Everything below concerns MC1R. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2026-07-06. Where a claim depends on a specific study, the study is described rather than over-claimed.
Melanotan II is a synthetic cyclic heptapeptide that acts as an agonist at melanocortin receptors. It was designed as a structural analogue of alpha-melanocyte-stimulating hormone, the endogenous peptide involved in pigment production. The analogue carries a lactam bridge that constrains the ring and slows enzymatic breakdown relative to the native hormone. In research literature it appears under several abbreviations, and naming conventions are not fully standardized. Published descriptions usually place it within the broader melanocortin agonist family.
Receptor binding at MC1R on melanocytes raises intracellular cyclic AMP and increases expression of tyrosinase and related enzymes. The downstream result is greater synthesis of eumelanin, the dark pigment, without ultraviolet exposure acting as the trigger. The compound is not selective, however, and also engages MC3R, MC4R and MC5R, which are expressed in the central nervous system and elsewhere. That lack of selectivity is the explanation usually offered for effects reported outside pigmentation, including appetite suppression and nausea. Selectivity remains a central theme in comparative studies of related peptides.
Lyophilised melanotan-2 is supplied as a solid, which is more stable than a solution. The material is hygroscopic, so weighing is done quickly, in low humidity, with the container kept sealed. Reconstitution usually uses water for injection or bacteriostatic water, added down the wall of the vial to limit foaming. A reconstituted solution is held at 2 to 8 °C and kept away from light. Repeated freezing and thawing of the same vial is avoided because ice crystal formation and concentration effects degrade the peptide.
Reversed-phase high-performance liquid chromatography is the routine method for purity assessment. Peptides absorb near 214 nm because of the peptide bond, and a gradient of acetonitrile in water separates the intact peptide from deletion sequences, oxidised products, and earlier-eluting fragments at neutral pH. Electrospray ionisation mass spectrometry provides an orthogonal check: the measured mass must agree with the theoretical value. Amino acid analysis and peptide mapping confirm structure but are used less often. Reference standards remain scarce because the peptide is not described in any pharmacopoeia.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic cyclic heptapeptide | Melanocortin receptor agonist |
| Molecular formula | C50H69N15O9 | Neutral form, mass near 1024.2 g/mol |
| Primary targets | MC1R, MC3R, MC4R, MC5R | Binding is non-selective across subtypes |
| Related compounds | Alpha-MSH, melanotan I, afamelanotide | Structurally or functionally related peptides |
| Common abbreviations | MT-II, MT-2 | Naming in the literature is not uniform |
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.
Lyophilized peptide powder is generally stored frozen, protected from light and moisture. Tryptophan residues are susceptible to oxidation, and the lactam bridge can hydrolyze under strongly acidic or basic conditions. Solutions prepared for laboratory work degrade faster than dry powder, and repeated freeze-thaw cycles accelerate loss. Common practice is to aliquot solutions before freezing and to avoid alkaline buffers. Reported stability windows vary with concentration, buffer, and temperature, so exact shelf lives are method-specific rather than universal.
Regulatory status differs by country, and in many places supplying the compound for human consumption is unlawful. Vendors frequently label material as intended for research use only, a designation that shifts stated purpose but does not create a legal pathway for personal use. Certificates of analysis accompanying such products vary widely in detail and provenance. Third-party testing exists but is voluntary, and results are rarely linked to a specific lot in a publicly verifiable way.
Thus, the person's blood clots too readily, and he is perpetually at an increased risk for thrombosis. Individuals heterozygous for the Factor VLeiden mutation carry a risk of venous thrombosis 5–7 times higher than in the general population. Homozygous subjects have a risk 80 times higher. This mutation is also the most common hereditary risk for venous thrombosis among Caucasians. Around 5% of APC resistance are not associated with the above mutation and Factor VLeiden. Other genetic mutations cause APC resistance, but none to the extent that Factor VLeiden does. These mutations include various other versions of Factor V, spontaneous generation of autoantibodies targeting Factor V, and dysfunction of any of APC's cofactors. Also, some acquired conditions may reduce the efficacy of APC in performing its anticoagulative functions. Studies suggest that between 20% and 60% of thrombophilic patients suffer from some form of APC resistance. Warfarin necrosis is an acquired protein C deficiency due to treatment with warfarin, which is a vitamin K antagonist and an anticoagulant itself. However, warfarin treatment may produce paradoxical skin lesions similar to those seen in purpura fulminans. A variant of this response presents as venous limb gangrene when warfarin is used to treat deep vein thrombosis associated with cancer. In these situations, warfarin may be restarted at a low dosage to ensure that the protein C deficiency does not present before the vitamin K coagulation factors II, IX and X are suppressed.
