A practical reference on cyclic heptapeptide: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
This page was last updated on 2026-01-15 and is reviewed periodically as new material appears.
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.
Regulatory treatment varies by country. In the United States the peptide is not approved as a medicine, and products offered for human use may be treated as unapproved new drugs; some states also restrict sale. Australia, the United Kingdom, and European Union member states apply comparable restrictions to unapproved peptide products. Border agencies have seized shipments labelled as research chemicals. Classification may change over time, and the legal position for personal importation is not clearly settled in most published guidance.
Lyophilised melanotan-2 is supplied as a solid, which is more stable than a solution. The material is hygroscopic, so weighing is done quickly, in low humidity, with the container kept sealed. Reconstitution usually uses water for injection or bacteriostatic water, added down the wall of the vial to limit foaming. A reconstituted solution is held at 2 to 8 °C and kept away from light. Repeated freezing and thawing of the same vial is avoided because ice crystal formation and concentration effects degrade the peptide.
Reversed-phase high-performance liquid chromatography is the routine method for purity assessment. Peptides absorb near 214 nm because of the peptide bond, and a gradient of acetonitrile in water separates the intact peptide from deletion sequences, oxidised products, and earlier-eluting fragments at neutral pH. Electrospray ionisation mass spectrometry provides an orthogonal check: the measured mass must agree with the theoretical value. Amino acid analysis and peptide mapping confirm structure but are used less often. Reference standards remain scarce because the peptide is not described in any pharmacopoeia.
| 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 |
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.
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.
Because the substance circulates mainly through informal markets, verification is a recurring theme in technical discussion. Independent analyses have found that labeled content and actual content can diverge, and that purity varies between samples. Analytical laboratories use reversed-phase chromatography to separate components and mass spectrometry to confirm identity. Isotope-labeled internal standards improve quantification in complex matrices. Such methods describe what a sample contains but say nothing about its sterility, lawful status, or suitability for any use. Open questions remain about how consistently testing is applied across the supply chain.
Regulatory treatment of this peptide varies by country. It holds no marketing authorization as a medicine in the United States, the European Union, or most other jurisdictions. Some countries classify products containing it as prescription-only or unlicensed medicines, which restricts lawful supply. Authorities have issued public notices warning that unregulated products may contain undeclared or incorrect ingredients. The molecule also appears on prohibited lists for competitive sport. These measures address supply oversight rather than any approved therapeutic role.
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.
Published pharmacokinetic information is limited and comes mainly from small studies rather than registrational trials. Plasma half-life is usually described as short, on the order of tens of minutes, followed by rapid tissue distribution and clearance of the intact peptide. Metabolites and low concentrations of parent compound have been reported in urine, a detail relevant to anti-doping and forensic testing. Whether repeated exposure changes receptor sensitivity or clearance over time remains an open question. Values differ noticeably between analytical assays, so published numbers should be read as approximate rather than definitive.
=== Bone marrow suppression === Chloramphenicol may cause bone marrow suppression during treatment; this is a direct toxic effect of the drug on human mitochondria. This effect manifests first as a fall in hemoglobin levels, which occurs quite predictably once a cumulative dose of 20 g has been given. The anaemia is fully reversible once the drug is stopped and does not predict future development of aplastic anaemia. Studies in mice have suggested existing marrow damage may compound any marrow damage resulting from the toxic effects of chloramphenicol.
== Human uses == Castor oil has been used orally to relieve constipation or to evacuate the bowel before intestinal surgery. The laxative effect of castor oil is attributed to ricinoleic acid, which is produced by hydrolysis in the small intestine. Use of castor oil for simple constipation is medically discouraged because it may cause violent diarrhea.
== Further reading == Cimaz, Rolando (2016). "Systemic-onset juvenile idiopathic arthritis". Autoimmunity Reviews. 15 (9): 931–934. doi:10.1016/j.autrev.2016.07.004. PMID 27392503. Mellins, Elizabeth D.; Macaubas, Claudia; Grom, Alexei A. (2011). "Pathogenesis of systemic juvenile idiopathic arthritis: some answers, more questions". Nature Reviews Rheumatology. 7 (7): 416–426. doi:10.1038/nrrheum.2011.68. ISSN 1759-4790. PMC 4180659. PMID 21647204.
