animal is the cheetah, capable of running at speeds of up to 93–104 km/h (58–65 mph). Among the fastest animals in the sea is the black marlin, with uncertain and conflicting reports of recorded speeds. When drawing comparisons between different classes of animals, an alternative unit is sometimes used for organisms: body length per second. On this basis the 'fastest' organism on earth, relative to its body length, is the Southern Californian mite, Paratarsotomus macropalpis, which has a speed of 322 body lengths per second. The equivalent speed for a human, running as fast as this mite, would be 1,300 mph (2,092 km/h), or approximately Mach 1.7. The speed of the P. macropalpis is far in excess of the previous record holder, the Australian tiger beetle Rivacindela eburneola, which is the fastest insect in the world relative to body size, with a recorded speed of 1.86 metres per second (6.7 km/h; 4.2 mph), or 171 body lengths per second. The cheetah, the fastest land mammal, scores at only 16 body lengths per second. Body mass can also be used to compare speed between species on a relative basis. Under this parameter the fastest animal for its body mass is the cheetah, followed by the pronghorn.
Sources: en.wikipedia.org
No. No major regulatory agency has granted a marketing authorisation for melanotan II as a medicine. Products sold under this name are generally presented as laboratory reagents and are not subject to the batch-release testing applied to approved drugs.
It was developed in the 1980s by researchers investigating analogues of alpha-melanocyte-stimulating hormone for pigmentation and related endpoints. Early work included small human studies during the 1990s. Development did not progress to licensing, and the compound remained a research and grey-market item.
Peptides are prone to truncation, oxidation and aggregation during synthesis and handling. Without independent testing, a buyer cannot confirm the identity or the content of a vial. Analytical surveys of unapproved peptide products have repeatedly found discrepancies between label claims and measured composition.
It is a synthetic cyclic heptapeptide modelled on alpha-melanocyte-stimulating hormone. A lactam bridge links two side chains, forming a ring that stabilises the molecule against proteolysis. It belongs to the broader melanocortin peptide family.