The short version of afamelanotide fits in a sentence. The long version — which is the one that helps — is below.
This page was last updated on 2026-06-27 and is reviewed periodically as new material appears.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white powder | Lyophilised material may be hygroscopic |
| Solubility class | Soluble in water, DMSO and DMF | Dilution into aqueous buffer can cause precipitation |
| Storage of solid | Minus 20 degrees C, desiccated, dark | Aliquot to limit repeated opening of the vial |
| Storage of solution | Minus 20 to minus 80 degrees C, aliquoted | Avoid repeated freeze-thaw cycles |
| Identity method | Reversed-phase HPLC with mass spectrometry | Retention time and mass are checked together |
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.
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.
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.
=== Historical background === Cryobiology history can be traced back to antiquity. As early as in 2500 BC, low temperatures were used in Egypt in medicine. The use of cold was recommended by Hippocrates to stop bleeding and swelling. With the emergence of modern science, Robert Boyle studied the effects of low temperatures on animals. In 1949, bull semen was cryopreserved for the first time by a team of scientists led by Christopher Polge. This led to a much wider use of cryopreservation today, with many organs, tissues and cells routinely stored at low temperatures. Large organs such as hearts are usually stored and transported, for short times only, at cool but not freezing temperatures for transplantation. Cell suspensions (like blood and semen) and thin tissue sections can sometimes be stored almost indefinitely in liquid nitrogen temperature (cryopreservation). Human sperm, eggs, and embryos are routinely stored in fertility research and treatments. Controlled-rate and slow freezing are well established techniques pioneered in the early 1970s which enabled the first human embryo frozen birth (Zoe Leyland) in 1984. Since then, machines that freeze biological samples using programmable steps, or controlled rates, have been used all over the world for human, animal, and cell biology – 'freezing down' a sample to better preserve it for eventual thawing, before it is deep frozen, or cryopreserved, in liquid nitrogen.
== Structure == The NDUFB2 gene, located on the q arm of chromosome 7 in position 34, is 9,966 base pairs long and is composed of 4 exons. The NDUFB2 protein weighs 12 kDa and is composed of 105 amino acids. NDUFB2 is a subunit of the enzyme NADH dehydrogenase (ubiquinone), the largest of the respiratory complexes. The structure is L-shaped with a long, hydrophobic transmembrane domain and a hydrophilic domain for the peripheral arm that includes all the known redox centers and the NADH binding site. NDUFB3 is one of about 31 hydrophobic subunits that form the transmembrane region of Complex I. It has been noted that the N-terminal hydrophobic domain has the potential to be folded into an alpha helix spanning the inner mitochondrial membrane with a C-terminal hydrophilic domain interacting with globular subunits of Complex I. The highly conserved two-domain structure suggests that this feature is critical for the protein function and that the hydrophobic domain acts as an anchor for the NADH dehydrogenase (ubiquinone) complex at the inner mitochondrial membrane. Hydropathy analysis revealed that this subunit and 4 other subunits have an overall hydrophilic pattern, even though they are found within the hydrophobic protein (HP) fraction of complex I.
Hong Kong is a special administrative region of China, with executive, legislative, and judicial powers devolved from the national government. The Sino-British Joint Declaration provided for economic and administrative continuity through the handover, resulting in an executive-led governing system largely inherited from the territory's history as a British colony. Under these terms and the "one country, two systems" principle, the Basic Law of Hong Kong is the regional constitution. The regional government is composed of three branches:
== Awards and honours == 1998 Founders Award for Excellence from the Canadian College of Medical Geneticists. 1996 Honoured by Human Genome Organization at a special presentation in Heidelberg. 1996 Fellow of the American Association for the Advancement of Science. Fellow of the Canadian College of Medical Geneticists.
Sources: en.wikipedia.org
==== Tongue ==== Food enters the mouth where the first stage in the digestive process takes place, with the action of the tongue and the secretion of saliva. The tongue is a fleshy and muscular sensory organ, and the first sensory information is received via the taste buds in the papillae on its surface. If the taste is agreeable, the tongue will go into action, manipulating the food in the mouth which stimulates the secretion of saliva from the salivary glands. The liquid quality of the saliva will help in the softening of the food and its enzyme content will start to break down the food whilst it is still in the mouth. The first part of the food to be broken down is the starch of carbohydrates (by the enzyme amylase in the saliva). The tongue is attached to the floor of the mouth by a ligamentous band called the frenum and this gives it great mobility for the manipulation of food (and speech); the range of manipulation is optimally controlled by the action of several muscles and limited in its external range by the stretch of the frenum. The tongue's two sets of muscles, are four intrinsic muscles that originate in the tongue and are involved with its shaping, and four extrinsic muscles originating in bone that are involved with its movement.
