This is a working overview of eumelanin, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-04-22. Anything still debated is marked as such rather than presented as settled.
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controlled human data on melanotan-2 remain sparse, and much of what circulates online derives from small studies or unpublished reports.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.
Receptor studies place melanotan-2 among non-selective melanocortin agonists, binding MC1R, MC3R, MC4R and MC5R rather than a single subtype. Activation of MC1R on cutaneous melanocytes raises tyrosinase activity and shifts pigment synthesis toward eumelanin, which is darker and more photostable than pheomelanin. Central receptors, particularly MC4R, are associated with appetite suppression and with reported effects on sexual function. Because subtype selectivity is low, the same molecule engages pigment, metabolic and vascular pathways at once, and this breadth is a common explanation offered for the range of adverse events described in user reports.
No regulatory authority has approved melanotan-2 for human use, and several countries classify it as a prescription-only or controlled substance, which restricts lawful supply. Material sold online is generally labelled as a research chemical and is not required to meet pharmaceutical standards of identity or purity. Published human data consist mainly of small uncontrolled studies, case reports and adverse-event notifications, so the evidence base is descriptive rather than confirmatory. Whether repeated melanocyte stimulation alters long-term naevus behaviour remains an open question that no completed trial has resolved.
Melanotan-2 is a synthetic cyclic heptapeptide designed as a structural analogue of alpha-melanocyte-stimulating hormone, the endogenous tridecapeptide that regulates pigment production. Two modifications distinguish it from the natural hormone: norleucine replaces methionine at the N-terminus, which limits oxidation, and a D-phenylalanine substitution raises receptor affinity. The ring is closed through an aspartate-lysine lactam bridge, giving the molecule a constrained conformation. The free base has a molecular mass near 1024 daltons, and commercial material is usually supplied as an acetate salt. It appears in the literature as a research peptide rather than an approved therapeutic agent.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic cyclic heptapeptide | Alpha-MSH analogue with a lactam ring |
| Molecular formula | C50H69N15O9 | Commonly cited value for the neutral peptide |
| Molecular weight | 1024.18 g/mol | Calculated for the free molecule |
| Appearance | White to off-white powder | Typically supplied as a lyophilised solid |
| Solubility | Soluble in water, DMSO and ethanol | Dissolution in pure water is often slow |
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.
Early published reports described melanotan-2 as a tanning agent without sun protection, which means darkening is not the same as protection against ultraviolet radiation. Later studies explored the peptide in erectile dysfunction, hemorrhagic shock, and some skin conditions. No regulator in the United States or Europe has approved it for clinical use. Many products labelled melanotan-2 are sold without approval and their identity and purity are unverified. Its long-term safety in humans remains an open question.
Melanotan-2, also written Melanotan II, is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone. Its sequence is Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, and the lactam bridge between the aspartate and lysine side chains constrains the peptide into a ring. This structural change increases receptor affinity and metabolic stability relative to the native hormone. The compound was created in the 1980s as a research tool for studying pigmentation biology.
=== MHC-I === MHC-I heavy chains may work as chaperones with the aid of the calnexin-calreticulin complex in the ER. In addition to this, β2-microglobulin (β2m) is attached to the heavy chains of the heterodimers and as a whole they act as receptors for antigenic peptides. When MHC-I chains are empty, they are recruited by calreticulin and form a transient PLC. Tapasin regularly plays a role in the stabilization of MHC-I. Only after MHC-I heterodimers are deployed for peptide proofreading or editing, stable pMHC-I (peptide-MHC-I) complexes are released to the cell surface for recognition and destruction of virus-infected or malignantly neoplastic cells. In general, each individual organism owns a collection of six MHC-I molecules (three from each parent). Thus, in autoimmune emergencies, compatible donors are relatives who own a similar collection of MHC-I molecules, apart from those of the recipient.
== Research == Nandrolone esters have been studied in several indications. They were intensively studied for osteoporosis, and increased calcium uptake and decreased bone loss, but caused virilization in about half of the women who took them and were mostly abandoned for this use when better drugs like the bisphosphonates became available. They have also been studied in clinical trials for chronic kidney failure, aplastic anemia, and as male contraceptives.
== Mechanism of action == P11-4 is an α-peptide that self-assembles into β-sheet amyloids with a hydrogel appearance at low pH. It builds a 3-D bio-matrix with binding sites for calcium ions serving as nucleation point for hydroxyapatite (tooth mineral) formation. The high affinity to tooth mineral is based on matching distances of Ca-ion binding sites on P11-4 and Ca spacing in the crystal lattice of hydroxyapatite. The matrix formation is pH controlled and thus allows control matrix activity and place of formation.
