This is a working overview of melanocortin receptor, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-03-04. Anything still debated is marked as such rather than presented as settled.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C50H69N15O9 | Cyclic heptapeptide, C-terminally amidated |
| Approximate molecular mass | 1024 Da | Monoisotopic mass of the free peptide |
| Appearance | White to off-white powder | Typically supplied as a lyophilised solid |
| Solubility class | Soluble in water and polar solvents | Also dissolves in neutral aqueous buffer |
| Common synonyms | Melanotan II, MT-II, MT-2 | Described as a melanocortin agonist in early literature |
Radiocarbon dating (also referred to as carbon dating or carbon-14 dating) is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of carbon. The method was developed in the late 1940s at the University of Chicago by Willard Libby. It is based on the fact that radiocarbon (14C) is constantly being created in the Earth's atmosphere by the interaction of cosmic rays with atmospheric nitrogen. The resulting 14C combines with atmospheric oxygen to form radioactive carbon dioxide, which is incorporated into plants by photosynthesis; animals then acquire 14C by eating the plants. When the animal or plant dies, it stops exchanging carbon with its environment, and thereafter the amount of 14C it contains begins to decrease as the 14C undergoes radioactive decay. Measuring the amount of 14C in a sample from a dead plant or animal, such as a piece of wood or a fragment of bone, provides information that can be used to calculate when the animal or plant died. The older a sample is, the less 14C there is to be detected. The half-life of 14C (the period of time after which half of a given sample will have decayed) is about 5,730 years, so the oldest dates that can be reliably measured by this process date to approximately 50,000 years ago, although special preparation methods occasionally make an accurate analysis of older samples possible. Libby received the Nobel Prize in Chemistry for his work in 1960.
== Determining quantity of carboamino in products == It is possible to determine how much carbamino is formed through the techniques of electron ionization and mass spectrometry. In determining the amount of product by mass spectrometry, a careful set of instructions are followed which allows for the carbamino adducts to be transferred to a vacuum for mass spectrometry. With the separation of the carbamino adducts in the ion sampling process, it should be that the pH does not change. Hence, mass spectrometry and electron ionization are a way to measure how much carbamino adduct there is in comparison to concentration of peptide in a solution.
The term behavioral addiction refers to a compulsion to engage in a natural reward despite adverse consequences. Addiction can exist without psychotropic drugs, an idea that was popularized by psychologist Stanton Peele. These are termed behavioral addictions. Such addictions may be passive or active, but they commonly contain reinforcing features, which are found in most addictions. Sexual behavior, eating, gambling, playing video games, and shopping are all associated with compulsive behaviors in humans and have been shown to activate the mesolimbic pathway and other parts of the reward system. Diagnostic manuals recognize only some of these as disorders. Gambling disorder is the only behavioral addiction classified as a clinical disorder in the DSM-5-TR, which lists internet gaming disorder as a condition requiring further study; the ICD-11 classifies both gambling disorder and gaming disorder as disorders due to addictive behaviors. Compulsive sexual behavior disorder, compulsive buying–shopping disorder, and problematic use of social media are discussed in the research literature as candidate addictive disorders, but are not classified as addictions in either manual.
== External links == McLetchie, N. G. (2002). "Alloxan Diabetes, a Discovery, albeit a Minor one" (PDF). Journal of the Royal College of Physicians of Edinburgh. 32 (2): 134–142. doi:10.1177/1478271520023202014. PMID 12434795. The history and chemistry of the Murexide dye Archived 2013-05-05 at the Wayback Machine
In late August 2025, the United States began a naval buildup in the southern Caribbean with the stated goal of combating drug trafficking. US president Donald Trump directed the United States Armed Forces to begin using military force against certain Latin American drug cartels, characterizing the smugglers as narcoterrorists. The first major increase came with the deployment of the USS Iwo Jima and its amphibious ready group in August. The arrival of the USS Gerald R. Ford carrier strike group in November marked the second increase. A sharper escalation came in mid-December, when the US began intercepting and seizing crude oil tankers, imposed a naval quarantine on sanctioned vessels transporting oil to or from Venezuela, and announced plans to designate the Venezuelan government a Foreign Terrorist Organization. The first operation of the campaign was the strike and sinking of a vessel—coming from Venezuela and purportedly involving Tren de Aragua gang members carrying illegal drugs—in September that killed 11 people. As the US continued the buildup of military assets to Puerto Rico and El Salvador, subsequent airstrikes destroyed other alleged drug-smuggling vessels, including those allegedly connected to the Colombian National Liberation Army. The Dominican Navy engaged to recover drugs from one of the destroyed vessels, and Trinidad and Tobago backed the US. By early November, the deployment of assets to the Caribbean region had become the largest in decades.