Flaminius had overseen the construction of the road named after him from Bononia (Bologna) to Arretium (Arezzo). Acidinus had conquered the Taurisci in 183. The triumvirate led 3,000 families to settle the area meaning Aquileia probably had a population of 20,000 soon after its founding. Meanwhile, based on the evidence of names chiselled on stone, the majority of colonizing families came from Picenum, Samnium, and Campania, which also explains why the colony was Latin and not Roman. Among these colonists, pedites received 50 iugera of land each, centuriones received 100 iugera each, and equites received 140 iugera each. Either at the founding or not long afterwards, colonists from the nearby Veneti supplemented these families. Roads soon connected Aquileia with the Roman colony of Bologna probably in 173 BC. In 148 BC, it was connected with Genua by the Via Postumia, which stretched across the Padanian plain from Aquileia through or near to Opitergium, Tarvisium, Vicetia, Verona, Bedriacum, and the three Roman colonies of Cremona, Placentia, and Dertona. The construction of the Via Popilia from the Roman colony of Ariminium to Ad Portum near Altinum in 132 BC improved communications still further. In the first century, the Via Gemina would link Aquileia with Emona to the east of the Julian Alps, and by 78 or 79 the Via Flavia would link Aquileia to Pula.
== Bibliography == Elyse; Houde, Alain (2002). "La PCR en temps réel: principes et applications" (PDF). Reviews in Biology and Biotechnology. 2 (2): 2–11. Archived from the original (PDF) on 2009-06-12. Bustin, SA (2000). "Absolute quantification of mRNA using real-time reverse transcription polymerase chain reaction assays". J Mol Endocrinol. 25 (2): 169–193. doi:10.1677/jme.0.0250169. PMID 11013345. Higuchi, R.; Dollinger, G.; Walsh, P.S.; Griffith, R. (1992). "Simultaneous amplification and detection of specific DNA-sequences". Bio-Technology. 10 (4): 413–417. doi:10.1038/nbt0492-413. PMID 1368485. S2CID 1684150. Holland, P.M.; Abramson, R.D.; Watson, R.; Gelfand, D.H. (1991). "Detection of specific polymerase chain reaction product by utilizing the 50 !30 exonuclease activity of Thermus aquaticus DNA polymerase". Proc. Natl. Acad. Sci. USA. 88 (16): 7276–7280. Bibcode:1991PNAS...88.7276H. doi:10.1073/pnas.88.16.7276. JSTOR 2357665. PMC 52277. PMID 1871133. Kubista, M; Andrade, JM; Bengtsson, M; Forootan, A; Jonak, J; Lind, K; Sindelka, R; Sjoback, R; Sjogreen, B; Strombom, L; Stahlberg, A; Zoric, N (2006). "The real-time polymerase chain reaction". Mol. Aspects Med. 27 (2–3): 95–125. doi:10.1016/j.mam.2005.12.007. PMID 16460794. Higuchi, R.; Fockler, C.; Dollinger, G.; Watson, R. (1993). "Kinetic PCR: Real time monitoring of DNA amplification reactions". Biotechnology. 11 (9): 1026–1030. doi:10.1038/nbt0993-1026. PMID 7764001. S2CID 5714001. Filion, M. (2012). Quantitative Real-time PCR in Applied Microbiology. Caister Academic Press. ISBN 978-1-908230-01-0.
Sources: en.wikipedia.org
Purity is normally stated as an area percentage from high-performance liquid chromatography, for example ninety-five or ninety-eight percent. That figure describes the proportion of ultraviolet-absorbing material eluting as the main peak. It says nothing about water content, counterions, residual solvents or mass fraction of the peptide itself.
Peptides are commonly isolated as acetate or trifluoroacetate salts, and the counterion contributes to total mass. Two vials with identical peptide content can therefore differ in weight and in measured response. Residual trifluoroacetate is also relevant in cell-based work because it can influence membrane behaviour.
Degradation products are often closely related to the parent molecule, making them hard to resolve with a single method. Counterion variability adds a further source of scatter between laboratories. Because no pharmacopoeial monograph exists for melanotan-2, groups rely on method-specific validation rather than a shared reference standard.
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.