Everything below concerns cyclic peptide. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Updated 2026-05-11. Numbers and descriptions here follow the published literature rather than marketing material.
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.
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.
Early published reports described melanotan-2 as a tanning agent without sun protection, which means darkening is not the same as protection against ultraviolet radiation. Later studies explored the peptide in erectile dysfunction, hemorrhagic shock, and some skin conditions. No regulator in the United States or Europe has approved it for clinical use. Many products labelled melanotan-2 are sold without approval and their identity and purity are unverified. Its long-term safety in humans remains an open question.
Melanotan-2, also written Melanotan II, is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone. Its sequence is Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, and the lactam bridge between the aspartate and lysine side chains constrains the peptide into a ring. This structural change increases receptor affinity and metabolic stability relative to the native hormone. The compound was created in the 1980s as a research tool for studying pigmentation biology.
Melanocytes are the pigment-producing cells of the skin, and they carry melanocortin-1 receptors on their surface. When the receptor is activated, cyclic adenosine monophosphate rises inside the cell and raises the activity of enzymes such as tyrosinase, which increases melanin output. Melanotan-2 binds melanocortin-1 receptors in vitro and in animal models, and this binding is generally described as the basis for the tanning effect. Other receptors account for different effects: melanocortin-4 receptors contribute to appetite and erectile signalling, while melanocortin-3 and melanocortin-5 receptors contribute to energy balance and exocrine function.
| Property | Value | Notes |
|---|---|---|
| Lyophilised storage | −20 °C, dry, protected from light | Vials are sealed and allowed to reach room temperature before opening |
| Reconstituted storage | 2 to 8 °C, protected from light | Short-term holding; avoid repeated freeze-thaw cycles |
| Reconstitution solvent | Water for injection or bacteriostatic water | Added slowly along the vial wall to reduce foaming and shear |
| Purity measurement | RP-HPLC with area normalisation | Acetonitrile-water gradient monitored at roughly 214 nm |
| Identity confirmation | Electrospray ionisation mass spectrometry | Observed mass compared against the calculated peptide mass |
Regulatory status differs by country, and in many places supplying the compound for human consumption is unlawful. Vendors frequently label material as intended for research use only, a designation that shifts stated purpose but does not create a legal pathway for personal use. Certificates of analysis accompanying such products vary widely in detail and provenance. Third-party testing exists but is voluntary, and results are rarely linked to a specific lot in a publicly verifiable way.
Identity testing for a synthetic peptide relies on several complementary methods. Reversed-phase high-performance liquid chromatography separates the target from related impurities and reports purity as a percentage of total peak area. Mass spectrometry confirms molecular mass and can reveal deletions or truncations. Amino acid analysis and peptide mapping provide sequence-level confirmation, while counter-ion content and residual solvents are measured separately. A purity figure alone does not establish identity, so a complete dataset combines chromatographic and spectrometric evidence.
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.
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.
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.
In the Meiji period, Japanese clothes began to be westernized and the number of people who wore kimono decreased, so the craftsmen who made netsuke and kiseru with ivory and wood lost their demand. Therefore, they tried to create a new field, ivory sculptures for interior decoration, and many elaborate works were exported to foreign countries or purchased by the Imperial Family. In particular, the works of Ishikawa Komei and Asahi Gyokuzan won praise in Japan.
Cy1: Curly; the wings curve away from the body, flight may be somewhat impaired e1: Ebony; black body and wings (heterozygotes are also visibly darker than wild type) Sb1: Stubble; bristles are shorter and thicker than wild type w1: White; eyes lack pigmentation and appear white bw: Brown; eye color determined by various pigments combined. y1: Yellow; body pigmentation and wings appear yellow, the fly analog of albinism
The foundation of all biomembranes consists of a bilayer structure of phospholipids. The phospholipid molecule is amphipathic; it contains a hydrophilic polar head and a hydrophobic nonpolar tail. The phospholipid heads interact with each other and aqueous media, while the hydrocarbon tails orient themselves in the center, away from water. These latter interactions drive the bilayer structure that acts as a barrier for ions and molecules. There are various types of phospholipids; consequently, their synthesis pathways differ. However, the first step in phospholipid synthesis involves the formation of phosphatidate or diacylglycerol 3-phosphate at the endoplasmic reticulum and outer mitochondrial membrane. The synthesis pathway is found below:
There are many geological issues concerning the rivers and streams of the Appalachians. In spite of the existence of the Great Appalachian Valley, many of the main rivers are transverse to the mountain system axis. The drainage divide of the Appalachians follows a tortuous course that crosses the mountainous belt just north of the New River in Virginia. South of the New River, rivers head into the Blue Ridge, cross the higher Unakas, receive important tributaries from the Great Valley, and traversing the Cumberland Plateau in spreading gorges (water gaps), escape by way of the Cumberland River and the Tennessee River rivers to the Ohio River and the Mississippi River, and thence to the Gulf of Mexico. In the central section, north of the New River, the rivers, rising in or just beyond the Valley Ridges, flow through great gorges to the Great Valley, and then across the Blue Ridge to tidal estuaries penetrating the coastal plain via the Roanoke River, James River, Potomac River, and Susquehanna River. In the northern section, the height of land lies on the inland side of the mountainous belt, and thus the main lines of drainage run from north to south, exemplified by the Hudson River. However, the valley through which the Hudson River flows was cut by the gigantic glaciers of the ice ages—the same glaciers that deposited their terminal moraines in southern New York and formed the east–west Long Island.
