This is a working overview of MC1R, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2025-11-08. 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.
Regulatory treatment varies between countries. Several national medicines agencies have classified the peptide as unapproved, and customs authorities in some jurisdictions seize shipments on that basis. A few jurisdictions channel supply through prescription-only frameworks that do not list the substance by name. Because the material circulates mainly through online vendors, composition and purity are rarely verified before sale. Surveys of unapproved peptide products have reported labels that did not match measured content in a substantial fraction of samples.
Melanotan II is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone, a naturally occurring peptide involved in pigmentation signalling. Its structure substitutes a lactam bridge between side chains to increase stability relative to the native hormone. The compound is also known by the shorthand MT-II and by several non-proprietary synonyms used in research catalogues. It is not an approved therapeutic product in any major jurisdiction; material sold under this name is typically offered as a laboratory reagent rather than as a medicine.
Activity is attributed to agonism at melanocortin receptors, particularly MC1R and MC4R. Activation of MC1R on melanocytes increases melanin synthesis, which underlies the reported tanning effect. MC4R engagement in the central nervous system is linked to appetite suppression and to effects on sexual arousal reported in early clinical studies. Those studies were small and were not designed to establish efficacy or long-term safety. Receptor selectivity among the melanocortin subtypes is not absolute, which complicates attribution of any effect to a single pathway.
| 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 |
Two structural changes distinguish the synthetic peptide from the natural hormone. A norleucine residue replaces methionine at one position, and a D-configured phenylalanine replaces the natural L-form at another. Both substitutions slow enzymatic breakdown, which extends the molecule's persistence relative to the parent hormone. The lactam bridge further constrains the backbone into a stable conformation. These features are standard design strategies in peptide chemistry and are not unique to this compound; they appear across many research peptides built for improved stability.
The compound was developed in the late 1980s and early 1990s by academic researchers investigating melanocortin signaling and pigmentation. Early work explored whether synthetic analogs could reproduce effects of the natural hormone under controlled conditions. The molecule never advanced through the full regulatory pathway required for approval as a medicine. From the mid-2000s onward it appeared in unregulated consumer markets, often distributed through informal channels. That gap between research origins and commercial availability shapes how the compound is discussed today.
Melanotan II is a synthetic cyclic heptapeptide analog derived from the core sequence of alpha-melanocyte-stimulating hormone. Researchers at the University of Arizona synthesized it during the 1980s while studying pigmentation and appetite signaling. The compound is not an approved medicine in any major jurisdiction and appears mainly in laboratory and research-chemical settings. Its structure incorporates a lactam bridge between side chains, which constrains the ring and slows enzymatic breakdown relative to the natural hormone.
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.
Receptor binding at MC1R on melanocytes raises intracellular cyclic AMP and increases expression of tyrosinase and related enzymes. The downstream result is greater synthesis of eumelanin, the dark pigment, without ultraviolet exposure acting as the trigger. The compound is not selective, however, and also engages MC3R, MC4R and MC5R, which are expressed in the central nervous system and elsewhere. That lack of selectivity is the explanation usually offered for effects reported outside pigmentation, including appetite suppression and nausea. Selectivity remains a central theme in comparative studies of related peptides.
Human data remain limited and mostly short-term. Reports describe small trials and observational accounts rather than large controlled studies, so questions about dose-response relationships and long-term effects on melanocytes stay open. Whether repeated exposure alters naevus behaviour is not settled in the published record. Researchers also note that self-administered use outside clinical settings makes actual exposure difficult to quantify. Statements about efficacy and safety should therefore be read as preliminary rather than established.
Melanotan II is a synthetic cyclic heptapeptide that acts as an agonist at melanocortin receptors. It was designed as a structural analogue of alpha-melanocyte-stimulating hormone, the endogenous peptide involved in pigment production. The analogue carries a lactam bridge that constrains the ring and slows enzymatic breakdown relative to the native hormone. In research literature it appears under several abbreviations, and naming conventions are not fully standardized. Published descriptions usually place it within the broader melanocortin agonist family.
Long bones are characterized by a shaft, the diaphysis, that is much longer than its width; and by an epiphysis, a rounded head at each end of the shaft. They are made up mostly of compact bone, with lesser amounts of marrow, located within the medullary cavity, and areas of spongy, cancellous bone at the ends of the bones. Most bones of the limbs, including those of the fingers and toes, are long bones. The exceptions are the eight carpal bones of the wrist, the seven articulating tarsal bones of the ankle and the sesamoid bone of the kneecap. Long bones such as the clavicle, that have a differently shaped shaft or ends are also called modified long bones. Short bones are roughly cube-shaped, and have only a thin layer of compact bone surrounding a spongy interior. Short bones provide stability and support as well as some limited motion. The bones of the wrist and ankle are short bones. Flat bones are thin and generally curved, with two parallel layers of compact bone sandwiching a layer of spongy bone. Most of the bones of the skull are flat bones, as is the sternum. Sesamoid bones are bones embedded in tendons. Since they act to hold the tendon further away from the joint, the angle of the tendon is increased and thus the leverage of the muscle is increased. Examples of sesamoid bones are the patella and the pisiform. Irregular bones do not fit into the above categories. They consist of thin layers of compact bone surrounding a spongy interior. As implied by the name, their shapes are irregular and complicated.
