This is a working overview of cyclic heptapeptide, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-04-04 and is reviewed periodically as new material appears.
Pharmacologically, melanotan-2 behaves as a non-selective agonist across the melanocortin receptor family. Binding at MC1R on dermal melanocytes promotes eumelanin synthesis, which underlies the tanning response described in early human work. Activity at the centrally expressed MC4R receptor is associated with reported effects on appetite and erectile function. Because the peptide does not discriminate strongly among receptor subtypes, attributing any single observed effect to one receptor pathway is generally not possible without selective antagonists or receptor knockout models.
Research interest has centred on photoprotection and pigmentation, with a smaller body of work on appetite and sexual function. Published human data remain limited to small, frequently uncontrolled studies, and the compound has never received marketing approval from a national medicines regulator. Most laboratory work treats it as a pharmacological tool for probing melanocortin signalling in cell culture or animal models. Whether pigmentation changes observed in people translate into measurable protection against ultraviolet-induced DNA damage remains an open question.
Regulatory status varies by jurisdiction, and the substance is frequently described as unapproved for therapeutic use. Some authorities classify it alongside prescription-only medicines or controlled categories, while others address it through general consumer protection rules. Analytical surveys have reported mismatches between label claims and measured content in products sold online, although the scope of such testing is limited. Whether these discrepancies are widespread remains an open question. Discussion in the literature therefore tends to combine chemistry, supply-chain observation and policy analysis.
The material is commonly handled as a lyophilized powder in sealed vials. The solid dissolves readily in water and in polar organic solvents, producing a clear solution after reconstitution. Light, heat and repeated freeze-thaw cycles are the concerns most often raised in handling guidance, because peptide bonds and the constrained ring can degrade. Working solutions are generally prepared fresh, and material left in solution is treated as less stable than the dry form. These properties shape how laboratories store and aliquot reference material.
Identity and purity are assessed mainly by reversed-phase high-performance liquid chromatography with ultraviolet detection, often paired with mass spectrometry. Retention time supports identity, while the mass spectrum confirms the molecular weight of the intact peptide. Purity is frequently reported as a percentage of total peak area, a figure that depends on the wavelength, column and gradient used. Impurity profiling may also look for truncated sequences, oxidised forms and residual counterions. Amino acid analysis and peptide mapping provide orthogonal confirmation when required.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | Melanotan II; MT-II; N-acetyl-norleucyl-cyclo[Asp-His-D-Phe-Arg-Trp-Lys] amide | Naming follows peptide convention; the numeral distinguishes it from melanotan-1 |
| Molecular formula | C50H69N15O9 | Includes the lactam bridge; no counter-ion assumed |
| Monoisotopic mass | 1023.53 Da | Free base; salts and counter-ions shift the observed value |
| Appearance | White to off-white lyophilised powder | Batch-to-batch colour variation is not itself proof of impurity |
| Typical analytical method | RP-HPLC purity determination with ESI-MS identity confirmation | Retention time alone does not establish sequence identity |
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.
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.
Testing during and for many weeks after a hemolytic episode will lead to false-negative results, as the G6PD-deficient RBC will have been excreted, and the young RBC (reticulocyte) will not yet be G6PD deficient. False-negative results will also be likely following any blood transfusions. For this reason, many hospitals wait three months after a hemolytic episode before testing for G6PD deficiency. Females should have their G6PD activity measured by a quantitative assay to avoid being misclassified by screening tests.
Studies of 9/11's economic effects show the Manhattan office real-estate market and office employment were less affected than first feared, because of the financial services industry's need for face-to-face interaction. North American air space was closed for several days after the attacks and air travel decreased upon its reopening, leading to a nearly 20% cutback in air travel capacity, and exacerbating financial problems in the struggling U.S. airline industry. The September 11 attacks also led to the U.S. wars in Afghanistan and Iraq, as well as additional homeland security spending, totaling at least US$5 trillion.
=== Radioactive isotopes === The existence of isotopes was first suggested in 1913 by the radiochemist Frederick Soddy, based on studies of radioactive decay chains that indicated about 40 different species referred to as radioelements (i.e. radioactive elements) between uranium and lead, although the periodic table only allowed for 11 elements between lead and uranium inclusive. Several attempts to separate these new radioelements chemically had failed. For example, Soddy had shown in 1910 that mesothorium (later shown to be 228Ra), radium (226Ra, the longest-lived isotope), and thorium X (224Ra) are impossible to separate. Attempts to place the radioelements in the periodic table led Soddy and Kazimierz Fajans independently to propose their radioactive displacement law in 1913, to the effect that alpha decay produced an element two places to the left in the periodic table, whereas beta decay emission produced an element one place to the right. Soddy recognized that emission of an alpha particle followed by two beta particles led to the formation of an element chemically identical to the initial element but with a mass four units lighter and with different radioactive properties. Soddy proposed that several types of atoms (differing in radioactive properties) could occupy the same place in the table. For example, the alpha-decay of uranium-235 forms thorium-231, whereas the beta decay of actinium-230 forms thorium-230.
