This is a working overview of cyclic heptapeptide, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-02-17. Anything still debated is marked as such rather than presented as settled.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C50H69N15O9 | Free base; salt forms differ |
| Molecular weight | Approximately 1024 g/mol | Calculated for the free base |
| Appearance | White to off-white powder | Typically supplied as a lyophilised solid |
| Solubility | Soluble in water and polar solvents | Poorly soluble in non-polar solvents |
| Typical storage | -20 degrees Celsius, dry, protected from light | Refers to the solid form |
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.
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.
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.
Melanotan II binds several melanocortin receptor subtypes rather than a single target. MC1R on melanocytes drives melanin synthesis, while MC3R and MC4R participate in energy balance, appetite, and sexual response pathways. This lack of selectivity explains why reported effects extend beyond skin darkening. Substitutions at positions four and seven, including norleucine and D-phenylalanine, increase potency and resistance to peptidases. Understanding which receptor mediates which effect remains an active area of investigation.
Published human data come mostly from small, short studies rather than large controlled trials. Reported outcomes include increased skin pigmentation and, in some reports, effects on appetite and libido, but sample sizes are small and follow-up is limited. Whether long-term use produces durable pigment changes or adverse effects is not established. Because products sold outside pharmacies are not standardized, the actual content of any given vial is often unknown. Independent testing of such material is uncommon.
Zenobi-Wong works in the area of tissue engineering, in particular for cartilage regeneration. She develops functional biomaterials which mimic the extracellular matrix. The biofabrication techniques used to develop these materials include electrospinning, casting, two-photon polymerization and bioprinting. Zenobi-Wong holds four licensed patents in the fields of tissue engineering, tissue engineering techniques, and gene expression assays. She was one of the originators of the MSc Biomedical Engineering program at ETH Zürich, and developed several graduate level courses in tissue engineering and biomedical engineering. Zenobi-Wong currently serves as President of the Swiss Society for Biomaterials and Regenerative Medicine, and as secretary general of the International Society of Biofabrication. ETH Zürich Department of Health Sciences and Technology - Tissue Engineering and Biofabrication Group Marcy Zenobi-Wong publications indexed by Google Scholar
Viruses containing positive-strand RNA or double-strand RNA, except retroviruses and Birnaviridae All positive-strand RNA eukaryotic viruses with no DNA stage, such as Coronaviridae All RNA-containing bacteriophages; the two families of RNA-containing bacteriophages are Fiersviridae (positive ssRNA phages) and Cystoviridae (dsRNA phages) dsRNA virus family Reoviridae, Totiviridae, Hypoviridae, Partitiviridae Mononegavirales (negative-strand RNA viruses with non-segmented genomes; InterPro: IPR016269) Negative-strand RNA viruses with segmented genomes (InterPro: IPR007099), such as orthomyxoviruses and bunyaviruses dsRNA virus family Birnaviridae (InterPro: IPR007100) Flaviviruses produce a polyprotein from the ssRNA genome. The polyprotein is cleaved to a number of products, one of which is NS5, an RdRp. It possesses short regions and motifs homologous to other RdRps. RNA replicase found in positive-strand ssRNA viruses are related to each other, forming three large superfamilies. Birnaviral RNA replicase is unique in that it lacks motif C (GDD) in the palm. Mononegaviral RdRp (PDB 5A22) has been automatically classified as similar to (+)−ssRNA RdRps, specifically one from Pestivirus and one from Leviviridae. Bunyaviral RdRp monomer (PDB 5AMQ) resembles the heterotrimeric complex of Orthomyxoviral (Influenza; PDB 4WSB) RdRp.
24. Semaglutide. Drugs and Lactation Database (LactMed®) [Internet]. Bethesda (MD): National Institute of Child Health and Human Development; 2006–. 2026 Aug 15. Semaglutide was not detectable in the milk of mothers taking the drug subcutaneously. Their breastfed infants experienced no adverse effects. Some brands of oral semaglutide, such as Rybelsus, contain the absorption enhancer salcaprozate sodium, which may enter milk and accumulate in infants. Only injectable forms of semaglutide should be used during breastfeeding. Some experts recommend closely monitoring of infant growth and developmental milestones and the nutritional status of the lactating woman.[1]
The word collagen is derived from the Greek κόλλα, kólla, meaning "glue", and the suffix -gen, meaning "giving birth to", as later used in the French collagène. The word was first used in English in 1843.
Sources: en.wikipedia.org
=== Inorganic compounds === Most binary compounds of thorium with nonmetals may be prepared by heating the elements together. In air, thorium burns to form ThO2, which has the fluorite structure. Thorium dioxide is a refractory material, with the highest melting point (3390 °C) of any known oxide. It is somewhat hygroscopic and reacts readily with water and many gases; it dissolves easily in concentrated nitric acid in the presence of fluoride. When heated in air, thorium dioxide emits intense blue light; the light becomes white when ThO2 is mixed with its lighter homologue cerium dioxide (CeO2, ceria): this is the basis for its previously common application in gas mantles. A flame is not necessary for this effect: in 1901, it was discovered that a hot Welsbach gas mantle (using ThO2 with 1% CeO2) remained at "full glow" when exposed to a cold unignited mixture of flammable gas and air. The mantle can also be heated electrically to produce light. The light emitted by thorium dioxide is higher in wavelength than the blackbody emission expected from incandescence at the same temperature, an effect called candoluminescence. It occurs because ThO2 : Ce acts as a catalyst for the recombination of free radicals that appear in high concentration in a flame, whose deexcitation releases large amounts of energy.
