The short version of MC1R fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-05-24. Anything still debated is marked as such rather than presented as settled.
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.
Melanotan-2 is a synthetic peptide designed as an analog of alpha-melanocyte-stimulating hormone, a signaling molecule produced in the pituitary and skin. Its structure is a linear chain of seven amino acids that folds into a ring through an internal lactam bridge joining two side chains. The compound is sometimes written as MT-II or MEL-2 in informal and commercial contexts. It belongs to the melanocortin peptide family, a group of short signaling molecules that share a conserved core sequence recognized by melanocortin receptors.
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.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic cyclic heptapeptide | Analogue of alpha-melanocyte-stimulating hormone |
| Common synonyms | MT-II; melanotan 2 | No internationally accepted non-proprietary name |
| Typical presentation | Lyophilised powder in a sealed vial | Often supplied alongside a separate diluent |
| Regulatory status | Unapproved therapeutic substance | Customs seizure reported in several jurisdictions |
| Reported route in use | Subcutaneous injection | Self-administered outside clinical settings |
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.
where dm/dt is the mass dissolution rate, D the diffusion coefficient, A the surface area of solid in contact with the dissolution medium, Cs the saturation solubility, C the bulk concentration, and h the thickness of the unstirred diffusion layer. Because A scales inversely with particle diameter, reducing median diameter from approximately 50 μm to 5 μm increases the available surface area roughly ten-fold and produces a corresponding increase in dissolution rate at constant solubility. At sub-micron diameters, Cs itself increases according to the Ostwald–Freundlich equation, providing an additional thermodynamic contribution to dissolution. Under the Biopharmaceutics Classification System (BCS), drugs are categorized by aqueous solubility and intestinal permeability. Micronization confers the greatest clinical benefit for BCS Class II compounds (low solubility, high permeability), where dissolution rate — not membrane permeation — limits absorption. For BCS Class III and IV compounds, in which permeability is the rate-limiting step, particle size reduction alone produces little change in bioavailability and must be combined with permeation enhancers or alternative delivery strategies.
== Signs and symptoms == Hypoglycemic symptoms are divided into two main categories. The first category is symptoms caused by low glucose in the brain, called neuroglycopenic symptoms. The second category of symptoms is caused by the body's reaction to low glucose in the blood, called adrenergic symptoms.
== Description == The neon tetra has a light-blue back over a silver-white abdomen. The fish is characterized by a bright iridescent blue horizontal stripe along each side of the fish from its nose to the base of the adipose fin, and an iridescent red stripe that begins at the middle of the body and extends posteriorly to the base of the caudal fin. The fish is partially transparent (including fins) except for these markings. Sexual dimorphism is slight, with the female having a slightly larger belly, and a bent iridescent stripe rather than the male's straight stripe. During the night, the blue and red become gray or black as the fish rests. It reactivates once it becomes active in the morning. This peculiar change is due to the neon tetras capacity to change the color of its iridescent stripe in response to lighting conditions. In a light-adapted state it is blue-green, likewise in a dark-adapted state its color changes to indigo. This change is produced by guanine crystals in their cells that reflect light. The neon tetra grows to approximately 4 cm (1.6 in) in overall length.
Sources: en.wikipedia.org
== Habitat degradation == Human activities such as urban development, agriculture, and dam construction lead to habitat degradation, posing significant threats to aquatic plants. Urbanization increases impervious surfaces, leading to higher runoff volumes that carry pollutants and sediments into water bodies. This runoff can smother aquatic plants and alter water chemistry. Agricultural practices contribute to nutrient loading and pesticide contamination, further stressing aquatic vegetation. Dam construction and water diversion projects alter natural flow regimes, affecting sediment transport and water temperature. These changes can disrupt the life cycles of aquatic plants and the species that depend on them. Aquatic plants are integral to healthy aquatic ecosystems, but they face numerous threats from invasive species, nutrient pollution, climate change, and habitat degradation. Addressing these challenges requires integrated management approaches, including controlling invasive species, reducing nutrient inputs, mitigating climate change impacts, and protecting and restoring aquatic habitats.
catabolism Any metabolic reaction or process involving the decomposition of large or complex substances into smaller, simpler compounds, especially the breakdown of organic compounds in order to liberate energy. Catabolic processes and pathways are usually exergonic and tend to involve oxidative steps that break chemical bonds, generating low-enthalpy, high-entropy products. Contrast anabolism.
The group takes its name from the most representative member: Bencubbin (Australia). Although these chondrites contain over 50% nickel-iron metal, they are not classified as mesosiderites because their mineralogical and chemical properties are strongly associated with CR chondrites.
Sources: en.wikipedia.org
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.
It was developed in the 1980s by researchers investigating analogues of alpha-melanocyte-stimulating hormone for pigmentation and related endpoints. Early work included small human studies during the 1990s. Development did not progress to licensing, and the compound remained a research and grey-market item.
Peptides are prone to truncation, oxidation and aggregation during synthesis and handling. Without independent testing, a buyer cannot confirm the identity or the content of a vial. Analytical surveys of unapproved peptide products have repeatedly found discrepancies between label claims and measured composition.
It is a synthetic seven-amino-acid peptide modeled on alpha-melanocyte-stimulating hormone. It carries two non-natural substitutions and a cyclic bridge that increase its stability relative to the natural hormone. It circulates as a research chemical and is not an approved medicine.