==== Xbox reception ==== The Xbox edition received mixed reviews from critics in comparison to the original game. On the topic of graphics, Matthew Kato from Game Informer wrote that there were "graphical updates here and there" and mentioned the game's inclusion of weather. Greg Kasavin of GameSpot felt that the visuals weren't extraordinary and not enough to make the game "good-looking". IGN's Aaron Boulding mentioned that they were "the biggest disappointment". He commented that the environments were noteworthy in design, but "not in their overall look and level of detail". The AI technology was a surplus for the Xbox edition, because of critics praising for its human-like behavior. Kato mentioned that the bot AI contained some "human-esque traits" and that it would start to understand the map after some rounds. Kasavin found it surprising that the bots weren't following real-life tactics of terrorists or counter-terrorists, but rather mimic the actions of a player. He pointed out that they would camp at a certain place and follow the orders of a player, such as following them or holding a position. Many critics also highlighted Xbox Live as one of the main reasons to purchase the game. Kasavin noted that it runs properly, with hosted matches able to hold 10 players. Boulding expressed that "online play over Xbox Live is going to be the greatest reason to buy this game" and that it's convenient.
During this period, also in response to rising levels of estrogen, the lower half of the pelvis and thus hips widen (providing a larger birth canal). Fat tissue increases to a greater percentage of the body composition than in males, especially in the typical female distribution of breasts, hips, buttocks, thighs, upper arms, and pubis. Progressive differences in fat distribution as well as sex differences in local skeletal growth contribute to the typical female body shape by the end of puberty. On average, at 10 years, females have 6% more body fat than males.
Sources: en.wikipedia.org
Increased heat production by increased muscle tone, shivering (muscle movements to produce heat) and release of hormones like epinephrine; and Prevention of heat loss, e.g., through vasoconstriction. When the hypothalamic set point moves back to baseline—either spontaneously or via medication—normal functions such as sweating, and the reverse of the foregoing processes (e.g., vasodilation, end of shivering, and nonshivering heat production) are used to cool the body to the new, lower setting. This contrasts with hyperthermia, in which the normal setting remains, and the body overheats through undesirable retention of excess heat or over-production of heat. Hyperthermia is usually the result of an excessively hot environment (heat stroke) or an adverse reaction to drugs. Fever can be differentiated from hyperthermia by the circumstances surrounding it and its response to anti-pyretic medications. In infants, the autonomic nervous system may also activate brown adipose tissue to produce heat (non-shivering thermogenesis). Increased heart rate and vasoconstriction contribute to increased blood pressure in fever.
=== Evolution === There are many theories on how mammary glands evolved. For example, it is thought that the mammary gland is a transformed sweat gland, more closely related to apocrine sweat glands. Because mammary glands do not fossilize well, supporting such theories with fossil evidence is difficult. Many of the current theories are based on comparisons between lines of living mammals—monotremes, marsupials, and eutherians. One theory proposes that mammary glands evolved from glands that were used to keep the eggs of early mammals moist and free from infection (monotremes still lay eggs). Other theories suggest that early secretions were used directly by hatched young, or that the secretions were used by young to help them orient to their mothers. Lactation is thought to have developed long before the evolution of the mammary gland and mammals; see evolution of lactation.
However, 1–5% of patients taking docetaxel may develop severe pneumotoxicity. Patients may develop exertional breathlessness and desaturation which needs to be detected early. Chest X-Ray may show bilateral opacities and High Resolution CT chest may reveal Organizing Pneumonia (OP) pattern or Non-Specific Organizing Pneumonia (NSIP) pattern or a combination. Docetaxel-induced DPLD is a fatal adverse effect, which can be managed by the cessation of the drug and starting on steroids in adequate doses. Observations of severe side effects in the above 40 phase II and phase III studies were also recorded. Many more side effects have been reported for conjunctive and adjuvant treatment with docetaxel as well as rare post-marketing events.
Simon (1973), art dealer and historian who discovered Da Vinci's Salvator Mundi Albie Hecht (1974), founder of Spike TV, head of HLN, and former president of Nickelodeon; creator of Nickelodeon Kids' Choice Awards; Academy Award-nominated producer Alan Goodman (1974), MTV founding executive and Nickelodeon executive Gara LaMarche (1976), former president and CEO of The Atlantic Philanthropies; president of advocacy group Democracy Alliance J. Ezra Merkin (1976), financier, hedge fund manager; former chairman of GMAC Inc. John Slosar (1978), chairman of Swire Pacific and Cathay Pacific airlines Daniel E. Straus (1978), founder of CareOne LLC and former vice chairman of Memphis Grizzlies Jeph Loeb (1979), television writer and EVP of Marvel Television, four-time Eisner Award winner Sami Mnaymneh (1981), billionaire, private equity executive, co-founder of H.I.G. Capital Charles Murphy (1981), hedge fund manager, executive of Fairfield Greenwich Group Tom Glocer (1981), former CEO of Thomson Reuters and Reuters Christopher Radko (1981), businessman and designer, founder of the eponymous Christmas ornaments company Donald F. Ferguson (1982), chief technology officer at Dell and professor of Professional Practice in Computer Science at Columbia University Wayne Allyn Root (1983), business mogul, TV personality and producer, author, 2008 Libertarian Party vice-presidential nominee Daniel S.
