melanocortin receptors 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 2026-02-06. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
Structurally, Melanotan-2 retains the core recognition motif of alpha-melanocyte-stimulating hormone while adding a lactam bridge that links two side chains and constrains the molecule into a ring. This modification lowers susceptibility to enzymatic degradation. The compound acts as an agonist at melanocortin receptors, particularly subtypes associated with melanin production. Because the same receptor family influences several physiological processes, researchers note that its activity is not confined to pigmentation alone. Receptor selectivity continues to be examined in published studies.
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.
| 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 |
Pharmacologically, melanotan-2 behaves as a non-selective agonist across the melanocortin receptor family. Binding at MC1R on dermal melanocytes promotes eumelanin synthesis, which underlies the tanning response described in early human work. Activity at the centrally expressed MC4R receptor is associated with reported effects on appetite and erectile function. Because the peptide does not discriminate strongly among receptor subtypes, attributing any single observed effect to one receptor pathway is generally not possible without selective antagonists or receptor knockout models.
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.
Published human data come mostly from small, short studies rather than large controlled trials. Reported outcomes include increased skin pigmentation and, in some reports, effects on appetite and libido, but sample sizes are small and follow-up is limited. Whether long-term use produces durable pigment changes or adverse effects is not established. Because products sold outside pharmacies are not standardized, the actual content of any given vial is often unknown. Independent testing of such material is uncommon.
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.
=== Drift tube ion mobility spectrometry === Drift tube ion mobility spectrometry (DTIMS) measures how long a given ion takes to traverse a given length in a uniform electric field through a given atmosphere. In specified intervals, a sample of the ions is let into the drift region; the gating mechanism is based on a charged electrode working in a similar way as the control grid in triodes works for electrons. For precise control of the ion pulse width admitted to the drift tube, more complex gating systems such as a Bradbury–Nielsen or a field switching shutter are employed. Once in the drift tube, ions are subjected to a homogeneous electric field ranging from a few volts per centimetre up to many hundreds of volts per centimetre. This electric field then drives the ions through the drift tube where they interact with the neutral drift molecules contained within the system and separate based on the ion mobility, arriving at the detector for measurement. Ions are recorded at the detector in order from the fastest to the slowest, generating a response signal characteristic for the chemical composition of the measured sample. The ion mobility K can then be experimentally determined from the drift time tD of an ion traversing within a homogeneous electric field the potential difference U in the drift length L.
=== Evaporation === Evaporation is used to pre-concentrate, increase the solid content, change the color, and reduce the water content of food and liquid products. This process is mostly seen when processing milk, starch derivatives, coffee, fruit juices, vegetable pastes and concentrates, seasonings, sauces, sugar, and edible oils. Evaporation is also used in food dehydration processes. The purpose of dehydration is to prevent the growth of molds in food, which only build when moisture is present. This process can be applied to vegetables, fruits, meats, and fish, for example.
The Open Insulin Project is a community of researchers and advocates working to develop an open-source protocol for producing insulin that is affordable, has transparent pricing, and is community-owned.
Steroid hormones are transported through the blood by being bound to carrier proteins—serum proteins that bind them and increase the hormones' solubility in water. Some examples are sex hormone-binding globulin (SHBG), corticosteroid-binding globulin, and albumin. Most studies say that hormones can only affect cells when they are not bound by serum proteins. In order to be active, steroid hormones must free themselves from their blood-solubilizing proteins and either bind to extracellular receptors, or passively cross the cell membrane and bind to nuclear receptors. This idea is known as the free hormone hypothesis. This idea is shown in Figure 1 to the right.
=== Horny goat weed === Horny goat weed (Epimedii herba) is used in Chinese folk medicine. It was thought to be useful for treating medical conditions and improving sexual desire, sexual pleasure, and/or sexual behavior. Horny goat weed contains icariin, a flavanol glycoside. Its exotic name comes from the tendency of goats in the region to seek out this weed. Once farmers saw its effects on the goat population they began to use it to increase the number of workers on their farms.
Sources: en.wikipedia.org
== DHIS2 software == As a digital solution for data collection and management, DHIS2 can be used for aggregate data (e.g. routine health facility data, staffing, equipment, infrastructure, population estimates, etc.), event data (e.g. disease outbreaks, survey/audit data, patient satisfaction surveys, etc.), and individual-level longitudinal data (e.g. vaccination records, lab sample collection and testing, patient treatment and follow-up, student progress, etc.). The system supports the capture of data linked to any level in an organizational hierarchy at any data collection frequency. DHIS2 includes built-in tools for analytics, including dashboards, charts, pivot tables and maps, as well as data validation and data quality features. It also includes tools to support collaborative data use, such as sharing, commenting and interpretation. The DHIS2 platform can be extended with custom applications (which can be published and shared through the DHIS2 App Hub) or integrated with third-party software or external data sources through the open web API. DHIS2 supports health data standards such as FHIR, SNOMED GPS, LOINC, and ICD-11, as well as the generic ADX format for aggregate data exchange. The DHIS2 data model and platform are generic by design, not specifically tailored to the health context, to facilitate the application of DHIS2 to a variety of use cases. DHIS2 is a web-based platform. The core software and database are hosted on a server, which can be either physically located in the country of ownership or cloud-based.
