If you have been reading about lactam bridge and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Last reviewed on 2026-02-22. Where a claim depends on a specific study, the study is described rather than over-claimed.
Published pharmacokinetic information is limited and comes mainly from small studies rather than registrational trials. Plasma half-life is usually described as short, on the order of tens of minutes, followed by rapid tissue distribution and clearance of the intact peptide. Metabolites and low concentrations of parent compound have been reported in urine, a detail relevant to anti-doping and forensic testing. Whether repeated exposure changes receptor sensitivity or clearance over time remains an open question. Values differ noticeably between analytical assays, so published numbers should be read as approximate rather than definitive.
Melanotan II is a synthetic cyclic heptapeptide with the sequence Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, corresponding to a molecular formula of C50H69N15O9 and a monoisotopic mass near 1024 daltons. It was designed as a structural analogue of alpha-melanocyte-stimulating hormone, a peptide hormone produced by cleavage of proopiomelanocortin. A lactam bridge between the aspartate and lysine side chains closes the ring, and the C-terminal amide removes a free carboxyl group. Both modifications increase resistance to enzymatic degradation compared with the linear parent hormone. Four substitutions distinguish it from afamelanotide, the linear analogue studied under the name melanotan I.
Regulatory treatment varies by jurisdiction and has changed over time. In several countries the peptide is handled as an unapproved prescription medicine, and import or sale for human use is restricted, while elsewhere it falls under poisons or controlled-substance schedules. Enforcement activity against online vendors has been reported in Australia, New Zealand, the United Kingdom and the United States. Scholarly writing discusses melanotan-2 chiefly as an experimental tool and as a case study in unregulated peptide supply, and its precise legal position in any given country should be checked against current national schedules.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C50H69N15O9 | Cyclic heptapeptide, C-terminally amidated |
| Approximate molecular mass | 1024 Da | Monoisotopic mass of the free peptide |
| Appearance | White to off-white powder | Typically supplied as a lyophilised solid |
| Solubility class | Soluble in water and polar solvents | Also dissolves in neutral aqueous buffer |
| Common synonyms | Melanotan II, MT-II, MT-2 | Described as a melanocortin agonist in early literature |
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.
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.
Melanotan-2 appears on the World Anti-Doping Agency prohibited list within the peptide hormone class, and several national regulators treat it as an unapproved prescription substance. Some countries restrict importation or sale for personal use. Because the compound is widely traded as a research chemical, the practical legal picture differs between jurisdictions and shifts over time. Human safety data covering long periods are limited, and whether repeated pigmentation changes carry any lasting risk to melanocytes remains an open question.
Freeze-dried melanotan-2 is normally kept as a desiccated powder at minus twenty degrees Celsius or lower, shielded from light and moisture. Peptides of this size degrade through hydrolysis, oxidation and deamidation, and each pathway accelerates as temperature and water activity rise. Repeated freeze-thaw cycles promote aggregation and loss of material, so aliquoting a stock solution before freezing is standard laboratory practice. Once dissolved, the solution is markedly less stable than the powder. In laboratory work, solutions are generally refrigerated and used within days rather than kept for months.
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.
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.
Handling guidance for melanotan II follows general practice for small synthetic peptides rather than a product-specific monograph. Lyophilized powder is typically kept at minus twenty degrees Celsius or colder, protected from light and moisture, because warmth and humidity accelerate degradation. Once reconstituted, solutions are usually refrigerated and used within a short window, as hydrolysis and microbial growth both become concerns. Repeated freeze-thaw cycles are generally avoided. These conventions come from laboratory peptide chemistry and not from formal stability studies on this specific compound.
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.
==== Absorption ==== 2C-B appears to have relatively low oral bioavailability. The time to peak levels is 2.0 to 2.4 hours. Peak levels of 2C-B have been reported to be 2.5 ng/mL with 10 mg orally, 3.3 to 4.6 ng/mL with 20 mg orally, and 5.4 to 6.4 ng/mL with 30 mg orally. The peak levels of 2C-B metabolites have also been described.
Ellen McLain (born 1952 or 1953) is an American voice actress. She is best known for providing the voice of GLaDOS, the primary antagonist of the Portal video game series, the Combine Overwatch AI in Half-Life 2, and the Administrator, the announcer in Team Fortress 2. Her voice roles also include the Jaeger A.I. in Pacific Rim and The Witch in Left 4 Dead 2.