=== In literature === Thorazine was often depicted in Tom Wolfe's The Electric Kool-Aid Acid Test to abort bad trips on LSD. Thorazine is also mentioned in Fear and Loathing in Las Vegas, where it was reported to negate the effects of LSD: "You better hope there's some Thorazine in that bag, because if there's not, you're in bad trouble."
== Products == B. animalis is present in many food products and dietary supplements. The probiotic is mostly found in dairy products. Bifidobacterium animalis subsp. lactis BB-12 is a bacterial subspecies within the animalis strain that exhibits rod-shaped structure and lacks catalase activity. The subspecies was initially identified as Bifidobacterium bifidum, however advancements in molecular classification later reclassified it as Bifidobacterium animalis, and subsequently as Bifidobacterium animalis subsp. lactis. It was first preserved in Chr. Hansen's cell culture bank in 1983 as part of the dairy culture collection. It exhibits suitability for producing probiotic dairy products and has found application in infant formula, dietary supplements, and fermented milk products. This is due to a variety of favorable technological characteristics such as its fermentation activity, high tolerance to air, stability, and resilience to acidic and bile environments, even in freeze-dried products. Moreover, Bifidobacterium animalis subsp. lactisBB-12 does not alter the taste, appearance, or texture of food products and maintains viability in probiotic foods until consumption.
Sources: en.wikipedia.org
== Fluorescence == The quinine in tonic water will fluoresce under ultraviolet light. In fact, quinine will visibly fluoresce in direct sunlight against a dark background. The quinine molecules release energy as light instead of heat, which is more common. The state is not stable, and the molecules will immediately return to a ground state and no longer glow once the UV source is removed.
=== Bulbs === Most light bulbs have either clear or coated glass. Coated glass bulbs have kaolin clay blown in and electrostatically deposited on the interior of the bulb. The powder layer diffuses the light from the filament. Pigments may be added to the clay to adjust the color of the light emitted. Kaolin diffused bulbs are used extensively in interior lighting because of their comparatively gentle light. Other kinds of colored bulbs are also made, including the various colors used for "party bulbs", Christmas tree lights and other decorative lighting. These are created by coloring the glass with a dopant; which is often a metal like cobalt (blue) or chromium (green). Neodymium-containing glass is sometimes used to provide a more natural-appearing light.
==== José Manuel Valdés Menéndez-Cuesta elected Grand Master ==== On October 25, 2025, the Grand Lodge of Cuba held general elections, and José Manuel Valdés Menéndez-Cuesta, a member of the Federico Valdés Lodge in Cotorro, was elected as Grand Master of the Grand Lodge of Cuba. Valdés has over 25 years of experience in Cuban Freemasonry. In November, 2025, Miriam García Mariño, the Director of the Office of Associations at the Ministry of Justice signed Resolution 7, in which the Ministry officially declared that the elections of October 25 were considered legal and appropriate. In Resolution 7, the Ministry officially stated that Former Grand Master Filema Duarte had disregarded the will of the majority by seeking to delay the institutional function of the Grand Lodge of Cuba. The Ministry also urged the new Grand Master to: "...“achieve unity, institutionalization, and the proper development of the transition process." Some Cuban Freemasons, while relieved that Filema Duarte was no longer protected by the Ministry of Justice, were skeptical that the government would not still attempt to control the fraternity, stating that they believed the institution would be manipulated in more subtle ways going forward, instead of the overt and direct methods they had been using.
Most specialties: the National Resident Matching Program (NRMP)—the American Osteopathic Association Match used to be a separate option for DOs but was merged with the NRMP Match after 2020 Urology Residency Match Program SF Match—ophthalmology, plastics Similarly, residency programs submit a list of their preferred applicants in rank order to this same service. The process is blinded, so neither applicant nor program will see each other's list. Aggregate program rankings can be found here, and are tabulated in real time based on applicants' anonymously submitted rank lists. The two parties' lists are combined by an NRMP computer, which creates stable (a proxy for optimal) matches of residents to programs using an algorithm. On the third Friday of March each year ("Match Day") these results are announced in Match Day ceremonies at the United States' 155 medical schools. By entering the Match system, applicants are contractually obligated to go to the residency program at the institution to which they were matched. The same applies to the programs; they are obligated to take the applicants who matched into them.
Sources: en.wikipedia.org
In any case, findings that bicalutamide helps to preserve body weight and lean body mass in castrated male rats also could not be explained by preservation of estrogen levels. Aside from muscle, bicalutamide has also been found to act not as an AR silent antagonist but as a weak partial agonist of the receptor with SARM-like activity in AR-positive MDA-MB-453 breast cancer cells. Whereas a pure AR antagonist should have no effect, bicalutamide regulated almost 50% of 189 DHT-responsive genes in this cell line and induced these genes around 25% as effectively as the highest tested concentration of DHT. DHT and SARMs like enobosarm and GTx-027 inhibit the proliferation of AR-expressing MDA-MB-231 breast cancer cells, whereas findings for bicalutamide are conflicting. Bicalutamide has also shown SARM-like or weak partial agonist activity in certain other in vitro AR bioassays. A very high (50 mg/kg) dose of bicalutamide has been found to suppress testosterone levels by about 91% in gonadally intact male mice, which was to a similar degree as the SARM MK-4541. These findings suggest that bicalutamide at very high doses may have antigonadotropic effects that may be mediated by SARM-like activity. Conversely however, lower doses of bicalutamide (1–25 mg/kg) have not been found to affect testosterone levels in gonadally intact male rats, and similar or higher doses of bicalutamide (20–100 mg/kg) did not affect testosterone levels in gonadally intact male dogs.
