This is a working overview of eumelanin, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-08-01. Anything still debated is marked as such rather than presented as settled.
Melanocortin receptors comprise five subtypes with distinct tissue distributions and functions. Melanotan-2 is described in the literature as a non-selective agonist that engages several of these subtypes, including MC1R, MC3R, MC4R, and MC5R. MC1R is the subtype most directly linked to melanin production in skin cells. Because the compound is not subtype-selective, its observed effects in experimental settings are generally attributed to activity across multiple receptor pathways rather than to a single target.
Melanotan-2 is a synthetic linear peptide built from seven amino acids arranged in a short chain. Its sequence is commonly written as Ac-Nle-Asp-His-D-Phe-Arg-Trp-Lys-NH2, which includes a modified N-terminus and an amidated C-terminus. The molecule belongs to the melanocortin family and acts as a receptor agonist. Structural features such as the D-phenylalanine residue and the Nle substitution are associated with increased stability against enzymatic degradation relative to the natural parent peptide.
The compound emerged from research programs in the 1980s that examined analogues of alpha-melanocyte-stimulating hormone for pigmentation and photoprotection. Investigators modified the native sequence to extend activity duration and potency. A related analogue, afamelanotide, was developed within the same broad line of inquiry and eventually gained approval in certain jurisdictions for a rare light-sensitivity condition. Melanotan-2 itself did not progress through the same regulatory route and has no approved therapeutic indication.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C50H69N15O9 | Free base; salt forms differ |
| Molecular weight | Approximately 1024 g/mol | Calculated for the free base |
| Appearance | White to off-white powder | Typically supplied as a lyophilised solid |
| Solubility | Soluble in water and polar solvents | Poorly soluble in non-polar solvents |
| Typical storage | -20 degrees Celsius, dry, protected from light | Refers to the solid form |
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.
Ghrelin receptors are located on neurons in this circuit. Hypothalamic ghrelin signalling is required for reward from alcohol and palatable/rewarding foods. Ghrelin has been linked to inducing appetite and feeding behaviors. Circulating ghrelin levels are the highest right before a meal and the lowest right after. Injections of ghrelin in both humans and rats have been shown to increase food intake in a dose-dependent manner. So the more ghrelin that is injected the more food that is consumed. However, ghrelin does not increase meal size, only meal number. Ghrelin injections also increase an animal's motivation to seek out food, behaviors including increased sniffing, foraging for food, and hoarding food. Body weight is regulated through energy balance, the amount of energy taken in versus the amount of energy expended over an extended period of time. Studies have shown that ghrelin levels are positively correlated with weight. This data suggests that ghrelin functions as an adiposity signal, a messenger between the body's energy stores and the brain. Ghrelin is not produced by some groups of animals. Among reptiles, snakes, chameleons and toadhead agamas have either lost the genes to produce ghrelin or the gene has become so mutated that it can no longer give rise to the protein hormone. A second gene, for MBOAT4 involved in ghrelin signalling is also absent. These animals can go for long periods without eating and commonly have their meals spaced weeks, months or even years apart.
=== Detection in body fluids === Metandienone is subject to extensive hepatic biotransformation by a variety of enzymatic pathways. The primary urinary metabolites are detectable for up to 3 days, and a recently discovered hydroxymethyl metabolite is found in urine for up to 19 days after a single 5 mg oral dose. Several of the metabolites are unique to metandienone. Methods for detection in urine specimens usually involve gas chromatography-mass spectrometry.
=== Water vascular system === The water vascular system of the starfish is a hydraulic system made up of a network of fluid-filled canals and is concerned with locomotion, adhesion, food manipulation and gas exchange. Water enters the system through the madreporite, a porous, often conspicuous, sieve-like ossicle on the aboral surface. It is linked through a calcareous-lined canal called the stone canal, to a ring canal around the mouth opening. A set of radial canals branch off from the ring canal; one radial canal runs along the ambulacral groove in each arm. There are short lateral canals branching off alternately to either side of the radial canal, each ending in an ampulla. These bulb-shaped organs are joined to tube feet (podia) on the exterior of the animal by short linking canals that pass through ossicles in the ambulacral groove. There are usually two rows of tube feet but in some species, the lateral canals are alternately long and short and there appear to be four rows. The interior of the whole canal system is lined with cilia. Water is pushed into the tube face when longitudinal muscles in the ampullae contract, and shut the valves in the lateral canals. This causes the tube feet to stretch and touch the substrate. Although the tube feet resemble suction cups in appearance, the gripping action is a function of adhesive chemicals rather than suction. Other chemicals and relaxation of the ampullae allow for release from the substrate. The tube feet latch on to surfaces and move in a wave, with one arm section attaching to the surface as another releases.
