Everything below concerns cyclic heptapeptide. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2026-08-01. Numbers and descriptions here follow the published literature rather than marketing material.
Melanotan-2 is handled in the laboratory as a lyophilised powder that dissolves readily in water, dimethyl sulfoxide and dimethylformamide, with limited solubility in ethanol. Stock solutions prepared in an organic solvent often precipitate when diluted into aqueous buffer, so gradual dilution with mixing is standard practice. The peptide carries a tryptophan residue and a histidine residue, both sensitive to oxidation and to alkaline conditions. Working solutions are therefore kept near neutral to slightly acidic pH, protected from light, and consumed within the same working session whenever that is practical.
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.
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.
Regulatory treatment varies between countries. Several national medicines agencies have classified the peptide as unapproved, and customs authorities in some jurisdictions seize shipments on that basis. A few jurisdictions channel supply through prescription-only frameworks that do not list the substance by name. Because the material circulates mainly through online vendors, composition and purity are rarely verified before sale. Surveys of unapproved peptide products have reported labels that did not match measured content in a substantial fraction of samples.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white powder | Lyophilised material may be hygroscopic |
| Solubility class | Soluble in water, DMSO and DMF | Dilution into aqueous buffer can cause precipitation |
| Storage of solid | Minus 20 degrees C, desiccated, dark | Aliquot to limit repeated opening of the vial |
| Storage of solution | Minus 20 to minus 80 degrees C, aliquoted | Avoid repeated freeze-thaw cycles |
| Identity method | Reversed-phase HPLC with mass spectrometry | Retention time and mass are checked together |
Freeze-dried melanotan-2 is normally kept as a desiccated powder at minus twenty degrees Celsius or lower, shielded from light and moisture. Peptides of this size degrade through hydrolysis, oxidation and deamidation, and each pathway accelerates as temperature and water activity rise. Repeated freeze-thaw cycles promote aggregation and loss of material, so aliquoting a stock solution before freezing is standard laboratory practice. Once dissolved, the solution is markedly less stable than the powder. In laboratory work, solutions are generally refrigerated and used within days rather than kept for months.
Identity and purity are usually assessed by reversed-phase high-performance liquid chromatography, which separates the target peptide from truncated or oxidised impurities. Mass spectrometry, most often coupled to liquid chromatography, confirms molecular mass and detects substitutions that chromatography alone may miss. Amino acid analysis and peptide mapping supply additional structural evidence, while nuclear magnetic resonance is reserved for full structural confirmation. Laboratories that examine samples sold online report wide variation in actual content, with some vials containing little or none of the labelled material.
Melanotan-2 appears on the World Anti-Doping Agency prohibited list within the peptide hormone class, and several national regulators treat it as an unapproved prescription substance. Some countries restrict importation or sale for personal use. Because the compound is widely traded as a research chemical, the practical legal picture differs between jurisdictions and shifts over time. Human safety data covering long periods are limited, and whether repeated pigmentation changes carry any lasting risk to melanocytes 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.
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.
Protactinium(IV) forms a tetrahedral complex tetrakis(cyclopentadienyl)protactinium(IV) (or Pa(C5H5)4) with four cyclopentadienyl rings, which can be synthesized by reacting protactinium(IV) chloride with Be(C5H5)2. One ring can be substituted with a halide atom. Another organometallic complex is the golden-yellow bis(π-cyclooctatetraene) protactinium, or protactinocene (Pa(C8H8)2), which is analogous in structure to uranocene. There, the metal atom is sandwiched between two cyclooctatetraene ligands. Similar to uranocene, it can be prepared by reacting protactinium tetrachloride with dipotassium cyclooctatetraenide (K2C8H8) in tetrahydrofuran.
U.S. Navy Fleet Admiral Hyman G. Rickover, nicknamed "Father of the Nuclear Navy", was forcibly retired four days after his 82nd birthday. Admiral Rickover's 63 years of active service in the U.S. Navy made him the longest-serving member of the U.S. armed forces. The fifth annual Charity Shield game of Australia's National Soccer League was played, matching the 1981 first-place finisher (Sydney City and the NSL Cup winner, the Brisbane Lions. Sydney City won, 3 to 1. Born: Marta Nieto, Spanish film and television actress known for the 2019 film Madre; in Murcia Jena Lee Nardella, American activist for clean water and ending AIDS in Africa; in Woodland, California Helena Paparizou, Swedish-born Greek singer; in Borås, Västergötland Died: Agnes Sligh Turnbull, 93, American novelist Kuljeet Singh and Jasbir Singha, convicted kidnappers and murderers who had killed two teenagers in India in 1978, were hanged at the Tihar Jail in New Delhi. Captain Cyril Gourley, 89, British Army officer and recipient of the Victoria Cross.
