cyclic heptapeptide is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Last reviewed on 2025-10-24. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
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.
No regulatory authority has approved melanotan-2 for human use, and several countries classify it as a prescription-only or controlled substance, which restricts lawful supply. Material sold online is generally labelled as a research chemical and is not required to meet pharmaceutical standards of identity or purity. Published human data consist mainly of small uncontrolled studies, case reports and adverse-event notifications, so the evidence base is descriptive rather than confirmatory. Whether repeated melanocyte stimulation alters long-term naevus behaviour remains an open question that no completed trial has resolved.
Melanotan-2 is a synthetic cyclic heptapeptide designed as a structural analogue of alpha-melanocyte-stimulating hormone, the endogenous tridecapeptide that regulates pigment production. Two modifications distinguish it from the natural hormone: norleucine replaces methionine at the N-terminus, which limits oxidation, and a D-phenylalanine substitution raises receptor affinity. The ring is closed through an aspartate-lysine lactam bridge, giving the molecule a constrained conformation. The free base has a molecular mass near 1024 daltons, and commercial material is usually supplied as an acetate salt. It appears in the literature as a research peptide rather than an approved therapeutic agent.
| Property | Value | Notes |
|---|---|---|
| Lyophilised storage | −20 °C, dry, protected from light | Vials are sealed and allowed to reach room temperature before opening |
| Reconstituted storage | 2 to 8 °C, protected from light | Short-term holding; avoid repeated freeze-thaw cycles |
| Reconstitution solvent | Water for injection or bacteriostatic water | Added slowly along the vial wall to reduce foaming and shear |
| Purity measurement | RP-HPLC with area normalisation | Acetonitrile-water gradient monitored at roughly 214 nm |
| Identity confirmation | Electrospray ionisation mass spectrometry | Observed mass compared against the calculated peptide mass |
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.
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.
The peptide was developed during the 1980s by researchers investigating melanocortin signalling and skin pigmentation pathways. Early work focused on analogues of alpha-melanocyte-stimulating hormone that would resist enzymatic breakdown more effectively than the parent molecule. Melanotan-2 emerged from that programme as a shortened, cyclised variant. Reports describing its synthesis and receptor activity later appeared in the scientific literature. Commercial availability grew through unregulated channels rather than through pharmaceutical approval.
Structurally, Melanotan-2 retains the core recognition motif of alpha-melanocyte-stimulating hormone while adding a lactam bridge that links two side chains and constrains the molecule into a ring. This modification lowers susceptibility to enzymatic degradation. The compound acts as an agonist at melanocortin receptors, particularly subtypes associated with melanin production. Because the same receptor family influences several physiological processes, researchers note that its activity is not confined to pigmentation alone. Receptor selectivity continues to be examined in published studies.
Melanotan-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone, a naturally occurring peptide involved in pigmentation signalling. Its sequence incorporates modified residues that increase potency and extend biological activity relative to the native hormone. The compound binds receptors of the melanocortin family and is examined mainly in laboratory research. It does not occur naturally and exists only as a manufactured chemical entity produced by solid-phase synthesis.
Lyophilised melanotan-2 is comparatively robust when kept dry, cold and dark, and a desiccated powder stored at minus twenty degrees Celsius or below is generally expected to retain its chemical integrity for extended periods. In solution the peptide is far less stable, with degradation proceeding through oxidation of tryptophan and histidine residues, hydrolysis adjacent to the lactam bridge, and aggregation at higher concentrations. Repeated freeze-thaw cycling accelerates loss of the parent peak. Working aliquots are therefore prepared once, held cold, and used without letting the stock return to ambient temperature.
Quality assessment of research-grade peptide rests mainly on reversed-phase high-performance liquid chromatography for purity and on mass spectrometry for identity confirmation. A single main peak above a stated threshold, commonly ninety-eight percent by peak area, is the usual release criterion applied by suppliers. Independent analyses commissioned by laboratories and consumer organisations have repeatedly reported discrepancies between label claims and measured content, including truncated sequences, residual trifluoroacetate, and lower-than-declared peptide mass. Those findings do not establish that every supplier is unreliable, but they indicate that purity figures printed on a vial are claims requiring verification rather than settled facts.
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.
In leagues such as the National Football League, there is a very rigorous process required to obtain an exemption to this rule even when the athlete has been medically prescribed the drug by their physician.