R = universal gas constant m = number of occupied lattice sites per molecule (for polymer solutions m1 is approximately equal to the degree of polymerization and m2=1) φ = volume fraction of the polymer and the solvent, respectively χ = interaction parameter A consequence of the Flory-Huggins theory is, for instance, that the UCST (if it exists) increases and shifts into the solvent-rich region when the molar mass of the polymer increases. Whether a polymer shows LCST and/or UCST behavior can be derived from the temperature-dependence of the interaction parameter (see figure). The interaction parameter not only comprises enthalpic contributions but also the non-ideal entropy of mixing, which again consists of many individual contributions (e.g., the strong hydrophobic effect in aqueous solutions). For these reasons, classical Flory-Huggins theory cannot provide much insight into the molecular origin of miscibility gaps.
=== Congress === In response to the investigation announcement, Republican U.S. Senator Thom Tillis, who sits on the Senate Banking Committee, announced that he would oppose any Federal Reserve nomination (including for the vacancy of Powell's seat as chair in May 2026) until the legal matter was resolved, stating: "If there were any remaining doubt whether advisers within the Trump Administration are actively pushing to end the independence of the Federal Reserve, there should now be none. It is now the independence and credibility of the Department of Justice that are in question". Tillis subsequently suggested that he would not support the nomination of National Economic Council Director Kevin Hassett as Federal Reserve Chair to succeed Powell in light of Hassett's past relationship with Trump. Hassett has stated that he is not involved in the investigation, but has stated that he supports it even though he does not expect findings of wrongdoing. Trump later made comments suggesting he would not appoint Hassett to replace Powell, leading to speculation that former Federal Reserve Governor Kevin Warsh had become the leading candidate rather than Hassett, current Federal Reserve Governor Christopher Waller, or Governor Michelle Bowman. Republican Senator Lisa Murkowski supported Tillis' proposal to block all Federal Reserve nominations in response to the investigation, while Susan Collins expressed concern that the investigation was launched in response to White House demands on the central bank's interest rate decisions.
Sources: en.wikipedia.org
=== Epitope databases === MHCBN: A database of MHC/TAP binder and T-cell epitopes Bcipep: A database of B-cell epitopes SYFPEITHI — First online database of T cell epitopes IEDB — Database of T and B cell epitopes with annotation of recognition context — NIH funded ANTIJEN — T and B cell epitope database at the Jenner institute, UK IMGT/3Dstructure-DB — Three-dimensional structures of B and T cell epitopes with annotation of IG and TR — IMGT, Montpellier, France SEDB: A Structural Epitope Database — Pondicheery University, DIT funded Epitopes at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
=== Separating-funnel method === In this method the solid particles present into the two immiscible liquids can be easily separated by suspending those solid particles directly into these immiscible or somewhat miscible liquids.
An ion-exchange resin such as chelex 100, which contains chelating ligands bound to a polymer, can be used in water softeners and in chromatographic separation techniques. In solvent extraction the formation of electrically neutral complexes allows cations to be extracted into organic solvents. For example, in nuclear fuel reprocessing uranium(VI) and plutonium(VI) are extracted into kerosene as the complexes [MO2(TBP)2(NO3)2] (TBP = tri-n-butyl phosphate). In phase-transfer catalysis, a substance which is insoluble in an organic solvent can be made soluble by addition of a suitable ligand. For example, potassium permanganate oxidations can be achieved by adding a catalytic quantity of a crown ether and a small amount of organic solvent to the aqueous reaction mixture, so that the oxidation reaction occurs in the organic phase. In all these examples, the ligand is chosen on the basis of the stability constants of the complexes formed. For example, TBP is used in nuclear fuel reprocessing because (among other reasons) it forms a complex strong enough for solvent extraction to take place, but weak enough that the complex can be destroyed by nitric acid to recover the uranyl cation as nitrato complexes, such as [UO2(NO3)4]2− back in the aqueous phase.
