Everything below concerns lactam bridge. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2025-12-22. Numbers and descriptions here follow the published literature rather than marketing material.
Scientific discussion of Melanotan-2 spans pharmacology, dermatology, and public-health literature. Laboratory studies examine its receptor binding and cellular effects, while clinical reports describe outcomes observed after unregulated use. These two bodies of work differ in rigour and intent. Peer-reviewed trials of the compound as a medicine are limited, so much of the available information comes from case reports and surveillance data. Authors frequently note the gap between experimental findings and real-world use.
Reported observations after unregulated use include shifts in skin pigmentation and, in some accounts, unintended changes to moles and other lesions. Whether these outcomes are causally linked to the compound, and how often they occur, remain open questions because controlled data are scarce. The absence of standardised dosing and verified product purity complicates interpretation. Researchers have called for better surveillance and analytical characterisation of samples obtained outside regulated channels. Conclusions drawn from anecdotal evidence should be treated as provisional.
Melanotan-2 has not received marketing authorisation from major regulatory agencies for any therapeutic indication. Several jurisdictions classify it as a prescription-only medicine or a controlled substance when supplied for human use. Because approved products do not exist, material sold online usually sits outside pharmaceutical supply chains and formal quality oversight. Regulators have issued public notices describing the compound as unapproved. Enforcement varies, and the legal position differs between countries, which complicates any single general statement about its status.
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.
Two structural changes distinguish the synthetic peptide from the natural hormone. A norleucine residue replaces methionine at one position, and a D-configured phenylalanine replaces the natural L-form at another. Both substitutions slow enzymatic breakdown, which extends the molecule's persistence relative to the parent hormone. The lactam bridge further constrains the backbone into a stable conformation. These features are standard design strategies in peptide chemistry and are not unique to this compound; they appear across many research peptides built for improved stability.
| Property | Value | Notes |
|---|---|---|
| Regulatory status | Unapproved for therapeutic use | No marketing authorisation from major agencies |
| Legal classification | Varies by jurisdiction | Prescription-only or controlled in several countries |
| Common synonyms | Melanotan II; MT-II | Also referenced by catalogue codes |
| Typical analytical method | Reverse-phase HPLC | Often paired with mass spectrometry |
| Primary literature focus | Receptor pharmacology | Pigmentation and melanocortin signalling |
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.
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.
Melanotan II is a synthetic peptide analog modeled on alpha-melanocyte-stimulating hormone, a naturally occurring signaling peptide involved in pigmentation. Its structure is a cyclic heptapeptide containing two non-natural substitutions, norleucine at position four and D-phenylalanine at position seven. These modifications resist enzymatic breakdown and extend the molecule's activity relative to the native hormone. The compound binds melanocortin receptors and is studied mainly as a pharmacological tool rather than a therapeutic product. It has never received approval as a medicine in any major jurisdiction.
The compound was developed in the late 1980s and 1990s by academic researchers investigating photoprotection. The rationale held that stimulating melanin production might reduce ultraviolet damage to skin and lower skin cancer risk. Early work examined receptor binding, pigment response, and short-term tolerability in small studies. That program did not produce an approved drug, and formal development stalled after early-phase trials. Whether induced pigmentation confers meaningful photoprotection remains an open question.
Outside regulated medicine, melanotan II circulates through online vendors as a research chemical, often marketed for tanning. Products sold this way vary widely in purity, concentration, and labeling accuracy, and independent testing has documented discrepancies. Published reports describe both pigment effects and adverse reactions, including nausea, flushing, and darkening of existing moles. Long-term safety data are sparse, and no large controlled trial has established a risk profile. Questions about cumulative effects on melanocytes remain unresolved in the literature.
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.
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.
Published human data come mostly from small, short studies rather than large controlled trials. Reported outcomes include increased skin pigmentation and, in some reports, effects on appetite and libido, but sample sizes are small and follow-up is limited. Whether long-term use produces durable pigment changes or adverse effects is not established. Because products sold outside pharmacies are not standardized, the actual content of any given vial is often unknown. Independent testing of such material is uncommon.