=== Absorption and transport === Inadequate absorption of vitamin B12 may be related to coeliac disease. Intestinal absorption of vitamin B12 requires successively three different protein molecules: haptocorrin, intrinsic factor and transcobalamin II.
Sources: en.wikipedia.org
This led to perchlorate release into Lake Mead in Nevada and the Colorado River which affected regions of Nevada, California and Arizona, where water from this reservoir is used for consumption, irrigation and recreation for approximately half the population of these states. Lake Mead has been attributed as the source of 90% of the perchlorate in Southern Nevada's drinking water. Based on sampling, perchlorate has been affecting 20 million people, with highest detection in Texas, southern California, New Jersey, and Massachusetts, but intensive sampling of the Great Plains and other middle state regions may lead to revised estimates with additional affected regions. An action level of 18 μg/L has been adopted by several affected states. In 2001, the chemical was detected at levels as high as 5 μg/L at Joint Base Cape Cod (formerly Massachusetts Military Reservation), over the Massachusetts then state regulation of 2 μg/L. As of 2009, low levels of perchlorate had been detected in both drinking water and groundwater in 26 states in the U.S., according to the Environmental Protection Agency (EPA).
=== 15 November === The SAF retook Um Dam Haj Ahmed and Kazgeil in North Kordofan from the RSF. One person was killed in a suspected RSF drone attack on the Bashayer oil processing station in Al Jabalayn, White Nile State.
== Contraindications == Based on the results of a systematic review, there is no evidence to suggest that people with cancer or people who are at risk of getting cancer should avoid photobiomodulation.
Disordered polymers: In the solid state, atactic polymers, polymers with a high degree of branching and random copolymers form amorphous (i.e. glassy structures). In melt and solution, polymers tend to form a constantly changing "statistical cluster", see freely-jointed-chain model. In the solid state, the respective conformations of the molecules are frozen. Hooking and entanglement of chain molecules lead to a "mechanical bond" between the chains. Intermolecular and intramolecular attractive forces only occur at sites where molecule segments are close enough to each other. The irregular structures of the molecules prevent a narrower arrangement.
==== Heat exchange ==== Water and steam are a common fluid used for heat exchange, due to its availability and high heat capacity, both for cooling and heating. Cool water may even be naturally available from a lake or the sea. It is especially effective to transport heat through vaporization and condensation of water because of its large latent heat of vaporization. A disadvantage is that metals commonly found in industries such as steel and copper are oxidized faster by untreated water and steam. In almost all thermal power stations, water is used as the working fluid (used in a closed-loop between boiler, steam turbine, and condenser), and the coolant (used to exchange the waste heat to a water body or carry it away by evaporation in a cooling tower). In the United States, cooling power plants is the largest use of water. In the nuclear power industry, water can also be used as a neutron moderator. In most nuclear reactors, water is both a coolant and a moderator. This provides something of a passive safety measure, as removing the water from the reactor also slows the nuclear reaction down. However other methods are favored for stopping a reaction and it is preferred to keep the nuclear core covered with water so as to ensure adequate cooling.
