If you have been reading about cyclic heptapeptide 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 2025-10-06. Numbers and descriptions here follow the published literature rather than marketing material.
Melanotan-2 appears on the World Anti-Doping Agency prohibited list within the peptide hormone class, and several national regulators treat it as an unapproved prescription substance. Some countries restrict importation or sale for personal use. Because the compound is widely traded as a research chemical, the practical legal picture differs between jurisdictions and shifts over time. Human safety data covering long periods are limited, and whether repeated pigmentation changes carry any lasting risk to melanocytes remains an open question.
Freeze-dried melanotan-2 is normally kept as a desiccated powder at minus twenty degrees Celsius or lower, shielded from light and moisture. Peptides of this size degrade through hydrolysis, oxidation and deamidation, and each pathway accelerates as temperature and water activity rise. Repeated freeze-thaw cycles promote aggregation and loss of material, so aliquoting a stock solution before freezing is standard laboratory practice. Once dissolved, the solution is markedly less stable than the powder. In laboratory work, solutions are generally refrigerated and used within days rather than kept for months.
Identity and purity are usually assessed by reversed-phase high-performance liquid chromatography, which separates the target peptide from truncated or oxidised impurities. Mass spectrometry, most often coupled to liquid chromatography, confirms molecular mass and detects substitutions that chromatography alone may miss. Amino acid analysis and peptide mapping supply additional structural evidence, while nuclear magnetic resonance is reserved for full structural confirmation. Laboratories that examine samples sold online report wide variation in actual content, with some vials containing little or none of the labelled material.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Typical storage temperature | -20 °C or below | For the lyophilised powder, desiccated |
| Storage form | Sealed vial, protected from light | Amber glass or foil-wrapped containers |
| Reconstituted stability | Short, refrigerate | Degradation accelerates in solution |
| Typical analytical method | Reversed-phase HPLC with mass spectrometry | Purity assessment plus identity confirmation |
| Common synonyms | Melanotan II, MT-II | Also written melanotan-2 |
Regulatory treatment varies by country. In the United States the peptide is not approved as a medicine, and products offered for human use may be treated as unapproved new drugs; some states also restrict sale. Australia, the United Kingdom, and European Union member states apply comparable restrictions to unapproved peptide products. Border agencies have seized shipments labelled as research chemicals. Classification may change over time, and the legal position for personal importation is not clearly settled in most published guidance.
Lyophilised melanotan-2 is supplied as a solid, which is more stable than a solution. The material is hygroscopic, so weighing is done quickly, in low humidity, with the container kept sealed. Reconstitution usually uses water for injection or bacteriostatic water, added down the wall of the vial to limit foaming. A reconstituted solution is held at 2 to 8 °C and kept away from light. Repeated freezing and thawing of the same vial is avoided because ice crystal formation and concentration effects degrade the peptide.
Reversed-phase high-performance liquid chromatography is the routine method for purity assessment. Peptides absorb near 214 nm because of the peptide bond, and a gradient of acetonitrile in water separates the intact peptide from deletion sequences, oxidised products, and earlier-eluting fragments at neutral pH. Electrospray ionisation mass spectrometry provides an orthogonal check: the measured mass must agree with the theoretical value. Amino acid analysis and peptide mapping confirm structure but are used less often. Reference standards remain scarce because the peptide is not described in any pharmacopoeia.
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.
The peptide was developed during the 1980s by researchers investigating melanocortin signalling and skin pigmentation pathways. Early work focused on analogues of alpha-melanocyte-stimulating hormone that would resist enzymatic breakdown more effectively than the parent molecule. Melanotan-2 emerged from that programme as a shortened, cyclised variant. Reports describing its synthesis and receptor activity later appeared in the scientific literature. Commercial availability grew through unregulated channels rather than through pharmaceutical approval.
Published research on the compound remains limited. Much of the human data comes from small, early-stage studies rather than large controlled trials, and several questions about effects and variability between individuals remain open. Investigators have examined receptor activity, pigment pathways, and related physiological responses in laboratory and animal models. Findings from those models do not automatically translate to human outcomes. Reviews frequently note the scarcity of rigorous clinical evidence and call for better-characterized study material.
