melanotan-2 raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
Reviewed 2026-04-30. Anything still debated is marked as such rather than presented as settled.
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 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.
Research interest has centred on photoprotection and pigmentation, with a smaller body of work on appetite and sexual function. Published human data remain limited to small, frequently uncontrolled studies, and the compound has never received marketing approval from a national medicines regulator. Most laboratory work treats it as a pharmacological tool for probing melanocortin signalling in cell culture or animal models. Whether pigmentation changes observed in people translate into measurable protection against ultraviolet-induced DNA damage remains an open question.
Melanotan-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone, the naturally occurring peptide involved in pigmentation signalling. Its sequence is conventionally written as Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, with a lactam bridge joining the aspartate side chain to the lysine side chain. The empirical formula is C50H69N15O9 and the monoisotopic mass lies near 1023.5 daltons. N-terminal acetylation and the D-configured phenylalanine both increase resistance to enzymatic breakdown compared with the parent hormone.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C50H69N15O9 | Cyclic heptapeptide, C-terminally amidated |
| Approximate molecular mass | 1024 Da | Monoisotopic mass of the free peptide |
| Appearance | White to off-white powder | Typically supplied as a lyophilised solid |
| Solubility class | Soluble in water and polar solvents | Also dissolves in neutral aqueous buffer |
| Common synonyms | Melanotan II, MT-II, MT-2 | Described as a melanocortin agonist in early literature |
=== Biofilms formation and cyclic di-GMP === As in most Gram negative bacteria, P. aeruginosa biofilm formation is regulated by one single molecule: cyclic di-GMP. At low cyclic di-GMP concentration, P. aeruginosa has a free-swimming mode of life. But when cyclic di-GMP levels increase, P. aeruginosa start to establish sessile communities on surfaces. The intracellular concentration of cyclic di-GMP increases within seconds when P. aeruginosa touches a surface (e.g.: a rock, plastic, host tissues...). This activates the production of adhesive pili, that serve as "anchors" to stabilize the attachment of P. aeruginosa on the surface. At later stages, bacteria will start attaching irreversibly by producing a strongly adhesive matrix. At the same time, cyclic di-GMP represses the synthesis of the flagellar machinery, preventing P. aeruginosa from swimming. When suppressed, the biofilms are less adherent and easier to treat. The biofilm matrix of P. aeruginosa is composed of nucleic acids, amino acids, carbohydrates, and various ions. It mechanically and chemically protects P. aeruginosa from aggression by the immune system and some toxic compounds. P. aeruginosa biofilm's matrix is composed of up to three types of sugar polymers (or "exopolysaccharides") named PSL, PEL, and alginate. Which exopolysaccharides are produced varies by strain.
== Applications == One of the potent applications of siRNAs is the ability to distinguish the target versus non-target sequence with a single-nucleotide difference. This approach has been considered therapeutically crucial for silencing dominant gain-of-function (GOF) disorders, where the mutant allele causing disease differs from the wild-type allele by a single nucleotide (nt). These types of siRNAs, which are capable of distinguishing a single-nucleotide difference, are termed allele-specific siRNAs. ASP-RNAi is an innovative category of RNAi with the objective of suppressing the dominant mutant allele while sparing expression of the corresponding normal allele with the specificity of single-nucleotide differences between the two. ASP-siRNAs are potentially a novel and better remedial alternative for the treatment of autosomal dominant genetic disorders, especially in cases where wild-type allele expression is crucial for organism survival, such as Huntington disease (HD), DYT1 dystonia (Gonzalez-Alegre et al. 2003, 2005), Alzheimer's disease (AD) (Sierant et al. 2011), Parkinson's disease (PD) (Takahashi et al. 2015), amyotrophic lateral sclerosis (ALS) (Schwarz et al. 2006), and Machado-Joseph disease (MJD) (Alves et al. 2008). Their therapeutic potential has also been assessed for various skin disorders like epidermolysis bullosa simplex (Atkinson et al. 2011), epidermolytic palmoplantar keratoderma (EPPK) (Lyu et al. 2016), and lattice corneal dystrophy type I (LCDI) (Courtney et al. 2014).
By layer, epithelium is classed as either simple epithelium, only one cell thick (unilayered), or stratified epithelium having two or more cells in thickness, or multi-layered – as stratified squamous epithelium, stratified cuboidal epithelium, and stratified columnar epithelium, and both types of layering can be made up of any of the cell shapes. However, when taller simple columnar epithelial cells are viewed in cross section showing several nuclei appearing at different heights, they can be confused with stratified epithelia. This kind of epithelium is therefore described as pseudostratified columnar epithelium. Transitional epithelium has cells that can change from squamous to cuboidal, depending on the amount of tension on the epithelium.