"[Nar]am-Sin, the mighty, <Lacuna> ..., Sidu[r-x] (and) the highlanders of Lullubum assembled together ... bat[tle]. For/to <Lacuna> the high[landers ...] <Lacuna> [heap]ed up [a burial mound over them], ... (and) dedicated (this object) [to the god ...] <Lacuna> Shutruk-Nahhunte added his own inscription to the stele, in Middle Elamite:
Sources: en.wikipedia.org
Although a liver biopsy is not required for diagnosis, the characteristic histological finding is concentric periductal fibrosis resembling onion skin. PSC is associated with increased risk of several cancers, most notably, a 400 times greater risk for cholangiocarcinoma compared to the general population. Patients with PSC also face elevated risk of pancreatic and colorectal cancer. Therefore, regular screening is recommended. No drugs are currently approved for treating PSC specifically. Although commonly given, ursodeoxycholic acid at moderate doses failed to improve transplant-free survival in randomized controlled trials. Due to disease progression, 40% of patients eventually require liver transplantation, which has survival rates (91% at 1 year, 82% at 5 years, and 74% at 10 years). However, the disease recurs in at least 25% of transplant recipients, particularly in those with IBD and an intact colon. Clinical trials are underway for several novel therapies, including obeticholic acid (a bile acid analogue), simtuzumab (a monoclonal antibody), and 24-norursodeoxycholic acid (a synthetic bile acid). Although the pathogenesis of PSC is poorly understood, three dominant theories have been proposed: 1) aberrant immune response, 2) increased intestinal permeability, and 3) dysbiosis of gut microbiota. The first theory involves immune-mediated damage to bile ducts by T cells. In PSC, cholangiocytes and hepatocytes display aberrant expression of adhesion molecules, which facilitate homing of intestinal T cells to the liver.
In the aftermath of the dissolution of the Soviet Union, Moscow remained the capital city of the newly reconstituted Russian Federation and has experienced continued growth. The northernmost and coldest megacity in the world, Moscow is governed as a federal city, where it serves as the political, economic, cultural, and scientific center of Russia and Eastern Europe. Moscow has one of the world's largest urban economies. Moscow has the second-highest number of billionaires of any city (tied with Hong Kong). The Moscow International Business Center is one of the largest financial centers in the world and features the majority of Europe's tallest skyscrapers. Moscow hosted the 1980 Summer Olympics and co-hosted the 2018 FIFA World Cup. The city contains several UNESCO World Heritage Sites and is known for its display of Russian architecture—particularly in areas such as Red Square, as well as buildings such as Saint Basil's Cathedral and the Moscow Kremlin, which serves as the seat of power of the Government of Russia. Russian companies in various industries are headquartered in Moscow, and the city is served by a comprehensive transit network; this includes four international airports, ten railway terminals, a tram system, a monorail system, and the Moscow Metro, which is the busiest metro system in Europe and one of the largest rapid transit systems in the world. More than 40% of the city's territory is covered by greenery, so it is one of the greenest cities in the world.
==== Planulae ==== The time from spawning to larval settlement is usually two to three days but can occur immediately or up to two months. Broadcast-spawned planula larvae develop at the water's surface before descending to seek a hard surface on the benthos to which they can attach and begin a new colony. The larvae often need a biological cue to induce settlement such as specific crustose coralline algae species or microbial biofilms. High failure rates afflict many stages of this process, and even though thousands of eggs are released by each colony, few new colonies form. During settlement, larvae are inhibited by physical barriers such as sediment, as well as chemical (allelopathic) barriers. The larvae metamorphose into a single polyp and eventually develops into a juvenile and then adult by asexual budding and growth.
The Downstream-peptide motif refers to a conserved RNA structure identified by bioinformatics in the cyanobacterial genera Synechococcus and Prochlorococcus and one phage that infects such bacteria. It was also detected in marine samples of DNA from uncultivated bacteria, which are presumably other species of cyanobacteria. Downstream-peptide RNAs are found upstream of short open reading frames (ORFs) that are predicted to encode short peptides (usually between 17 and 100 amino acids). One of the ORFs is apparently down-regulated when cells are grown with an insufficient supply of nitrogen sources. The Downstream-peptide motif has a structural resemblance to a different candidate RNA structure called the glnA RNA motif which was shown to be a functional glutamine binding riboswitch in cyanobacteria. The most striking similarity is the nucleotide conservation within the P1 stem of both motifs, and this and other similarities was discussed previously. It was hypothesized that Downstream-peptide RNAs correspond to riboswitches, based on multiple lines of evidence. First, glnA RNAs are often located in the presumed 5′ untranslated regions of multiple classes of genes involved in nitrogen metabolism. This, and other evidence, suggests that glnA RNAs are riboswitches, and their structural similarity to Downstream-peptide RNAs in turn suggests that Downstream-peptide RNAs are also riboswitches.
