cyclic heptapeptide raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2026-08-01. Anything still debated is marked as such rather than presented as settled.
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.
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.
Pharmacologically, melanotan-2 behaves as a non-selective agonist across the melanocortin receptor family. Binding at MC1R on dermal melanocytes promotes eumelanin synthesis, which underlies the tanning response described in early human work. Activity at the centrally expressed MC4R receptor is associated with reported effects on appetite and erectile function. Because the peptide does not discriminate strongly among receptor subtypes, attributing any single observed effect to one receptor pathway is generally not possible without selective antagonists or receptor knockout models.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic cyclic heptapeptide | Analog of alpha-melanocyte-stimulating hormone |
| Primary receptor family | Melanocortin receptors MC1R through MC5R | Binding is not subtype-selective |
| Development period | 1980s | Synthesized during pigmentation and appetite research |
| Regulatory status | Not an approved medicine | No major regulator has authorized human use |
| Related compound | Afamelanotide | Linear analog studied for photoprotection |
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.
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.
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.
The major part of the PAP is the nèiwèi bùduì (Chinese: 内卫部队); translations include "internal security forces", "internal security troops", and "internal guards corps". Internal security forces are divided into provincial-level formations with geographical areas of responsibility. They are subordinated to PAP headquarters; the 2017-2018 reforms removed control of PAP units from local government. Internal security forces are focused on domestic security missions, maintaining stability in western China, guarding government compounds, disaster relief, and responding to major anti-government unrest. The zǒngduì (Chinese: 总队) is the provincial formation. They are called "corps" by the PAP; Western analysts have used "contingent", "general corps", and "detachment". Most are corps deputy leader grade formations. The exceptions are the Beijing and Xinjiang corps which are corps leader grade; their subordinate entities, except for the logistics and equipment bureaus, are one grade higher than in the other corps. Hong Kong and Macau do not have corps. Corps have mobile detachments and duty detachments (Chinese: 执勤支队; pinyin: zhíqín zhīduì). Duty detachments protect government compounds and perform routine duties; they may exist because the CCP lacks confidence in the ability of local public security forces to handle "mass incidents". Mobile detachments (Chinese: 机动支队; pinyin: jīdòng zhīduì) are rapid reaction units roughly corresponding to PLAGF regiments. Some were existing corps mobile units before the reforms. Most were transferred from the disbanded mobile divisions.
== History == The application for imipenem/cilastatin/relebactam was granted Qualified Infectious Disease Product (QIDP), fast track, and priority review designations by the U.S. Food and Drug Administration (FDA). The FDA granted the approval of Recarbrio to Merck & Co., Inc. The determination of efficacy of imipenem/cilastatin/relebactam was supported in part by the findings of the efficacy and safety of imipenem-cilastatin for the treatment of complicated urinary tract infections (cUTI) and complicated intra-abdominal infections (cIAI). The contribution of relebactam to imipenem/cilastatin/relebactam was assessed based on data from in vitro studies and animal models of infection. The safety of imipenem/cilastatin/relebactam, administered via injection, was studied in two trials (Trial 1/NCT01505634, Trial 2/NCT01506271), one each for cUTI and cIAI. The cUTI trial included 298 adult participants with 99 treated with the proposed dose of imipenem/cilastatin/relebactam. The cIAI trial included 347 participants with 117 treated with the proposed dose of imipenem/cilastatin/relebactam. Trial 1 enrolled adult participants hospitalized with cUTI. Trial 2 enrolled adult participants hospitalized with cIAI that required surgery or drainage. In both trials, participants were assigned to either imipenem/cilastatin with varying doses of relebactam or imipenem/cilastatin with placebo intravenously, every 6 hours for 4 to 14 days. Neither the participants nor the investigators knew which treatment was being given until after the trial was completed.
== Chemistry == Dextromoramide is the right-handed isomer of the moramide molecule. The left-handed molecule is called levomoramide, and a mixture of the two is called racemoramide. Its full chemical name is (+)-1-(3-Methyl-4-morpholino-2,2-diphenylbutyryl)pyrrolidine, and its molecular formula: C25H32N2O2, with an atomic weight of ~392.5. Dextromoramide was discovered during the course of research into a related family of compounds, the α,α-Diphenyl-γ-Dialkyamino-Butyramides, which show no analgesic activity, but are extremely active physiologically as inhibitors of gastric secretions in man. Other drugs from this series show antispasmodic and antihistamine effects, but most research was put into researching analgesics. The structure-activity relationships of this family of drugs was investigated extensively, with dextromoramide representing the optimisation of several different structural features; (i) at the 1-amide group only the pyrrolidine and dimethylamide substituents were active, with pyrrolidine being more potent (ii) the alkyl chain was more potent when methylated, 3-methylation was more potent than 4-methylation, and in the 3-methyl analogues the dextro isomer was more active (iii) while morpholine, dimethylamine, pyrrolidine and piperidine were all active at the 4-amine group, morpholine was the most active (iv) any substitution on the phenyl rings reduces activity.
Ripasudil had no effect on respiratory or neurological function. Although no carcinogenicity studies were performed on the drug, developers believed it to be non-carcinogenic due to its rapid elimination and therefore lack of accumulation in tissue, as well as the lack of inflammatory response in the eye post-administration.
