A practical reference on cyclic heptapeptide: what it is, how it behaves, what the literature reports, and where the honest uncertainties sit.
Reviewed 2026-05-31. Anything still debated is marked as such rather than presented as settled.
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.
Structurally, Melanotan-2 retains the core recognition motif of alpha-melanocyte-stimulating hormone while adding a lactam bridge that links two side chains and constrains the molecule into a ring. This modification lowers susceptibility to enzymatic degradation. The compound acts as an agonist at melanocortin receptors, particularly subtypes associated with melanin production. Because the same receptor family influences several physiological processes, researchers note that its activity is not confined to pigmentation alone. Receptor selectivity continues to be examined in published studies.
Melanotan-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone, a naturally occurring peptide involved in pigmentation signalling. Its sequence incorporates modified residues that increase potency and extend biological activity relative to the native hormone. The compound binds receptors of the melanocortin family and is examined mainly in laboratory research. It does not occur naturally and exists only as a manufactured chemical entity produced by solid-phase synthesis.
| 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 |
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.
Melanotan-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone, the naturally occurring peptide involved in pigmentation signalling. Its sequence is conventionally written as Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, with a lactam bridge joining the aspartate side chain to the lysine side chain. The empirical formula is C50H69N15O9 and the monoisotopic mass lies near 1023.5 daltons. N-terminal acetylation and the D-configured phenylalanine both increase resistance to enzymatic breakdown compared with the parent hormone.
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.
Melanotan II is a synthetic cyclic heptapeptide analog derived from the core sequence of alpha-melanocyte-stimulating hormone. Researchers at the University of Arizona synthesized it during the 1980s while studying pigmentation and appetite signaling. The compound is not an approved medicine in any major jurisdiction and appears mainly in laboratory and research-chemical settings. Its structure incorporates a lactam bridge between side chains, which constrains the ring and slows enzymatic breakdown relative to the natural hormone.
A range of test have been developed including smartphone based platforms, and tests targeting blood, saliva, faecal matter, urine, and tears have been proposed. Saliva in particular may offer sufficiently high detection rates in tandem with a non-invasive and user friendly procedure, although reliability requires improvement. Emerging technology at the point of care setting is being developed to allow for rapid assessment of micronutrient deficiency. The Cornell NutriPhone is a technology for determining nutritional status at the point of care. This technology allows assessment of iron, vitamin A, vitamin D, and vitamin B12 from a single drop of blood in around 15 minutes. Building on this same platform, there are proof-of-concept studies for fever and cancer.
While both members bear S-glycosyl groups, RiPPs bearing O- or N-linked carbohydrates will also be included in this family as they are discovered. Linaridins are characterized by C-terminal aminovinyl cysteine residues. While this posttranslational modification is also seen in the lanthipeptides epidermin and mersacidin, linaridins do not have Lan or MeLan residues. In addition, the linaridin moiety is formed from modification of two Cys residues, whereas lanthipeptide aminovinyl cysteines are formed from Cys and dehydroalanine (Dha). The first linaridin to be characterized was cypemycin. Microviridins are cyclic N-acetylated trideca- and tetradecapeptides with ω-ester and/or ω-amide bonds. Lactone formation through glutamate or aspartate ω-carboxy groups and the lysine ε-amino group forms macrocycles in the final natural product. This class of RiPPs function as protease inhibitors and were originally isolated from Microcystis viridis. Gene clusters encoding microviridins have also been identified in genomes across the Bacteroidetes and Proteobacteria phyla. Orbitides are plant-derived N-to-C cyclized peptides with no disulfide bonds. Also referred to as Caryophyllaceae-like homomonocyclopeptides, orbitides are 5-12 amino acids in length and are composed of mainly hydrophobic residues. Similar to the amatoxins and phallotoxins, the gene sequences of orbitides suggest the presence of a C-terminal recognition sequence.
== Medical uses == Amitriptyline is indicated for the treatment of major depressive disorder, neuropathic pain, and for the prevention of migraine and chronic tension headache. It can be used for the treatment of nocturnal enuresis in children older than 6 after other treatments have failed.