== Press freedom == The 2020 World Press Freedom Index published by Reporters without Borders ranked Thailand 140 of 180 (1=best; 180=worst) nations in press freedom. Other ASEAN nations were ranked: Malaysia, 101; Indonesia, 119; Philippines, 136; Myanmar, 139; Cambodia, 144; Brunei, 152; Singapore, 158; Laos, 172; Vietnam, 175. The 2019 World Press Freedom Index published by Reporters without Borders ranked Thailand 136 of 180 (1=best; 180=worst) nations in press freedom. Other ASEAN nations were ranked: Malaysia, 123; Indonesia, 124; Philippines, 134; Myanmar, 138; Cambodia, 143; Singapore, 151; Brunei, 152; Laos, 171; Vietnam, 176. The 2018 World Press Freedom Index published by Reporters without Borders ranked Thailand 140 of 180 (1=best; 180=worst) nations in press freedom. Other ASEAN nations were ranked: Indonesia, 124; Philippines, 133; Myanmar, 137; Cambodia, 142; Malaysia, 145; Singapore, 151; Brunei, 153; Laos, 170; Vietnam, 175. The World Press Freedom Index 2016: Reporters Without Borders ranked Thailand 136 of 180 (1=best, 180=worst) countries. ASEAN as a whole ranked poorly, with Cambodia the best at 128 and Vietnam the worst at 175. The World Press Freedom Index 2015: Reporters Without Borders ranked Thailand 134 of 180 (1=best, 180=worst) countries Freedom of the Press 2015: Thailand was ranked 166 of 199 (1=best, 199=worst) nations by Freedom House.
Sources: en.wikipedia.org
== Ethical, legal and social implications == Genetic information provides a unique type of knowledge about an individual and his/her family, fundamentally different from a typically laboratory test that provides a "snapshot" of an individual's health status. The unique status of genetic information and inherited disease has a number of ramifications with regard to ethical, legal, and societal concerns. On 19 March 2015, scientists urged a worldwide ban on clinical use of methods, particularly the use of CRISPR and zinc finger, to edit the human genome in a way that can be inherited. In April 2015 and April 2016, Chinese researchers reported results of basic research to edit the DNA of non-viable human embryos using CRISPR. In February 2016, British scientists were given permission by regulators to genetically modify human embryos by using CRISPR and related techniques on condition that the embryos were destroyed within seven days. In June 2016 the Dutch government was reported to be planning to follow suit with similar regulations which would specify a 14-day limit.
DNA-encoded chemical libraries (DECL) is a technology for the synthesis and screening on an unprecedented scale of collections of small molecule compounds. DECL is used in medicinal chemistry to bridge the fields of combinatorial chemistry and molecular biology. The aim of DECL technology is to accelerate the drug discovery process and in particular early phase discovery activities such as target validation and hit identification. DECL technology involves the conjugation of chemical compounds or building blocks to short DNA fragments that serve as identification bar codes and in some cases also direct and control the chemical synthesis. The technique enables the mass creation and interrogation of libraries via affinity selection, typically on an immobilized protein target. A homogeneous method for screening DNA-encoded libraries (DELs), known as Binder Trap Enrichment (BTE), was described in 2015 and uses water-in-oil emulsion technology to isolate, count and identify individual ligand-target complexes in a single-tube approach. In contrast to conventional screening procedures such as high-throughput screening, biochemical assays are not required for binder identification, in principle allowing the isolation of binders to a wide range of proteins historically difficult to tackle with conventional screening technologies.
== Gene == In humans, COL21A1 is located on the short arm of chromosome 6 at band 6p12.3–p11.2. The gene spans approximately 337 kb of genomic DNA and contains 31 exons; its 5′-untranslated exons (exon 1 and exon 1a) are alternatively spliced, and alternative splicing of the gene gives rise to multiple transcript variants. The exon–domain organization of COL21A1 resembles that of other genes encoding FACIT collagens.
One study found that the elimination half-life of hydroxyzine in adults was as short as 3 hours, but this may have just been due to methodological limitations. Although hydroxyzine has a long elimination half-life and acts, in-vivo, as an antihistamine for as long as 24 hours, the predominant CNS effects of hydroxyzine and other antihistamines with long half-lives seem to diminish after 8 hours. Administration in geriatrics differs from the administration of hydroxyzine in younger patients; according to the FDA, there have not been significant studies made (2004), which include population groups over 65, which provide a distinction between elderly aged patients and other younger groups. Hydroxyzine should be administered carefully in the elderly with consideration given to possible reduced elimination.