Because the substance circulates mainly through informal markets, verification is a recurring theme in technical discussion. Independent analyses have found that labeled content and actual content can diverge, and that purity varies between samples. Analytical laboratories use reversed-phase chromatography to separate components and mass spectrometry to confirm identity. Isotope-labeled internal standards improve quantification in complex matrices. Such methods describe what a sample contains but say nothing about its sterility, lawful status, or suitability for any use. Open questions remain about how consistently testing is applied across the supply chain.
Regulatory treatment of this peptide varies by country. It holds no marketing authorization as a medicine in the United States, the European Union, or most other jurisdictions. Some countries classify products containing it as prescription-only or unlicensed medicines, which restricts lawful supply. Authorities have issued public notices warning that unregulated products may contain undeclared or incorrect ingredients. The molecule also appears on prohibited lists for competitive sport. These measures address supply oversight rather than any approved therapeutic role.
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.
Messenger ribonucleic acid (mRNA) is a single-stranded molecule of RNA that corresponds to the genetic sequence of a gene, and is read by a ribosome in the process of synthesizing a protein. mRNA is created during the process of transcription, where an enzyme (RNA polymerase) converts the gene into primary transcript mRNA (also known as pre-mRNA). This pre-mRNA usually still contains introns, regions that will not go on to code for the final amino acid sequence. These are removed in the process of RNA splicing, leaving only exons, regions that will encode the protein. This exon sequence constitutes mature mRNA. Mature mRNA is then read by the ribosome, and the ribosome creates the protein utilizing amino acids carried by transfer RNA (tRNA). This process is known as translation. All of these processes form part of the central dogma of molecular biology, which describes the flow of genetic information in a biological system. As in DNA, genetic information in mRNA is contained in the sequence of nucleotides, which are arranged into codons consisting of three ribonucleotides each. Each codon codes for a specific amino acid, except the stop codons, which terminate protein synthesis. The translation of codons into amino acids requires two other types of RNA: transfer RNA, which recognizes the codon and provides the corresponding amino acid, and ribosomal RNA (rRNA), the central component of the ribosome's protein-manufacturing machinery. The concept of mRNA was first conceived by Sydney Brenner and Francis Crick in 1960 during a conversation with François Jacob.
=== Confluent === Sometimes, the blisters merged into sheets, forming a confluent rash, which began to detach the outer layers of skin from the underlying flesh. Patients with confluent smallpox often remained ill even after scabs had formed over all the lesions. In one case series, the case-fatality rate in confluent smallpox was 62%.
In 1956, Crick and Watson speculated on the structure of small viruses. They suggested that spherical viruses such as Tomato bushy stunt virus had icosahedral symmetry and were made from 60 identical subunits. After his short time in New York, Crick returned to Cambridge where he worked until 1976, at which time he moved to California. Crick engaged in several X-ray diffraction collaborations such as one with Alexander Rich on the structure of collagen. However, Crick was quickly drifting away from continued work related to his expertise in the interpretation of X-ray diffraction patterns of proteins. George Gamow established a group of scientists interested in the role of RNA as an intermediary between DNA as the genetic storage molecule in the nucleus of cells and the synthesis of proteins in the cytoplasm (the RNA Tie Club). It was clear to Crick that there had to be a code by which a short sequence of nucleotides would specify a particular amino acid in a newly synthesised protein. In 1956, Crick wrote an informal paper about the genetic coding problem for the small group of scientists in Gamow's RNA group. In this article, Crick reviewed the evidence supporting the idea that there was a common set of about 20 amino acids used to synthesise proteins. Crick proposed that there was a corresponding set of small "adaptor molecules" that would hydrogen bond to short sequences of a nucleic acid, and also link to one of the amino acids. He also explored the many theoretical possibilities by which short nucleic acid sequences might code for the 20 amino acids.
smURFP has a large extinction coefficient (180,000 M−1 cm−1) and has a modest quantum yield (0.20), which makes it comparable biophysical brightness to eGFP and ~2-fold brighter than most red or far-red fluorescent proteins derived from coral. smURFP spectral properties are similar to the organic dye Cy5.