Blockage of voltage-dependent sodium channels (after activation of the channel, diclofenac inhibits its reactivation, also known as phase inhibition) Blockage of acid-sensing ion channels (ASICs) Positive allosteric modulation of KCNQ- and BK-potassium channels (diclofenac opens these channels, leading to hyperpolarization of the cell membrane) The duration of action (i.e., duration of pain relief) of a single dose is longer (6 to 8 h) than the drug's 1.2–2 h half-life. This may be partly due to its persistence for over 11 hours in synovial fluids.
The study also highlights economy-specific gap analyses, which illustrate gaps in policy coverage and estimate potential energy savings achieved through the adoption of world’s most comprehensive standards. Compliance Counts: A Practitioners Guidebook on Best Practice Monitoring, Verification, and Enforcement (MV&E) for Appliance Standards &Labeling The Guidebook, published in collaboration with Mark Ellis & Associates, is designed as a step-by-step manual for policymakers and S&L program administrators to design and implement a successful compliance regime. Drawing on the experiences of existing S&L programs worldwide, the Guidebook provides different approaches to implementing and improving all aspects of a compliance framework, including establishment of a legal basis for MV&E activities and enforcement options for non-compliance. According to the guidebook, effective compliance regimes: ensure that consumers receive the products they expect when making purchasing decisions; provide industry participants a fair market in which to operate; and safeguard current and future energy and greenhouse gas emissions savings from S&L programs, among other benefits. Energy Efficiency Labels and Standards: A Guidebook for Appliances, Equipment, And Lighting (also available in Chinese, Spanish and Korean) This guidebook is designed as a manual for government officials and others around the world responsible for developing, implementing, enforcing, monitoring, and maintaining energy efficiency labeling and standard-setting programs. Tools
=== Electrochemical synthesis === Electrochemical synthesis can exfoliate graphene. Varying a pulsed voltage controls thickness, flake area, and number of defects and affects its properties. The process begins by bathing the graphite in a solvent for intercalation. The process can be tracked by monitoring the solution's transparency with an LED and photodiode.
A series of 3-benzazepine derivatives, such as Lorcaserin (Figure 6) have been evaluated for their potency and selectivity for the 5-HT2C receptors. Lorcaserin is a very potent agonist, but the potency is dependent on the presence of a chloro substituent in position 8. Arylpiperazine-containing compounds such as mCPP (Figure 7), show good potency toward the 5-HT2C receptors, but do not have sufficient selectivity for the 5-HT2C receptors over the other two receptor subtypes. Many derivatives have been examined in an attempt to increase the selectivity. Derivatives lacking the arylpiperazine core, such as 4-aryl-1,2,3,6-tetrahydropyridinum chlorine analogues, are more favorable for potency and selectivity over the other two receptors (Figure 7).
Sources: en.wikipedia.org
Conversely, if the UK had such a device, the population could be protected. In 1934, along with a movement to establish a scientific committee to examine these new types of weapons, the RAF offered a £1,000 prize to anyone who could demonstrate a working model of a death ray that could kill a sheep at 100 yards; it went unclaimed.
Germany has a social market economy with a highly skilled labour force, a low level of corruption, and a high level of innovation. It is the largest economy in Europe by nominal GDP, as well as the world's third-largest by nominal GDP and sixth-largest by PPP-adjusted GDP. Its PPP-adjusted GDP per capita amounted to 115% of the EU average in 2024. The country's service sector contributes approximately 72% of the total GDP, the industrial sector 27%—with Germany having the largest manufacturing output in Europe—and its agricultural sector 1%, as of 2023. The unemployment rate published by Eurostat amounts to 3.2% as of January 2020, which is the fourth-lowest in the EU. Germany is part of the European single market which represents more than 450 million consumers. In 2017, the country accounted for 28% of the eurozone economy according to the International Monetary Fund. Germany introduced the common EU currency, the euro, in 2002. Its monetary policy is set by the European Central Bank, which is based in Frankfurt, the country's largest financial centre. Germany is the world's third-largest exporter and third-largest importer, and it has the second-largest trade surplus after China. Its largest trading partners in 2025 were China, the United States and the Netherlands. Germany's main exports are vehicles, machinery, and chemical goods. The German automotive industry is among the most competitive and innovative in the world. It was the sixth-largest by production and largest by export value in 2023.
