Melanotan II comes up often in conversation and rarely with the context attached. Here we lay out the basics in order, then work through the practical considerations.
Last reviewed on 2026-07-07. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
No regulatory authority has approved melanotan-2 for human use, and several countries classify it as a prescription-only or controlled substance, which restricts lawful supply. Material sold online is generally labelled as a research chemical and is not required to meet pharmaceutical standards of identity or purity. Published human data consist mainly of small uncontrolled studies, case reports and adverse-event notifications, so the evidence base is descriptive rather than confirmatory. Whether repeated melanocyte stimulation alters long-term naevus behaviour remains an open question that no completed trial has resolved.
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 |
|---|---|---|
| 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 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.
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 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 linear peptide built from seven amino acids arranged in a short chain. Its sequence is commonly written as Ac-Nle-Asp-His-D-Phe-Arg-Trp-Lys-NH2, which includes a modified N-terminus and an amidated C-terminus. The molecule belongs to the melanocortin family and acts as a receptor agonist. Structural features such as the D-phenylalanine residue and the Nle substitution are associated with increased stability against enzymatic degradation relative to the natural parent peptide.
The compound emerged from research programs in the 1980s that examined analogues of alpha-melanocyte-stimulating hormone for pigmentation and photoprotection. Investigators modified the native sequence to extend activity duration and potency. A related analogue, afamelanotide, was developed within the same broad line of inquiry and eventually gained approval in certain jurisdictions for a rare light-sensitivity condition. Melanotan-2 itself did not progress through the same regulatory route and has no approved therapeutic indication.
=== High population densities === Since sea ice pockets are confined and highly-concentrated ecosystems, they are able to house several orders of magnitude greater population densities of bacteria and protists than are found in the open ocean (up to thousands of individuals per liter for protists). This high abundance of organisms can pose challenges, as different bacteria and protists will compete for resources. A high density of microorganisms can result in the accumulation of metabolic byproducts, such as oxygen, dissolved organic matter, ammonia, and dimethylsulfoniopropionate (DMSP). Some organisms can gain a selective advantage within brine pockets as the high population density can result in increased rates of horizontal gene transfer because organisms are in close proximity. Horizontal gene transfer can allow certain organisms to obtain genes from bacteria that may be advantageous in a light-limited, extremely cold environment.
Pazopanib, sold under the brand name Votrient, is an anti-cancer medication marketed worldwide by Novartis. It is a potent and selective multi-targeted receptor tyrosine kinase inhibitor that blocks tumour growth and inhibits angiogenesis. It has been approved for renal cell carcinoma and soft tissue sarcoma by numerous regulatory administrations worldwide.
== References == Catalog of Copyright Entries: Third Series Volume 24, Parts 12-13, Number 1: Motion Pictures and Filmstrips 1970 Library of Congress [966] Catalog of Copyright Entries: Third Series Volume 25, Parts 12–13, Number 1: Motion Pictures and Filmstrips 1971 Library of Congress [967] Catalog of Copyright Entries: Third Series Volume 27, Parts 12–13, Number 1: Motion Pictures 1973 Library of Congress [968] Catalog of Copyright Entries: Third Series Volume 28, Parts 12–13, Number 1: Motion Pictures 1974 Library of Congress [969] Catalog of Copyright Entries: Third Series Volume 29, Parts 12–13, Number 1: Motion Pictures 1975 Library of Congress [970] Catalog of Copyright Entries: Third Series Volume 30, Parts 12–13, Number 1: Motion Pictures 1976 Library of Congress [971] Catalog of Copyright Entries: Third Series Volume 31, Parts 12–13, Number 1: Motion Pictures 1977 Library of Congress [972] Catalog of Copyright Entries: Fourth Series Volume 31, Part 4: Motion Pictures & Filmstrips 1980 Library of Congress [973] Educational Film Guide 1947 H. W. Wilson Company [974] Educational Film Guide 1959 Annual Supplement 1959 H. W. Wilson Company [975] Motion Pictures 1912–1939 Catalog of Copyright Entries 1951 Library of Congress [976] Motion Pictures 1940–1949 Catalog of Copyright Entries 1953 Library of Congress [977] Motion Pictures 1950–1959 Catalog of Copyright Entries 1960 Library of Congress [978] Motion Pictures 1960–1969 Catalog of Copyright Entries 1971 Library of Congress [979]
Sources: en.wikipedia.org
=== Survival during freeze-drying processes === In 2017, a study was done to see the effects of six different substances on the growth and freeze- drying of Lactobacillus. Using Lactobacillus as starter cultures for the dairy industry depends on the number of viable and active cells. Currently, the preferred method to preserve the bacterial cells is through freeze-drying, however this also results in some strains being killed. This is due to various complications of freeze-drying, including the formation of ice crystals, loss of membrane fluidity, and the denaturation of important macromolecules. Regardless, freeze-drying has been used for decades in microbiological research as a way to store and stabilize cultures. Six substances, being sodium chloride, sorbitol, mannitol, mannose, monosodium glutamate, and betaine were tested to determine if they had any effect on the survivability of the cells after freeze-drying. Three of the six substances added had a positive effect on the growth and freeze-drying of Lactobacillus, being sodium chloride, sorbitol, and sodium glutamate. The results suggest that these substances have protective effects on Lactobacillus delbrueckii subsp. bulgaricus in small concentrations, but have little effect or even some harmful effects in higher concentrations. The optimal concentrations for sorbitol, sodium chloride and sodium glutamate for the desired protective effects were 0.15%, 0.6%, and 0.09% respectively. This was shown to increase cell viability drastically.
Algae are used as foods in many countries: China consumes more than 70 species, including fat choy, a cyanobacterium considered a vegetable; Japan, over 20 species such as nori and aonori; Ireland, dulse; Chile, cochayuyo. Laver is used to make laverbread in Wales, where it is known as bara lawr. In Korea, green laver is used to make gim. Some of the most commonly used microalgae as food are:
Competition with endogenous aldehydes or ketones in metabolites and cofactors, resulting in low yields and impaired specificity. Side reactions, such as oxidation or unwanted addition of endogenous nucleophiles. Restrained set of probes that form sufficiently stable products. Aldehydes and ketones are therefore best used in compartments where such unwanted side reactions are decreased. For experiments with live cells, cell surfaces and extracellular space are typical fielding areas. Nevertheless, a feature of carbonyl groups is the vast number of organic reactions that involve them as electrophiles. Some of these reactions are readily convertible to ligations for probing aldehydes. A reaction recently employed for bioconjugation by Agarwal et al. is the adaptation of the Pictet-Spengler reaction as a ligation. The reaction is known from natural product biosynthetic pathways and has the major advantage of forming a new carbon-carbon bond. This guarantees long-term stability compared to carbon-heteroatom bonds with similar reaction kinetics. The modification of cysteine or, more rarely, serine by FGE is an uncommon posttranslational modification that was discovered in the late 1990s. The deficiency of FGE leads to an overall deficiency of functional sulfatases due to a lack of α-formylglycine formation vital for the sulfatases to perform their function. FGE is essential for protein modification and need of high specificity and conversion rate is given in the native setting, which makes this reaction applicable in chemical and synthetic biology.
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 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.