If you have been reading about Related impurities and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Last reviewed on 2026-05-10. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
Melanocytes are the pigment-producing cells of the skin, and they carry melanocortin-1 receptors on their surface. When the receptor is activated, cyclic adenosine monophosphate rises inside the cell and raises the activity of enzymes such as tyrosinase, which increases melanin output. Melanotan-2 binds melanocortin-1 receptors in vitro and in animal models, and this binding is generally described as the basis for the tanning effect. Other receptors account for different effects: melanocortin-4 receptors contribute to appetite and erectile signalling, while melanocortin-3 and melanocortin-5 receptors contribute to energy balance and exocrine function.
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.
Lyophilised peptide powder is comparatively stable when kept dry, cold and protected from light. Once dissolved, the molecule is exposed to hydrolysis, oxidation and microbial growth, and degradation accelerates at higher temperatures and in alkaline solution. Repeated freeze-thaw cycles concentrate solutes and promote aggregation. Handling guidance for research peptides commonly clusters around freezer temperatures for powder and short refrigerated use for reconstituted solutions, with pH control and sterile technique applied throughout.
Verification of a purchased sample requires documentation linking a batch to a certificate of analysis, and that document should be read for the methods used rather than the headline purity figure. A single chromatographic percentage does not establish identity. Independent laboratories can perform identity and content assays, but no such test establishes that a product is suitable for human use. Claims about efficacy rest largely on small, early studies rather than on replicated controlled trials, and that gap remains open.
Identity testing for a cyclic peptide of this size usually relies on reversed-phase high-performance liquid chromatography coupled to mass spectrometry. The mass spectrum confirms molecular weight, while the chromatographic trace indicates the proportion of related impurities. Tandem mass spectrometry can provide sequence-level information when fragmentation data are compared against a reference standard. Nuclear magnetic resonance is sometimes used to confirm the lactam bridge, although it requires more material and greater operator expertise than routine chromatographic methods.
| Property | Value | Notes |
|---|---|---|
| Compound class | Synthetic cyclic heptapeptide | Alpha-MSH analogue containing a D-phenylalanine residue |
| Molecular formula | C50H69N15O9 | Average molecular mass approximately 1024.2 g/mol |
| Appearance | White to off-white lyophilised powder | Normally supplied as a freeze-dried solid in a sealed vial |
| Solubility | Freely soluble in water and polar solvents | Dissolves readily in aqueous buffers and in alcohol-water mixtures |
| Receptor targets | MC1R, MC3R, MC4R, MC5R | Acts as a non-selective melanocortin receptor agonist |
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.
Solid peptide kept dry at minus twenty degrees Celsius, shielded from light and moisture, is generally considered stable for extended periods. Solutions are divided into single-use aliquots and held at minus twenty or minus eighty degrees Celsius, because repeated freeze-thaw cycles promote aggregation and loss of material to container surfaces. Hydrolysis of the backbone and oxidation of tryptophan are the principal degradation routes in aqueous solution, and both accelerate at ambient temperature. Hygroscopic uptake after a vial is opened can also shift the actual mass weighed, which affects any concentration calculated from it.
Routine characterisation relies on reversed-phase high-performance liquid chromatography with ultraviolet detection near 214 nanometres, using a C18 column and a water-acetonitrile gradient containing trifluoroacetic acid. Electrospray ionisation mass spectrometry confirms the expected molecular mass and can reveal truncated or oxidised by-products that co-elute poorly. Sequence and stereochemistry require additional work, such as peptide mapping or amino acid analysis, because a chromatographic purity figure alone does not distinguish a diastereomer from the target peptide. Independent testing of research-grade material frequently shows measured content below the stated label, so a certificate of analysis is best read together with the method that produced it.
=== 2 December === The commander of the SAF's 22nd Infantry Division, Major-General Abdelmajid al-Haj, and an unidentified brigadier general who commanded the SAF's 170th Artillery Brigade were killed in an RSF ambush while retreating from Babanusa towards Heglig. The SAF retook the town of Mabsouta in South Kordofan from the SPLM-N (al-Hilu), which had occupied the area since 2011.
Scarring during healing can create both physical and psychological problems, and is a significant clinical burden. Collagen, for instance, is abnormally organised in scar tissue; collagen in scars is arranged in parallel bundles of collagen fibers, whilst healthy scar free tissue has a "basket weave" structure (Figure 1). The difference in collagen arrangement along with a lack of difference in the dermal tissue when healing has taken place with or without scarring is indicative of regenerative failure of normal skin. Severe scarring resulting from these collagen deposits is known as hypertrophic scarring and is of great concern worldwide with an incidence ranging from 32–72%.
