cyclic heptapeptide 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 2025-08-23. Where a claim depends on a specific study, the study is described rather than over-claimed.
The compound was developed in the late 1980s and early 1990s by academic researchers investigating melanocortin signaling and pigmentation. Early work explored whether synthetic analogs could reproduce effects of the natural hormone under controlled conditions. The molecule never advanced through the full regulatory pathway required for approval as a medicine. From the mid-2000s onward it appeared in unregulated consumer markets, often distributed through informal channels. That gap between research origins and commercial availability shapes how the compound is discussed today.
Melanotan-2 is a synthetic peptide designed as an analog of alpha-melanocyte-stimulating hormone, a signaling molecule produced in the pituitary and skin. Its structure is a linear chain of seven amino acids that folds into a ring through an internal lactam bridge joining two side chains. The compound is sometimes written as MT-II or MEL-2 in informal and commercial contexts. It belongs to the melanocortin peptide family, a group of short signaling molecules that share a conserved core sequence recognized by melanocortin receptors.
Analytical confirmation of identity relies on mass spectrometry, most often coupled to liquid chromatography. Reversed-phase high-performance liquid chromatography separates the peptide from related impurities and provides a purity estimate based on peak area. Electrospray ionization mass spectrometry then confirms the expected molecular mass, while tandem mass spectrometry can map the fragment sequence. For research-grade material, these two techniques together form the standard minimum. Purity figures reported by vendors are frequently not traceable to an independent laboratory.
Independent verification is central to quality control because the compound is not produced under pharmaceutical manufacturing standards. Third-party laboratories can measure purity, identity, residual solvents, and microbial contamination, though the scope of testing varies between services. Reported analyses of vendor samples have shown batch-to-batch variation in peptide content and the presence of truncated or oxidized species. How much of this variation reflects synthesis conditions versus storage and shipping is not well characterized. No harmonized reference standard exists for the material as sold.
| Property | Value | Notes |
|---|---|---|
| Molecular class | Synthetic cyclic heptapeptide | Analog of alpha-MSH with an internal lactam bridge |
| Molecular weight | Approximately 1024 daltons | Free base value; salt forms differ |
| Appearance | White to off-white powder | Usually supplied as a lyophilized solid |
| Solubility | Freely soluble in water | Poorly soluble in nonpolar solvents |
| Typical storage | −20 °C, dry, protected from light | Repeated freeze-thaw cycles degrade peptides |
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.
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.
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.
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.
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.
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.
An extremely important application of serum S100B testing is in the selection of patients with minor head injury who do not need further neuroradiological evaluation, as studies comparing CT scans and S100B levels have demonstrated S100B values below 0.12 ng/mL are associated with low risk of obvious neuroradiological changes (such as intracranial hemorrhage or brain swelling) or significant clinical sequelae. The excellent negative predictive value of S100B in several neurological conditions is due to the fact that serum S100B levels reflect blood–brain barrier permeability changes even in absence of neuronal injury. In addition, S100B, which is also present in human melanocytes, is a reliable marker for melanoma malignancy both in bioptic tissue and in serum.
=== Funding and revenue === In 2023, Breakthrough T1D raised $224 million; of this, 78% went toward programs including research funding, 15% was spent on fundraising, and 7% was spent on administrative costs. Cumulatively, Breakthrough T1D was funding approximately $568 million in T1D research projects worldwide in 2018.
The North American Hetman movement reached the height of its influence around 1937–1938, when it was visited by Danylo Skoropadskyi, the hetman's son and successor. However, the organizations lost their influence during WW2 and in the following years due to internal splits and government investigations into their activity.
== Selected publications == Bounous, G; Molson, JH (2003). "The antioxidant system". Anticancer Research. 23 (2B): 1411–5. PMID 12820403. Kennedy, RS; Konok, GP; Bounous, G; Baruchel, S; Lee, TD (1995). "The use of a whey protein concentrate in the treatment of patients with metastatic carcinoma: A phase I-II clinical study". Anticancer Research. 15 (6B): 2643–9. PMID 8669840. Bounous, Gustavo; Somersall, Allan (April 1999). Breakthrough In Cell-Defense. GOLDENeight Publishing. ISBN 978-1-890412-86-9.
