mass spectrometry raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
This page was last updated on 2025-08-01 and is reviewed periodically as new material appears.
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.
Human data remain limited and mostly short-term. Reports describe small trials and observational accounts rather than large controlled studies, so questions about dose-response relationships and long-term effects on melanocytes stay open. Whether repeated exposure alters naevus behaviour is not settled in the published record. Researchers also note that self-administered use outside clinical settings makes actual exposure difficult to quantify. Statements about efficacy and safety should therefore be read as preliminary rather than established.
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.
Regulatory treatment varies by country. In the United States the peptide is not approved as a medicine, and products offered for human use may be treated as unapproved new drugs; some states also restrict sale. Australia, the United Kingdom, and European Union member states apply comparable restrictions to unapproved peptide products. Border agencies have seized shipments labelled as research chemicals. Classification may change over time, and the legal position for personal importation is not clearly settled in most published guidance.
| 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.
Released in May 2016, Battleborn was a cooperative first-person shooter video game with multiplayer online battle arena (MOBA) elements. Battleborn takes place in a space fantasy setting where multiple races contest possession of the universe's last star. Players select one of multiple pre-defined heroes, customized with passive abilities gained through end-of-mission loot, to complete both player-vs-player and player-vs-environment events. During such events, characters are leveled up through their "Helix tree", granting one of two abilities at each level. It was released within a month of Blizzard Entertainment's Overwatch, a hero shooter with similar concepts, and which quickly overshadowed Battleborn. The title went free-to-play in June 2017 and was shut down in January 2021.
=== Intracrines and regenerative Medicine === The discovery of intracrine loops in stem cell regulation has profound implications for regenerative medicine. Because intracrines can establish long-lasting differentiation programs, they offer potential therapeutic targets for tissue regeneration and repair. For example, in cardiac repair, HMGB1 has been shown to enhance the proliferation and differentiation of cardiac stem cells following myocardial infarction, suggesting that modulating intracrine pathways could improve heart regeneration. The ability of certain intracrines to reprogram cells into pluripotent-like states also opens new avenues for regenerative therapies. Oct3/4, Sox2, and Nanog, all of which are involved in maintaining stem cell pluripotency, can potentially be introduced into cells to drive reprogramming without the need for genetic modification. This approach could provide safer and more controlled methods for generating patient-specific stem cells.
The decisive victory of Lieutenant-General Bernard Montgomery's Eighth Army over the Germans and Italians at the Second Battle of El Alamein in October–November 1942 turned the tide of the North African war strongly in favour of the Allies, and did much to revive Allied morale. The Rhodesians of the KRRC took part in the battle as part of the 7th Armoured Division under the XIII Corps, forming part of the initial thrust in the southern sector. The Rhodesian Anti-Tank Battery under Major Guy Savory also fought at El Alamein, supporting the Australian 9th Division as part of the XXX Corps. The fighting around "Thompson's Post" between 1 and 3 November was some of the fiercest Rhodesians took part in during the war. Hoping to knock out the Allied anti-tank guns before counter-attacking, the Germans concentrated intense artillery fire on the Australian and Rhodesian guns before advancing 12 Panzer IV tanks towards the weakest point of the Australian line. The Australian six-pounders had been largely disabled by the bombardment but most of the Rhodesian guns remained operational. The Rhodesian gunners disabled two Panzers and seriously damaged two more, compelling an Axis retreat, and held their position until being relieved on 3 November. One Rhodesian officer and seven other ranks were killed and more than double that number were wounded. For his actions at Thompson's Post, Sergeant J A Hotchin received the Distinguished Conduct Medal; Lieutenants R J Bawden and H R C Callon won the Military Cross and Trooper P Vorster the Military Medal.
Sources: en.wikipedia.org
The rate of change of NB, that is dNB/dt, is related to the changes in the amounts of A and B, NB can increase as B is produced from A and decrease as B produces C. Re-writing using the previous results:
=== Production of acrylonitrile === Currently, most acrylonitrile (90% in 2008) is produced by the SOHIO method, which is based on the catalytic oxidation of propylene in the presence of ammonia and bismuth phosphomolybdate. However, until 1960 a key production process was addition of hydrogen cyanide to ethylene oxide, followed by dehydration of the resulting cyanohydrin:
Many macromolecules are synthetic polymers (plastics, synthetic fibers, and synthetic rubber). Polyethylene is produced on a particularly large scale such that ethylenes are the primary product in the chemical industry. Examples or different types of synthetic macromolecules include:
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.