melanocortin receptor is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Last reviewed on 2025-11-10. Where a claim depends on a specific study, the study is described rather than over-claimed.
The compound was developed in the late 1980s and 1990s by academic researchers investigating photoprotection. The rationale held that stimulating melanin production might reduce ultraviolet damage to skin and lower skin cancer risk. Early work examined receptor binding, pigment response, and short-term tolerability in small studies. That program did not produce an approved drug, and formal development stalled after early-phase trials. Whether induced pigmentation confers meaningful photoprotection remains an open question.
Outside regulated medicine, melanotan II circulates through online vendors as a research chemical, often marketed for tanning. Products sold this way vary widely in purity, concentration, and labeling accuracy, and independent testing has documented discrepancies. Published reports describe both pigment effects and adverse reactions, including nausea, flushing, and darkening of existing moles. Long-term safety data are sparse, and no large controlled trial has established a risk profile. Questions about cumulative effects on melanocytes remain unresolved in the literature.
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 |
|---|---|---|
| Chemical class | Synthetic cyclic heptapeptide | Belongs to the melanocortin agonist family |
| Key substitutions | Nle4 and D-Phe7 | Improve resistance to enzymatic degradation |
| Molecular formula | C50H69N15O9 | Approximately 1024 g/mol |
| Regulatory status | Not approved as a medicine | Distributed as a research chemical |
| Common synonyms | Melanotan II, MT-II, MT-2 | Spelling varies across sources |
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.
Melanocytes are the pigment-producing cells of the skin, and they carry melanocortin-1 receptors on their surface. When the receptor is activated, cyclic adenosine monophosphate rises inside the cell and raises the activity of enzymes such as tyrosinase, which increases melanin output. Melanotan-2 binds melanocortin-1 receptors in vitro and in animal models, and this binding is generally described as the basis for the tanning effect. Other receptors account for different effects: melanocortin-4 receptors contribute to appetite and erectile signalling, while melanocortin-3 and melanocortin-5 receptors contribute to energy balance and exocrine function.
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 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.
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.
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.
=== Cultivation === Royal jelly is harvested by stimulating colonies with movable frame hives to produce queen bees. Royal jelly is collected from each individual queen cell (honeycomb) when the queen larvae are about four days old. These are the only cells in which large amounts are deposited. This is because when royal jelly is fed to worker larvae, it is fed directly to them, and they consume it as it is produced, while the cells of queen larvae are "stocked" with royal jelly much faster than the larvae can consume it. Therefore, only in queen cells is the harvest of royal jelly practical. A well-managed hive during a season of 5–6 months can produce approximately 500 g (18 oz) of royal jelly. Since the product is perishable, producers must have immediate access to proper cold storage (e.g., a household refrigerator or freezer) in which the royal jelly is stored until it is sold or conveyed to a collection center. Sometimes honey or beeswax is added to the royal jelly, which is thought to aid its preservation. The Vegetarian Society considers royal jelly to be non-vegan.
=== Schwann cells and endoneural fibroblasts in PNS === In healthy nerves, nerve growth factor (NGF) is produced in very small amounts. However, upon injury, NGF mRNA expression increases by five to seven-fold within a period of 14 days. Nerve fibroblasts and Schwann cells play an important role in increased expression of NGF mRNA. Macrophages also stimulate Schwann cells and fibroblasts to produce NGF via macrophage-derived interleukin-1. Other neurotrophic molecules produced by Schwann cells and fibroblasts together include brain-derived neurotrophic factor, glial cell line-derived neurotrophic factor, ciliary neurotrophic factor, leukemia inhibitory factor, insulin-like growth factor, and fibroblast growth factor. These factors together create a favorable environment for axonal growth and regeneration. Apart from growth factors, Schwann cells also provide structural guidance to further enhance regeneration. During their proliferation phase, Schwann cells begin to form a line of cells called Bands of Bungner within the basal laminar tube. Axons have been observed to regenerate in close association to these cells. Schwann cells upregulate the production of cell surface adhesion molecule ninjurin further promoting growth. These lines of cell guide the axon regeneration in proper direction. The possible source of error that could result from this is possible mismatching of the target cells as discussed earlier. Due to lack of such favorable promoting factors in CNS, regeneration is stunted in CNS.
There have been some studies of how religion relates to happiness. Causal relationships remain unclear, but more religion is seen in happier people. Consistent with PERMA, religion may provide a sense of meaning and connection to something bigger, beyond the self. Religion may also provide community membership and hence relationships. Another component may have to do with ritual. Religion and happiness have been studied by a number of researchers, and religion features many elements addressing the components of happiness, as identified by positive psychology. Its association with happiness is facilitated in part by the social connections of organized religion, and by the neuropsychological benefits of prayer and belief.