Cuts the Medicaid provider tax, which helps states fund their Medicaid costs, from 6% to 3.5% by 2031; Adds work requirements for Medicaid recipients for the first time, with individuals ages 19 to 64 required to work at least 80 hours per month, and this requirement can also be met through volunteer work or school. Some exemptions exist for adults with dependent children ages 14 and under and those with medical conditions. Requires states to charge enrollees in Medicaid expansion states with family incomes between 100 and 138 percent of the federal poverty level up to $35 for each health care service, if they qualify for Medicaid based on income alone. Requires states to check eligibility of people on Medicaid expansion every six months instead of annually; Prevents expansion states from using state contributions to pay Medicaid providers higher prices than Medicare would pay; Requires minimum staffing ratios for nursing homes; Requires a five-year waiting period for green card holders before applying to Medicaid, and reduces retroactive Medicaid payments from three months to one month; Limits premium tax credits for immigrants; Reduces Medicaid payments to states with errors and other improper payments; and Prohibits Medicaid from being used for funding Planned Parenthood and similar organizations for one year. In July 2025, Planned Parenthood sued the Trump administration over the provision and a federal judge issued a temporary injunction on the provision. In September 2025, the First U.S. Circuit Court of Appeals overrode the injunction, allowing defunding.
Sources: en.wikipedia.org
=== Misinformation === TikTok has banned Holocaust denial, but other conspiracy theories have become popular on the platform, such as Pizzagate and QAnon (two conspiracy theories popular among the US alt-right) whose hashtags reached almost 80 million views and 50 million views respectively by June 2020. The platform has also been used to spread misinformation about the COVID-19 pandemic, such as clips from Plandemic. TikTok removed some of these videos and has generally added links to accurate COVID-19 information on videos with tags related to the pandemic. In January 2020, left-leaning media watchdog Media Matters for America said that TikTok hosted misinformation related to the COVID-19 pandemic despite a recent policy against misinformation. In April 2020, the government of India asked TikTok to remove users posting misinformation related to the COVID-19 pandemic. There were also multiple conspiracy theories that the government is involved with the spread of the pandemic. It reported that in the second half of 2020, over 340,000 videos in the US about election misinformation and 50,000 videos of COVID-19 misinformation were removed. To combat misinformation in the 2022 midterm election in the US, TikTok announced a midterms Elections Center available in-app to users in 40 different languages. TikTok partnered with the National Association of Secretaries of State to give accurate local information to users.
=== Category:EC 3.13 (act on carbon–sulfur bonds) === EC 3.13.1.1: UDP-sulfoquinovose synthase EC 3.13.1.3: 2'-hydroxybiphenyl-2-sulfinate desulfinase EC 3.13.1.4: 3-sulfinopropanoyl—CoA desulfinase EC 3.13.1.5: Carbon disulfide hydrolase EC 3.13.1.6: (CysO sulfur-carrier protein)-S-L-cysteine hydrolase EC 3.13.1.7: Carbonyl sulfide hydrolase EC 3.13.1.8: S-adenosyl-L-methionine hydrolase (adenosine-forming)
Several antibiotics exert their action by targeting the translation process in bacteria. They exploit the differences between bacterial and eukaryotic translation mechanisms to selectively inhibit protein synthesis in bacteria without affecting the host.
Insulin may not be necessary and it may be possible to switch a person from insulin injections to oral agents without loss of glycemic control. It may prompt screening of relatives and so help identify other cases in family members. As it occurs infrequently, many cases of MODY are initially assumed to be more common forms of diabetes: type 1 if the patient is young and not overweight, type 2 if the patient is overweight, or gestational diabetes if the patient is pregnant. Standard diabetes treatments (insulin for type 1 and gestational diabetes, and oral hypoglycemic agents for type 2) are often initiated before the doctor suspects a more unusual form of diabetes.
Sources: en.wikipedia.org
Low temperature slows hydrolysis and oxidation, the two main routes by which the peptide backbone and side chains are modified. A lyophilised powder stored at −20 °C is more stable than one kept at room temperature, and once the material is dissolved the degradation rate rises, making refrigeration more important.
Liquid chromatography coupled to mass spectrometry is the most common approach because it combines a retention time with a mass measurement. A chromatographic peak alone cannot establish which peptide is present, so mass determination or amino acid analysis is used as an orthogonal confirmation alongside the separation.
This depends on buffer, pH, and concentration, and published stability data for this peptide are limited. In practice laboratories work through a refrigerated solution within a few weeks and discard samples that show cloudiness or visible particles. Freezing and thawing repeatedly is generally discouraged.
No. It is a laboratory-made peptide, while the natural hormone is alpha-melanocyte-stimulating hormone, a longer peptide produced by the pituitary gland and by skin cells. Melanotan-2 mimics only a short active region of that hormone and contains non-natural residues such as D-phenylalanine.