The drug combination fenfluramine/phentermine, usually called fen-phen, is an anti-obesity medication that is no longer widely available. It was sold in the early 1990s, and utilized two anorectics. Fenfluramine was marketed by American Home Products (later known as Wyeth) as Pondimin, but was shown to cause potentially fatal pulmonary hypertension and heart valve problems, which eventually led to its withdrawal in 1997 and legal damages of over $13 billion. On the other hand, phentermine has side effects such as a fast heart beat, high blood pressure, trouble sleeping, dizziness, and restlessness. Fenfluramine acts as a serotonin releasing agent, phentermine as primarily a norepinephrine releasing agent. Phentermine also induces the release of serotonin and dopamine, although to a far lesser extent than it induces the release of norepinephrine.
The use of displacement chromatography is rather limited, and is mostly used for preparative chromatography. The basic principle is based on a molecule with a high affinity for the chromatography matrix (the displacer) which is used to compete effectively for binding sites, and thus displace all molecules with lesser affinities. There are distinct differences between displacement and elution chromatography. In elution mode, substances typically emerge from a column in narrow, Gaussian peaks. Wide separation of peaks, preferably to baseline, is desired in order to achieve maximum purification. The speed at which any component of a mixture travels down the column in elution mode depends on many factors. But for two substances to travel at different speeds, and thereby be resolved, there must be substantial differences in some interaction between the biomolecules and the chromatography matrix. Operating parameters are adjusted to maximize the effect of this difference. In many cases, baseline separation of the peaks can be achieved only with gradient elution and low column loadings. Thus, two drawbacks to elution mode chromatography, especially at the preparative scale, are operational complexity, due to gradient solvent pumping, and low throughput, due to low column loadings. Displacement chromatography has advantages over elution chromatography in that components are resolved into consecutive zones of pure substances rather than "peaks".
== Background == The first successful delivery of a drug across the BBB occurred in 1995. The drug used was hexapeptide dalargin, an anti-nociceptive peptide that cannot cross the BBB alone. It was encapsulated in polysorbate 80 coated nanoparticles and intravenously injected. This was a huge breakthrough in the nanoparticle drug delivery field, and it helped advance research and development toward clinical trials of nanoparticle delivery systems. Nanoparticles range in size from 10 - 1000 nm (or 1 μm) and they can be made from natural or artificial polymers, lipids, dendrimers, and micelles. Most polymers used for nanoparticle drug delivery systems are natural, biocompatible, and biodegradable, which helps prevent contamination in the CNS. Several current methods for drug delivery to the brain include the use of liposomes, prodrugs, and carrier-mediated transporters. Many different delivery methods exist to transport these drugs into the body, such as peroral, intranasal, intravenous, and intracranial. For nanoparticles, most studies have shown increasing progression with intravenous delivery. Along with delivery and transport methods, there are several means of functionalizing, or activating, the nanoparticle carriers. These means include dissolving or absorbing a drug throughout the nanoparticle, encapsulating a drug inside the particle, or attaching a drug on the surface of the particle.
Parmotrema perlatum is globally widespread lichen found on all continents except Antarctica and predominantly in oceanic areas in Europe, primarily grows on bark and occasionally on siliceous rocks amongst mosses. While it is seeing an increase in the Netherlands due to global warming, it is critically endangered in the Czech Republic, Slovakia, and Poland due to susceptibility to air pollution, and is listed as extinct in certain regional Red Data Books due to a lack of recent findings. In contrast, it has been increasing in sightings in the Netherlands, a phenomenon attributed to both global warming decreases in the levels or air pollution in recent decades. Its recent recurrence in Hungary, particularly on some unusual hosts (Catalpa bignonioides, Prunus serotina, and Robinia pseudoacacia) have been suggested as a possible consequence of "a recolonisation process, due to the improving air quality".
Sources: en.wikipedia.org
It is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone, containing seven amino acids with a lactam ring and a D-configured phenylalanine residue. It is supplied as a lyophilised powder for laboratory research.
The natural hormone is a linear tridecapeptide that is rapidly degraded in circulation. Melanotan-2 is shortened, cyclised, N-terminally acetylated, and carries a D-amino acid substitution, all of which slow enzymatic breakdown.
No national medicines regulator has approved melanotan-2 for therapeutic or cosmetic use. In several jurisdictions it is treated as an unapproved prescription medicine, and its legal classification differs from country to country.
The dry powder is more stable during transport and storage than a solution. It also allows a known amount of material to be reconstituted at a chosen concentration.