If the reaction is more complicated, then the output is not uniquely determined by the RTD. It also depends on the degree of micromixing, the mixing between molecules that entered at different times. If there is no mixing, the system is said to be completely segregated, and the output can be given in the form
His career has spanned the academic world and the BBC, while his books include Kissing Cousins (a comparative study of British and American social attitudes); critical portraits of the Amadeus Quartet and of Plácido Domingo; a study of the cultural impact of The Hitler Émigrés; an anthology of essays about today's leading historians; The Gilded Stage: A Social History of Opera and Just Passing Through – Interactions with the World 1938 – 2021; born in London, his parents coming from Anglo-Jewish families with roots in 19th-century Eastern Europe. Flora Solomon, (née Benenson; 28 September 1895 – 18 July 1984) was an influential Zionist. The first woman hired to improve working conditions at Marks & Spencer in London, Solomon was later instrumental in the exposure of the spy Kim Philby. She was the mother of Peter Benenson, founder of Amnesty International and founder of Blackmore Press, a British printing house. Her life was described in her autobiography A Woman's Way, written in collaboration with Barnet Litvinoff and published in 1984 by Simon & Schuster. The work was also titled Baku to Baker Street: The Memoirs of Flora Solomon.
If available, computed tomography (CT) is the most convenient tool in diagnosing NF due to its speed and resolution (detects about 80% of NF cases). CT scan may show fascial thickening, edema, or abscess formation. CT can pick up on gas within tissues better than MRI, but it is not unusual for NF to present without gas on imaging. In addition, CT helps evaluate complications due to NF and find possible sources of infections. Its use may be limited in pregnant patients and patients with kidney issues.
Sources: en.wikipedia.org
== Chemical composition and reservoirs == Third-hand smoke and its components have been detected in various indoor environments. The possibility of nitrosamine formation on vehicular surfaces was identified via the spraying of "high but reasonable" levels of nitrous acid (about 4–12 times the levels typically found in homes) onto cellulose substrates and wiping surfaces in a vehicle that had experienced heavy smoking. Similar results were found when cellulose substrates were kept (without wiping) in the vehicle for three days when smoking occurred. Additionally, the persistence of various third-hand smoke components was quantified on wool, cotton, and polyester fibers with THS the most persistent on wool and least persistent on polyester. Washing clothing without detergent was found to remove some THS, though a substantial amount remained after standard laundering. Because of the growing resolving power and improved detection limits of analytical instruments (sometimes called the "vanishing zero" phenomenon), studies have demonstrated the transport of THS into other spaces via various media. For instance, third-hand smoke signatures have been detected in particles, which can effectively transport such compounds between indoor and outdoor air. Additionally, both gas-phase and aerosol-phase compounds linked to third-hand smoke were detected and quantified in a non-smoking movie theater, possibly via moviegoers' clothes and breath.
=== Sugar profile === Honey is mainly fructose (51% of sugars) and glucose (44%) (table), with remaining sugars including galactose, maltose, and sucrose, each supplying 3% or less of total sugars (table, USDA reference). The glycemic index of honey has a possible range of 31–78, depending on the variety. The specific composition, color, aroma, and flavor of any batch of honey depend on the flowers foraged by bees that produced the honey.
The Five Guys menu focuses on hamburgers offered with Kraft American cheese or applewood-smoked bacon and kosher style hot dogs (Hebrew National all-beef franks), as well as grilled cheese, BLT and vegetable sandwiches. Five Guys uses buns that are sweeter and "eggier" than normal buns. The hamburgers come in two sizes: regular (two patties) and little (one patty). Customers may select from 15 toppings at no charge. Fresh-cut french fries are the sole side item, available salted only in "Five Guys style" or seasoned "Cajun style". Conventionally, Five Guys employees are directed to give customers an extra scoop of fries for free when they order. The rationale was to persuade the customer that they were getting a good deal by giving them more fries than they'd paid for. However, the extras were already accounted for in the initial pricing. Complimentary roasted in-shell peanuts are offered for on-site consumption at most locations, with signage alerting potential customers who may have a peanut allergy; for these allergen reasons, customers are not allowed to take peanuts off-site.
== Research == There is little evidence that turkey tail mushroom extracts or PSK are useful for treating cancer or any medical condition. Polysaccharide-K, an extract of T. versicolor, is approved in Japan as an adjuvant therapy in cancer treatment.