Some cultures ascribe social and sexual characteristics to female breasts, and may regard bare breasts in public as immodest or indecent. Breasts can represent fertility, femininity, or abundance. Breasts have been featured in ancient and modern sculpture, art, and photography.
Sources: en.wikipedia.org
MDMA was first synthesized and patented in 1912 by Merck chemist Anton Köllisch. At the time, Merck was interested in developing substances that stopped abnormal bleeding. Merck wanted to avoid an existing patent held by Bayer for one such compound: hydrastinine. Köllisch developed a preparation of a hydrastinine analogue, methylhydrastinine, at the request of fellow lab members, Walther Beckh and Otto Wolfes. MDMA (called methylsafrylamin, safrylmethylamin or N-Methyl-a-Methylhomopiperonylamin in Merck laboratory reports) was an intermediate compound in the synthesis of methylhydrastinine. Merck was not interested in MDMA itself at the time. On 24 December 1912, Merck filed two patent applications that described the synthesis and some chemical properties of MDMA and its subsequent conversion to methylhydrastinine. Merck records indicate its researchers returned to the compound sporadically. A 1920 Merck patent describes a chemical modification to MDMA. MDMA's analogue 3,4-methylenedioxyamphetamine (MDA) was first synthesized in 1910 as a derivative of adrenaline. Gordon A. Alles, the discoverer of the psychoactive effects of amphetamine, also discovered the psychoactive effects of MDA in 1930 in a self-experiment in which he administered a high dose (126 mg) to himself. However, he did not subsequently describe these effects until 1959. MDA was later tested as an appetite suppressant by Smith, Kline & French and for other uses by other groups in the 1950s. In relation to the preceding, the psychoactive effects of MDA were discovered well before those of MDMA.
...what John [Wagner] does [in the comic] is have Dredd evolve, in the way that a glacier moves: you look a year later and something actually has shifted! I tried to be true to that ... I didn't think Dredd could have a great epiphany, but there is definitely a change in him over the course of the movie. He makes a very clear statement at the beginning of the film which he then contradicts at the end. That's about as far as the shift goes." Garland intentionally gave the traditional character development to Anderson to compensate for Dredd's character stability. Discussing the film's setting within the Peach Trees Block tower, Garland said the buildings were "like micro city states ... you could live and die in those buildings". He also considered that the setting met Wagner's suggestion that the future portrayed in Dredd should relate to modern ways of living. Garland named the tower after a restaurant called "The Peach Tree" in Shrewsbury, England, where he first met with Wagner. The budget limited his ability to represent some of the comic aspects of Mega-City One, such as robots and aliens. Throughout the production, Garland would send his script to Wagner, who would revise some of the dialogue. Urban would then further revise the script during his performance.
Clinical Allergology Clinical Chemistry Clinical Haematology Clinical Immunology and Blood Banking Clinical Microbiology Clinical Pharmacology Molecular Biology and Genetics Reproduction and Fertility Thrombosis and Haemostasis Toxicology The NPU terminology is supported by a joint committee (C-SC-NPU) of the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) and a subcommittee of the International Union of Pure and Applied Chemistry (IUPAC). The terminology is freely available for download in its generic version (in English [3]) and various language versions. The specific syntax and the references to international terminologies, classifications and nomenclatures make the terminology definitions language-independent.
Sufentanil, sold under the brand names Sufenta among others, is a synthetic opioid analgesic drug approximately 5 to 10 times as potent as its parent drug, fentanyl, and 500 to 1,000 times as potent as morphine. Structurally, sufentanil differs from fentanyl through the addition of a methoxymethyl group on the piperidine ring (which increases potency but is believed to reduce duration of action), and the replacement of the phenyl ring by thiophene. Sufentanil first was synthesized at Janssen Pharmaceutica in 1974.
=== Popular culture === In the 2001 comedy film Evolution selenium was mentioned as an active ingredient of the anti-dandruff shampoo Head & Shoulders. A group of academics, therefore, tried to use this brand of shampoo to stop an alien invasion after discovering that the alien life form was sensitive to selenium.
Sources: en.wikipedia.org
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.
No national medicines agency has approved melanotan-2 for clinical use. Afamelanotide, a related but distinct peptide, holds a marketing authorisation in the European Union for a rare photosensitivity disorder. Melanotan-2 itself is handled as a laboratory chemical.
Its broad activity across melanocortin receptors makes it a tool for probing pigmentation, appetite and vascular signalling. Early trials recorded skin darkening and other effects that were not the original focus of the work. Those observations generated hypotheses that later studies have examined.
No regulatory agency has authorised melanotan-2 as a medicine for any indication. It circulates mainly as a research chemical or through unregulated channels. As a result, identity, purity and content are not independently guaranteed.