Sources: en.wikipedia.org
Aged mouse tissues exhibit globally increased malonylation, potentially due to elevated expression of acetyl-CoA carboxylase and reduced activity of the deacylase SIRT5, which depends on declining NAD+ levels. These findings suggest a role for histone malonylation in the epigenetic regulation of aging processes. In type 2 diabetes, lysine malonylation is significantly elevated in liver tissue, as shown in obese mouse models such as db/db and ob/ob mice. Many of the affected proteins are involved in glucose and lipid metabolism, and malonylation of glycolytic enzymes has been shown to suppress their activity, leading to reduced glycolytic flux. Six of the ten glycolytic enzymes are malonylated at sites regulated by the demalonylase SIRT5, which counteracts this inhibition and may serve as a therapeutic target, along with other yet unidentified enzymes that regulate malonylation. In osteoarthritis, SIRT5 expression decreases in cartilage during aging while lysine malonylation increases. In mice, the combination of Sirt5 deficiency and high-fat diet–induced obesity exacerbates joint degeneration, accompanied by widespread hypermalonylation of glycolytic enzymes and impaired chondrocyte metabolism. A rare missense mutation in human SIRT5 (F101L) found in familial osteoarthritis further confirms a direct link between hypermalonylation and osteoarthritis. In resting macrophages, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) binds to inflammatory mRNAs such as TNFα and suppresses their translation.
Symmetric spin and symmetric under parity. In this case, the exchange of the two nucleons will multiply the deuterium wavefunction by (−1) from isospin exchange, (+1) from spin exchange and (+1) from parity (location exchange), for a total of (−1) as needed for antisymmetry. Antisymmetric spin and antisymmetric under parity. In this case, the exchange of the two nucleons will multiply the deuterium wavefunction by (−1) from isospin exchange, (−1) from spin exchange and (−1) from parity (location exchange), again for a total of (−1) as needed for antisymmetry. In the first case the deuteron is a spin triplet, so that its total spin s is 1. It also has an even parity and therefore even orbital angular momentum l. The lower its orbital angular momentum, the lower its energy. Therefore, the lowest possible energy state has s = 1, l = 0. In the second case the deuteron is a spin singlet, so that its total spin s is 0. It also has an odd parity and therefore odd orbital angular momentum l. Therefore, the lowest possible energy state has s = 0, l = 1. Since s = 1 gives a stronger nuclear attraction, the deuterium ground state is in the s = 1, l = 0 state. The same considerations lead to the possible states of an isospin triplet having s = 0, l = even or s = 1, l = odd. Thus, the state of lowest energy has s = 1, l = 1, higher than that of the isospin singlet.
However, he is caught by the HECU Marines and dumped in a trash compactor. He escapes, and infiltrates a waste processing facility. In "Questionable Ethics", Freeman stumbles upon a secret part of Black Mesa that studies aliens. In "Surface Tension", Freeman crosses a hydroelectric dam, evading a Boeing AH-64 Apache. In "Forget About Freeman!", Freeman makes his way past a battle between aliens and the military to reach the Lambda Complex. In "Lambda Core", Gordon floods the facility's nuclear reactor with coolant, fighting off aliens along the way. Navigating through a maze of teleporters in a teleportation lab, he is finally allowed by scientists into a giant teleportation chamber that sends him to Xen, ending the Black Mesa portion of the game.
Ramelteon has no appreciable affinity for the GABA receptors or for receptors that bind neuropeptides, cytokines, serotonin, dopamine, noradrenaline, acetylcholine, and opioids. Ramelteon also does not interfere with the activity of a number of selected enzymes in a standard panel.
Sources: en.wikipedia.org
Jess A. Cliffe (born June 27, 1981) is a video game designer who co-created the Half-Life mod Counter-Strike with Minh Le and started the Counter-Strike series. In the first entry of the series, he is the voice of the radio commands, the voiceline "Counter-Terrorists Win!" and various sound effects. He has worked on maps for Half-Life: Deathmatch.