Sources: en.wikipedia.org
== History == It was formed in 1975, by the remnants of the Organization of Spanish Marxist-Leninists (OMLE) which was dissolved that year. OMLE, which was operating from exile, had been formed through a 1968 split in the Communist Party of Spain (PCE). Following the famous revolts in Paris in 1968, certain groups of leftist Spanish exiles were disappointed with the staunchly pro-Soviet and “frozen” stance of the Spanish Communist Party, the PCE and its leader Santiago Carrillo. This led in September of the same year to the foundation of the Organización de Marxistas Leninistas Españoles (OMLE) (Organization of Spanish Marxist-Leninists) in Brussels. In 1974 Organización Obreira, a Galician organization, joined the OMLE. During the following years, this splinter group of Spanish Communists was inspired by ETA’s rise and by the military coup in Portugal that led to the Carnation Revolution. Thus it accumulated a number of sympathizers and well-wishers, especially among left-wing circles in the Spanish youth. Franco’s illness was also interpreted as an omen for a wide-open future and a promise of success for the PCE(r)'s ambitions and goals. The OMLE renamed itself “Partido Comunista de España Reconstituido” in June 1975. Two months after Franco’s death, in January 1976, during the Spanish political transition from dictatorship to democracy, the PCE(r) began a "revolutionary struggle" against the political reforms of the newly established monarchy of King Juan Carlos I. In order to carry about its struggle, the PCE(r) restructured itself into different commissions.
If RA is adequate, T helper cell subtype Th1 is suppressed and subtypes Th2, Th17 and iTreg (for regulatory) are induced. Dendritic cells located in intestinal tissue have enzymes that convert retinal to all-trans-retinoic acid, to be taken up by retinoic acid receptors on lymphocytes. The process triggers gene expression that leads to T cell types Th2, Th17 and iTreg moving to and taking up residence in mesenteric lymph nodes and Peyer's patches, respectively outside and on the inner wall of the small intestine. The net effect is a down-regulation of immune activity, seen as tolerance of food allergens, and tolerance of resident bacteria and other organisms in the microbiome of the large intestine. In a vitamin A deficient state, innate immunity is compromised and pro-inflammatory Th1 cells predominate.
Britain's first response to Napoleon's Continental System was to launch a major naval attack against Denmark. Although ostensibly neutral, Denmark was under heavy French and Russian pressure to pledge its fleet to Napoleon. London could not take the chance of ignoring the Danish threat. In August 1807, the Royal Navy besieged and bombarded Copenhagen, leading to the capture of the Dano–Norwegian fleet, and assuring use of the sea lanes in the North and Baltic seas for the British merchant fleet. Denmark joined the war on the side of France, but without a fleet it had little to offer, beginning an engagement in a naval guerrilla war in which small gunboats attacked larger British ships in Danish and Norwegian waters. Denmark also committed themselves to participate in a war against Sweden together with France and Russia. At Tilsit, Napoleon and Alexander had agreed that Russia should force Sweden to join the Continental System, which led to a Russian invasion of Finland in February 1808, followed by a Danish declaration of war in March. Napoleon also sent an auxiliary corps, consisting of troops from France, Spain and Holland, led by Marshal Jean-Baptiste Bernadotte, to Denmark to participate in the invasion of Sweden. But British naval superiority prevented the armies from crossing the Øresund strait, and the war came mainly to be fought along the Swedish–Norwegian border.
The oxidative burst is a defense mechanism in which neutrophils produce and release reactive oxidative species in the vicinity of bacteria or fungi to destroy the foreign cells. Glutathione Reductase deficient neutrophils were shown to produce a more transient oxidative burst in response to bacteria than neutrophils that express GR at ordinary levels. The mechanism of Glutathione Reductase in sustaining the oxidative burst is still unknown.
Lokivetmab, trade name Cytopoint, is a monoclonal antibody used to treat atopic dermatitis in dogs. It acts against interleukin 31 (IL-31), which is a cytokine involved in causing itchiness (pruritus). Lokivetmab is administered by subcutaneous injection; each dose is effective for four to eight weeks. The United States Department of Agriculture (USDA) approved lokivetmab (manufactured by Zoetis and sold under the trade name Cytopoint) in December 2016, and it was approved by the European Medicines Agency in 2017. Lokivetmab was the first monoclonal antibody to be approved for use in animals in the European Union.
Sources: en.wikipedia.org
No. It is a synthetic analogue carrying four amino acid changes, a lactam ring and an amidated C-terminus. The natural hormone is a linear thirteen-amino-acid peptide processed from proopiomelanocortin.
Afamelanotide is the linear analogue [Nle4-D-Phe7]-alpha-MSH, sometimes called melanotan I, while melanotan II is cyclic and carries three further substitutions. The two are distinct molecules and are not interchangeable in analytical testing.
Binding to the four melanocortin receptor subtypes is well documented in vitro. The relative contribution of each subtype to whole-body effects in humans is far less certain.
Solutions are best kept cold, protected from light, and buffered to a pH that limits hydrolysis. Dividing a stock into single-use aliquots avoids repeated freeze-thaw cycles, which measurably reduce the intact parent peak over time.