The short version of reference standard fits in a sentence. The long version — which is the one that helps — is below.
Reviewed 2026-07-14. Anything still debated is marked as such rather than presented as settled.
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.
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.
The peer-reviewed record is dominated by small early-phase studies, case reports and pharmacovigilance summaries rather than large randomised trials. Papers typically examine tanning response, receptor selectivity or patterns of reported adverse events. Many note that participants obtained the peptide outside a clinical setting, which limits verification of composition and administered amount. Reported events vary widely, and causality is frequently unclear because the identity and purity of self-sourced material are unknown. Open questions include whether repeated melanocortin receptor stimulation produces cumulative effects, and how often label claims match actual content.
Identification in laboratories relies on reversed-phase liquid chromatography coupled with tandem mass spectrometry, with product-ion spectra compared against a certified reference standard. High-resolution mass spectrometry supplies accurate mass confirmation, and peptide mapping after enzymatic digestion separates melanotan II from closely related analogues. Quantitation of seized material is complicated by unknown counter-ions and residual trifluoroacetate left from purification. Immunoassays raised against alpha-melanocyte-stimulating hormone can cross-react, so chromatographic confirmation is normally required. Urinary detection windows are short, and reported limits of detection differ substantially between laboratories.
| 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 |
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.
Identity and purity are assessed mainly by reversed-phase high-performance liquid chromatography with ultraviolet detection, often paired with mass spectrometry. Retention time supports identity, while the mass spectrum confirms the molecular weight of the intact peptide. Purity is frequently reported as a percentage of total peak area, a figure that depends on the wavelength, column and gradient used. Impurity profiling may also look for truncated sequences, oxidised forms and residual counterions. Amino acid analysis and peptide mapping provide orthogonal confirmation when required.
Regulatory status varies by jurisdiction, and the substance is frequently described as unapproved for therapeutic use. Some authorities classify it alongside prescription-only medicines or controlled categories, while others address it through general consumer protection rules. Analytical surveys have reported mismatches between label claims and measured content in products sold online, although the scope of such testing is limited. Whether these discrepancies are widespread remains an open question. Discussion in the literature therefore tends to combine chemistry, supply-chain observation and policy analysis.
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.
Receptor studies place melanotan-2 among non-selective melanocortin agonists, binding MC1R, MC3R, MC4R and MC5R rather than a single subtype. Activation of MC1R on cutaneous melanocytes raises tyrosinase activity and shifts pigment synthesis toward eumelanin, which is darker and more photostable than pheomelanin. Central receptors, particularly MC4R, are associated with appetite suppression and with reported effects on sexual function. Because subtype selectivity is low, the same molecule engages pigment, metabolic and vascular pathways at once, and this breadth is a common explanation offered for the range of adverse events described in user reports.
==== Antigonadotropic effects ==== EMP at a dosage 280 mg/day has been found to suppress testosterone levels in men into the castrate range (to 30 ng/dL) within 20 days and to the low castrate range (to 10 ng/dL) within 30 days. Similarly, a dosage of 70 mg/day EMP suppressed testosterone levels into the castrate range within 4 weeks.
is the net fluid movement between compartments. By convention, outward force is defined as positive, and inward force is defined as negative. The solution to the equation is known as the net filtration or net fluid movement (Jv). If positive, fluid will tend to leave the capillary (filtration). If negative, fluid will tend to enter the capillary (absorption). This equation has a number of important physiologic implications, especially when pathologic processes grossly alter one or more of the variables. According to Starling's equation, the movement of fluid depends on six variables:
==== 1990s ==== 1993 – Supelco, Inc. acquired to enter the chromatography market 1994 – LabKemi AB 1997 – Research Biochemicals International, Riedel-de-Haen, Techcares Systems, Carbolabs, YA Kemia 1998 – Genosys
Bats provide humans with some direct benefits, at the cost of some disadvantages. Bat dung has been mined as guano from caves and used as fertiliser. Bats consume insect pests, reducing the need for pesticides and other insect management measures. Bats are sometimes numerous enough and close enough to human settlements to serve as tourist attractions, and they are used as food in Africa, Asia, the Pacific and the Caribbean. Due to their physiology, bats are one type of animal that acts as a natural reservoir of many pathogens, such as rabies, and since they are highly mobile, social, and long-lived, they can readily spread disease among themselves. If humans interact with bats, these traits become potentially dangerous to humans. Depending on the culture, bats may be symbolically associated with positive traits, such as protection from certain diseases or risks, rebirth, or long life, but in the West, bats are popularly associated with darkness, malevolence, witchcraft, and vampires.
