This is a working overview of melanogenesis, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-06-04. Anything still debated is marked as such rather than presented as settled.
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.
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.
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.
| 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 |
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-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.
== Summary table for classes of nuclides, stable and radioactive == Following is a summary table for the list of 986 nuclides with half-lives greater than one hour. A total of 251 nuclides have never been observed to decay, and are classically considered stable. Of these, 90 are believed to be absolutely stable except to proton decay (which has never been observed), while the rest are "observationally stable" and theoretically can undergo radioactive decay with extremely long half-lives. The remaining tabulated radionuclides have half-lives longer than 1 hour, and are well-characterized (see list of nuclides for a complete tabulation). They include 31 nuclides with measured half-lives longer than the estimated age of the universe (13.8 billion years), and another four nuclides with half-lives long enough (> 100 million years) that they are radioactive primordial nuclides, and may be detected on Earth, having survived from their presence in interstellar dust since before the formation of the Solar System, about 4.6 billion years ago. Another 60+ short-lived nuclides can be detected naturally as daughters of longer-lived nuclides or cosmic-ray products. The remaining known nuclides are known solely from artificial nuclear transmutation. Numbers may change slightly in the future as some nuclides now classified as stable are observed to be radioactive with very long half-lives. This is a summary table for the 986 nuclides with half-lives longer than one hour (including those that are stable), given in list of nuclides.
=== London, 1933–1939 === Thomas was a teenager when many of the poems for which he became famous were published: "And death shall have no dominion", "Before I Knocked" and "The Force That Through the Green Fuse Drives the Flower". "And death shall have no dominion" appeared in the New English Weekly in May 1933. In May 1934, Thomas made his first visit to Laugharne, "the strangest town in Wales", as he described it in an extended letter to Pamela Hansford Johnson, in which he also writes about the town's estuarine bleakness, and the dismal lives of the women cockle pickers working the shore around him.
The four-engined Fw 200 airliner flew nonstop between Berlin and New York City on 10 August 1938, making the journey in 24 hours and 56 minutes. It was the first aircraft to fly that route without stopping. The return trip on 13 August 1938, took 19 hours and 47 minutes. These flights are commemorated with a plaque in the Böttcherstraße street of Bremen. The Fw 190 Würger (Shrike/butcher-bird), designed from 1938 on, and produced in quantity from early 1941–1945, was a mainstay single-seat fighter for the Luftwaffe during World War II.
A surface charge is an electric charge present on a two-dimensional surface. These electric charges are constrained on this 2-D surface, and surface charge density, measured in coulombs per square meter (C•m−2), is used to describe the charge distribution on the surface. The electric potential is continuous across a surface charge and the electric field is discontinuous, but not infinite; this is unless the surface charge consists of a dipole layer. In comparison, the potential and electric field both diverge at any point charge or linear charge. In physics, at equilibrium, an ideal conductor has no charge on its interior; instead, the entirety of the charge of the conductor resides on the surface. However, this only applies to the ideal case of infinite electrical conductivity; the majority of the charge of an actual conductor resides within the skin depth of the conductor's surface. For dielectric materials, upon the application of an external electric field, the positive charges and negative charges in the material will slightly move in opposite directions, resulting in polarization density in the bulk body and bound charge at the surface. In chemistry, there are many different processes which can lead to a surface being charged, including adsorption of ions, protonation or deprotonation, and, as discussed above, the application of an external electric field. Surface charge emits an electric field, which causes particle repulsion and attraction, affecting many colloidal properties.