Melanotan II is a synthetic cyclic heptapeptide analog derived from the core sequence of alpha-melanocyte-stimulating hormone. Researchers at the University of Arizona synthesized it during the 1980s while studying pigmentation and appetite signaling. The compound is not an approved medicine in any major jurisdiction and appears mainly in laboratory and research-chemical settings. Its structure incorporates a lactam bridge between side chains, which constrains the ring and slows enzymatic breakdown relative to the natural hormone.
Melanotan II binds several melanocortin receptor subtypes rather than a single target. MC1R on melanocytes drives melanin synthesis, while MC3R and MC4R participate in energy balance, appetite, and sexual response pathways. This lack of selectivity explains why reported effects extend beyond skin darkening. Substitutions at positions four and seven, including norleucine and D-phenylalanine, increase potency and resistance to peptidases. Understanding which receptor mediates which effect remains an active area of investigation.
=== Stem cells and cellular plasticity === Multipotent adult stem cells have the capacity to be self-renewing and give rise to different cell types. Stem cells give rise to progenitor cells, which are cells that are not self-renewing, but can generate several types of cells. The extent of stem cell involvement in cutaneous (skin) wound healing is complex and not fully understood. Stem cell injection leads to wound healing primarily through stimulation of angiogenesis. It is thought that the epidermis and dermis are reconstituted by mitotically active stem cells that reside at the apex of rete ridges (basal stem cells or BSC), the bulge of hair follicles (hair follicular stem cell or HFSC), and the papillary dermis (dermal stem cells). Moreover, bone marrow may also contain stem cells that play a major role in cutaneous wound healing. In rare circumstances, such as extensive cutaneous injury, self-renewal subpopulations in the bone marrow are induced to participate in the healing process, whereby they give rise to collagen-secreting cells that seem to play a role during wound repair. These two self-renewal subpopulations are (1) bone marrow-derived mesenchymal stem cells (MSC) and (2) hematopoietic stem cells (HSC). Bone marrow also harbors a progenitor subpopulation (endothelial progenitor cells or EPC) that, in the same type of setting, are mobilized to aid in the reconstruction of blood vessels.
For example, when treated with potassium fluoride and hydrofluoric acid, Th4+ forms the complex anion [ThF6]2− (hexafluorothorate(IV)), which precipitates as an insoluble salt, K2[ThF6] (potassium hexafluorothorate(IV)). Thorium borides, carbides, silicides, and nitrides are refractory materials, like those of uranium and plutonium, and have thus received attention as possible nuclear fuels. All four heavier pnictogens (phosphorus, arsenic, antimony, and bismuth) also form binary thorium compounds. Thorium germanides are also known. Thorium reacts with hydrogen to form the thorium hydrides ThH2 and Th4H15, the latter of which is superconducting below 7.5–8 K; at standard temperature and pressure, it conducts electricity like a metal. The hydrides are thermally unstable and readily decompose upon exposure to air or moisture.
Since native human amylin is highly amyloidogenic and potentially toxic, the strategy for designing pramlintide was to substitute residues from rat amylin, which is less amyloidogenic but presumably retains clinical activity. Proline residues are known to be structure-breaking residues, so these were directly grafted into the human sequence. Despite its enhanced stability compared to human amylin, however, pramlintide is still able to organize into amyloid material. Amino acid sequences:
Sources: en.wikipedia.org
Outer space has very low density and pressure, and is the closest physical approximation of a perfect vacuum. But no vacuum is truly perfect, not even in interstellar space, where there are still a few hydrogen atoms per cubic meter. Stars, planets, and moons keep their atmospheres by gravitational attraction, and as such, atmospheres have no clearly delineated boundary: the density of atmospheric gas simply decreases with distance from the object. The Earth's atmospheric pressure drops to about 32 millipascals (4.6×10−6 psi) at 100 kilometres (62 mi) of altitude, the Kármán line, which is a common definition of the boundary with outer space. Beyond this line, isotropic gas pressure rapidly becomes insignificant when compared to radiation pressure from the Sun and the dynamic pressure of the solar winds, so the definition of pressure becomes difficult to interpret. The thermosphere in this range has large gradients of pressure, temperature and composition, and varies greatly due to space weather. Astrophysicists prefer to use number density to describe these environments, in units of particles per cubic centimetre. But although it meets the definition of outer space, the atmospheric density within the first few hundred kilometers above the Kármán line is still sufficient to produce significant drag on satellites. Most artificial satellites operate in this region, called low Earth orbit, and must fire their engines every couple of weeks or a few times a year (depending on solar activity).