Sources: en.wikipedia.org
In 2009, Professor Mas Subramanian and former graduate student Andrew Smith at Oregon State University discovered that indium can be combined with yttrium and manganese to form an intensely blue, non-toxic, inert, fade-resistant pigment, YInMn Blue, the first new inorganic blue pigment discovered in 200 years. According to one overview, "[there is] no evidence of any health hazard from industrial use of indium."
=== Distribution === The drug is distributed rapidly and widely to most tissues and fluids, including sputum, pleural fluid, peritoneal fluid, interstitial fluid, bile, aqueous humor, reproductive organs, and bone; highest concentrations occur in pleural fluid, interstitial fluid, peritoneal fluid, and reproductive organs; low concentrations occur in CSF; it crosses the placenta, and enters breast milk
==== Provincial development ==== It can be said that Liu Wenhui's development policies were biased towards the Kham area (Kangding–Luding), as per-capita spending and credit volumes were much higher here than anywhere else in Xikang. Although Liu did comment that the Ningshu area (Xichang) was favorable towards agricultural programs, he continued prioritizing Kham. Meanwhile, population boomed in Kangding and Han agricultural settlements slowly spread throughout the province. From 1933 to 1935, some rudimentary infrastructure was constructed in his domain. This included a weapons repair shop (later expanded into a factory) and a military-political school to maintain his 24th Army. Technical schools were established for his administration and policing was strengthened. Several roads (including from Ya'an to Fulin) and canals were built or improved, hospitals and libraries were opened, and terraced farming was introduced in the rugged region. Xikang maintained an open economy encouraging private enterprise to increase trade incomes. Liu would boast of this as his "Ten Great Constructions", claiming it brought order and development to the province. For his fortieth birthday in 1935, Liu allegedly donated the money he had received from gifts to build a bridge over the Ya River. State media such as The Paper mentions the existence of a bridge built in Ya'an, but it was constructed in 1944. From 1939 on, Liu, as Governor of Xikang Province, tried to establish infrastructure to support it.
Skin cancer can be categorized into two groups: melanoma, which is considered more severe, and nonmelanoma skin cancer, which includes basal cell carcinoma and cutaneous squamous cell carcinoma. Mohs micrographic surgery is used for high-risk nonmelanoma skin cancers located in cosmetically critical or sensitive areas like the face, ears, scalp, neck, genitalia, hands, and feet, where tissue conservation is of utmost importance. It is also indicated when the tumor is recurrent, aggressive, large, or painful, which tells us there is invasion of the nerve or vasculature.
=== Creative food design === Food presentation and food appearance customization for individuals is a big trend in the food industry. So far food customization and creative designs have required hand-made skills, which results in low production rate and high cost. 3D food printing can overcome this problem by providing the necessary tools for creative food design even for home users. 3D food printing has enabled some intricate designs which cannot be accomplished with traditional food manufacturing. Brand logos, text, signatures, pictures can now be printed on some food products like pastries and coffee. Complex geometric shapes have also been printed, mainly using sugar. With 3D printing, chefs can now turn their visual inspirations into signature culinary creations. Another benefit is being able to print nutritious meals in shapes that appeal to children.
Sources: en.wikipedia.org
== Protein turnover in the exercise science == Four weeks of aerobic exercise has been shown to increase skeletal muscle protein turnover in previously unfit individuals. A diet high in protein increases whole body turnover in endurance athletes. Some bodybuilding supplements claim to reduce the protein breakdown by reducing or blocking the number of catabolic hormones within the body. This is believed to increase anabolism. However, if protein breakdown falls too low then the body would not be able to remove muscle cells that have been damaged during workouts which would in turn prevent the growth of new muscle cells.