=== Brand names === As of 2018, the combination is marketed under several brand names, including Efficib, Janmet, Januet, Janumet, Jznumet, Ristaben Met, Ristfor, Siglimet, Sitamet, Sitar-M, Sliptin-M, Treviamet, Velmetia, Istamet, Emsita, Sitaglyn, Sitazit-M, and Zaxoran.
In correspondence with Snopes, White House spokesman Steven Cheung denied the rumor that Trump had defecated at the event. On March 2, Trump was photographed with a dark red rash on his neck. Trump's physician Sean Barbabella issued a statement saying that the president was using a medicated cream as a "preventative" treatment of the skin condition which was expected to last "a few weeks"; he did not explain the skin condition or disclose what the medication was. On March 12, during a White House gathering for Women's History Month, Trump referred to his current White House Press Secretary Karoline Leavitt as "Kellyanne," appearing to mistake her for the former senior counselor from his first presidency Kellyanne Conway.
Clinical trials are prospective biomedical or behavioral research studies on human participants designed to answer specific questions about biomedical or behavioral interventions, including new treatments (such as novel vaccines, drugs, dietary choices, dietary supplements, and medical devices) and known interventions that warrant further study and comparison. Clinical trials generate data on dosage, safety and efficacy. They are conducted only after they have received health authority/ethics committee approval in the country where approval of the therapy is sought. These authorities are responsible for vetting the risk/benefit ratio of the trial—their approval does not mean the therapy is "safe" or effective, only that the trial may be conducted. Depending on product type and development stage, investigators initially enroll volunteers or patients into small pilot studies, and subsequently conduct progressively larger scale comparative studies. Clinical trials can vary in size and cost, and they can involve a single research center or multiple centers, in one country or in multiple countries. Clinical study design aims to ensure the scientific validity and reproducibility of the results. Costs for clinical trials can range into the billions of dollars per approved drug, and the complete trial process to approval may require 7–15 years. The sponsor may be a governmental organization or a pharmaceutical, biotechnology or medical-device company.
Enzymes are not rigid, static structures; instead they have complex internal dynamic motions – that is, movements of parts of the enzyme's structure such as individual amino acid residues, groups of residues forming a protein loop or unit of secondary structure, or even an entire protein domain. These motions give rise to a conformational ensemble of slightly different structures that interconvert with one another at equilibrium. Different states within this ensemble may be associated with different aspects of an enzyme's function. For example, different conformations of the enzyme dihydrofolate reductase are associated with the substrate binding, catalysis, cofactor release, and product release steps of the catalytic cycle, consistent with catalytic resonance theory. The transitions between the different conformations during the catalytic cycle involve internal viscoelastic motion that is facilitated by high-strain regions where amino acids are rearranged.
Sources: en.wikipedia.org
There are special risks to consider for older adults, and women who are pregnant. When a person ages, the body becomes less able to rid itself of barbiturates. As a result, people over the age of 65 are at higher risk of experiencing the harmful effects of barbiturates, including drug dependence and accidental overdose. When barbiturates are taken during pregnancy, the drug passes through the placenta to the fetus. After the baby is born, it may experience withdrawal symptoms and have trouble breathing. In addition, nursing mothers who take barbiturates may transmit the drug to their babies through breast milk. A rare adverse reaction to barbiturates is Stevens–Johnson syndrome, which primarily affects the mucous membranes.
Transgenic mice with a fluorescently tagged UBE3A were used to test the effectiveness of unsilencing the paternal copy. When tested on mice in vivo, topotecan affected the hippocampus, striatum and cerebral cortex but not the cerebellum unless a higher dose was administered (21.6 micrograms/hour for five days). The study suggested that the topoisomerase inhibitors have the potential to produce a normally functioning UBE3A protein. Most symptoms due to Angelman syndrome are traditionally treated by speech therapy, physical therapy and occupational therapy. Anti-seizure medication is often prescribed as seizures are a common symptom of Angelman syndrome. These treatments target only symptoms. This drug has been administered to cancer patients. It was well tolerated when administered to pediatric and adult patients.
==== Huntington's Disease ==== Mutant huntingtin protein disrupts AMPAR-mediated synaptic transmission by impairing receptor trafficking, leading to synaptic dysfunction and neuronal loss in Huntington's disease models.
Unlike animals, many plant cells, particularly those of the parenchyma, do not terminally differentiate, remaining totipotent with the ability to give rise to a new individual plant. Exceptions include highly lignified cells, the sclerenchyma and xylem which are dead at maturity, and the phloem sieve tubes which lack nuclei. While plants use many of the same epigenetic mechanisms as animals, such as chromatin remodelling, an alternative hypothesis is that plants set their gene expression patterns using positional information from the environment and surrounding cells to determine their developmental fate. Epigenetic changes can lead to paramutations, which do not follow the Mendelian heritage rules. These epigenetic marks are carried from one generation to the next, with one allele inducing a change on the other.
Sources: en.wikipedia.org
No. Melanotan-2 is manufactured synthetically. The naturally occurring peptide in the same family is alpha-melanocyte-stimulating hormone, which the body produces as part of normal endocrine and neural signalling.
Both are synthetic analogues derived from the same parent hormone. Reference descriptions usually characterise afamelanotide as more selective for the MC1R subtype, whereas melanotan-2 is reported to interact with a wider range of melanocortin receptors.
Early studies explored melanocortin signalling and pigmentation, which later led to informal use of the label tanning peptide. That label is not a regulatory category and does not imply approved status for any purpose.
No. No major regulatory agency has granted a marketing authorisation for melanotan II as a medicine. Products sold under this name are generally presented as laboratory reagents and are not subject to the batch-release testing applied to approved drugs.