The short version of melanotan-2 fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2025-12-14. Anything still debated is marked as such rather than presented as settled.
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.
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.
Melanocortin receptors comprise five subtypes with distinct tissue distributions and functions. Melanotan-2 is described in the literature as a non-selective agonist that engages several of these subtypes, including MC1R, MC3R, MC4R, and MC5R. MC1R is the subtype most directly linked to melanin production in skin cells. Because the compound is not subtype-selective, its observed effects in experimental settings are generally attributed to activity across multiple receptor pathways rather than to a single target.
| Property | Value | Notes |
|---|---|---|
| Molecular class | Synthetic cyclic heptapeptide | Analog of alpha-MSH with an internal lactam bridge |
| Molecular weight | Approximately 1024 daltons | Free base value; salt forms differ |
| Appearance | White to off-white powder | Usually supplied as a lyophilized solid |
| Solubility | Freely soluble in water | Poorly soluble in nonpolar solvents |
| Typical storage | −20 °C, dry, protected from light | Repeated freeze-thaw cycles degrade peptides |
Melanotan-2 is frequently confused with afamelanotide, a linear analogue authorised in the European Union for erythropoietic protoporphyria. The two compounds differ in chain length, ring structure and receptor selectivity, so findings for one cannot be transferred directly to the other. Published controlled human data on melanotan-2 remain sparse, and much of what circulates online derives from small studies or unpublished reports. Questions about effect size, dose-response behaviour and long-term safety therefore remain unresolved.
Melanotan-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone. Its sequence incorporates a lactam bridge that constrains the peptide into a ring, which increases resistance to enzymatic breakdown relative to the natural hormone. Researchers at the University of Arizona synthesised the compound in the late 1980s and early 1990s while studying pigmentation pathways. It has never received marketing approval from any national medicines regulator. In the scientific literature it is usually described as a laboratory research reagent rather than a therapeutic product.
The peptide acts as a non-selective agonist at melanocortin receptors, showing affinity for MC1R, MC3R, MC4R and MC5R. Activation of MC1R on melanocytes drives the conversion of tyrosine into melanin and shifts production toward the darker eumelanin form. MC4R signalling in the central nervous system is linked to appetite and energy balance, which helps explain why reduced food intake appeared in early human studies. Effects on MC4R and on vascular tone also account for the erectile responses recorded as unexpected findings in those same trials.
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, 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.
=== Enzymatic labeling === In enzymatic labeling, a DNA construct is first formed, using a gene and the DNA of a fluorescent protein. After transcription, a hybrid RNA + fluorescent is formed. The object of interest is attached to an enzyme that can recognize this hybrid DNA. Usually fluorescein is used as the fluorophore.
=== Medication and lifestyle === Lifestyle factors such as smoking may also increase the chances of developing OSA, as the chemical irritants in smoke tend to inflame the soft tissue of the upper airway and promote fluid retention, both of which can narrow the upper airway. Cigarettes may also have an impact due to a decline in blood nicotine levels, which alters sleep stability. Smokers thus show a higher risk of developing OSA, but the effect of cigarettes on increased OSA is reversible with the cessation of smoking. Children exposed to cigarette smoke may also develop OSA, as the lymphoid tissue will proliferate excessively in contact with the irritants. An individual may also experience or exacerbate OSA with the consumption of alcohol, sedatives, or any other medication that increases sleepiness as most of these drugs are also muscle relaxants. Allergic rhinitis and asthma have also been shown to be implicated in the increased prevalence of adenotonsillar hypertrophy and OSA.
== Research == Anastrozole is surprisingly ineffective at treating gynecomastia, in contrast to selective estrogen receptor modulators like tamoxifen. Anastrozole was under development for the treatment of female infertility but did not complete development and hence was never approved for this indication. An anastrozole and levonorgestrel vaginal ring (developmental code name BAY 98–7196) was under development for use as a hormonal contraceptive and treatment for endometriosis. Development was discontinued in November 2018, and the formulation was never marketed. Anastrozole increases testosterone levels in males and has been studied as an alternative method of androgen replacement therapy in men with hypogonadism. However, there are concerns about its long-term influence on bone mineral density in this patient population, as well as other adverse effects.