Sources: en.wikipedia.org
==== Genetically induced ==== Type 1 diabetes (T1D) is a multifactorial autoimmune disease with a strong genetic component. Although environmental factors also play a significant role, the genetic susceptibility to T1D is well established, with several genes and loci implicated in disease development. The most significant genetic contribution to T1D comes from the human leukocyte antigen (HLA) region on chromosome 6p21. The HLA class II genes, particularly HLA-DR and HLA-DQ, are the strongest genetic determinants of T1D risk. Specific combinations of alleles such as HLA-DR3-DQ2 and HLA-DR4-DQ8 have been associated with a higher risk of developing T1D. Individuals carrying both of these haplotypes (heterozygous DR3/DR4) are at an even greater risk. These HLA variants are thought to influence the immune system's ability to differentiate between self and non-self antigens, leading to the autoimmune destruction of pancreatic beta cells. Conversely, some HLA haplotypes, such as HLA-DR15-DQ6, are associated with protection against T1D, suggesting that variations in these immune-related genes can either predispose or protect against the disease. In addition to HLA, multiple non-HLA genes have been implicated in T1D susceptibility. Genome-wide association studies (GWAS) have identified over 50 loci associated with an increased risk of T1D. Some of the most notable genes include:
After Commodore Perry opened up trade with Japan in 1854, Japanese green tea became the bulk of America’s tea imports. The 19th century saw the rise of iced tea, especially in the South. One of the earliest recipes for American iced tea appeared in Housekeeping in Old Virginia, a cookbook from 1879. It stated: “After scalding the teapot, put into it one quart of boiling water and two teaspoonfuls of green tea. ... Fill the goblets with ice and sugar. A squeeze of lemon will make this delicious and healthful, as it will correct the astringent tendency.” Alcoholic iced tea punches with cream, sugar, and liquor also became popular in the 19th century, especially in southern towns like Charleston and Savannah. These iced tea drinks resemble the modern Sweet bourbon punch and Long Island iced tea. Fish house punch was often also diluted with tea. The 19th century also saw the growth of various tea companies, like The Great American Tea Company, later renamed The Great Atlantic & Pacific (A&P) and the Oriental & Occidental Tea Company. During the hot days of the 1904 World's Fair in St. Louis, iced tea became the most popular drink at the fair among its 20 million visitors. This was a major moment in the rise in popularity of American iced tea. Prohibition (1920–1933) saw the rise of non-alcoholic iced teas, as clubs, hotels and other venues sought to re-stock their drink menus with other strong flavorful drinks. The introduction of the home refrigerator (1920s and '30s) also made it much easier for iced tea to be made at home.
This is a list of notable restaurant chains in Australia. A restaurant chain is a set of related restaurants with the same name in many different locations that are either under shared corporate ownership (e.g., McDonald's in the U.S.) or franchising agreements. Typically, the restaurants within a chain are built to a standard format through architectural prototype development and offer a standard menu and/or services.
== Measurement == Follicle-stimulating hormone is typically measured in the early follicular phase of the menstrual cycle, typically day three to five, counted from last menstruation. At this time, the levels of estradiol (E2) and progesterone are at the lowest point of the menstrual cycle. FSH levels in this time is often called basal FSH levels, to distinguish from the increased levels when approaching ovulation. FSH is measured in international units (IU). For Human Urinary FSH, one IU is defined as the amount of FSH that has an activity corresponding to 0.11388 mg of pure Human Urinary FSH. For recombinant FSH, one IU corresponds to approximately 0.065 to 0.075 μg of a "fill-by-mass" product. The mean values for women before ovulation are around (3.8-8.8) IU/L. After ovulation these levels drop to between (1.8-5.1) IU/L. At the mid of the menstrual cycle it reaches its highest value, between (4.5-22.5) IU/L. During menopause, the values goes up even more, between (16.74-113.59) IU/L. For men, the mean values are around (1.5-12.4) IU/L.
Sources: en.wikipedia.org
No. Melanotan-2 is manufactured synthetically. The naturally occurring peptide in the same family is alpha-melanocyte-stimulating hormone, which the body produces as part of normal endocrine and neural signalling.
Both are synthetic analogues derived from the same parent hormone. Reference descriptions usually characterise afamelanotide as more selective for the MC1R subtype, whereas melanotan-2 is reported to interact with a wider range of melanocortin receptors.
Early studies explored melanocortin signalling and pigmentation, which later led to informal use of the label tanning peptide. That label is not a regulatory category and does not imply approved status for any purpose.
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.