If you have been reading about cyclic heptapeptide and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Updated 2025-12-09. Numbers and descriptions here follow the published literature rather than marketing material.
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.
Regulatory treatment varies by country. In the United States, melanotan-2 is not approved for any indication, and products marketed for human use fall outside the approved drug framework. Some other jurisdictions have placed it under prescription controls or listed it as a prohibited or restricted substance. Online listings frequently describe the material as a research chemical, a category that does not carry the same manufacturing and labelling requirements as approved medicines.
Solid peptide material is generally stable when kept cold and dry. Common practice is storage at -20 degrees Celsius or lower, with desiccant and protection from light. Repeated freeze-thaw cycles and exposure to moisture are associated with degradation, aggregation, or loss of material. Once dissolved, stability depends on solvent, concentration, and temperature, and solutions are usually treated as short-lived unless stability data support longer periods. Handling notes typically emphasise minimising time at ambient temperature.
| 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 |
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.
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.
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.
Published research on the compound remains limited. Much of the human data comes from small, early-stage studies rather than large controlled trials, and several questions about effects and variability between individuals remain open. Investigators have examined receptor activity, pigment pathways, and related physiological responses in laboratory and animal models. Findings from those models do not automatically translate to human outcomes. Reviews frequently note the scarcity of rigorous clinical evidence and call for better-characterized study material.
=== Ayahuasca religions === Although mestizo, vegetalista and indigenous ayahuasca use was part of a longer tradition, these several configurations of mestizo vegetalismo were not isolated phenomena. In the end of the nineteenth century, several messianic/millennialist cults sparkled across semi-urban areas across the entire Amazon region, merging different elements of indigenous and mestizo folk culture with Catholicism, Spiritism and Protestantism. In this context, the use of ayahuasca will take form of urban, organized non-indigenous religions in outskirts of main cities of northwest of Brazil, (along the basins of Madeira, Juruá and Purus River) within the cauchero/seringueiro cultural complex, resignifying and adapting both the vegetalista and mestizo shamanism to new urban formations, unifying essential elements to building a cosmology for the new emerging cult/faith, merging with elements of folk Catholicism, African-Brazilian religions and Kardecist spiritism. These new cults arise from charismatic leaderships, often messianic and prophetic, who came from rural areas after migration movements, sometimes called ayahuasqueiros, in semi-urban communities across the borders of Brazil, Bolívia and Peru (a region that will later form the state of Acre).
Affecting generosity by increasing empathy during perspective taking: In a neuroeconomics experiment, intranasal oxytocin increased generosity in the Ultimatum Game by 80%, but had no effect in the Dictator Game that measures altruism. Perspective-taking is not required in the Dictator Game. However, the researchers in this experiment explicitly induced perspective-taking in the Ultimatum Game by not informing participants which role they would be placed. Serious methodological questions have arisen, however, about the role of oxytocin in trust and generosity. Empathy in healthy males is increased after intranasal oxytocin This is most likely due to the effect of oxytocin in enhancing eye gaze. There is some discussion about which aspect of empathy oxytocin might alter – for example, cognitive vs. emotional empathy. While studying wild chimpanzees, it was noted that after a chimpanzee shared food with a non-kin related chimpanzee, the subjects' levels of oxytocin increased, as measured through their urine. In comparison to other cooperative activities between chimpanzees that were monitored, including grooming, food sharing generated higher levels of oxytocin. This comparatively higher level of oxytocin after food sharing parallels the increased level of oxytocin in nursing mothers, sharing nutrients with their kin. Trust is increased by oxytocin. Study found that with the oxytocin nasal spray, people place more trust to strangers in handling their money. Disclosure of emotional events is a sign of trust in humans.