== Use and effects == In his book PiHKAL (Phenethylamines I Have Known And Loved) and other publications, Alexander Shulgin lists thiobuscaline's dose range as 60 to 120 mg orally and its duration as about 8 hours. Its onset is about 1 hour. The effects of thiobuscaline have been reported to include a "benign and beautiful experience which never quite popped into anything psychedelic", subtle threshold effects, a vague awareness of something, being in a "wonderful place spiritually" but with "some dark edges", it being "pleasant, but certainly not psychedelic", and body discomfort. No clear hallucinogenic effects were described. Thiobuscaline is listed as being 4 times more potent as a psychoactive drug than mescaline. Thiobuscaline produced perpetual threshold psychoactive effects that did not further increase across a wide dose range of 35 to 120 mg orally. Shulgin described it as "always the simple and ephemeral catalyst of euphoria without substance and without body". In addition, he said that it could not easily be classified, for instance as a psychedelic or stimulant. Instead, Shulgin likened thiobuscaline to Ariadne (4C-D), which he noted had been called an "antidepressant". He hypothesized that thiobuscaline might be beneficial for treatment of depression in certain people in the exact same way as Ariadne.
In herbal medicine, aqueous extracts of bay laurel have been used as an astringent and salve for open wounds. It is also used in massage therapy and aromatherapy. A folk remedy for rashes caused by poison ivy, poison oak, and stinging nettle is a poultice soaked in boiled bay leaves. The Roman naturalist Pliny the Elder listed a variety of conditions which laurel oil was supposed to treat: paralysis, spasms, sciatica, bruises, headaches, catarrhs, ear infections, and rheumatism.
Sources: en.wikipedia.org
=== Principle and measurement methods === In the U.S., standard methods have been established by the National Institute for Occupational Safety and Health (NIOSH) and another by U.S. OSHA. Each method uses a single component solvent; butanol and hexane cannot be sampled, however, on the same sample matrix using the NIOSH or OSHA method. VOCs are quantified and identified by two broad techniques. The major technique is gas chromatography (GC). GC instruments allow the separation of gaseous components. When coupled to a flame ionization detector (FID) GCs can detect hydrocarbons at the parts per trillion levels. Using electron capture detectors, GCs are also effective for organohalide such as chlorocarbons. The second major technique associated with VOC analysis is mass spectrometry, which is usually coupled with GC, giving the hyphenated technique of GC-MS. Direct injection mass spectrometry techniques are frequently utilized for the rapid detection and accurate quantification of VOCs. PTR-MS is among the methods that have been used most extensively for the on-line analysis of biogenic and anthropogenic VOCs. PTR-MS instruments based on time-of-flight mass spectrometry have been reported to reach detection limits of 20 pptv after 100 ms and 750 ppqv after 1 min. measurement (signal integration) time. The mass resolution of these devices is between 7000 and 10,500 m/Δm, thus it is possible to separate most common isobaric VOCs and quantify them independently.
In 2014 the same team from the Scripps Research Institute reported that they synthesized a stretch of circular DNA known as a plasmid containing natural T-A and C-G base pairs along with the best-performing UBP Romesberg's laboratory had designed, and inserted it into cells of the common bacterium E. coli that successfully replicated the unnatural base pairs through multiple generations. This is the first known example of a living organism passing along an expanded genetic code to subsequent generations. This was in part achieved by the addition of a supportive algal gene that expresses a nucleotide triphosphate transporter which efficiently imports the triphosphates of both d5SICSTP and dNaMTP into E. coli bacteria. Then, the natural bacterial replication pathways use them to accurately replicate the plasmid containing d5SICS–dNaM. The successful incorporation of a third base pair into a living micro-organism is a significant breakthrough toward the goal of greatly expanding the number of amino acids which can be encoded by DNA, thereby expanding the potential for living organisms to produce novel proteins. The artificial strings of DNA do not encode for anything yet, but scientists speculate they could be designed to manufacture new proteins which could have industrial or pharmaceutical uses.
The draining of the Qurna Marshes was an irrigation project in Iraq during and immediately after the war, to drain a large area of marshes in the Tigris–Euphrates river system. Formerly covering an area of around 3,000 km2 (1,200 sq mi), the large complex of wetlands were nearly emptied of water, and the local Shi'ite population relocated, following the war and 1991 uprisings. By 2000, the United Nations Environment Programme estimated that 90% of the marshlands had disappeared, causing desertification of over 7,500 square miles (19,000 km2). The draining occurred in Iraq and to a smaller degree in Iran between the 1950s and 1990s to clear large areas of the marshes. Formerly covering an area of around 20,000 km2 (7,700 sq mi), the large complex of wetlands was 90% drained before the 2003 Invasion of Iraq. The marshes are typically divided into three main sub-marshes, the Hawizeh, Central, and Hammar Marshes and all three were drained at different times for different reasons. Initial draining of the Central Marshes was intended to reclaim land for agriculture but later all three marshes would become a tool of war and revenge. Many international organizations such as the UN Human Rights Commission, the Islamic Supreme Council of Iraq, the Wetlands International, and Middle East Watch have described the project as a political attempt to force the Marsh Arabs out of the area through water diversion tactics.