It concludes that the 40 °C heatwave was "extraordinary", but would be considered an average year by 2060 and a cool year by 2100, if current emission trends continue. 26-year-old Louis De Zoysa is sentenced to a whole life order for the murder of police officer Matt Ratana in 2020. Peter Flavel resigns as chief executive of Coutts Bank over controversy surrounding the closure of Nigel Farage's account. 28 July – The High Court concludes that Sadiq Khan's plan to extend the Ultra Low Emission Zone (ULEZ) around London is lawful and can proceed. 30 July Media outlets, including BBC News, report that the Infrastructure and Projects Authority has given the HS2 project an "unachievable" rating in a report published on 20 July. Sunak orders a review of Low Traffic Neighbourhoods, declaring himself to be on the side of drivers. 31 July Sunak announces that over 100 new licenses will be granted for oil and gas drilling in the North Sea, a decision heavily criticised by environmental groups and opposition MPs as incompatible with the UK's climate change commitments. Sunak insists the plan is "entirely consistent" with reaching net zero, and says that a quarter of UK energy needs will come from oil and gas even after 2050. New rules come into force from the Financial Conduct Authority requiring banks to prove they are offering their customers fair value, such as passing on interest rate rises to savers. The final date on which non-barcoded stamps can be used when posting mail.
=== Novel applications === Due to the versatility of SPR instrumentation, this technique pairs well with other approaches, leading to novel applications in various fields, such as biomedical and environmental studies. When coupled with nanotechnology, SPR biosensors can use nanoparticles as carriers for therapeutic implants. For instance, in the treatment of Alzheimer's disease, nanoparticles can be used to deliver therapeutic molecules in targeted ways. In general, SPR biosensing is demonstrating advantages over other approaches in the biomedical field due to this technique being label-free, lower in costs, applicable in point-of-care settings, and capable of producing faster results for smaller research cohorts. In the study of environmental pollutants, SPR instrumentation can be used as a replacement for former chromatography-based techniques. Current pollution research relies on chromatography to monitor increases in pollution in an ecosystem over time. When SPR instrumentation with a Kretschmann prism configuration was used in the detection of chlorophene, an emerging pollutant, it was demonstrated that SPR has similar precision and accuracy levels as chromatography techniques. Furthermore, SPR sensing surpasses chromatography techniques through its high-speed, straightforward analysis.
Lord Advocate Dorothy Bain, Scotland's most senior lawyer, apologises to victims of the Post Office scandal, saying they were let down by the justice system. Finance Secretary Shona Robison confirms that the Scottish Government is to cut at least 1,200 funded university places as they cannot afford to continue paying for additional places created during the COVID-19 pandemic. 17 January – The UK government is seeking legal expenses from the Scottish Government over its challenge against the veto of the Gender Recognition Reform (Scotland) Bill. 18 January – Community Safety Minister Siobhian Brown announces that Scotland will introduce legislation to ban the sale, breeding and abandonment of American XL bully dogs, replicating the law for England and Wales, at a date to be confirmed later. Nuns Sister Sarah McDermott and Sister Eileen Igoe, and carer Margaret Hughes, who mistreated children at Smyllum Park, an orphanage in Lanark from 1969 until 1981 when it closed, are each sentenced to three years in prison. Helen Goss, the mother of an eleven-year-old girl from Aberdeenshire with long COVID, launches legal action against NHS Grampian for what she says are the health board's "multiple failings" in the care and treatment of her daughter. 21 January – Scotland's First Minister, Humza Yousaf, tells the BBC's Sunday with Laura Kuenssberg he is willing to work with Sir Keir Starmer if he becomes prime minister after the next general election. ScotRail cancels all services from 7pm until after the following day's rush hour because of high winds caused by Storm Isha.
