If you have been reading about afamelanotide 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.
Updated 2026-03-16. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white solid | Lyophilised cake or flake |
| Solubility class | Soluble in water and aqueous buffer | Also soluble in some polar organic solvents |
| Typical storage temperature | Minus 20 degrees Celsius or below | Desiccated and protected from light |
| Typical analytical method | LC-MS/MS | Reversed-phase separation with mass detection |
| Molecular formula | C50H69N15O9 | Free base; salt forms differ |
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.
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.
The compound emerged from research programs in the 1980s that examined analogues of alpha-melanocyte-stimulating hormone for pigmentation and photoprotection. Investigators modified the native sequence to extend activity duration and potency. A related analogue, afamelanotide, was developed within the same broad line of inquiry and eventually gained approval in certain jurisdictions for a rare light-sensitivity condition. Melanotan-2 itself did not progress through the same regulatory route and has no approved therapeutic indication.
Melanocortin receptors comprise five subtypes with distinct tissue distributions and functions. Melanotan-2 is described in the literature as a non-selective agonist that engages several of these subtypes, including MC1R, MC3R, MC4R, and MC5R. MC1R is the subtype most directly linked to melanin production in skin cells. Because the compound is not subtype-selective, its observed effects in experimental settings are generally attributed to activity across multiple receptor pathways rather than to a single target.
Melanotan-2 is a synthetic linear peptide built from seven amino acids arranged in a short chain. Its sequence is commonly written as Ac-Nle-Asp-His-D-Phe-Arg-Trp-Lys-NH2, which includes a modified N-terminus and an amidated C-terminus. The molecule belongs to the melanocortin family and acts as a receptor agonist. Structural features such as the D-phenylalanine residue and the Nle substitution are associated with increased stability against enzymatic degradation relative to the natural parent peptide.
== Honey bees == Honey bees deposit vitellogenin molecules in fat bodies in their abdomen and heads. The fat bodies apparently act as a food storage reservoir. The glycolipoprotein vitellogenin has additional functionality as it acts as an antioxidant to prolong Queen bee and forager lifespan as well as a hormone that affects future foraging behavior. The health of a honey bee colony is dependent upon the vitellogenin reserves of the nurse bees – the foragers having low levels of vitellogenin. As expendable laborers, the foragers are fed just enough protein to keep them working their risky task of collecting nectar and pollen. Vitellogenin levels are important during the nest stage and thus influence honey bee worker division of labor. A nurse bee's vitellogenin titer that developed in the first four days after emergence, affects its subsequent age to begin foraging and whether it preferentially forages for nectar or pollen. If young workers are short on food their first days of life, they tend to begin foraging early and preferentially for nectar. If they are moderately fed, they forage at normal age preferentially for nectar. If they are abundantly fed, immediately after emergence, their vitellogenin titer is high and they begin foraging later in life, preferentially collecting pollen. Pollen is the only available protein source for honey bees.
The club, like most other organizations in Germany, including sports and football clubs, was dissolved by the occupying Allied authorities in the aftermath of the war. Club members reconstituted the team in 1946 as SG Probstheida under the auspices of the occupying Soviets. After playing as BSG Erich Zeigner Probstheida and then BSG Einheit Ost, the club merged with sports club SC Rotation Leipzig in 1954 and played in the DDR-Oberliga, East Germany's top-flight league, but earned only mediocre results. In 1963, the city of Leipzig's two most important sports clubs, SC Rotation and SC Lokomotive Leipzig, were merged, resulting in the founding of two new sides: SC Leipzig and BSG Chemie Leipzig.
