afamelanotide 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 2026-05-19. Where a claim depends on a specific study, the study is described rather than over-claimed.
Receptor-binding studies classify melanotan II as a non-selective melanocortin agonist. It interacts with MC1R, MC3R, MC4R and MC5R, with reported affinities in the low nanomolar range and no strong subtype preference. Activation of MC1R on dermal melanocytes shifts pigment synthesis toward eumelanin, the dark polymer deposited in melanosomes and transferred to keratinocytes. Because the same peptide engages MC4R in the hypothalamus, it also appears in animal work on food intake and erectile response, which is why it is discussed in both pigment and metabolic research. Which receptor populations dominate after systemic exposure in humans is not fully established.
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.
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.
| 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 |
Activity is attributed to agonism at melanocortin receptors, particularly MC1R and MC4R. Activation of MC1R on melanocytes increases melanin synthesis, which underlies the reported tanning effect. MC4R engagement in the central nervous system is linked to appetite suppression and to effects on sexual arousal reported in early clinical studies. Those studies were small and were not designed to establish efficacy or long-term safety. Receptor selectivity among the melanocortin subtypes is not absolute, which complicates attribution of any effect to a single pathway.
Regulatory treatment varies between countries. Several national medicines agencies have classified the peptide as unapproved, and customs authorities in some jurisdictions seize shipments on that basis. A few jurisdictions channel supply through prescription-only frameworks that do not list the substance by name. Because the material circulates mainly through online vendors, composition and purity are rarely verified before sale. Surveys of unapproved peptide products have reported labels that did not match measured content in a substantial fraction of samples.
Regulatory treatment varies by country. In the United States, melanotan-2 is not approved for any indication, and products marketed for human use fall outside the approved drug framework. Some other jurisdictions have placed it under prescription controls or listed it as a prohibited or restricted substance. Online listings frequently describe the material as a research chemical, a category that does not carry the same manufacturing and labelling requirements as approved medicines.
Solid peptide material is generally stable when kept cold and dry. Common practice is storage at -20 degrees Celsius or lower, with desiccant and protection from light. Repeated freeze-thaw cycles and exposure to moisture are associated with degradation, aggregation, or loss of material. Once dissolved, stability depends on solvent, concentration, and temperature, and solutions are usually treated as short-lived unless stability data support longer periods. Handling notes typically emphasise minimising time at ambient temperature.
nirantarāndhakārita-digantara-kandaladamanda-sudhārasa-bindu-sāndratara-ghanāghana-vṛnda-sandehakara-syandamāna-makaranda-bindu-bandhuratara-mākanda-taru-kula-talpa-kalpa-mṛdul̥a-sikatā-jāla-jaṭila-mūla-tala-maruvaka-miladalaghu-laghu-laya-kalita-ramaṇīya-pānīya-śālikā-bālikā-karāra-vinda-galantikā-galadelā-lavaṅga-pāṭala-ghanasāra-kastūrikātisaurabha-medura-laghutara-madhura-śītalatara-saliladhārā-nirākariṣṇu-tadīya-vimala-vilocana-mayūkha-rekhāpasārita-pipāsāyāsa-pathika-lokān from the Varadāmbikā Pariṇaya Campū by Tirumalāmbā, composed of 195 Sanskrit letters (428 letters in the roman transliteration, dashes excluded), thus making it the longest word ever to appear in worldwide literature. Each hyphen separates every individual word this word is composed of. The approximate meaning of this word is:
=== Diver's telephone === The communications equipment is relatively straightforward and may be of the two-wire or four-wire type. Two wire systems use the same wires for surface to diver and diver to surface messages, whereas four wire systems allow the diver's messages and the surface operator's messages to use separate wire pairs. In a two wire system the standard arrangement for diver communications is to have the diver's side normally on, so that the surface team can hear anything from the diver at all times except when the surface is sending a message. In a four-wire system the diver's side is always on, even when the surface operator is talking. This is considered an important safety feature, as the surface team can monitor the diver's breathing sounds, which can give early warning of problems developing, and confirms that the diver is alive. Heliox divers may need a decoder system (unscrambler) which reduces the frequency of the sound to make it more intelligible.
=== TG-IR (thermogravimetric analysis-infrared spectrometry) === Measuring the gas evolved as a material is heated allows qualitative identification of the species to complement the purely quantitative information provided by measuring the weight loss.