The Oddo–Harkins rule holds that elements with even atomic numbers are more common than those with odd atomic numbers, with the exception of hydrogen and beryllium. This rule argues that elements with odd atomic numbers have one unpaired proton and are more likely to capture another, thus increasing their atomic number. In elements with even atomic numbers, protons are paired, with each member of the pair offsetting the spin of the other, enhancing stability. All the alkali metals have odd atomic numbers and they are not as common as the elements with even atomic numbers adjacent to them (the noble gases and the alkaline earth metals) in the Solar System. The heavier alkali metals are also less abundant than the lighter ones as the alkali metals from rubidium onward can only be synthesised in supernovae and not in stellar nucleosynthesis. Lithium is also much less abundant than sodium and potassium as it is poorly synthesised in both Big Bang nucleosynthesis and in stars: the Big Bang could only produce trace quantities of lithium, beryllium and boron due to the absence of a stable nucleus with 5 or 8 nucleons, and stellar nucleosynthesis could only pass this bottleneck by the triple-alpha process, fusing three helium nuclei to form carbon, and skipping over those three elements.
Sources: en.wikipedia.org
=== Videos === "Time Thief" (1990) "Half-Life, Remembered" (1990) "Kinky Love" (1991) "Blue Flower" (1992) "Throwing Back the Apple" (1992) "Fine Friend" (1994) "Angel (Will You Be My)" (1994) "Sight of You" (2020)
=== Regulation === Methaqualone was initially placed in Schedule I as defined by the UN Convention on Psychotropic Substances, but was moved to Schedule II in 1979. In Canada, methaqualone is listed in Schedule III of the Controlled Drugs and Substances Act and requires a prescription, but it is no longer manufactured. Methaqualone is banned in India. In the United States it was withdrawn from the market in 1983 and made a Schedule I drug in 1984.
=== Tenure === In 2018, Dingell introduced a law that would give the Consumer Product Safety Commission the authority to recall defective firearms. John Dingell was a key lawmaker who initially granted the firearms industry this exemption from the 1972 Consumer Product Safety Act that created the Consumer Product Safety Commission. In July 2019, Dingell voted against a House resolution introduced by Representative Brad Schneider opposing efforts to boycott the State of Israel and the Global Boycott, Divestment, and Sanctions Movement. The resolution passed 398–17. In April 2021, Dingell introduced the Recovering America's Wildlife Act of 2021, a bill that would provide funding for conserving and protecting endangered and threatened species, strategies to do so, and wildlife-related recreational activities. The bill passed the House by 230–190 on June 14, 2022. In 2023, Dingell was among 56 Democrats to vote in favor of H.Con.Res. 21, which directed President Joe Biden to remove U.S. troops from Syria within 180 days.
=== Subdivision === Traditionally Rhodiola was divided into subgenera, sections and series, based on plant characteristics. Four subgenera were recognised; Rhodiola, Primuloides, Crassipedes and Clementsia. However molecular studies have failed to demonstrate monophyly of these subtaxa.
== Research == The best known CCK receptor antagonist is the non-selective antagonist proglumide, which blocks both CCKA and CCKB receptors, and was originally developed for the treatment of stomach ulcers. This action derived from its blockade of CCKA receptor in the gut and consequent reduction in secretion of gastric acid, however a side effect of proglumide was found, namely that it increases the analgesic effects of opioid painkillers, and decreases the development of tolerance. This was subsequently found to result from its blockade of CCKB receptors in the brain. Another CCK receptor antagonist is benzotript, which is likewise non-selective. Newer drugs have since been developed which are selective for one or other of the CCK receptors. Selective CCKA receptor antagonists such as lorglumide and devazepide have been developed both for their anti-ulcer effects and as potential drugs to limit the development of gastrointestinal cancers such as colon cancer. A centrally selective antagonist—Ranquilon—has recently undergone clinical approval for the treatment of anxiety in Russia. The main focus of CCK receptor antagonist research has focused on the development of selective CCKB receptor antagonists as novel medications which have been primarily investigated for the treatment of anxiety and panic attacks, as well as for other roles such as analgesic effects.
Sources: en.wikipedia.org
==== Elderly ==== According to the package insert, clinical studies did not show differences in efficacy and safety of ceftriaxone in geriatrics compared to younger patients but "greater sensitivity of some older individuals cannot be ruled out."
Some receptor agonists may cause downregulation of their respective receptors, while most receptor antagonists temporarily upregulate their respective receptors. The disequilibrium caused by these changes often causes withdrawal when the long-term use of a drug is discontinued. Upregulation and downregulation can also happen as a response to toxins or hormones. An example of upregulation in pregnancy is hormones that cause cells in the uterus to become more sensitive to oxytocin.