The EPA have some regulations and guidelines for monitoring nitrogen dioxide levels. Historically, some states in the US including Chicago, Northeast corridor and Los Angeles have had high levels of nitrogen dioxide. In 2006, the WHO estimated that over 2 million deaths result annually from air pollution in which nitrogen dioxide constitute one of the pollutants. While over 50% of the disease that results from these pollutants are common in developing countries and the effects in developed countries is also significant. An EPA survey in the US suggests that 16 percent of United States' housing units are sited close to an airport, highway or railroad increasing in the United States the exposure risk of approximately 48 million people. A feasibility study of the ozone formed from the oxidation of nitrogen dioxide in ambient air reported by the WHO suggested that daily deaths of 1 to 2% is attributed to exposure to ozone concentration above 47.3 ppb and exposure above 75.7 ppb is attributed to 3 to 5% increase in daily mortality. A level of 114 ppb was attributed to 5 to 9% increase daily mortality. Silo filler's disease is pervasive during the harvest seasons of food grains. In May 2015, the National Green Tribunal directed Delhi and other states in India to ban diesel vehicles over 10 years old as a measure to reduce nitrogen dioxide emission that may result in nitrogen dioxide poisoning. In 2008, the report of United Kingdom Committee on the Medical Effects of Air Pollutants (COMEAP) suggested that air pollution is the cause of about 29,000 deaths in UK.
== Personal life and death == Yonath was married to Moshe Yonath. Their marriage ended in divorce. They had one daughter, Hagit Yonath, a doctor at Sheba Medical Center, and a granddaughter, Noa. Yonath was the cousin of anti-occupation activist Ruchama Marton as their mothers were sisters. Yonath died on 31 August 2026, at the age of 87.
Sources: en.wikipedia.org
=== Purifications and measurements of mass === The minimum molecular weight suggested by Mulder's analyses was roughly 9 kDa, hundreds of times larger than other molecules being studied. Hence, the chemical structure of proteins (their primary structure) was an active area of research until 1949, when Fred Sanger sequenced insulin. The (correct) theory that proteins were linear polymers of amino acids linked by peptide bonds was proposed independently and simultaneously by Franz Hofmeister and Emil Fischer at the same conference in 1902. However, some scientists were sceptical that such long macromolecules could be stable in solution. Consequently, numerous alternative theories of the protein primary structure were proposed, e.g., the colloidal hypothesis that proteins were assemblies of small molecules, the cyclol hypothesis of Dorothy Wrinch, the diketopiperazine hypothesis of Emil Abderhalden and the pyrrol/piperidine hypothesis of Troensgard (1942). Most of these theories had difficulties in accounting for the fact that the digestion of proteins yielded peptides and amino acids. Proteins were finally shown to be macromolecules of well-defined composition (and not colloidal mixtures) by Theodor Svedberg using analytical ultracentrifugation. The possibility that some proteins are non-covalent associations of such macromolecules was shown by Gilbert Smithson Adair (by measuring the osmotic pressure of hemoglobin) and, later, by Frederic M. Richards in his studies of ribonuclease S.
== Catabolism == Degradation of glycosphingolipids occurs in the lysosome, which contains digestive enzymes in animal cells. The lysosome breaks down the glycosphingolipid to its primary components, fatty acids, sphingosine, and saccharide.