Sources: en.wikipedia.org
In the lead-up to his second inauguration, Trump proposed plans and ideas that would expand the United States' political influence and territory. It has been characterized as a revival of the Monroe Doctrine. The last territory acquired by the United States was in 1947 when the Mariana, Caroline, and Marshall Islands were acquired.
=== Magnesium sulfate overdose === It is also used to counteract an overdose of Epsom salts magnesium sulfate, which is often administered to pregnant women in order to prophylactically prevent seizures (as in a patient experiencing preeclampsia). Magnesium sulfate is no longer given to pregnant women who are experiencing premature labor in order to slow or stop their contractions (other tocolytics are now used instead due to better efficacy and side effect profiles). Excess magnesium sulfate results in magnesium sulfate toxicity, which results in both respiratory depression and a loss of deep tendon reflexes (hyporeflexia).
The other settings were available to block out interference, but did so by also blocking some of the signal which reduced the overall sensitivity of the system. The output of the mixer was sent to the Y-axis deflection plates in a specially designed high-quality CRT. For reasons not well explained in the literature, this was arranged to deflect the beam downward with increasing signal. When combined with the X-axis signal from the time base generator, echoes received from distant objects caused the display to produce blips along the display. By measuring the centre point of the blip against a mechanical scale along the top of the display, the range to the target could be determined. This measurement was later aided by the addition of the calibrator unit or strobe, which caused additional sharp blips to be drawn every 10 miles (16 km) along the display. The markers were fed from the same electronic signals as the time base, so it was always properly calibrated.
In 1939, at the Sir William Dunn School of Pathology at the University of Oxford, Ernst Boris Chain drew the attention of the professor in charge of the school, the Australian scientist Howard Florey, to Fleming's largely forgotten 1929 paper. They decided that the study of antibacterial substances produced by micro-organisms might be a fruitful avenue of research. Florey led an interdisciplinary research team that included Edward Abraham, Mary Ethel Florey, Arthur Duncan Gardner, Norman Heatley, Margaret Jennings, Jean Orr-Ewing and Gordon Sanders. Each member of the team tackled a particular aspect of the problem in their area of expertise, with simultaneous research along different lines building up a complete picture. This sort of collaboration was practically unknown in the United Kingdom at the time. Three sources were initially chosen for investigation: Bacillus subtilis, Trueperella pyogenes and penicillin. "[The possibility] that penicillin could have practical use in clinical medicine", Chain later recalled, "did not enter our minds when we started our work on penicillin." The broad subject area was deliberately chosen as one requiring long-term funding. Florey approached the Medical Research Council (MRC) for support in September 1939. The secretary of the council, Edward Mellanby authorized the project, allocating £250 (equivalent to £14,000 in 2025) to launch the project, with £300 for salaries (equivalent to £17,000 in 2025) and £100 for expenses (equivalent to £6,000 in 2025) per annum for three years.
Sources: en.wikipedia.org
It is a synthetic cyclic heptapeptide and a non-selective melanocortin receptor agonist. Structurally it is modelled on alpha-melanocyte-stimulating hormone, a peptide that occurs naturally in the body.
Activation of MC1R increases pigment synthesis independently of ultraviolet exposure, which is the mechanism usually cited for darkening without sun exposure. Ultraviolet light still influences skin response through separate biological pathways.
Because the peptide binds several melanocortin receptor subtypes, its effects are not confined to pigmentation. This complicates interpretation of both intended and unintended outcomes reported in studies.
Low temperature slows hydrolysis and oxidation, the two main routes by which the peptide backbone and side chains are modified. A lyophilised powder stored at −20 °C is more stable than one kept at room temperature, and once the material is dissolved the degradation rate rises, making refrigeration more important.