Garvan Medal, 1985 as a distinguished woman in chemistry. Maryland Chemist of the Year, American Chemical Society, 1989. Eastern Analytical Symposium Award for Outstanding Achievements in the Fields of Analytical Chemistry, 1999 National Institutes of Health MERIT Award, 1991–2001. Distinguished Service Award, Human Proteome Organization, 2006 Field & Franklin Award for Contributions in Mass spectrometry, American Chemical Society (ACS), 2008. Thomson Medal, International Mass Spectrometry Foundation, 2009. Ralph N. Adams Award in Bioanalytical Chemistry, 2010 John B. Fenn Award for a Distinguished Contribution in Mass Spectrometry, American Society for Mass Spectrometry, 2012. Eastern Analytical Symposium Award for Outstanding Achievements in Mass Spectrometry, 2014 Distinguished Contribution Award, the Association for Mass Spectrometry and Advances in Clinical Lab (MSACL), 2017 US Human Proteome Organization Catherine E. Costello Lifetime Achievement in Proteomics Award, 2022. Fellow of the American Society for Mass Spectrometry, 2025.
β-pleated sheet structures are made from extended β-strand polypeptide chains, with strands linked to their neighbours by hydrogen bonds. Due to this extended backbone conformation, β-sheets resist stretching. β-sheets in proteins may carry out low-frequency accordion-like motion as observed by the Raman spectroscopy and analyzed with the quasi-continuum model. A β-helix is formed from repeating structural units consisting of two or three short β-strands linked by short loops. These units "stack" atop one another in a helical fashion so that successive repetitions of the same strand hydrogen-bond with each other in a parallel orientation. See the β-helix article for further information. In lefthanded β-helices, the strands themselves are quite straight and untwisted; the resulting helical surfaces are nearly flat, forming a regular triangular prism shape, as shown for the 1QRE archaeal carbonic anhydrase at right. Other examples are the lipid A synthesis enzyme LpxA and insect antifreeze proteins with a regular array of Thr sidechains on one face that mimic the structure of ice.
Sources: en.wikipedia.org
Žarković, N.; Zarković, K.; Schaur, R. J. R.; Stolc, S.; Schlag, G. N.; Redl, H.; Waeg, G.; Borović, S.; Loncarić, I.; Jurić, G.; Hlavka, V. (1999). "4-Hydroxynonenal as a second messenger of free radicals and growth modifying factor". Life Sciences. 65 (18–19): 1901–1904. doi:10.1016/S0024-3205(99)00444-0. PMID 10576434. Sharma, R.; Brown, D.; Awasthi, S.; Yang, Y.; Sharma, A.; Patrick, B.; Saini, M. K.; Singh, S. P.; Zimniak, P.; Singh, S. V.; Awasthi, Y. C. (2004). "Transfection with 4-hydroxynonenal-metabolizing glutathione S-transferase isozymes leads to phenotypic transformation and immortalization of adherent cells". European Journal of Biochemistry. 271 (9): 1690–1701. doi:10.1111/j.1432-1033.2004.04067.x. PMID 15096208.
==== List of P-CABs in the markets (First year of approval for clinical use) ==== Revaprazan (2006) Vonoprazan (2014) Tegoprazan (2018) Fexuprazan (2021) Keverprazan (2023/China) Zastaprazan (2024/South Korea)
The pharmaceutical sciences are a group of interdisciplinary areas of study concerned with the design, manufacturing, action, delivery, and classification of drugs. They apply knowledge from chemistry (inorganic, physical, biochemical and analytical), biology (anatomy, physiology, biochemistry, cell biology, and molecular biology), epidemiology, statistics, chemometrics, mathematics, physics, and chemical engineering. The pharmaceutical sciences are further subdivided into several specific specialties, with four main branches:
=== Sex and Gender === Jung believed in biologically based psychological differences between males and females. He articulated this view in his distinction between Eros or feminine psychology and Logos or masculine psychology. While he acknowledged that both Eros and Logos exist in males and females, in Jung's view Eros is more characteristic of female psychology and Logos of male psychology, and hence these categories retain 'statistical validity'. As Jung writes when reflecting on the genetic basis of these differences:
Sources: en.wikipedia.org
=== Protein quantification === For genes encoding proteins, the expression level can be directly assessed by a number of methods with some clear analogies to the techniques for mRNA quantification. One of the most commonly used methods is to perform a Western blot against the protein of interest. This gives information on the size of the protein in addition to its identity. A sample (often cellular lysate) is separated on a polyacrylamide gel, transferred to a membrane and then probed with an antibody to the protein of interest. The antibody can either be conjugated to a fluorophore or to horseradish peroxidase for imaging and/or quantification. The gel-based nature of this assay makes quantification less accurate, but it has the advantage of being able to identify later modifications to the protein, for example proteolysis or ubiquitination, from changes in size.
