This is a working overview of cyclic heptapeptide, written for readers who want more than a one-paragraph summary but less than a textbook.
This page was last updated on 2026-03-09 and is reviewed periodically as new material appears.
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.
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.
| Property | Value | Notes |
|---|---|---|
| Compound class | Synthetic cyclic heptapeptide | Alpha-MSH analogue containing a D-phenylalanine residue |
| Molecular formula | C50H69N15O9 | Average molecular mass approximately 1024.2 g/mol |
| Appearance | White to off-white lyophilised powder | Normally supplied as a freeze-dried solid in a sealed vial |
| Solubility | Freely soluble in water and polar solvents | Dissolves readily in aqueous buffers and in alcohol-water mixtures |
| Receptor targets | MC1R, MC3R, MC4R, MC5R | Acts as a non-selective melanocortin receptor agonist |
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.
Melanotan II is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone, a naturally occurring peptide involved in pigmentation signalling. Its structure substitutes a lactam bridge between side chains to increase stability relative to the native hormone. The compound is also known by the shorthand MT-II and by several non-proprietary synonyms used in research catalogues. It is not an approved therapeutic product in any major jurisdiction; material sold under this name is typically offered as a laboratory reagent rather than as a medicine.
Analytical confirmation of identity relies on mass spectrometry, most often coupled to liquid chromatography. Reversed-phase high-performance liquid chromatography separates the peptide from related impurities and provides a purity estimate based on peak area. Electrospray ionization mass spectrometry then confirms the expected molecular mass, while tandem mass spectrometry can map the fragment sequence. For research-grade material, these two techniques together form the standard minimum. Purity figures reported by vendors are frequently not traceable to an independent laboratory.
Independent verification is central to quality control because the compound is not produced under pharmaceutical manufacturing standards. Third-party laboratories can measure purity, identity, residual solvents, and microbial contamination, though the scope of testing varies between services. Reported analyses of vendor samples have shown batch-to-batch variation in peptide content and the presence of truncated or oxidized species. How much of this variation reflects synthesis conditions versus storage and shipping is not well characterized. No harmonized reference standard exists for the material as sold.
== History == The concept of residence time originated in models of chemical reactors. The first such model was an axial dispersion model by Irving Langmuir in 1908. This received little attention for 45 years; other models were developed such as the plug flow reactor model and the continuous stirred-tank reactor, and the concept of a washout function (representing the response to a sudden change in the input) was introduced. Then, in 1953, Peter Danckwerts resurrected the axial dispersion model and formulated the modern concept of residence time.
== Specialist uses == In some species, hemolymph has other uses than transporting nutrients. As the insect or arachnid grows, the hemolymph works something like a hydraulic system, enabling the insect or arachnid to expand segments before they are sclerotized. It can also be used hydraulically as a means of assisting movement, such as in arachnid locomotion. Some species of insect or arachnid are able to autohaemorrhage when they are attacked by predators. Queens of the ant genus Leptanilla are fed with hemolymph produced by the larvae. On the other hand, Pemphigus spyrothecae utilize hemolymph as an adhesive, allowing the species to stick to predators and subsequently attack the predator; it was found that with larger predators, more aphids were stuck after the predator was defeated.
== Incenter == The incenter of a tangential quadrilateral lies on its Newton line (which connects the midpoints of the diagonals). The ratio of two opposite sides in a tangential quadrilateral can be expressed in terms of the distances between the incenter I and the vertices according to
=== Metatropic dysplasia === Metatropic means "changing form" and refers to this form of skeletal dysplasia as there is an abnormality in the growth plates. Skeletal changes continue over time and may need surgical intervention to help protect the lungs. Symptoms starting at birth may be mild or can be fatal. There are recognizable features in individuals with this genetic disorder. Some are short stature, narrow chest, "facial features such as a prominent forehead, underdevelopment of the upper jaw, cheekbones and eye sockets (midface hypoplasia), and a squared-off jaw." It is considered a more severe skeletal dysplasia, but is very rare, with the exact number of those affected unknown. Prognosis is largely on a case-by-case basis depending on the severity, and life expectancy may not be impacted unless there are respiratory complications.