BRINP2-related peptide (BRP) is a synthetic peptide that displays anti-obesity action similar to semaglutide. It does this without significant muscle loss or anxiety and without impacting bowel movement when administered to mice and pigs. BRP primarily stimulates receptors in the hypothalamus and is consistent with GPCR activation leading to stimulation of CREB and Fos activity in neuronal cells. Researchers at Stanford University derived BRP from the BRINP2 protein, corresponding to amino acids 386–397 (THRILRRLFNLC) of BRINP2. This 12-amino acid peptide is flanked by KK and KR recognition sites within the BRINP2 protein, which are cleaved by proprotein convertases to release the peptide. BRP has been detected in human cerebrospinal fluid by mass spectrometry. Additionally, BRP undergoes C-terminal amidation, resulting in the sequence THRILRRLFNLC-NH2. The non-amidated form of the peptide is inactive.
== Food additive == Diglycerides, generally in a mix with monoglycerides (E471), are common food additives largely used as emulsifiers. The values given in the nutritional labels for total fat, saturated fat, and trans fat do not include those present in mono- and diglycerides. They often are included in bakery products, beverages, ice cream, peanut butter, chewing gum, shortening, whipped toppings, margarine, confections, and some snack products, such as Pringles.
Sources: en.wikipedia.org
== Further reading == Ahnström, M. L.; Seyfert, M.; Hunt, M. C.; Johnson, D. E. (2006). "Dry aging of beef in a bag highly permeable to water vapor". Meat Science. 73 (4): 674–679. doi:10.1016/j.meatsci.2006.03.006. PMID 22062568. DeGeer, S. L.; Hunt, M. C.; Bratcher, C. L.; Crozier-Dodson, B. A.; Johnson, D. E.; Stika, J. F. (2009). "Effects of dry aging of bone-in and boneless strip loins using two aging processes for two aging times". Meat Science. 83 (4): 768–774. doi:10.1016/j.meatsci.2009.08.017. PMID 20416624.
== Side effects == The most common side effects affecting more than 5% of patients are headache, upper respiratory tract infection, abdominal pain, diarrhea, rash, alanine aminotransferase increase, nasal congestion, blood creatine phosphokinase increase, aspartate aminotransferase increase, rhinorrhea, rhinitis, influenza, sinusitis, and blood bilirubin increase.
In March 2020, the release of 15.ai, a free web application created by an anonymous MIT researcher that could generate convincing character voices using minimal training data, was one of the earliest publicly available uses for generative AI. The platform is credited as the first mainstream service for audio deepfakes. In 2021, DALL-E, a closed-source transformer-based generative model developed by OpenAI, drew widespread attention to text-to-image generation. Other projects, including open-source approaches such as VQGAN+CLIP and DALL·E Mini (later renamed Craiyon), made similar systems more accessible to the public. Dream by Wombo was released at the end of 2021, followed by the releases of Midjourney and Stable Diffusion in 2022. In November 2022, ChatGPT was released to the public. By 2023, it popularized generative AI for general-purpose text-based tasks.
Sources: en.wikipedia.org
Purity is normally stated as an area percentage from high-performance liquid chromatography, for example ninety-five or ninety-eight percent. That figure describes the proportion of ultraviolet-absorbing material eluting as the main peak. It says nothing about water content, counterions, residual solvents or mass fraction of the peptide itself.
Peptides are commonly isolated as acetate or trifluoroacetate salts, and the counterion contributes to total mass. Two vials with identical peptide content can therefore differ in weight and in measured response. Residual trifluoroacetate is also relevant in cell-based work because it can influence membrane behaviour.
Degradation products are often closely related to the parent molecule, making them hard to resolve with a single method. Counterion variability adds a further source of scatter between laboratories. Because no pharmacopoeial monograph exists for melanotan-2, groups rely on method-specific validation rather than a shared reference standard.
No. No major regulatory agency has granted a marketing authorisation for melanotan II as a medicine. Products sold under this name are generally presented as laboratory reagents and are not subject to the batch-release testing applied to approved drugs.