The potential of epitaxial graphene on SiC for metrology has been shown since 2010, displaying quantum Hall resistance quantization accuracy of three parts per billion in monolayer epitaxial graphene. Over the years precisions of parts-per-trillion in the Hall resistance quantization and giant quantum Hall plateaus have been demonstrated. Developments in the encapsulation and doping of epitaxial graphene have led to the commercialization of epitaxial graphene quantum resistance standards. Novel uses for graphene continue to be researched and explored. One such use is in combination with water-based epoxy resins to produce anticorrosive coatings. The van der Waals nature of graphene and other two-dimensional (2D) materials also permits van der Waals heterostructures and integrated circuits based on Van der Waals integration of 2D materials. Graphene is utilized in detecting gasses and chemicals in environmental monitoring, developing highly sensitive biosensors for medical diagnostics, and creating flexible, wearable sensors for health monitoring. Graphene's transparency also enhances optical sensors, making them more effective in imaging and spectroscopy.
== Relation to fertility == The characteristics measured by semen analysis are only some of the factors in semen quality. One source states that 30% of men with a normal semen analysis actually have abnormal sperm function. Conversely, men with poor semen analysis results may go on to father children. In NICE guidelines, mild male factor infertility is defined as when two or more semen analyses have one or more variables below the 5th percentile, and confers a chance of pregnancy occurring naturally through vaginal intercourse within two years similar to people with mild endometriosis.
Gas: Volatile vapors often used for fuel. Charcoal: The solid carbon residue remaining in the kiln. Liquid distillate: The condensed vapors that form the basis for further refinement. Separation of the liquid: The liquid distillate naturally separates (or is processed) into two distinct layers:
Sources: en.wikipedia.org
Since Operation Inherent Resolve began, U.S. airstrikes have been supported by Green Beret adviser teams, helping stop the advances of ISIL. Green Berets from the 5th SFG deployed to Jordan in support of OIR. On November 4, 2016, a small convoy carrying Green Berets was returning to the base after a training exercise when a Jordanian guard, after waving the first vehicle through the entry control point at the base, then opened fire on the second vehicle killing 2 Green Berets, U.S. troops from the vehicle behind opened fire, another Green Beret was killed but a fourth, who was wounded, shot the Jordanian, severely wounding him.
Periostin (POSTN, PN, or osteoblast-specific factor OSF-2) is a protein that in humans is encoded by the POSTN gene. Periostin functions as a ligand for alpha-V/beta-3 and alpha-V/beta-5 integrins to support adhesion and migration of epithelial cells. Periostin is a gla domain vitamin K dependent factor.
L.L. Bartlett (2010). "Cold Case". A Jeff Resnick Mystery. ASIN B003I84LYW. Polaris Press. This short story inspired the fourth Jeff Resnick book, Bound by Suggestion. Philip Gourevitch (2002). A Cold Case. Macmillan. ISBN 978-0312420024. True crime. Julia Platt Leonard (2012). Cold Case. Aladdin. ISBN 978-1442420090. A children's book/mystery. Nichelle Walker (2012). Cold Case Love. NWHoodTales Publishing. ISBN 978-0979402838. An urban novel. Richard H. Walton, ed. (2006). Cold Case Homicides: Practical Investigative Techniques. CRC Press. ISBN 084932209X. An education and reference book. Stephen White (2001). Cold Case. Alan Gregory. ISBN 978-0525945260. Kate Wilhelm (2009). Cold Case. Barbara Holloway Novels. ISBN 978-0778326656.
== Other uses == Some Native American tribes use the hard outer shell of the pine nut as a bead for decorative purposes in traditional regalia and jewelry. In the Great Basin area of the US, collecting pine nuts is a protected right through state law and treaty. In northern California, pine nuts are collected from the grey pine or bull pine. Tribes burn designs into the hard shell, reflecting the same design they use in baskets; however, they are often left blank or burned to blacken. These are more often used in women's regalia and jewelry.
Nicotinate riboside kinase (EC 2.7.1.173, ribosylnicotinic acid kinase, nicotinic acid riboside kinase, NRK1) is an enzyme that in humans is encoded by the genes NMRK1 and NMRK2. Its systematic name ATP:beta-D-ribosylnicotinate 5-phosphotransferase, and it catalyses the following chemical reaction:
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 and an analogue of alpha-melanocyte-stimulating hormone. The molecule is produced by chemical synthesis rather than extracted from a biological source.