Sources: en.wikipedia.org
The Institut National de la Recherche Biomédicale (INRB) is the national medical research organization of the Democratic Republic of the Congo. The responsible ministry is the Ministry of Scientific Research and Technology. The National Biomedical Research Institute (INRB) was founded in 1984. It is a 70,000 m² establishment. It has been a collaborating center of the World Health Organization since 2018, headed by Professor Jean-Jacques Muyembe-Tamfum, MD, PhD, and serving as a national biomedical research laboratory for the Ministry of Health of the Democratic Republic of Congo (DRC). It is a multidisciplinary institute which collectively has hundreds of years of experience in the identification, treatment and prevention of diseases in the DRC. Its foundations are the performance of medical and biological analyzes, applied and translational research, surveillance of communicable diseases and the promotion of professional growth and development. The INRB has continuously developed and trained high-quality researchers and produced exceptional results. More recently, it has made concrete efforts in terms of control, prevention, and research in response to the current Ebola epidemic. It has continuously brought it's expertise to the government of the DRC in the areas of disease surveillance, prevention and intervention. In 30 years of existence, the INRB has quickly become recognized worldwide and has played an essential role in tropical health research.
=== Physical Response === When exposed to ultrasound, microbubbles oscillate in response to the incoming pressure waves in one of two ways. With lower pressures, higher frequencies, and larger microbubble diameter, microbubbles oscillate, or cavitate, stably. This causes microstreaming near the surrounding vasculature and tissues, inducing shear stresses that can create pores on the endothelial layer. This pore formation enhances endocytosis and permeability. At lower frequencies, higher pressures, and lower microbubble diameter, microbubbles oscillate inertially; they expand and contract violently, ultimately leading to microbubble collapse. This phenomenon can create mechanical stresses and microjets along the vascular wall, which has been shown to disrupt tight cellular junctions as well as induce cellular permeability. Extremely high pressures cause small vessel destruction, but the pressure can be tuned to only create transient pores in vivo. microbubble destruction serves as a desirable method for drug delivery vehicles. The resulting force from destruction can dislodge the therapeutic payload present on the microbubble and simultaneously sensitize the surrounding cells for drug uptake.
== Causes == There are many causes of back pain, including blood vessels, internal organs, infections, mechanical and autoimmune causes. Approximately 90 percent of people with back pain are diagnosed with nonspecific, idiopathic acute pain with no identifiable underlying pathology. In approximately 10 percent of people, a cause can be identified through diagnostic imaging. Fewer than two percent of cases are attributed to secondary factors, with metastatic cancers and serious infections, such as spinal osteomyelitis and epidural abscesses, accounting for approximately one percent.
=== Structure === Tirzepatide is an analog of the human GIP hormone with a C20 fatty diacid portion attached, used to optimise the uptake and metabolism of the compound. The fatty-diacid section (eicosanedioic acid) is linked via a glutamic acid and two (2-(2-aminoethoxy)ethoxy)acetic acid units to the side chain of the lysine residue. This arrangement allows for a much longer half-life, extending the time between doses, because of its high affinity to albumin.
== Research works == After completing his PhD, he returned to the Indian Institute of Science, Bangalore, India in 1949 as an assistant professor of physics. In 1952, he moved to Madras University as professor and head of the Department of Physics where he continued his work on crystal physics. His interest, however, shifted to the structure of biological macromolecules. Using X-ray diffraction Ramachandran along with Gopinath Kartha proposed and published the triple helical structure of collagen in 1954 in the journal Nature, drawing worldwide scientific attention to the "Madras group". At Madras University, Professor Ramachandran was the favourite of the famous vice-chancellor and celebrated doctor and medical scientist, Sir Arcot Laksmanaswamy Mudaliar. Wanting to tackle problems at a more fundamental level, Ramachandran decided to use this information to examine the various polypeptide conformations then known and also to develop a good 'yardstick' that could be used for examining and assessing any structure in general, but peptides in particular. The result which emerged from these calculations in 1962, – now commonly known as the Ramachandran plot – was published in the Journal of Molecular Biology in 1963 and has become an essential tool in the field of protein conformation. When it was first calculated, crystal structures had barely been obtained for any protein.
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.
Low temperature slows hydrolysis and oxidation, the two main routes by which the peptide backbone and side chains are modified. A lyophilised powder stored at −20 °C is more stable than one kept at room temperature, and once the material is dissolved the degradation rate rises, making refrigeration more important.