=== Uptake === Tau protein has been found in the extracellular environment including Cerebrospinal fluid (CSF) and Interstitial fluid (ISF) under physiological and pathological conditions. Low-density lipoprotein receptor-related protein 1 (LRP1) has been shown as the receptor for Tau internalization into cells. However, studying Tau uptake in human neurons revealed that physiological Tau monomers mainly use LRP1 for internalization, while the uptake of pathological Tau aggregates depend on heparan sulfate proteoglycans.
== Treatment == Treatment of hirsutism is indicated when hair growth causes patient distress. The two main approaches to treatment are pharmacologic therapies targeting androgen production/action, and direct hair removal methods including electrolysis and photo-epilation. These may be used independently or in combination.
Sources: en.wikipedia.org
With the university requiring the VCA to introduce its Melbourne Model course structure, necessitating a reduction in the amount of hands-on arts training that students receive, critics feared that future students might be unable to find employment upon graduation. Staff of the former VCA accused the dean, Sharman Pretty, of having "little or no recognition of the need for focused arts training, or any esteem for the arts themselves", and the University of Melbourne of trying to mislead the public about the effects. Students were also fearful a reduction in the quality of education and programs on offer whilst the school remained under the University of Melbourne.
Magnesium has three stable isotopes: 24Mg, 25Mg and 26Mg. All are present in significant amounts in nature (see table of isotopes above). About 79% of Mg is 24Mg. The isotope 28Mg is radioactive and in the 1950s to 1970s was produced by several nuclear power plants for use in scientific experiments. This isotope has a relatively short half-life (21 hours) and its use was limited by shipping times. The nuclide 26Mg has found application in isotopic geology, similar to that of aluminium. 26Mg is a radiogenic daughter product of 26Al, which has a half-life of 717,000 years. Excessive quantities of stable 26Mg have been observed in the Ca-Al-rich inclusions of some carbonaceous chondrite meteorites. This anomalous abundance is attributed to the decay of its parent 26Al in the inclusions, and researchers conclude that such meteorites were formed in the solar nebula before the 26Al had decayed. These are among the oldest objects in the Solar System and contain preserved information about its early history. It is conventional to plot 26Mg/24Mg against an Al/Mg ratio. In an isochron dating plot, the Al/Mg ratio plotted is 27Al/24Mg. The slope of the isochron has no age significance, but indicates the initial 26Al/27Al ratio in the sample at the time when the systems were separated from a common reservoir.
Solid organ transplant recipients After undergoing solid organ transplant (liver, kidney, pancreas, etc.), patients are prescribed immunosuppressive agents, such as tacrolimus or cyclosporine. These medications target CD4 immune cells, suppressing their function. IRIS in these patients is thought to be due to the pro-inflammatory response after withdrawal of immunosuppressants. Common infections associated with IRIS in these patients are cryptococcosis, cytomegalovirus (CMV), and tuberculosis. Neutropenic patients When the absolute neutrophil count (ANC) is less than 500 per microliter, there is an increased risk of fungal and viral opportunistic infections (OI), such as Aspergillus or CMV. While the patient is immunosuppressed, these infections may remain latent and asymptomatic. However, when the ANC improves, the infections may become symptomatic and present as IRIS. Common infections associated with IRIS in these patients are invasive pulmonary aspergillosis and chronic disseminated candidiasis. Postpartum patients During pregnancy, the immune system is relatively suppressed to prevent fetal rejections or miscarriages. In the immediate postpartum period (3 to 6 weeks), this process is reversed, resulting in a relative pro-inflammatory state. There is an increased risk of IRIS during this period. Common infections associated with IRIS in these patients include cryptococcosis, human papillomavirus reactivation, herpes virus, tuberculosis, leprosy, viral hepatitis.
==== Antibody target for animal model of glomerulonephritis ==== Single tail vein intravenous injection of antibody (OX7 mouse monoclonal IgG) against Thy1.1 in rats is used as a standard animal model to produce experimental mesangioproliferative glomerulonephritis which is popularly known in the field of nephrology as antiThy1 GN.
Sources: en.wikipedia.org
No. It is a laboratory-made peptide, while the natural hormone is alpha-melanocyte-stimulating hormone, a longer peptide produced by the pituitary gland and by skin cells. Melanotan-2 mimics only a short active region of that hormone and contains non-natural residues such as D-phenylalanine.
No approved regulatory indication exists in major markets. An approval exists for a different peptide, afamelanotide, which is used for a rare photosensitivity disorder called erythropoietic protoporphyria. Melanotan-2 itself remains a research compound with no cleared clinical role.
Melanocortin-1 receptors on melanocytes are the receptor most closely linked to pigment production. The peptide is not selective, however, and also activates melanocortin-3, melanocortin-4, and melanocortin-5 receptors. That lack of selectivity is the usual explanation offered for both its range of observed effects and its off-target effects.
Mass spectrometry combined with liquid chromatography provides both molecular weight confirmation and a measure of related impurities. Tandem mass spectrometry adds sequence information. A purity percentage reported without a mass measurement does not confirm what the material is.