==== African plate ==== Mount Etna (47) 37°45′N 15°00′E Hoggar hotspot (13) 23°18′N 5°36′E, w= 0.3 az= 046° ±12° Tibesti hotspot (40) 20°48′N 17°30′E, w= 0.2 az= 030° ±15° Jebel Marra/Darfur hotspot (6) 13°00′N 24°12′E, w= 0.5 az= 045° ±8° Afar hotspot (29, misplaced in map) 7°00′N 39°30′E, w= 0.2 az= 030° ±15° rate= 16 ±8 mm/yr Possibly related to the Afar triple junction, 30 Ma. Cameroon hotspot (17) 2°00′N 5°06′E, w= 0.3 az= 032° ±3° rate= 15 ±5 mm/yr Madeira hotspot (48) 32°36′N 17°18′W, w= 0.3 az= 055° ±15° rate= 8 ±3 mm/yr Canary hotspot (18) 28°12′N 18°00′W, w= 1 az= 094° ±8° rate= 20 ±4 mm/yr New England/Great Meteor hotspot (28) 29°24′N 29°12′W, w= 0.8 az= 040° ±10° Cape Verde hotspot (19) 16°00′N 24°00′W, w= 0.2 az= 060° ±30° Sierra Leone hotspot St. Helena hotspot (34) 16°30′S 9°30′W, w= 1 az= 078° ±5° rate= 20 ±3 mm/yr Gough hotspot (49), at 40°19' S 9°56' W. 40°18′S 10°00′W, w= 0.8 az= 079° ±5° rate= 18 ±3 mm/yr Tristan hotspot (42), at 37°07′ S 12°17′ W. 37°12′S 12°18′W Vema hotspot (Vema Seamount, 43), at 31°38' S 8°20' E. 32°06′S 6°18′W Related maybe to the Paraná and Etendeka traps (c. 132 Ma) through the Walvis Ridge. Discovery hotspot (50) (Discovery Seamounts) 43°00′S 2°42′W, w= 1 az= 068° ±3° Bouvet hotspot (51) 54°24′S 3°24′E Shona/Meteor hotspot (27) 51°24′S 1°00′W, w= 0.3 az= 074° ±6° Réunion hotspot (33) 21°12′S 55°42′E, w= 0.8 az= 047° ±10° rate= 40 ±10 mm/yr Possibly related to the Deccan Traps (main events: 68.5–66 Ma) Comoros hotspot (21) 11°30′S 43°18′E, w= 0.5 az=118 ±10° rate=35 ±10 mm/yr
=== Scaffold === Scaffolds are used to display the heterologous protein on the bacterial cell surface. There are various scaffolds which have been used such as outer membrane proteins, fimbriae/flagella proteins and CPX (circularly permuted OmpX). The CPX scaffold allows peptide fusion at both termini of the scaffold. OMPs are common scaffolds for bacterial display. Proteins can also be displayed on the bacterial cell surface through the use of autotransporters. Autotransporters form part of the type V secretion system. They usually have three domains: leader sequence at the N-terminal; central passenger domain; autotransporter domain at the C-terminal. The heterologous protein is inserted at the passenger domain. Another method of heterologous protein fusion is fusion with fimbriae/flagella, which are filamentous protrusions on the cell surface. There are many fimbriae on mainly Gram-negative bacteria, so displaying proteins on fimbriae is advantageous over some other surface proteins which are less numerous. A disadvantage of using fimbriae is that there is a relatively small insert size limit of 10-30 amino acids.
== Function in medicine == Arenobufagin has been widely used in traditional Chinese medicine (TCM) to attempt to treat carcinogenesis, since it inhibits cell growth in several cancer cells. It is one of the central active ingredients of toad toxin for this treatment. This happens both in purified form or in combination with other ingredients, which are mostly herbal components. Toad toxin is in fact still used in clinical practice in TCM to treat hepatocellular carcinoma (HCC). So far there is still little known about the anti-angiogenic properties of Arenobufagin. One study shows that Arenobufagin inhibits VEGF-induced endothial cell tube formation.
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.
Regulatory treatment varies by country. In the United States, the European Union and Australia it is an unapproved drug and its sale is restricted, while some other jurisdictions list it as prescription-only or controlled. The applicable rules depend on the country of import.