Sources: en.wikipedia.org
A total solar eclipse occurs at the Moon's descending node of the orbit in North America and Europe. The total eclipse passes over the Arctic, Greenland, Iceland, the Atlantic Ocean and northern Spain. Trump announces that White House Press Secretary Karoline Leavitt will leave the office at the end of the month to spend more time with her family. 2026 Iran war: US media reports that sailors on the Abraham Lincoln attempted to jump overboard owing to poor conditions such as food shortages, a mental health crisis, and broken toilets that affected all crew members, including female soldiers. Pete Hegseth, the US secretary of defense, denounces the sailors as liars. The US eventually opts to send the aircraft carrier USS George Washington to the Middle East to replace the Lincoln, removing its last aircraft carrier in the Pacific. August 13 – The United States sees the first triple execution on the same day, since 2010. August 14 Six people are killed, including the perpetrator, and one person is injured in a mass shooting at three different locations in Missaukee County, Michigan. Trump announces that the US will annex the Strait of Hormuz "pretty soon" after defeating the Iranian regime in the war. 2026 NFL season: The National Football League suspends Atlanta Falcons linebacker James Pearce Jr. for eight games in violation of the league's personal conduct policy after his arrest in February on domestic violence charges. August 15 – The Democratic National Committee votes to approve South Carolina as the first U.S.
Altria, like other tobacco companies, has invested in science and medical companies which develop and produce medical products for conditions caused or aggravated by smoking. As of 2024, Altria's three medical subsidiaries included the following: Cronos group (maker of recreational cannabis), Lexaria Bioscience (Developer of proprietary drug delivery technology, DehydraTECH, to improve active pharmaceutical ingredients entrance into the bloodstream) and Micreos (biotech company focused on discovering and developing recombinant proteins for chronic dermatology and oncology conditions). It has also designed and marketed electronic cigarettes. Altria launched the MarkTen and Green Smoke brands. Both of these were discontinued in December 2018. The company returned to this market through the acquisition of NJOY.
In a DNA double helix, each type of nucleobase on one strand bonds with just one type of nucleobase on the other strand. This is called complementary base pairing. Purines form hydrogen bonds to pyrimidines, with adenine bonding only to thymine in two hydrogen bonds, and cytosine bonding only to guanine in three hydrogen bonds. This arrangement of two nucleotides binding together across the double helix (from six-carbon ring to six-carbon ring) is called a Watson-Crick base pair. DNA with high GC-content is more stable than DNA with low GC-content. A Hoogsteen base pair (hydrogen bonding the 6-carbon ring to the 5-carbon ring) is a rare variation of base-pairing. As hydrogen bonds are not covalent, they can be broken and rejoined relatively easily. The two strands of DNA in a double helix can thus be pulled apart like a zipper, either by a mechanical force or high temperature. As a result of this base pair complementarity, all the information in the double-stranded sequence of a DNA helix is duplicated on each strand, which is vital in DNA replication. This reversible and specific interaction between complementary base pairs is critical for all the functions of DNA in organisms.
Interpretation challenges: Complex laboratory results require proper context and clinical expertise to interpret correctly. Misinterpretation may lead to unnecessary anxiety or inappropriate self-treatment. Insurance coverage: Self-directed laboratory testing is not covered by health insurance; insurers generally pay only for tests ordered under the authorization of a physician. Care fragmentation: Testing conducted outside the patient-provider relationship may not be integrated into medical records or coordinated with ongoing care. The following table compares biomarkers and services offered by major DTC blood testing providers as of November 2025. Clinical laboratory Blood test Laboratory developed test Point-of-care testing Personalized medicine
It is a bioactive sphingoid which derives from the sphinganine. It is formed by a sphingoid and an amino alcohol and it constitutes the conjugated base of 1-deoxymethylsphinganine (1+). Its role is accepting a hydron from a donor via its organic amino compound; it is a Brønsted base. It is also known as deoxymethyl-SA, (2R)-1-aminoheptadecan-2-ol and 1-desoxymethylsphinganine. The molecular weight of this compound is 271,48 g/mol and its molecular formula is C17H37NO, which means it has 17 carbons. In relation to its appearance, it has a powder form. Other physical and chemical properties are not certainly known.