Sources: en.wikipedia.org
The company's Advanced Technology Investment Company (ATIC) in 2008, is an investment company in the high-technology sector. ATIC owns the semiconductor foundry companies GlobalFoundries, and Chartered Semiconductor Manufacturing (which later merged with GlobalFoundries). ATIC has invested in Calxeda, a start-up company for producing ARM architecture–based computers for the server market. In 2011, ATIC announced investments of $5.5 billion to expand chip manufacturing in Singapore, Dresden, and New York. It also announced a $6–$8 billion computer chip factory in Abu Dhabi for completion in 2012. The company supports research initiatives in Khalifa University, UAE University, American University of Sharjah, Masdar Institute and New York University Abu Dhabi. In 2014, ATIC became Mubadala Technology.
== History == For thousands of years, glassmakers were able to make colored glass by adding different dusts and powdered elements such as silver, gold and cadmium and then used different temperatures to produce shades of glass. In the 19th century, scientists started to understand how glass color depended on elements and heating-cooling techniques. It was also found that for the same element and preparation, the color depended on the dust particles' size. Herbert Fröhlich in the 1930s first explored the idea that material properties can depend on the macroscopic dimensions of a small particle due to quantum size effects. The first quantum dots were synthesized in a glass matrix by Alexei A. Onushchenko and Alexey Ekimov in 1981 at the Vavilov State Optical Institute and independently in colloidal suspension by Louis E. Brus team at Bell Labs in 1983. They were first theorized by Alexander Efros in 1982. It was quickly identified that the optical changes that appeared for very small particles were due to quantum mechanical effects. The term quantum dot first appeared in a paper first authored by Mark Reed in 1986. According to Brus, the term "quantum dot" was coined by Daniel S. Chemla while they were working at Bell Labs. In 1993, David J. Norris, Christopher B. Murray and Moungi Bawendi at the Massachusetts Institute of Technology reported on a hot-injection synthesis method for producing reproducible quantum dots with well-defined size and with high optical quality.
=== HLA-DM Structure === The structure and sequence of HLA-DM proteins is very similar to other MHC class II molecules, all of which consist of a heterodimer composed of an alpha and beta chain. However, HLA-DM differs in that it is nonclassical (meaning it lacks a transport signal N-terminus), and does not have the capability to bind peptides. This is due to lack of a deep peptide binding groove – instead, it contains a shallow, negatively charged indent with two disulfide bonds. On its beta chain cytoplasmic tail, a tyrosine-based motif YTPL regulates trafficking to specific endosomal compartments called MHC class II compartments (MIICs) from the ER.
Sources: en.wikipedia.org
=== Solubility === Bronopol is readily soluble in water; the dissolution process is endothermic. Solutions containing up to 28% w/v are possible at ambient temperature. Bronopol is poorly soluble in non-polar solvents but shows a high affinity for polar organic solvents.
=== In pharmacology === Bioavailability is a term used to describe the percentage of an administered dose of a xenobiotic that reaches the systemic circulation unchanged. It is denoted by the letter f (or, if expressed in percent, by F).
direct zoonotic transmission to humans (spillover), assessed as "possible to likely" introduction through an intermediate host followed by a spillover, assessed as "likely to very likely" introduction through the (cold) food chain, assessed as "possible" introduction through a laboratory incident, assessed as "extremely unlikely" The report mentions that direct zoonotic transmission to humans has a precedent, as most current human coronaviruses originated in animals. Zoonotic transmission is also supported by the fact that RaTG13 binds to hACE2, although the fit is not optimal. The investigative team noted the requirement for further studies, noting that these would "potentially increase knowledge and understanding globally."
Sources: en.wikipedia.org
It is a synthetic cyclic peptide designed as an analog of alpha-melanocyte-stimulating hormone. It acts on melanocortin receptors and is best known from research into pigmentation. It is not an approved pharmaceutical product.
No regulatory agency has approved it for any indication. It is encountered as a research chemical sold outside pharmaceutical supply chains. Products marketed this way are not subject to the manufacturing and labeling requirements that apply to approved drugs.
Reports describe increased skin pigmentation as well as side effects such as nausea, flushing, and changes to existing moles. Much of the evidence comes from small studies and case reports rather than large trials. The long-term safety profile is therefore uncertain.
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.