Sources: en.wikipedia.org
The cap of P. semilanceata is 5–25 mm (0.20–0.98 in) in diameter and 6–22 mm (0.24–0.87 in) tall. It varies in shape from sharply conical to bell-shaped, often with a prominent papilla (a nipple-shaped structure), and does not change shape considerably as it ages. The cap margin is initially rolled inward but unrolls to become straight or even curled upwards in maturity. The cap is hygrophanous, meaning it assumes different colors depending on its state of hydration. When it is moist, the cap is ochraceous to pale brown to dark chestnut brown, but darker in the center, often with a greenish-blue tinge. When moist, radial grooves (striations) can be seen on the cap that correspond to the positions of the gills underneath. When the cap is dry, it becomes much paler, a light yellow-brown color. Moist mushrooms have sticky surfaces that result from a thin gelatinous film called a pellicle. This film becomes apparent if a piece of the cap is broken by bending it back and peeling away the piece. When the cap dries from exposure to the sun, the film turns whitish and is no longer peelable. On the underside of the mushroom's cap, there are between 15 and 27 individual narrow gills that are moderately crowded together, and they have a narrowly adnexed to almost free attachment to the stipe. Their color is initially pale brown, but becomes dark gray to purple-brown with a lighter edge as the spores mature. The slender yellowish-brown stipe is 4.5–14 cm (1.8–5.5 in) long by 1–3.5 mm (0.04–0.14 in) thick, and usually slightly thicker towards the base.
While initially credited for China's suppression of the COVID-19 outbreak, the policy was later criticized by foreign and some domestic observers for being out of touch with the rest of the world and taking a heavy toll on the economy. This approach has especially come under criticism during a 2022 lockdown on Shanghai, which forced millions to their homes and damaged the city's economy. Conversely, Xi has said that the policy was designed to protect people's life safety. On 23 July 2022, the National Health Commission reported that Xi and other top leaders have taken the local COVID-19 vaccines. At the 20th CCP Congress, Xi confirmed the continuation of the zero-COVID policy, stating he would "unswervingly" carry out "dynamic zero-COVID" and promising to "resolutely win the battle", though China started a limited easing of the policies in the following weeks. In November 2022, protests broke out against China's COVID-19 policies, with a fire in a high-rise apartment building in Ürümqi being the trigger. The protests were held in multiple major cities, with some of the protesters demanding the end of Xi's and the CCP's rule. The protests were mostly suppressed by December. Follwing the protests, the government further eased COVID-19 restrictions. On 7 December 2022, China announced large-scale changes to its COVID-19 policy, including allowing quarantine at home for mild infections, reducing of PCR testing, and decreasing the power of local officials to implement lockdowns, effectively ending the zero-COVID policy.
Advanced characterization of bacterial organisms can be also performed, allowing to obtain the necessary depth and breadth of coverage for genetic characterization results. Gene calling can be performed in a variety of ways, including RAST or using NCBI services at the time of full genome submission. Results of multiple annotation tools can be compared for accuracy and completeness and, if necessary, merged using BEACON. For characterization of antibiotic resistance genes, the Resistance Gene Identifier from the Comprehensive Antibiotic Resistance Database (CARD) is commonly used. To characterize virulence factor genes, ShortBRED offers analyses with a customized database from the Virulence Factor Database.
Sources: en.wikipedia.org
Major regulatory agencies have not approved it for any indication. Some countries permit it only under prescription frameworks, while others classify it as a controlled substance.
Much of the evidence comes from case reports and accounts of unregulated use rather than controlled trials. Differences in product purity and dosing add further variability.
Laboratory work focuses on receptor binding and cellular signalling. Observational reports document outcomes after use, and analytical chemists examine samples to assess content and purity.
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.