Synthetic organisms may offer increased hazard control because they can be engineered with "intrinsic" biocontainment methods that limit their growth in an uncontained environment, or prevent horizontal gene transfer to natural organisms. Examples of intrinsic biocontainment include auxotrophy, biological kill switches, inability of the organism to replicate or to pass modified or synthetic genes to offspring, and the use of xenobiological organisms using alternative biochemistry, for example using artificial xeno nucleic acids (XNA) instead of DNA.
== Applications == Pumps that use oil either as their working fluid (diffusion pumps), or as their lubricant (mechanical rotary pumps), are often the sources of contamination in vacuum systems. Placing a cold trap at the mouth of such a pump greatly lowers the risk that oil vapours will backstream into the cavity. Cold traps can also be used for experiments involving vacuum lines such as small-scale very low temperature distillations/condensations. This is accomplished through the use of a coolant such as liquid nitrogen or a freezing mixture of dry ice in acetone or a similar solvent with a low melting point. Liquid nitrogen is only used when dry ice or other cryogenic approaches will not condense the desired gasses since liquid nitrogen will also condense oxygen. Any oxygen gas content in the vacuum line or any leak in the vacuum line will result in liquid oxygen mixed with the target vapors, often with explosive results. When performed on a larger scale, this technique is called freeze-drying, and the cold trap is referred to as the condenser. Cold traps are also used in cryopump systems to generate hard vacua by condensing the major constituents of the atmosphere (nitrogen, oxygen, carbon dioxide and water) into their liquid or solid forms. An igloo or other snow bivouac may exploit the same principle – confinement of denser cool air within an impermeable lower volume – to reduce cold air reaching the occupants through use of a sump or cill around a raised sleeping platform within.
=== Early academic research === In academic discourse, the initial mention of ayahuasca dates back to Manuel Villavicencio's 1858 book, "Geografía de la República del Ecuador." This work vividly delineates the employment and rituals involving ayahuasca by the Jivaro people. Concurrently, Richard Spruce embarked on an Amazonian expedition in 1852 to collect and classify previously unidentified botanical specimens. During this journey, Spruce encountered and documented Banisteriopsis caapi (at time named Banisteria caapi) and observed an ayahuasca ceremony among the Tucano community situated along the Vaupés River. Subsequently, Spruce uncovered the usage and cultivation of B. caapi among various indigenous groups dispersed across the Amazon and Orinoco basins, like the Guahibo and Sápara. These multifarious encounters, together with Spruce's personal accounts of subjective ayahuasca experiences, were collated in his work, "Notes of a Botanist On The Amazon and Andes.". By the end of the century, other explorers and anthropologists contributed more extensive documentation concerning ayahuasca, notably the Theodor Koch-Grünberg's documents about Tucano and Arecuna's rituals and ceremonies, Stradelli's first-hand reports of ayahuasca rituals and mythology along the Jurupari and Vaupés and Alfred Simson's first description of admixture of several ingredients in the making of ayahuasca in Putumayo region, published in 1886.
=== Boiled === Eto is a Ghanaian traditional dish made from boiled and mashed yam or plantain and typically savored with boiled eggs, groundnut (peanuts) and sliced avocado. For the plantain option called 'Boodie eto', the plantain can be used unripe, slightly ripe or fully ripe. Culturally, eto was fed to a bride on the day of her marriage, but is now a popular dish enjoyed outside of special occasions as well. A traditional mangú from the Dominican Republic consists of peeled and boiled green plantains, mashed with hot water to reach a consistency slightly stiffer than mashed potatoes. It is traditionally eaten at breakfast, topped with sautéed red onions in apple cider vinegar and accompanied by fried eggs, fried cheese or fried bologna sausage, known as Dominican salami. Plantain porridge is also a common dish throughout the Caribbean, in which cooking bananas are boiled with milk, cinnamon, and nutmeg to form a thick porridge typically served at breakfast.
Sources: en.wikipedia.org
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.
Afamelanotide is the linear analogue [Nle4-D-Phe7]-alpha-MSH, sometimes called melanotan I, while melanotan II is cyclic and carries three further substitutions. The two are distinct molecules and are not interchangeable in analytical testing.
Binding to the four melanocortin receptor subtypes is well documented in vitro. The relative contribution of each subtype to whole-body effects in humans is far less certain.
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.