== Long-lasting erections == Antiandrogens can considerably relieve and prevent priapism (potentially painful penile erections that last more than four hours) via direct blockade of penile ARs. In accordance, bicalutamide, at low dosages (50 mg every other day or as little as once or twice weekly), has been found in a series of case reports to completely resolve recurrent priapism in men without producing significant side effects, and is used for this indication off-label. In the reported cases, libido, rigid erections, the potential for sexual intercourse, orgasm, and subjective ejaculatory volume have all remained intact or unchanged, and gynecomastia has not developed when bicalutamide is administered at a total dosage of 25 mg/day or less. Some gynecomastia and breast tenderness developed in one patient treated with 50 mg/day, but significantly improved upon the dosage being halved. The observed tolerability profile of bicalutamide in these subjects has been regarded as significantly more favorable than that of GnRH analogues and estrogens (which are also used in the treatment of this condition). However, although successful and well tolerated, very few cases have been reported. Despite the apparent efficacy of bicalutamide for priapism, a small clinical study found that bicalutamide monotherapy at a dosage of 50 mg/day had no effect on nocturnal erections in men with prostate cancer.
==== Cyprus ==== The New York Times published an exposé revealing an extensive three-year phishing campaign aimed against diplomats based in Cyprus. After accessing the state system the hackers had access to the European Union's entire exchange database. By login into Coreu, hackers accessed communications linking all EU states, on both sensitive and not so sensitive matters. The event exposed poor protection of routine exchanges among European Union officials and a coordinated effort from a foreign entity to spy on another country. "After over a decade of experience countering Chinese cyberoperations and extensive technical analysis, there is no doubt this campaign is connected to the Chinese government", said Blake Darche, one of the Area 1 Security experts – the company revealing the stolen documents. The Chinese Embassy in the US did not return calls for comment. In 2019, another coordinated effort took place that allowed hackers to gain access to government (gov.cy) emails. Cisco's Talos Security Department revealed that "Sea Turtle" hackers carried out a broad piracy campaign in the DNS countries, hitting 40 different organizations, including Cyprus.
== Non-specific DNA-protein interactions == Structural proteins that bind DNA are well-understood examples of non-specific DNA-protein interactions. Within chromosomes, DNA is held in complexes with structural proteins. These proteins organize the DNA into a compact structure called chromatin. In eukaryotes, this structure involves DNA binding to a complex of small basic proteins called histones. In prokaryotes, multiple types of proteins are involved. The histones form a disk-shaped complex called a nucleosome, which contains two complete turns of double-stranded DNA wrapped around its surface. These non-specific interactions are formed through basic residues in the histones making ionic bonds to the acidic sugar-phosphate backbone of the DNA, and are therefore largely independent of the base sequence. Chemical modifications of these basic amino acid residues include methylation, phosphorylation and acetylation. These chemical changes alter the strength of the interaction between the DNA and the histones, making the DNA more or less accessible to transcription factors and changing the rate of transcription. Other non-specific DNA-binding proteins in chromatin include the high-mobility group (HMG) proteins, which bind to bent or distorted DNA. Biophysical studies show that these architectural HMG proteins bind, bend and loop DNA to perform its biological functions. These proteins are important in bending arrays of nucleosomes and arranging them into the larger structures that form chromosomes.
Sources: en.wikipedia.org
==== Absorption ==== When taken orally, DMT is metabolized by monoamine oxidase (MAO) enzymes in the liver and gut, and is thus not orally bioavailable unless a monoamine oxidase inhibitor (MAOI) is taken (as is naturally found in the ayahuasca brew). As such, DMT by itself is instead taken by parenteral administration. Closely coextending with peak psychedelic effects, the mean time to reach peak concentration (Tmax) has been determined to be 10 to 15 minutes in whole blood after intramuscular injection, and 2 to 3 minutes after intravenous administration. When taken orally mixed in an ayahuasca decoction or in freeze-dried ayahuasca gel caps, DMT Tmax is considerably delayed to 1.8 hours on average, and 1.5 to 2 hours, respectively. DMT peak level concentrations (Cmax) measured in the blood after intramuscular (IM) injection (0.7 mg/kg, n = 11) and in plasma following intravenous administration (0.4 mg/kg, n = 10) of fully psychedelic doses are in the range of around 14 to 154 μg/L and 32 to 204 μg/L, respectively. The corresponding molar concentrations of DMT are therefore in the range of 0.074–0.818 μmol/L in whole blood and 0.170–1.08 μmol in plasma.
