If you have been reading about melanocortin receptor and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Last reviewed on 2026-02-13. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C50H69N15O9 | Free base; salt forms add to total mass |
| Molecular mass | About 1024 daltons | Calculated for the free base |
| Structural class | Cyclic heptapeptide | Contains D-phenylalanine and norleucine |
| Parent hormone | Alpha-melanocyte-stimulating hormone | Endogenous tridecapeptide of 13 residues |
| Receptor profile | Non-selective melanocortin agonist | Interacts with MC1R, MC3R, MC4R and MC5R |
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.
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.
Once again, the East Berlin communists attempted to disrupt the Berlin municipal elections, which were held on 5 December 1948 and produced a turnout of 86% and an overwhelming victory for the non-communist parties. The results effectively divided the city into East and West, the latter comprising US, British and French sectors. 300,000 Berliners demonstrated and urged the international airlift to continue, and US Air Force pilot Gail Halvorsen created "Operation Vittles", which supplied candy to German children. The Airlift was as much a logistical as a political and psychological success for the West; it firmly linked West Berlin to the United States. In May 1949, Stalin lifted the blockade. In 1952, Stalin repeatedly proposed a plan to unify East and West Germany under a single government chosen in elections supervised by the United Nations, if the new Germany were to stay out of Western military alliances, but this proposal was turned down by the Western powers. Some sources dispute the sincerity of the proposal.
=== Books === Separation Processes (1971); 2nd edition (1980) Freeze Drying of Foods (1971) The University of California: Creating, Nurturing, and Maintaining Academic Quality in a Public University Setting (2018)
Border control in many countries in Asia and the Americas prioritizes enforcing customs laws pertaining to narcotics. For instance, India and Malaysia are focusing resources on eliminating drug smuggling from Myanmar and Thailand, respectively. The issue stems largely from the high output of dangerous and illegal drugs in the Golden Triangle as well as in regions further west, such as Afghanistan. A similar problem exists east of the Pacific. It has resulted in countries such as Mexico and the United States tightening border control in response to the northward flow of illegal substances from regions such as Colombia. The Mexican drug war and similar cartel activity in neighboring areas have exacerbated the problem. In certain countries, illegal importing, exporting, selling, or possessing drugs constitutes capital offences and may result in a death sentence. A 2015 article by The Economist says that the laws of 32 countries provide for capital punishment for drug smuggling. Still, only in six countries – China, Iran, Saudi Arabia, Vietnam, Malaysia, and Singapore –are drug offenders known to be routinely executed. Additionally, Singapore, Malaysia, and Indonesia impose mandatory death sentences on individuals caught smuggling restricted substances across their borders. For example, Muhammad Ridzuan Ali was executed in Singapore on 19 May 2017, for drug trafficking.
Sources: en.wikipedia.org
== Inhibitors == Granzyme B's most common inhibitor is SERPINB9 also known as proteinase inhibitor nine (PI-9) which is 376 amino acids long and found in the nucleus and cytoplasm. It is produced by many types of cell to protect themselves from accidental granzyme B mediated cell death. PI-9 is metastable and forms an energetically favourable conformation when bound to granzyme B. The reactive loop centre (RCL) of the PI-9 molecule acts as a pseudosubstrate and initially forms a reversible Michaelis complex. Once the peptide bond of the RCL is cleaved between positions P1 and P1', granzyme B is permanently inhibited. However, if the RCL is cleaved efficiently, PI-9 does not act as a 1:1 suicide substrate and granzyme B is left uninhibited. Granzyme M can also cleave PI-9 in the nucleus and cytoplasm to relieve granzyme B of inhibition. Protein L4-100K from adenoviruses can also inhibit granzyme B by binding at exosites and specific binding pockets. L4-100K is an assembly protein that can transport hexon capsomeres into the nucleus of an adenovirus. 100k can be cleaved to a 90kDa fragment by granzyme H to relieve this inhibition which is important in adenovirus 5 infected cells.