Naturally occurring samarium (62Sm) is composed of five stable isotopes, 144Sm, 149Sm, 150Sm, 152Sm and 154Sm, and two extremely long-lived radioisotopes, 147Sm (half life: 1.066×1011 y) and 148Sm (6.3×1015 y), with 152Sm being the most abundant (26.75% natural abundance). 146Sm (9.20×107 y) is also fairly long-lived, but is not long-lived enough to have survived in significant quantities from the formation of the Solar System on Earth, although it remains useful in radiometric dating in the Solar System as an extinct radionuclide. It is the longest-lived nuclide that has not yet been confirmed to be primordial. Its instability is due to having 84 neutrons (two more than 82, which is a magic number corresponding to a stable neutron configuration), and so it may emit an alpha particle (which has 2 neutrons) to form neodymium-142 with 82 neutrons. Other than those, the longest-lived radioisotopes are 151Sm, which has a half-life of 94.6 years, and 145Sm, which has a half-life of 340 days. All of the remaining radioisotopes, which range from 129Sm to 168Sm, have half-lives that are less than two days, and the majority of these have half-lives that are less than 48 seconds. The most stable of the known isomers is 141mSm (half-life 22.6 minutes). The long-lived isotopes, 146Sm, 147Sm, and 148Sm, decay by alpha emission to isotopes of neodymium. Lighter unstable isotopes of samarium primarily decay by electron capture to isotopes of promethium, while heavier ones decay by beta decay to isotopes of europium.
Rosiglitazone is a member of the thiazolidinedione class of drugs. Thiazolidinediones act as insulin sensitizers. They reduce glucose, fatty acid, and insulin blood concentrations. They work by binding to the peroxisome proliferator-activated receptors (PPARs). PPARs are transcription factors that reside in the nucleus and become activated by ligands such as thiazolidinediones. Thiazolidinediones enter the cell, bind to the nuclear receptors, and alter the expression of genes. The several PPARs include PPARα, PPARβ/δ, and PPARγ. Thiazolidinediones bind to PPARγ. PPARs are expressed in fat cells, cells of the liver, muscle, heart, and inner wall (endothelium) and smooth muscle of blood vessels. PPARγ is expressed mainly in fat tissue, where it regulates genes involved in fat cell (adipocyte) differentiation, fatty acid uptake and storage, and glucose uptake. It is also found in pancreatic beta cells, vascular endothelium, and macrophages Rosiglitazone is a selective ligand of PPARγ and has no PPARα-binding action. Other drugs bind to PPARα. Rosiglitazone also appears to have an anti-inflammatory effect in addition to its effect on insulin resistance. Nuclear factor kappa-B (NF-κB), a signaling molecule, stimulates the inflammatory pathways. NF-κB inhibitor (IκB) downregulates the inflammatory pathways. When patients take rosiglitazone, NF-κB levels fall and IκB levels increase.
=== Molecular mechanisms of action === Quisqualic acid is functionally similar to glutamate, which is an endogenous agonist of glutamate's receptors. It functions as a neurotransmitter in insect neuromuscular junction and CNS. It passes the blood brain barrier and binds to cell surface receptors AMPA and Kainate receptors in the brain. AMPA receptor is a type of ionotropic glutamate receptor coupled to ion channels and when bound to a ligand, it modulates the excitability by gating the flow of calcium and sodium ions into the intracellular domain. On the other hand, kainate receptors are less understood than AMPA receptors. Although, the function is somewhat similar: the ion channel permeates the flow of sodium and potassium ions, and to a lower extent the Calcium ions. As mentioned, binding of quisqualic acid to these receptors leads to an influx of calcium and sodium ions into the neurons, which triggers downstream signaling cascades. Calcium signaling involves protein effectors such as kinases (CaMK, MAPK/ERKs), CREB-transcription factor and various phosphatases. It regulates gene expression and may modify the properties of the receptors. Sodium and calcium ions together generate an excitatory postsynaptic potential (EPSP) that triggers action potentials. It's worthwhile to mention that overactivation of glutamate receptors and kainate receptors lead to excitotoxicity and neurological damage. A greater dose of quisqualic acid over activates these receptors that can induce seizures, due to prolonged action potentials firing the neurons.
=== International System === The SI unit for elasticity and the elastic modulus is the pascal (Pa). This unit is defined as force per unit area, generally a measurement of pressure, which in mechanics corresponds to stress. The pascal and therefore elasticity have the dimension L−1⋅M⋅T−2. For most commonly used engineering materials, the elastic modulus is on the scale of gigapascals (GPa, 109 Pa).