Für Sebastian Wedler (1919) 6 Studies for string quartet (1920) Piano piece (1921) String quartet (1921) 3 stories by Theodor Däubler for female chorus (1923–1945) 2 Pieces for string quartet, Op. 2 (1925/26) 7 short works for orchestra, Op. 4 (1929) 3 Short Pieces for piano (1934) 2 songs for voice & orchestra after Mark Twain's "Indian Joe" (1932/33) Kinderjahr – Six Piano pieces from op. 68 of Robert Schumann (1941) 2 songs with orchestra
Sources: en.wikipedia.org
In 1971, New York Times reporter James Reston published an article on his acupuncture experiences in China, which led to more investigation of and support for acupuncture. The US President Richard Nixon visited China in 1972. During one part of the visit, the delegation was shown a patient undergoing major surgery while fully awake, ostensibly receiving acupuncture rather than anesthesia. Later it was found that the patients selected for the surgery had both a high pain tolerance and received heavy indoctrination before the operation; these demonstration cases were also frequently receiving morphine surreptitiously through an intravenous drip that observers were told contained only fluids and nutrients. One patient receiving open heart surgery while awake was ultimately found to have received a combination of three powerful sedatives as well as large injections of a local anesthetic into the wound. After the National Institute of Health expressed support for acupuncture for a limited number of conditions, adoption in the US grew further. In 1972 the first legal acupuncture center in the US was established in Washington DC and in 1973 the American Internal Revenue Service allowed acupuncture to be deducted as a medical expense. Ronald Reagan, as the governor of California, vetoed a law which decriminalized acupuncture. In 2006, a BBC documentary Alternative Medicine filmed a patient undergoing open heart surgery allegedly under acupuncture-induced anesthesia. It was later revealed that the patient had been given a cocktail of anesthetics.
== See also == Trade Incense trade route, a large network around the Mediterranean and beyond Land of Frankincense (Frankincense Trail), site in Oman Nabataeans, a trader tribe Literature Desi Sangye Gyatso, author of a Tibetan herbal Historia Plantarum (Theophrastus book) Similar plants and products Agarwood Benzoin (resin) Copal Elemi, resin or tree Myrrh, resin Palo santo (Bursera graveolens), tree Pistacia lentiscus (mastic tree), and Mastic (plant resin)
Saffron ( SAF-rən, -ron; Persian: زعفران, romanized: zafarān) is a spice derived from the sterile autumn-blooming flower of Crocus sativus, commonly known as the "saffron crocus". The vivid crimson stigma and styles (in industry jargon: 'threads') are collected and dried for use mainly as a food seasoning and colourant. Saffron crocus was slowly propagated throughout much of Eurasia and later brought to parts of North Africa, North America, even as far as Fiji in Oceania by its Indian migrant descendant population. Saffron's taste and iodoformic or hay-like fragrance result from the phytochemicals picrocrocin and safranal. It also contains a carotenoid pigment, crocin, which imparts a rich golden-yellow hue to dishes and textiles. Saffron quality is objectively measured under the ISO 3632 standard, which evaluates the concentration of active phytochemicals—specifically crocin (color), picrocrocin (taste), and safranal (aroma) via spectrophotometric laboratory analysis. The grading depends largely on the ratio of dark red stigmas to yellow styles, with higher concentrations of red parts yielding premium-grade products. Although market prices fluctuate, premium saffron regularly exceeds US$5,000 per kilogram, sustained by its labor-intensive hand-harvesting process. Saffron originated in Iran especially in the Khorasan region descended from wild relatives in the eastern Mediterranean and later spread to Kashmir, the Mediterranean region, and Asia Minor.