== Experimental design == The apparatus consists of a gas chromatograph equipped with an odour port (ODP), in place of or in addition to conventional detectors, from with human assessors sniff the eluates. The odour port is characterised by its nose-cone design connected to the GC instrument by a transfer line. The odour port is commonly glass or polytetrafluoroethylene. It is generally placed 30–60 cm away from the instrument, extending from the side such that it is not affected by the hot GC oven. The deactivated silica transfer line is generally heated to prevent the condensation of less-volatile compounds. It is flexible so that the assessor can adjust it according to their comfortable sitting position. As traditional warm and dry carrier gases may dehydrate the mucous membrane of the nose, volatiles are delivered via auxiliary gas or humidified carrier gas, with relative humidity (RH) of 50–75%, to ease the dehydration. The olfactometric detector may be coupled with, or connected in parallel to, a flame ionization detector (FID) or mass spectrometer (MS). Moreover, multiple odour ports may be set-up. In these cases, the eluate is generally split evenly between the detectors to allow it to reach the detectors simultaneously.
== Branding times == The length of time the brand is applied depends on several factors, such as the thermal conductivity of the metal used, the age of the animal, the thickness of its skin, the color or pigment to its coat, and the amount of hair, if any, that remains between brand and skin after shaving. Although the animal is shaved, the time of brand application also depends on the stage of the animal's hair growth, with rapidly growing spring coats requiring less time and those with winter coats requiring more. It is hypothesized that the pigment-producing melanocytes are more easily destroyed during periods of rapid hair, and hence rapid pigmentation, production. It is important to adhere to brand time guidelines because melanocytes that are merely stressed rather than killed often react by producing even more melanin than they did before their injury. This is the same reaction responsible for skin tanning and the darkening of skin under regular mechanical strain. These failed brands then regrow as dark skin producing even darker hair than was present before, creating a very low-contrast marking.
Sources: en.wikipedia.org
=== Accelerating methods for shelf life prediction === The kinetic process of destabilization can be rather long – up to several months, or even years for some products. Often the formulator must accelerate this process in order to test products in a reasonable time during product design. Thermal methods are the most commonly used – these consist of increasing the emulsion temperature to accelerate destabilization (if below critical temperatures for phase inversion or chemical degradation). Temperature affects not only the viscosity but also the interfacial tension in the case of non-ionic surfactants or, on a broader scope, interactions between droplets within the system. Storing an emulsion at high temperatures enables the simulation of realistic conditions for a product (e.g., a tube of sunscreen emulsion in a car in the summer heat), but also accelerates destabilization processes up to 200 times. Mechanical methods of acceleration, including vibration, centrifugation, and agitation, can also be used. These methods are almost always empirical, without a sound scientific basis.
space. The boundaries of the shaded regions in the figure are the boundaries of stability in the two directions (also known as boundaries of bands). The domain of overlap of the two regions is the trapping domain. For calculation of these boundaries and similar diagrams as above see Müller-Kirsten.
== Legal status == Thebacon is a Schedule I controlled substance in the United States, never having been in medical use there. The US DEA Administrative Controlled Substance Control Number assigned by the Controlled Substances Act (1970) for thebacon and all of its salts is 9315.
Sources: en.wikipedia.org
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.
Melanotan-1, also called afamelanotide, is a linear analogue with greater selectivity for MC1R and has received approval in some jurisdictions for a specific photosensitivity disorder. Melanotan-2 is cyclic, less selective, and reaches central receptors more readily. The two are often confused in online discussion despite different pharmacology and regulatory status.
Alpha-MSH is an endogenous tridecapeptide derived from pro-opiomelanocortin. Melanotan-2 reproduces its core receptor-binding sequence inside a shortened, stabilised ring. The result is a molecule with a longer effective half-life and higher potency than the parent hormone.
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.