== Z == Zeaxanthin 7,8-dioxygenase - Zfp14 zinc finger protein - Zfp28 zinc finger protein - zinc finger - Zinc finger and scan domain containing 30 - Zinc finger containing ubiquitin peptidase 1 - Zinc finger nfx1-type containing 1 - Zinc finger protein 93 - Zinc finger protein 101 - Zinc finger protein 175 - Zinc finger protein 222 - Zinc finger protein 230 - Zinc finger protein 280b - Zinc finger protein 296 - Zinc finger protein 414 - Zinc finger protein 433 - Zinc finger protein 490 - Zinc finger protein 530 - Zinc finger protein 556 - Zinc finger protein 562 - Zinc finger protein 574 - Zinc finger protein 577 - Zinc finger protein 585b - Zinc finger protein 586 - Zinc finger protein 730 - Zinc finger protein 770 - Zinc finger protein 773 - Zinc finger protein 780a - Zinc finger protein 780b - Zinc finger protein 791 - Zinc finger protein 836 - Zinc finger protein 846
Sources: en.wikipedia.org
=== Prescription drug history === Antibiotics first arrived on the medical scene in 1932 thanks to Gerhard Domagk; and were coined the "wonder drugs". The introduction of the sulfa drugs led to the mortality rate from pneumonia in the U.S. to drop from 0.2% each year to 0.05% (i.e., 1⁄4 as much) by 1939. Antibiotics inhibit the growth or the metabolic activities of bacteria and other microorganisms by a chemical substance of microbial origin. Penicillin, introduced a few years later, provided a broader spectrum of activity compared to sulfa drugs and reduced side effects. Streptomycin, found in 1942, proved to be the first drug effective against the cause of tuberculosis and also came to be the best known of a long series of important antibiotics. A second generation of antibiotics was introduced in the 1940s: aureomycin and chloramphenicol. Aureomycin was the best known of the second generation. Lithium was discovered in the 19th century for nervous disorders and its possible mood-stabilizing or prophylactic effect; it was cheap and easily produced. As lithium fell out of favor in France, valpromide came into play. This antibiotic was the origin of the drug that eventually created the mood stabilizer category. Valpromide had distinct psychotrophic effects that were of benefit in both the treatment of acute manic states and in the maintenance treatment of manic depression illness. Psychotropics can either be sedative or stimulant; sedatives aim at damping down the extremes of behavior. Stimulants aim at restoring normality by increasing tone.
The Gibson assembly method is a relatively straightforward DNA assembly method, requiring only a few additional reagents: the 5' T5 exonuclease, Phusion DNA polymerase, and Taq DNA ligase. The DNA fragments to be assembled are synthesised to have overlapping 5' and 3' ends in the order that they are to be assembled in. These reagents are mixed together with the DNA fragments to be assembled at 50 °C and the following reactions occur:
=== Other === Deformity type Erlenmeyer flask gives a distal femur similar to an Erlenmeyer flask. It may result from Gaucher disease. Kashin–Beck disease Melnick–Needles syndrome Ovine chondrodysplasia Familial osteodysplasia, Anderson type Ulna metaphyseal dysplasia syndrome
Serotonin syndrome is typically caused by the use of two or more serotonergic drugs, including SSRIs. Serotonin syndrome is a condition that can range from mild (most common) to deadly. Mild symptoms may consist of increased heart rate, fever, shivering, sweating, dilated pupils, myoclonus (intermittent jerking or twitching), as well as hyperreflexia. Concomitant use of SSRIs or SNRIs for depression with a triptan for migraine does not appear to heighten the risk of the serotonin syndrome. Taking monoamine oxidase inhibitors (MAOIs) in combination with SSRIs can be fatal, since MAOIs disrupt monoamine oxidase, an enzyme which is needed to break down serotonin and other neurotransmitters. Without monoamine oxidase, the body is unable to eliminate excess neurotransmitters, allowing them to build up to dangerous levels. The prognosis for recovery in a hospital setting is generally good if serotonin syndrome is correctly identified. Treatment consists of discontinuing any serotonergic drugs and providing supportive care to manage agitation and hyperthermia, usually with benzodiazepines.
Sources: en.wikipedia.org
Mass spectrometry combined with liquid chromatography provides both molecular weight confirmation and a measure of related impurities. Tandem mass spectrometry adds sequence information. A purity percentage reported without a mass measurement does not confirm what the material is.
No. Lyophilisation slows degradation rather than stopping it, and the rate depends on residual moisture, temperature and light exposure. Freezer storage extends useful life but does not make the material permanent.
A certificate is only as good as its traceability to a specific batch and a named laboratory. Documents lacking batch numbers, method descriptions or laboratory identifiers carry little weight. Confirming what was actually received generally requires a separate test of the material in hand.
It is a synthetic cyclic heptapeptide modelled on alpha-melanocyte-stimulating hormone. A lactam bridge links two side chains, forming a ring that stabilises the molecule against proteolysis. It belongs to the broader melanocortin peptide family.