A glycome is the entire complement or complete set of all sugars, whether free or chemically bound in more complex molecules, of an organism. An alternative definition is the entirety of carbohydrates in a cell. The glycome may in fact be one of the most complex entities in nature. "Glycomics, analogous to genomics and proteomics, is the systematic study of all glycan structures of a given cell type or organism" and is a subset of glycobiology. "Carbohydrate", "glycan", "saccharide", and "sugar" are generic terms used interchangeably in this context and includes monosaccharides, oligosaccharides, polysaccharides, and derivatives of these compounds. Carbohydrates consist of "hydrated carbon", i.e. [CH2O]n. Monosaccharides are a carbohydrate that cannot be hydrolyzed into a simpler carbohydrate and are the building blocks of oligosaccharides and polysaccharides. Oligosaccharides are linear or branched chains of monosaccharides attached to one another via glycosidic linkages. The number of monosaccharide units can vary. Polysaccharides are glycans composed of repeating monosaccharides, generally greater than ten monosaccharide units in length. The glycome exceeds the complexity of the proteome as a result of the even greater diversity of the glycome's constituent carbohydrates and is further complicated by the sheer multiplicity of possibilities in the combination and interaction of the carbohydrates with each other and with proteins. "The spectrum of all glycan structures — the glycome — is immense.
The group takes its name from Mighei (Ukraine), but the most famous member is the extensively studied Murchison meteorite. Many falls of this type have been observed and CM chondrites are known to contain a rich mix of complex organic compounds such as amino-acids and purine/pyrimidine nucleobases. CM chondrite famous falls:
==== MeSH D13.695.740 – pyrimidine nucleotides ==== MeSH D13.695.740.050 – apurinic acid MeSH D13.695.740.246 – cytosine nucleotides MeSH D13.695.740.246.050 – arabinofuranosylcytosine triphosphate MeSH D13.695.740.246.115 – cyclic cmp MeSH D13.695.740.246.150 – cytidine diphosphate MeSH D13.695.740.246.150.180 – cytidine diphosphate choline MeSH D13.695.740.246.150.210 – cytidine diphosphate diglycerides MeSH D13.695.740.246.370 – cytidine monophosphate MeSH D13.695.740.246.370.250 – cytidine monophosphate n-acetylneuraminic acid MeSH D13.695.740.246.400 – cytidine triphosphate MeSH D13.695.740.246.425 – deoxycytosine nucleotides MeSH D13.695.740.246.425.300 – deoxycytidine monophosphate MeSH D13.695.740.600 – pyrimidine dimers MeSH D13.695.740.706 – thymine nucleotides MeSH D13.695.740.706.788 – thymidine monophosphate MeSH D13.695.740.850 – uracil nucleotides MeSH D13.695.740.850.210 – deoxyuracil nucleotides MeSH D13.695.740.850.210.200 – fluorodeoxyuridylate MeSH D13.695.740.850.600 – uridine diphosphate MeSH D13.695.740.850.600.677 – uridine diphosphate sugars MeSH D13.695.740.850.600.677.100 – uridine diphosphate n-acetylgalactosamine MeSH D13.695.740.850.600.677.120 – uridine diphosphate n-acetylglucosamine MeSH D13.695.740.850.600.677.150 – uridine diphosphate n-acetylmuramic acid MeSH D13.695.740.850.600.677.300 – uridine diphosphate galactose MeSH D13.695.740.850.600.677.350 – uridine diphosphate glucose MeSH D13.695.740.850.600.677.375 – uridine diphosphate glucuronic acid MeSH D13.695.740.850.600.677.800 – uridine diphosphate xylose MeSH D13.695.740.850.877 – uridine monophosphate MeSH D13.695.740.850.950 – uridine triphosphate
The relatively quick heteronuclear single quantum correlation experiment helps determine the feasibility of doing subsequent longer, more expensive, and more elaborate experiments. It is not possible to assign peaks to specific atoms from the heteronuclear single quantum correlation alone.
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.
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.