Sources: en.wikipedia.org
Combined with a better understanding of female pelvic floor connective tissue, these ideas would go on to influence surgical approaches for the treatment of uterine prolapse. By the early 20th century, different techniques for vaginal hysterectomies had been described and performed. As a result, post-hysterectomy vaginal vault prolapse became more common and a growing concern for some surgeons, and new techniques to correct this complication were attempted. In 1957, Arthure and Savage of London's Charing Cross Hospital, suspecting that uterine prolapse could not be cured with hysterectomy alone, published their surgical technique of sacral hysteropexy. Their technique is still used in modern practice with the addition of a graft.
== Business segments == Bio-Rad's life science products primarily include instruments, software, consumables, reagents, and content for the areas of cell biology, gene expression, protein purification, protein quantitation, drug discovery and manufacture, food safety, and science education. These products are based on technologies to separate, purify, identify, analyze, and amplify biological materials such as antibodies, proteins, nucleic acids, cells, and bacteria. Bio-Rad's diagnostic products and systems use a range of technologies and provide clinical information in the blood transfusion, diabetes monitoring, autoimmune, and infectious disease testing markets. These products are used to support the diagnosis, monitoring, and treatment of diseases and other medical conditions.
=== Turkevich method === This simple method was pioneered by J. Turkevich et al. in 1951 and refined by G. Frens in the 1970s. It produces modestly monodisperse spherical gold nanoparticles of around 10–20 nm in diameter. Larger particles can be produced, but at the cost of monodispersity and shape. In this method, hot chloroauric acid is treated with sodium citrate solution, producing colloidal gold. The Turkevich reaction proceeds via formation of transient gold nanowires. These gold nanowires are responsible for the dark appearance of the reaction solution before it turns ruby-red.
The Serbsky Center, Moscow Institute of Psychiatry, and Russian Center of Vegetative Pathology are reported to have confirmed the effectiveness of phenylpiracetam describing the following effects: improvement of regional blood flow in ischemic regions of the brain, reduction of depressive and anxiety disorders, increase the resistance of brain tissue to hypoxia and toxic effects, improving concentration and mental activity, a psycho-activating effect, increase in the threshold of pain sensitivity, improvement in the quality of sleep, and an anticonvulsant action, though with the side effect of an anorexic effect in extended use.
The rest of the world was slow to adopt lithium as a treatment, largely because of deaths that resulted from even relatively minor overdosing, including those reported from the use of lithium chloride as a substitute for table salt. However, other scientists had already read John Cade's 1949 article on lithium and continued their research of the effect of lithium on mania. In 1951, Edward Trautner and colleagues at the University of Melbourne followed up on Cade's 1949 research paper and used flame photometry to identify the range of lithium blood levels that are safe for patients. By 1952 Cade was superintendent of the prestigious Royal Park Hospital in Melbourne. He prohibited the use of lithium, his own discovery, in the hospital. By 1953 he had changed his mind, and he hired biochemist Shirley Andrews to run the hospital's clinical laboratory and test the lithium levels of patients using a flame photometer. Shirley Andrews not only published research papers while at Royal Park Hospital, but also became famous for her work on Australian folk dance and Aboriginal rights activism. Shirley Andrews and John Cade were both eventually honored with the Order of Australia; Andrews for her work with Australian folk dance and Cade for his work with lithium.
Sources: en.wikipedia.org
== Global Research Infrastructure == Widespread interest and funding for research on regenerative medicine has prompted institutions in the United States and around the world to establish departments and research institutes that specialize in regenerative medicine including: The Department of Rehabilitation and Regenerative Medicine at Columbia University, the Institute for Stem Cell Biology and Regenerative Medicine at Stanford University, the Center for Regenerative and Nanomedicine at Northwestern University, the Wake Forest Institute for Regenerative Medicine, and the British Heart Foundation Centers of Regenerative Medicine at the University of Oxford. In China, institutes dedicated to regenerative medicine are run by the Chinese Academy of Sciences, Tsinghua University, and the Chinese University of Hong Kong, among others.