In a related change, Twitter introduced additional gold and gray checkmarks, used by Verified Organizations and government-affiliated accounts, respectively. Twitter claims that the changes to verification are required to "reduce fraudulent accounts and bots". Twitter users who had been verified through the previous system were known as "legacy verified" accounts; legacy verification was deprecated in April 2023, and stripped from accounts who do not meet the new payment requirements. Musk later implied that he had been personally paying for the X Premium subscriptions of several notable celebrities.
Sources: en.wikipedia.org
While the 30-day stunt was not an officially endorsed marketing campaign by Taco Bell, then CEO Mark King later invited Reid to Taco Bell's headquarters in Irvine, California. Reid was also a guest on an official Taco Bell podcast in 2023, discussing the stunt and its effect on his physical health. In 2023, the company test-marketed a vegan Crunchwrap Supreme in Los Angeles, New York, and Orlando to gauge the potential of a national roll out. Bon Appétit tested a vegan Crunchwrap alongside a non-vegan Crunchwrap purchased at the store in midtown Manhattan and said "the differences between the two were also genuinely difficult to discern." On August 29, 2025, the company announced that it would be abrogating its artificial intelligence-powered drive-thrus due to technical difficulties and "trolling," including one instance where a customer ordered 18,000 waters. According to reports, the AI would erroneously tell customers that the store was out of all ingredients except for soda and sauce packets. There were also reports of the AI bots simply disallowing customers to modify their orders, such as replacing meat with beans. The phenomenon quickly became an internet meme. One video on TikTok appeared to show a customer attempting to order McDonald's food items from Taco Bell, which was allowed by the system. Dane Mathews, the chain's Chief Digital and Technology Officer, told the Wall Street Journal: "We’re learning a lot, I’m going to be honest with you. [...] I can tell you it's a very active conversation inside Taco Bell in partnership with our franchisees.
While Waglerin-1 interacts with other members of the ligand-gated superfamily of ion channels, the potency is much less than for inhibition of the adult mouse muscle acetylcholine receptor. Structural study suggests that Waglerin-1 may undergo molecular rearrangement that allows for binding to multiple receptors. The actions of Waglerin-1 reverse upon removal of the peptide. Waglerin-1 is included in some skin creams marketed as wrinkle removers. There is no scientific evidence supporting the manufacturers' suggestion that the Waglerin-1 included in their products relaxes wrinkle producing skeletal muscles.
From the 1860s to around 1890 a theory originally proposed by William Thomson and expanded by and JJ Thomson viewed atoms as vortices in a pervasive continuous fluid medium. The idea was to view matter as stable rotations in the frictionless fluid akin to smoke rings which were used to visually illustrate the concept. The mathematical formulation built on the vortex hydrodynamics theory of Hermann von Helmholtz even though he was not a supporter of this atomic theory. The theory overlapped the rise of the theory of luminiferous aether in concept and in time frame but the two theories were not identical. While the theory had a significant impact on mathematics, inspiring the theory of knots for example, its own advocates eventually concluded that the vortices were not stable and furthermore the theory offered no account of phenomena such as magnetism and gravitation.
==== Waterboarding ==== Hitchens was asked by Vanity Fair to experience waterboarding for himself at a U.S. Army training facility. In May 2008, Hitchens voluntarily underwent the procedure. Hitchens stopped the procedure after 11 seconds and subsequently endorsed the view that it was "torture." He concluded, "If waterboarding does not constitute torture, then there is no such thing as torture."
Sources: en.wikipedia.org
== Further reading == Jarvis, Lisa M.; Morrison, Jessica (2015-10-24). "What's nitro cold brew, and why is it so damn delicious?". Chemical & Engineering News. Calderone, Julia; Bartels, Meghan (2016-06-01). "Why Starbucks is pumping nitrogen into its coffee". Business Insider. The Best Coffee For Cold Brew
=== 2020 recalls of Nitrofurantoin and Aripiprazole products === In 2020 Dr. Reddy's Laboratories (UK) Ltd recalled a specific batch of nitrofurantoin 50 mg tablets from pharmacies and wholesalers due to dissolution during routine stability testing and a specific batch of aripiprazole due to the potential for small particles of aripiprazole active material to be present which may affect the efficacy of the product.
=== Contact inhibition of locomotion === Contact inhibition of locomotion (CIL) is a process in which the cell changes its direction of movement after colliding into another cell. Those cells could be of the same cell type or different types. The contacts (cell-junctions) are created by transmembrane glycoproteins named cadherins (E-cadherin, N-cadherin or cadherin 11) and other proteins. After cell-cell contact, the protrusions of cells in the contact direction are inhibited. In the CIL process, cells migrate away from each other by repolarizing in the new direction, so that new protrusions are formed in the front while contractions pull the back from contact.
Sources: en.wikipedia.org
No regulator in a major market has approved it for human use. It appears in research settings and in products marketed outside pharmacy channels. Legal status for personal possession varies by country.
Afamelanotide is a linear analog that has received approval in some jurisdictions for a specific photoprotection indication. Melanotan II is cyclic and less selective across melanocortin receptors. The two are related but are not interchangeable in regulatory or clinical terms.
A compound that activates several receptor subtypes may produce effects beyond pigmentation. Selectivity influences which tissues respond and shapes the side-effect profile described in reports. Designing subtype-selective analogs is a stated goal of melanocortin research.
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.