Sources: en.wikipedia.org
Naturally occurring gadolinium (64Gd) is composed of six stable isotopes, 154Gd, 155Gd, 156Gd, 157Gd, 158Gd and 160Gd, and one long-lived radioisotope, 152Gd, with 158Gd being the most abundant (24.84% natural abundance). The predicted double beta decay of 160Gd has not been observed. In all, 32 radioisotopes of gadolinium have been characterized, with the three most stable being alpha emitters: 152Gd (naturally occurring) with a half-life of 1.08×1014 years, 150Gd with a half-life of 1.79×106 years, and 148Gd (theoretically not beta-stable) with a half-life of 86.9 years. All of the remaining radioactive isotopes have half-lives less than a year, the majority of these having half-lives less than two minutes. There are also 16 metastable isomers, with the most stable being 143mGd (t1/2 = 110 seconds), 145mGd (t1/2 = 85 seconds) and 141mGd (t1/2 = 24.5 seconds). The isotopes with atomic masses lower than the most abundant stable isotope, 158Gd, primarily decay by electron capture to isotopes of europium. For higher atomic masses, the primary decay mode is beta decay to isotopes of terbium.
In mid September, the US House of Representatives voted for a third time, to end the war, shortly after a CBO report warned the conflict had already cost at least $38 billion, was depleting defensive missile stockpiles to the point of a five-year rebuild, and would add roughly $3 billion per month while fueling inflation.
The household was managed by a former naval quartermaster with the help of Black servants, and provisions were generally abundant except for flour. The initial weeks were spent testing scientific instruments and botanizing in the surrounding plains, astonished by the rapid growth and size of local vegetation. Humboldt noted the presence of plant species newly described by science, indicating the region’s botanical richness and the likelihood that many smaller plants remained undocumented. The scientific curiosity of the local population matched that of the visitors. The house became a destination for townspeople eager to observe scientific demonstrations, especially with the microscope, which fascinated Cumana's women. Humboldt reciprocated by attending local dances, learning both traditional and modern forms. Despite social distractions, Humboldt’s chief focus was meteorological observation, taking advantage of the region’s stable climate to collect data on atmospheric conditions. Humboldt’s house, situated on the main square, also exposed him to the realities of the local slave market. He was deeply disturbed by the sight of enslaved Africans being prepared for sale, their bodies oiled and inspected by buyers. While generally tolerant and patient in his dealings with others, Humboldt’s abhorrence of slavery was absolute. He could not accept rationalizations for the system, regardless of claims that Spanish slaves fared better than those elsewhere.
=== Imaging === Imaging is not routinely indicated. It typically does not change plantar fasciitis management. When the diagnosis is not clinically apparent, lateral view X-rays of the ankle are the standard imaging modality to consider other causes, such as stress fractures or bone spur development. The plantar fascia has three fascicles; the central fascicle is the thickest at 4 mm, the lateral fascicle is 2 mm, and the medial less than one millimeter thick. In theory, plantar fasciitis becomes more likely with increased thickness at the calcaneal insertion. A thickness of more than 4.5 mm ultrasound and 4 mm on MRI are diagnostic. Other imaging findings, such as thickening of the plantar aponeurosis, are nonspecific and have limited diagnostic value. A Three-phase bone scan is a sensitive imaging modality. It can be used to monitor response to therapy, as demonstrated by decreased uptake after corticosteroid injections.
Sources: en.wikipedia.org
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.
No approved regulatory indication exists in major markets. An approval exists for a different peptide, afamelanotide, which is used for a rare photosensitivity disorder called erythropoietic protoporphyria. Melanotan-2 itself remains a research compound with no cleared clinical role.
Melanocortin-1 receptors on melanocytes are the receptor most closely linked to pigment production. The peptide is not selective, however, and also activates melanocortin-3, melanocortin-4, and melanocortin-5 receptors. That lack of selectivity is the usual explanation offered for both its range of observed effects and its off-target effects.
Only a small number of early-stage human studies have been reported, and most were limited in size and duration. No large late-stage program has established a general efficacy or safety profile. The evidence base is therefore thin compared with approved medicines.