Sources: en.wikipedia.org
=== Deactivation === The bioactivity of calcitriol is terminated by hydroxylation at position 24 by vitamin D3 24-hydroxylase, coded for by gene CYP24A1, forming calcitetrol. Further metabolism yields calcitroic acid, an inactive water-soluble compound that is excreted in bile. Vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol) share a similar but not identical mechanism of action. Metabolites produced by vitamin D2 are named with an er- or ergo- prefix to differentiate them from the D3-based counterparts (sometimes with a chole- prefix).
Cárdenas' capture in 2003 and extradition in 2007 weakened the cartel, but the resulting fragmentation and the independence of Los Zetas intensified violence in the context of the drug war, leaving a lasting legacy of conflict in Mexico in the decades that followed. Following the capture of Osiel Cárdenas Guillén in 2003 and his extradition in 2007, leadership fell to Jorge Eduardo Costilla Sánchez, a key figure in the Gulf Cartel, who led the criminal organization until 2012. Internal dynamics and rivalries, especially with Los Zetas, defined his era. The pursuit of Joaquín "El Chapo" Guzmán from 2001 to 2014 is a pivotal case in the context of the 21st-century global war on drugs, as it exemplifies the challenges of combating sophisticated transnational criminal organizations. Guzmán, as the leader of the Sinaloa Cartel, orchestrated one of the most powerful drug trafficking networks, responsible for smuggling vast quantities of narcotics into the United States and Europe, generating billions in illicit revenue. His 2001 escape from a high-security Mexican prison and subsequent evasion until his 2014 capture highlighted the systemic corruption, institutional weaknesses, and cross-border complexities that hinder effective counter-narcotics strategies. The operation to apprehend him, involving Mexican authorities and U.S.
=== Origins === The first investigative radiochemical measurements began in the early days of nuclear fission. In 1944, the US Air Force made the first attempts to detect fissiogenic 133Xe in the atmosphere in order to indicate the production of plutonium through the irradiation of uranium and chemical reprocessing in an effort to gather intelligence on the status of the German nuclear program. However, no 133Xe was detected.
There is evidence humans have been processing fish since the early Holocene. For example, fishbones (c. 8140–7550 BP, uncalibrated) at Atlit-Yam, a submerged Neolithic site off Israel, have been analysed. What emerged was a picture of "a pile of fish gutted and processed in a size-dependent manner, and then stored for future consumption or trade. This scenario suggests that technology for fish storage was already available, and that the Atlit-Yam inhabitants could enjoy the economic stability resulting from food storage and trade with mainland sites."
Sources: en.wikipedia.org
An international zone is any area not fully subject to the border control policies of the state in which it is located. There are several types of international zones, ranging from special economic zones and sterile zones at ports of entry exempt from customs rules to concessions over which administration is ceded to one or more foreign states. International zones may also maintain distinct visa policies from the rest of the surrounding state.
Indoors ozone (O3) is produced by certain high-voltage electric devices (such as air ionizers), and as a by-product of other types of pollution. It appears in lower concentrations indoors than outdoors, usually at 0.2–0.7 of the outdoor concentration. Typically, most ozone is lost to surface reactions indoors, rather than to reactions in air, due to the large surface to volume ratios found indoors. Outdoor air used for ventilation may have sufficient ozone to react with common indoor pollutants as well as skin oils and other common indoor air chemicals or surfaces. Particular concern is warranted when using "green" cleaning products based on citrus or terpene extracts, because these chemicals react rapidly with ozone to form toxic and irritating chemicals as well as fine and ultrafine particles. Ventilation with outdoor air containing elevated ozone concentrations may complicate remediation attempts. The WHO standard for ozone concentration is 60 μg/m3 for long-term exposure and 100 μg/m3 as the maximum average over an 8-hour period. The EPA standard for ozone concentration is 0.07 ppm average over an 8-hour period.
=== Chicken and eggs === Japanese and South Korean authorities' tests on imported powdered eggs from China found melamine contamination. Japan found melamine in frozen fried chicken imported from China. The South Korean supplies were traced to two companies in Dalian. On 26 October, Hong Kong authorities discovered 4.7ppm melamine in eggs from Dalian. Hong Kong Secretary for Food and Health, York Chow, suspected the melamine came from feed given to the chickens that laid the eggs. On 29 October, Hong Kong authorities discovered a third batch of eggs containing excessive melamine. The Taiwanese Department of Health said that six batches of protein powder from Jilin and Dalian were found to contain 1.90 to 5.03ppm of melamine. Agriculture officials speculated that adulterated feed given to hens could explain melamine in eggs. The Web sites of Xinhua and People's Daily both carried a story from the Nanfang Daily that mixing melamine into animal feed was an "open secret" in the industry: melamine scrap was mixed into an inexpensive "protein powder" resold to feed suppliers. People in the trade interviewed by BusinessWeek also confirmed it was common practice, and had been going on for "years", with most believing it to be non-toxic to animals. Melamine dealers said after Sanlu, the government started clamping down on melamine sales to food processing companies or to manufacturers of animal feed.
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. No major regulatory agency has granted a marketing authorisation for melanotan II as a medicine. Products sold under this name are generally presented as laboratory reagents and are not subject to the batch-release testing applied to approved drugs.