Evocative/suppression testing refers to a class of tests performed where one substance is measured both before and after the administration of another substance to determine if the levels are stimulated ("evocative") or suppressed. They are most commonly performed in the evaluation of possible endocrine disorders. Certain tests are performed in the evaluation of multiple conditions, and not all listed substances may be measured in each test. Examples include:
Hunter requested greater control by authorities in England and an excise duty on rum. He issued an order restricting the amount of convict labour that officers could use, but again had no means to enforce it. Hunter was strongly opposed by officers of the Corps, and pamphlets and letters against him were circulated. John Macarthur wrote a letter accusing Hunter of ineffectiveness and trading in rum. Hunter was required by the Colonial Office to answer the charges, and soon after was recalled for being ineffective. In 1799 Paterson, now a Lieutenant Colonel, returned from England with orders to stamp out the trading in rum by officers of the Corps. In 1800, he charged Major George Johnston, who had served as Hunter's aide-de-camp, with giving a sergeant part payment in rum at an exorbitant rate. Johnston claimed he was being unfairly persecuted and demanded that he be sent to England for trial. The English courts decided that colonial affairs were not a matter for them and, as all the evidence and witnesses were in Sydney, that any trial should be held there. They decided that, as proper court martial could not be constituted in Sydney, no further action should be taken against Johnston. Governor Philip King, appointed in September 1800, continued Hunter's efforts to prevent the Corps trading in rum. He had the power to levy an excise duty on alcohol, and the Transit Board now required all ships to lodge a bond which was forfeit for disobeying the Governor's orders, which included the prohibition of the landing of more than 500 gallons of rum.
Sources: en.wikipedia.org
== Function == The main biological function of metallothioneins is to maintain homeostasis of the essential metals zinc and copper, but metallothioneins also protect against metal toxicity and oxidative stress.
=== Military and political escalation (1972–1976) === By December 1972, ZANLA had cached arms and established a vast underground network of informants and supporters in northeastern Rhodesia. As a result of the erosion of Portuguese authority in Mozambique's border provinces due to the Mozambican War of Independence, ZANLA was also able to establish external sanctuaries there. It was also in the process of cultivating a military alliance with the leading black nationalist movement in Mozambique, the Front for the Liberation of Mozambique (FRELIMO). On 21 December, a group of ZANLA insurgents under Rex Nhongo crossed into Rhodesia from Mozambique and raided an isolated commercial farm. In the successive months, this attack was followed by a succession of raids on white farmers throughout the northeastern districts of the country and resulted in several casualties among the security forces. The propaganda value of these raids, coupled with the success of ZANLA's politicisation campaign, denied intelligence to the security forces and furnished more recruits for the insurgents. In response, the Rhodesian security forces began coordinating operations in Mozambique with the Portuguese Army to intercept ZANLA insurgents before they could cross the border. The practical alliances between ZIPRA and MK, and later ZANLA and FRELIMO, prompted Rhodesia to look increasingly towards South Africa and Portugal for active assistance.
== Reactive Histiocytosis == Systemic Histiocytosis (SH) was originally recognized in closely related Bernese Mountain Dogs. SH is a generalized histiocytic proliferative disease with a marked tendency to involve skin, ocular and nasal mucosa, and peripheral lymph nodes. The disease predominately affects young to middle aged male dogs (2–8 years), although cases in females have been observed. SH has been observed in other breeds less commonly (e.g. Irish Wolfhounds, Basset Hounds and others). Clinical signs vary with the severity and extent of the disease and include anorexia, marked weight loss, stertorous respiration and conjunctivitis with marked chemosis. Multiple cutaneous nodules may be distributed over the entire body, but are especially prevalent in the scrotum, nasal apex, nasal planum and eyelids. Peripheral lymph nodes are often palpably enlarged. The disease course may be punctuated by remissions and relapses, which may occur spontaneously especially early in the disease course. In severe disease, lesions become persistent and do not respond to immunosuppressive doses of corticosteroids. Cutaneous histiocytosis (CH) is a histiocytic proliferative disorder that primarily involves skin and subcutis and does not extend beyond the local draining lymph nodes. CH occurs in a number of breeds. Evidence of spread beyond the skin would invoke the diagnosis of SH, a closely related disorder. Lymphadenopathy has not been emphasized in published reports, and has only been documented in a small number of our cases.
=== Heart and blood vessels === Bradycardia: Fentanyl decreases the heart rate by increasing vagal nerve tone in the brainstem, which increases the parasympathetic drive. Vasodilation: It also vasodilates arterial and venous blood vessels through a central mechanism, primarily by slowing down vasomotor centers in the brainstem. To a lesser extent, it does this by directly affecting blood vessels. This is much more profound in patients who have an already increased sympathetic drive, like patients who have high blood pressure or congestive heart failure. It does not affect the contractility of the heart when regular doses are administered.
Sources: en.wikipedia.org
No. It is a synthetic analogue carrying four amino acid changes, a lactam ring and an amidated C-terminus. The natural hormone is a linear thirteen-amino-acid peptide processed from proopiomelanocortin.
Afamelanotide is the linear analogue [Nle4-D-Phe7]-alpha-MSH, sometimes called melanotan I, while melanotan II is cyclic and carries three further substitutions. The two are distinct molecules and are not interchangeable in analytical testing.
Binding to the four melanocortin receptor subtypes is well documented in vitro. The relative contribution of each subtype to whole-body effects in humans is far less certain.
It is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone, containing seven amino acids with a lactam ring and a D-configured phenylalanine residue. It is supplied as a lyophilised powder for laboratory research.