== Function == The encoded 22 kDa protein contains an N-terminal secretion signal and two coiled-coil domains and is a member of the angiopoietin-like (ANGPTL) protein family. However, in contrast to other ANGPTL proteins, ANGPTL8 lacks the C-terminal fibrinogen-like domain, and therefore it is an atypical member of the ANGPTL family. ANGPTL8 has been shown to form complexes with ANGPTL3 with an apparent stoichiometry of 3:1 of ANGPTL3 to ANGPTL8 respectively. Formation of these complexes appears to require intracellular co-folding as mixing of ANGPTL8 and ANGPTL3 extracellularly does not result in complex formation. ANGPTL8 is expressed in the hepatic tissue and secreted into circulation, in order for the efficient secretion of ANGPTL8 it must form a complex with ANGPTL3. ANGPTL8 alone shows little inhibitory capacity and must form a complex with ANGPTL3 to inhibit the enzyme Lipoprotein lipase (LPL) and has been shown to greatly promote the ability of ANGPTL3 to inhibit LPL. In mice ANGPTL8 is secreted by the liver and by adipose tissue, hepatic overexpression of ANGPTL8 causes elevation of circulating Triglyceride levels. Despite having elevated post-heparin plasma LPL activity, mice lacking ANGPTL8 exhibit markedly decreased uptake of Very low-density lipoprotein-derived fatty acids into white adipose tissue (WAT). The defect in fatty acids uptake by WAT in ANGPTL8-null mice is likely due to the enhanced fatty acid uptake by the heart and skeletal muscle, because of the elevated LPL activity in these two tissues, as suggested by the ANGPTL3-4-8 model.
The game's production was turbulent, as the design's scope exceeded the available resources, and the team was left without a producer for nearly a year until Activision appointed David Mullich to the role, where he found designs and levels unfinished or abandoned. After three years in development with no end in sight and running over budget, Activision set a strict deadline for completion, and Bloodlines was released incomplete in November 2004. Released in competition with Half-Life 2 and several other titles, Bloodlines sold fewer than 80,000 copies during its initial release, which was considered a poor performance. It received generally positive reviews from contemporary critics, who praised the game's writing and the scale of choice, although they criticized its technical flaws. It was Troika Games's last production before its failure in early 2005, when it could not secure additional projects. The game has a cult following as a rarely replicated example of gameplay and narrative, and modern reception recognizes it as a flawed masterpiece. Since its original release, Bloodlines received post-release support from fans, supplying unofficial fixes and re-adding unused content. A sequel, Vampire: The Masquerade – Bloodlines 2, was released in 2025.
=== Brand names === Pioglitazone is marketed as Actos in the United States, Canada, the UK and Germany, Glustin in the European Union, Glizone and Pioz in India by Zydus Cadila and USV Limited, respectively, and Zactos in Mexico by Takeda Pharmaceuticals. On 17 August 2012, the US FDA announced its approval of the first generic version of Actos.
On 15 September 2008, RIA Novosti reported that Russian foreign minister Sergey Lavrov said: "There were excesses by all parties, but this was a war, and when you see on night, that you are being fired upon and you're on the move, while you're advancing to help Tskhinvali, then your response can not be precisely accurate and cannot avoid hurting anyone." On 21 September 2008, Russia-1 TV reported that the wife of Lieutenant Sergey Shevelev, intelligence officer of the peacemaking battalion who died in South Ossetia, said that her husband called her every day and they talked casually. However, on 1 August he sent her text message saying "Everything is normal ... Watch TV. That's all." Konstantin Timerman, the commander of the Russian peacekeeping battalion, said in 2017 that as soon as his combat buddy Sergey Shevelev arrived in Tskhinvali on 1 August 2008, the escalation of the conflict began.
Sources: en.wikipedia.org
It is a synthetic seven-amino-acid peptide modeled on alpha-melanocyte-stimulating hormone. It carries two non-natural substitutions and a cyclic bridge that increase its stability relative to the natural hormone. It circulates as a research chemical and is not an approved medicine.
Melanotan-1, also called afamelanotide, is a shorter linear analog with a different amino acid sequence and no lactam ring. It has been evaluated in formal clinical programs, while melanotan-2 has not. The two are distinct molecules and are not interchangeable.
No. Bremelanotide is a related but distinct cyclic peptide that reached approved status for one specific clinical indication. Melanotan-2 is a separate molecule with its own sequence and properties. Shared ancestry in the melanocortin family does not make them the same substance.
The lyophilized powder is generally held at minus twenty degrees Celsius or below, away from light and moisture. Reconstituted solutions are typically refrigerated and used quickly. These practices derive from general peptide handling rather than a formal stability study.