=== 2003 === 15 March Space Shuttle: Human Time Bomb? about STS-107, which broke up on 1 February 2003; Bill Readdy of NASA; technology writer Dwayne A. Day; the shuttle engines burned 1.5 tonnes per second; physicist Ted Postol of MIT; Vladimir Titov and Gennady Strekalov deployed a launch escape system on Soyuz 7K-ST No.16L on 26 September 1983; the shuttle design was hampered by a need for a large-enough payload bay, to take 60-ft spy satellites for the USAF, and the shuttle's original companion launch vehicle (similar to the North American DC-3) was exchanged for a disposable fuel tank; in May 1995 for STS-70, woodpeckers destroyed a large part of the foam coating on the fuel tank next to Discovery on the launch pad - NASA bought six lifesize owls from a nearby supermarket to frighten the woodpeckers away; on 7 October 2002 on the launch of STS-112, foam broke away from the fuel tank, causing damage, which NASA ignored; Jeff Hoffmann; on 1 February 2003 at around 8am Nacogdoches, Texas was hit by debris. Narrated by Heather Couper, produced by Stuart Carter, directed by Alex Hearle, made by Pioneer Productions. Filmed, edited and broadcast only twenty three days after being commissioned Self-Experimenters, about self-experimentation in medicine; neuroscientist Simon Gandevia from the Prince of Wales Medical Research Institute (since 2010, Neuroscience Research Australia); Canadian thermophysiologist Gordon Giesbrecht at the University of Manitoba in Winnipeg; medicinal chemist and psychopharmacologist Sasha Shulgin; medicinal chemist David E.
== External links == http://www.asap.unimelb.edu.au/asap_inf.htm – Australian Science Archives Project From http://www.asap.unimelb.edu.au/bsparcs/aasmemoirs AAS Biographical Memoirs (1966–1996) From http://www.sciencearchive.org.au "Fellows elected in 2005". Australian Academy of Science. Archived from the original on 25 March 2016. "Fellows elected in 2006". Australian Academy of Science. Archived from the original on 23 March 2016. "Fellows elected in 2007". Australian Academy of Science. Archived from the original on 1 April 2016. "Fellows elected in 2008". Australian Academy of Science. Archived from the original on 23 March 2016. "Fellows elected in 2009". Australian Academy of Science. Archived from the original on 24 September 2015. "Fellows elected in 2010". Australian Academy of Science. Archived from the original on 3 April 2016. "Fellows elected in 2011". Australian Academy of Science. Archived from the original on 24 September 2015. "Fellows elected in 2012". Australian Academy of Science.{{cite web}}: CS1 maint: deprecated archival service (link) "Fellows elected in 2013". Australian Academy of Science. Archived from the original on 25 March 2016. From https://www.science.org.au "Fellows elected in 2010". Australian Academy of Science. "Fellows elected in 2011". Australian Academy of Science. "Fellows elected in 2012". Australian Academy of Science. "Fellows elected in 2013". Australian Academy of Science. "Fellows elected in 2014". Australian Academy of Science. "Fellows elected in 2015". Australian Academy of Science. "Fellows elected in 2016".
===== Alloc and miscellaneous groups ===== The allyloxycarbonyl (alloc) protecting group is sometimes used to protect an amino group (or carboxylic acid or alcohol group) when an orthogonal deprotection scheme is required. It is also sometimes used when conducting on-resin cyclic peptide formation, where the peptide is linked to the resin by a side-chain functional group. The Alloc group can be removed using tetrakis(triphenylphosphine)palladium(0). For special applications like synthetic steps involving protein microarrays, protecting groups sometimes termed "lithographic" are used, which are amenable to photochemistry at a particular wavelength of light, and so which can be removed during lithographic types of operations.
Sources: en.wikipedia.org
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.
Liquid chromatography coupled to mass spectrometry is the most common approach because it combines a retention time with a mass measurement. A chromatographic peak alone cannot establish which peptide is present, so mass determination or amino acid analysis is used as an orthogonal confirmation alongside the separation.
This depends on buffer, pH, and concentration, and published stability data for this peptide are limited. In practice laboratories work through a refrigerated solution within a few weeks and discard samples that show cloudiness or visible particles. Freezing and thawing repeatedly is generally discouraged.
No regulatory agency has authorised melanotan-2 as a medicine for any indication. It circulates mainly as a research chemical or through unregulated channels. As a result, identity, purity and content are not independently guaranteed.