==== Turkic cultures ==== Among Turkic peoples, circumcision (sünnet in Turkish, sünnət in Azerbaijani, sunnat in Uzbek, сүндет/sündet in Kazakh) is viewed as both a religious obligation and a significant rite of passage for boys. The practice is nearly universal among Turkic Muslim populations in Turkey, Azerbaijan, Uzbekistan, Kazakhstan, Kyrgyzstan, Turkmenistan, and among Turkic minorities such as the Uyghurs in China.The ceremony, known as sünnet düğünü (circumcision celebration) in Turkey, is typically one of the most important events in a boy's life, often rivaling weddings in scale and expense. Boys are usually circumcised between the ages of 2 and 14, with the timing varying by region and family preference. The celebration commonly includes the boy wearing special ceremonial attire, often resembling a prince's costume or military uniform, and parading through the community on horseback or in a decorated vehicle. Among the Uyghurs, the tradition is called xetne toyi and remains an important rite of passage. In traditional practice, the ceremony was accompanied by feasting, music, and gift-giving, serving as an important occasion for community bonding and the affirmation of cultural identity.
Later, the dynamins migrate under the outer plastid dividing ring, into direct contact with the chloroplast's outer membrane, to cleave the chloroplast in two daughter chloroplasts. A remnant of the outer plastid dividing ring remains floating between the two daughter chloroplasts, and a remnant of the dynamin ring remains attached to one of the daughter chloroplasts. Of the five or six rings involved in chloroplast division, only the outer plastid-dividing ring is present for the entire constriction and division phase—while the Z-ring forms first, constriction does not begin until the outer plastid-dividing ring forms.
Angelopoulos was awarded honorary doctorates by the Université libre de Bruxelles, Belgium in 1995, by Paris West University Nanterre La Défense, France, by the University of Essex, UK in July 2001, by the University of Western Macedonia, Greece in December 2008, and by the University of the Aegean, Greece in December 2009.
Sources: en.wikipedia.org
Therefore, the open-chain isomer D-glucose gives rise to four distinct cyclic isomers: α-D-glucopyranose, β-D-glucopyranose, α-D-glucofuranose, and β-D-glucofuranose. These five structures exist in equilibrium and interconvert, and the interconversion is much more rapid with acid catalysis.
Sistocyclin was the brand name of a product containing 10 mg microcrystalline estradiol benzoate and 200 mg microcrystalline progesterone in an aqueous suspension which was marketed in the 1950s. The medication was reported to have a duration of action of 10 to 12 days in terms of the progestogen component, relative to a duration of only 2 days for estradiol benzoate and progesterone in oil solution. Unfortunately, intramuscular injections of aqueous suspensions of progesterone and other steroids is painful, often severely so. As a result, they were largely discontinued in favor of other preparations, such as progesterone in oil solution and longer-acting progestins. Progesterone in aqueous suspensions by intramuscular injection appears to be more potent in terms of progestogenic effects than progesterone in oil solutions by intramuscular injection. Whereas 25 mg doses of progesterone as microcrystals were needed to induce decidualization in women, doses of 35 to 50 mg were needed of progesterone in oil. This was attributed to the steadier and longer-lasting progesterone levels with aqueous suspensions relative to oil solutions. Medroxyprogesterone acetate (brand names Depo-Provera, Depo-SubQ Provera 104), a progestin and structural modification of progesterone with a methyl group at the C6α position and an acetoxy group at the C17α position, is formulated as a microcrystalline aqueous suspension for use by intramuscular or subcutaneous injection. As with progesterone, the formulation of medroxyprogesterone acetate in this way dramatically extends its duration.
=== 26 June === An RSF unit attacked the Kober and Dagrees prisons in Nyala in an attempt to free one of its commanders, triggering clashes that left at least 23 people dead and dozens of inmates escaping.
A pathologists' assistant (PA or PathA) is a physician extender whose expertise lies in gross examination of surgical specimens as well as performing hospital, medicolegal, and forensic autopsies. Their education is analogous to physician assistants, consisting of a didactic and a clinical component and concluding in a master's degree. Certification of pathologists' assistants is through a board exam by the American Society for Clinical Pathology (ASCP). In the United States, the profession is represented by the American Association of Pathologists' Assistants (AAPA). Pathologists' Assistants in the United States are currently only required to be licensed in three states: Nevada, West Virginia, and New York. In most other states, the scope of PAs falls under CLIA high complexity testing which requires an associate degree.
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.
Laboratory confirmation typically combines retention time matching on a chromatographic system with mass measurement. A reference standard of known identity is needed for a meaningful comparison. Sequence-level techniques can add further confirmation.