Number average molar mass (Mn), also loosely referred to as number average molecular weight (NAMW). Mass average molar mass (Mw), where w stands for weight; also commonly referred to as weight average or weight average molecular weight (WAMW). Z-average molar mass (Mz), where z stands for centrifugation (from German Zentrifuge). Viscosity average molar mass (Mv).
Sources: en.wikipedia.org
As a practical matter, when platinum group metals are purified through dissolution in aqua regia, gold (commonly associated with PGMs) is precipitated by treatment with iron(II) chloride. Platinum in the filtrate, as hexachloroplatinate(IV), is converted to ammonium hexachloroplatinate by the addition of ammonium chloride. This ammonium salt is extremely insoluble, and it can be filtered off. Ignition (strong heating) converts it to platinum metal: 3 [NH4]2[PtCl6] → 3 Pt + 2 N2 + 2 [NH4]Cl + 16 HCl Unprecipitated hexachloroplatinate(IV) is reduced with elemental zinc, and a similar method is suitable for small scale recovery of platinum from laboratory residues. Aqua regia reacts with tin to form tin(IV) chloride, containing tin in its highest oxidation state: 4 HCl + 2 HNO3 + Sn → SnCl4 + NO2 + NO + 3 H2O Aqua regia can react with iron pyrite to form iron(III) chloride: FeS2 + 5 HNO3 + 3 HCl → FeCl3 + 2 H2SO4 + 5 NO + 2 H2O
The most important isotope for nuclear power applications is uranium-235. It is used in the thermal reactor, and its concentration in natural uranium does not exceed 0.72%. This isotope strongly absorbs thermal neutrons releasing much energy. One fission act of 1 gram of 235U converts into about 1 MW·day. Of importance, is that 23592U emits more neutrons than it absorbs; upon reaching the critical mass, 23592U enters into a self-sustaining chain reaction. Typically, uranium nucleus is divided into two fragments with the release of 2–3 neutrons, for example:
Hsc70 (Hsp73/HSPA8) is a constitutively expressed chaperone protein. It typically makes up one to three percent of total cellular protein. Hsp70 (encoded by three very closely related paralogs: HSPA1A, HSPA1B, and HSPA1L) is a stress-induced protein. High levels can be produced by cells in response to hyperthermia, oxidative stress, and changes in pH. Binding immunoglobulin protein (BiP or Grp78) is a protein localized to the endoplasmic reticulum. It is involved in protein folding there, and can be upregulated in response to stress or starvation. mtHsp70 or Grp75 is the mitochondrial Hsp70. The following is a list of human Hsp70 genes and their corresponding proteins:
Brent ( ) is a borough in west and north-west London, England; it forms part of Outer London. It is known for landmarks such as Wembley Stadium, the Swaminarayan Temple and the Kiln Theatre. It also contains the Welsh Harp reservoir and the Park Royal commercial estate. The local authority is Brent London Borough Council. Brent's population was estimated to be 353,000 as of 2024. Major districts are Kenton, Kilburn, Willesden, Wembley and Harlesden, with sub-districts Stonebridge, Kingsbury, Kensal Green, Neasden, and Queen's Park. Brent has a mixture of residential, industrial and commercial land. It includes many districts of inner-city character in the east and a more distinct suburban character in the west, part of which formed part of the early 20th century Metroland developments.
== Species complex == While traditionally described as a cosmopolitan species, recent genetic research has identified Octopus vulgaris as a species complex. There are currently six recognized members of the Octopus vulgaris species complex. Each member of the complex is associated with specific geographic regions, often associated with continental coastlines.
Sources: en.wikipedia.org
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.
Melanotan-1, also called afamelanotide, is a shorter linear analog with a different amino acid sequence and no lactam ring. It has been evaluated in formal clinical programs, while melanotan-2 has not. The two are distinct molecules and are not interchangeable.
No. Bremelanotide is a related but distinct cyclic peptide that reached approved status for one specific clinical indication. Melanotan-2 is a separate molecule with its own sequence and properties. Shared ancestry in the melanocortin family does not make them the same substance.
No. Melanotan-2 is manufactured synthetically. The naturally occurring peptide in the same family is alpha-melanocyte-stimulating hormone, which the body produces as part of normal endocrine and neural signalling.