Born: Vyacheslav Gryaznov, Russian classical pianist; in Yuzhno-Sakhalinsk, Sakhalin, Russian SFSR, Soviet Union Filip Karadordević, U.S.-born Serbian businessman and heir to the throne of the abolished monarchy of Serbia and Yugoslavia as the eldest son of the former Crown Prince Alexander Karadordević, who was the only child of King Peter II of Yugoslavia; in Vienna, Virginia Died: Red Smith, 76, American sportswriter and columnist, died four days after he had published a column, which he headlined "Writing Less— and Better?" where he announced that he would be writing only three columns per week rather than four.
Cirrhosis is most commonly caused by medical conditions including alcohol-related liver disease, metabolic dysfunction–associated steatohepatitis (MASH – the progressive form of metabolic dysfunction–associated steatotic liver disease, previously called non-alcoholic fatty liver disease or NAFLD), heroin abuse, chronic hepatitis B, and chronic hepatitis C. Chronic heavy drinking can cause alcoholic liver disease. Liver damage has also been attributed to heroin usage over an extended period of time as well. MASH has several causes, including obesity, high blood pressure, abnormal levels of cholesterol, type 2 diabetes, and metabolic syndrome. Less common causes of cirrhosis include autoimmune hepatitis, primary biliary cholangitis, and primary sclerosing cholangitis that disrupts bile duct function, genetic disorders such as Wilson's disease and hereditary hemochromatosis, and chronic heart failure with liver congestion. Diagnosis is based on blood tests, medical imaging, and liver biopsy. Hepatitis B vaccine can prevent hepatitis B and the development of cirrhosis from it, but no vaccination against hepatitis C is available. No specific treatment for cirrhosis is known, but many of the underlying causes may be treated by medications that may slow or prevent worsening of the condition. Hepatitis B and C may be treatable with antiviral medications. Avoiding alcohol is recommended in all cases. Autoimmune hepatitis may be treated with steroid medications. Ursodiol may be useful if the disease is due to blockage of the bile duct.
Sources: en.wikipedia.org
Our knowledge concerning the natural history and effects of different cross-sex hormone therapies on breast development in [transgender] women is extremely sparse and based on low quality of evidence. Current evidence does not provide evidence that progestogens enhance breast development in [transgender] women. Neither do they prove the absence of such an effect. This prevents us from drawing any firm conclusion at this moment and demonstrates the need for further research to clarify these important clinical questions. Data on menstruating women shows there is no correlation between water retention, and levels of progesterone or estrogen. Despite this, some theorise progesterone might cause temporary breast enlargement due to local fluid retention, and may thus give a misleading appearance of breast growth. Aside from a hypothetical involvement in breast development, progestogens are not otherwise known to be involved in physical feminization.
Triple-stranded DNA (also known as H-DNA or Triplex-DNA) is a DNA structure in which three oligonucleotides wind around each other and form a triple helix. In triple-stranded DNA, the third strand binds to a B-form DNA (via Watson–Crick base-pairing) double helix by forming Hoogsteen base pairs or reversed Hoogsteen hydrogen bonds.
== Diagnosis == FOP is diagnosed based on a combination of clinical features, imaging studies, and genetic testing. Hallmark clinical features of FOP include congenital malformations of the large toes (hallux valgus) and episodes of painful soft tissue swelling. The characteristic features of FOP on radiographs and CT scan include extraosseous bone formation in soft tissue, forming corticated bone in ribbons, sheets or bridges across joints. During flare-ups, MRI and ultrasound are sensitive for preosseous lessions, including soft tissue edema and enhancement prior to ossification. PET scans can identify early, metabolically active lesions, and can predict future sites of ossification. Molecular genetic testing for FOP includes sequence analysis of the ACVR1 gene. Early diagnosis of this disorder through radiology is very important to avoid unnecessary invasive investigations like biopsies. The smallest or trivial trauma or intramuscular injections can amplify progression of the disease through inflammation hence the favorability of radiology. Clinicians should be aware of this rare entity, as it is frequently misdiagnosed as cancer or other benign entities such as infection, resulting in biopsies that can often hasten disease progression.
== References == Cooper, Paul W. (1996). Explosives Engineering. New York: Wiley-VCH. ISBN 978-0-471-18636-6. OCLC 34409473. Retrieved 9 June 2014. Urbanski, Tadeusz (1967). Chemistry and Technology of Explosives. Vol. III. Warszawa: Polish Scientific Publishers.
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.
It is a synthetic cyclic heptapeptide and an analogue of alpha-melanocyte-stimulating hormone. The molecule is produced by chemical synthesis rather than extracted from a biological source.