Taliban officials had not commented on the reports of airstrikes on military sites in Kandahar province. Pakistani troops attacked and destroyed Taliban border checkpoints in Zabul Province inflicting losses. Taliban authorities claimed that Pakistani conducted mortar strikes into Samkani district in Paktia province and artillery into Kunar with 82 shells hitting Sarkano District, 15 striking Dangam District and four in Shultan District. The Taliban claimed that one child was wounded and several residential properties were damaged, elsewhere, skirmishes in Kamdesh district of Nuristan killed two civilians, a mortar strike in Khost wounded a child and a civilian was killed and another wounded in skirmishes in Shkin District of Paktika Province. A policeman was killed in a militant sniper attack in Bajaur. A cylinder bomb attack on Miranshah camp killed two government officials. The Norwegian Refugee Council reported that a Pakistani artillery attack on an earthquake-affected refugee camp in Khas Kunar District, Kunar province, resulted in three people being killed and seven others being injured, while forcing 650 families from the camp to flee to safety. An Afghan media outlet reported that the Taliban were forcibly recruiting and deploying fighters, including civilians, from northern and northeastern Afghanistan to front lines along the Pakistan border, sometimes using financial incentives. It said that many were sent without their families' consent, causing concern among residents.
In clitoridectomy, the clitoris may be removed as part of a radical vulvectomy to treat cancer such as vulvar intraepithelial neoplasia; however, modern treatments favor more conservative approaches, as invasive surgery can have psychosexual consequences. Clitoridectomy more often involves parts of the clitoris being partially or completely removed during FGM, which may be additionally known as female circumcision or female genital cutting (FGC). Removing the glans does not mean that the whole structure is lost, since the clitoris reaches deep into the genitals. In reduction clitoroplasty, a common intersex surgery, the glans is preserved and parts of the erectile bodies are excised. Problems with this technique include loss of sensation, loss of sexual function, and sloughing of the glans. One way to preserve the clitoris with its innervations and function is to imbricate and bury the glans; however, Şenaylı et al. state that "pain during stimulus because of trapped tissue under the scarring is nearly routine. In another method, 50 percent of the ventral clitoris is removed through the level base of the clitoral shaft, and it is reported that good sensation and clitoral function are observed in follow-up"; additionally, it has "been reported that the complications are from the same as those in the older procedures for this method".
== Biography == He is a member of the editorial board of the journal Intelligence. His PhD was completed in 1994 at the University of Auckland (New Zealand) and integrated the Eysenckian dimensional model of psychosis with the categorical model of schizotypy proposed by Paul E. Meehl, using measures of personality, creativity, evoked potentials, and smooth pursuit eye movement dysfunction. The title of his doctoral thesis was Psychometric & psychophysiological measures for schizotypy, creativity & psychoticism. Subsequent academic publications include demonstrating the existence of two separate forms of dyslexia, underpinned by distinct genes, and, subsequently, demonstrating that the genes associated with dyslexia are also linked to normal variation in reading ability. This work lead to searches for specific genes involved in reading and language. In positive psychology, he showed (along with Alexander Weiss and Michelle Luciano) that the genes for happiness are genes for personality, suggesting that a general factor of genetic well-being and specific genetic influences from the five factor model traits of Extraversion, Neuroticism/Stability, and Conscientiousness completely explain the heritable component of differences in happiness. With Caroline Rae, Bates showed that creatine supports cognitive function – finding that creatine supplements in vegans substantially increased their cognitive ability and working memory by comparison with placebo. This supported a literal 'mental energy' model of intelligence, first postulated by Charles Spearman.
Sources: en.wikipedia.org
The lyophilised solid is best kept cold, dry and dark, typically at minus twenty degrees Celsius. Moisture and repeated warming cycles are the main causes of degradation. Solutions prepared from the powder are less stable and are normally used quickly.
Reversed-phase liquid chromatography assesses purity, while mass spectrometry confirms molecular mass and detects sequence errors. Amino acid analysis and peptide mapping add structural detail. These techniques are complementary rather than interchangeable.
It is listed as a prohibited peptide hormone by the World Anti-Doping Agency. No medicines regulator has approved it for human use. Import and sale rules vary by country.
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.