Choi has formed a militant band consisting of former police officers who were expelled or faked their own deaths, who had helped Lee take the fall for an operation he led in 1995. He promises Lee not only the position of commissioner, but also of security secretary later on, upon which Lee gives into temptation and help his son. Despite this, Lee tries to convince Joe to leave Choi's team for his safety. Legislator Oswald Kan is convinced by his old friend and junior Edward Lai, the current secretary of justice, to participate in the public inquiry into Lau. He chastises Lau for his methods of "desperate times, desperate measures" and disagrees with the "Cold War" operation being a successful failure. During another hearing, Kan is taken aback when Lee openly criticizes Lau, rather than defending him initially. Kan and Lau deduce that Lee is being controlled, as Kan tells his one of his pupils, Bella Au, to investigate. Lau also asks Cheung and his independent team to monitor both Lee and Kan, who he finds suspicious as Kan did not sign up for the public hearing until deadline and likely changed his mind. Au decides to secretly follow Lee, and later Choi whom Lee confers with. Realizing that they are being followed in a tunnel, Choi orders his subordinate to crash into Au's car, causing a chain collision in which Au is killed, and Choi's car is trapped. Lau arrives to investigate, and a shoot-out occurs, in which Joe is shot and severely injured by Lau, but Choi escapes. Lee accosts Lau for failing to keep his promise of Joe's safety and nearly fight before Kan interferes.
Sources: en.wikipedia.org
=== Generic names === Ketoconazole is the generic name of the drug and its INNTooltip International Nonproprietary Name, USANTooltip United States Adopted Name, BANTooltip British Approved Name, and JANTooltip Japanese Accepted Name.
Since ALCL was thought to be diagnosed in only 1 woman in half a million, 60 women was a much higher number than would be expected. The researchers pointed out that BIA-ALCL could be fatal. If women with implants present with delayed swelling or fluid collection, cytologic studies and a test for the marker CD30 are suggested. The American Society of Plastic Surgery (ASPS) states, "CD30 is the main diagnostic test that must be performed on the seroma fluid as routine pathology or H&E staining can frequently miss the diagnosis." Diagnosis and treatment of breast implant-associated ALCL now follows standardized guidelines established by the National Comprehensive Cancer Network. The current lifetime risk of BIA-ALCL in the U.S. is unknown, but estimates have ranged between one in 70,000 and one in 500,000 women with breast implants, according to the MD Anderson Cancer Center. Countries with breast implant registries have the best data on the risks of BIA-ALCL. For example, as of October 2020, the Therapeutic Goods Administration of Australia and New Zealand reported a "1:3,345 risk with Allergan Biocell and a 1:86,029 risk with Mentor Siltex." AIn the U.S., estimates of the risk of BIA-ALCL in textured implants ranges from 1.79 per 1,000 (1 woman with BIA-ALCL per 559 implants) to 2.82 per 1,000 (1 woman per 355 implants)[2]. As of April 2022, the FDA reported 1,130 medical device reports (MDRs) of BIA-ALCL. Of those MDRs, 59 of the women died.
Early in the morning (10 August 1792) 30,000 Fédérés, and sans-culottes militants from the sections led a successful assault upon the Tuileries; according to Robespierre a triumph for the "passive" (non-voting) citizens. Sulpice Huguenin, head of the sans-culottes in the Faubourg Saint-Antoine, was appointed provisional president of the Insurrectionary Commune. In Spring 1793, after the defection of Dumouriez, Robespierre urged the creation of a "sans-culotte army" to sweep away any conspirator. On 1 May, the crowds threatened armed insurrection if the emergency measures demanded (price control) were not adopted. On 8 and 12 May Robespierre repeated in the Jacobin club the necessity of founding a revolutionary army consisting of sans-culottes, paid by a tax on the rich, to beat the aristocrats inside France and the convention. Every public square should be used to produce arms and pikes. On 18 May, Marguerite-Élie Guadet proposed to examine the "exactions" and to replace municipal authorities. As rioting persisted, a commission of inquiry of twelve members, with a very strong Girondin majority, was set up to investigate the anarchy in the communes and the activities of the sans-culottes. On 28 May, the Paris Commune accepted the creation of a sans-culottes army to enforce revolutionary laws. Petitioners from the sections and the Commune appeared at the bar of the Convention at about five o'clock in the afternoon on 31 May.
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. It is a synthetic analogue carrying four amino acid changes, a lactam ring and an amidated C-terminus. The natural hormone is a linear thirteen-amino-acid peptide processed from proopiomelanocortin.