Everything below concerns melanocortin receptor. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2025-10-18. Where a claim depends on a specific study, the study is described rather than over-claimed.
Melanotan-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone. Its sequence incorporates a lactam bridge that constrains the peptide into a ring, which increases resistance to enzymatic breakdown relative to the natural hormone. Researchers at the University of Arizona synthesised the compound in the late 1980s and early 1990s while studying pigmentation pathways. It has never received marketing approval from any national medicines regulator. In the scientific literature it is usually described as a laboratory research reagent rather than a therapeutic product.
The peptide acts as a non-selective agonist at melanocortin receptors, showing affinity for MC1R, MC3R, MC4R and MC5R. Activation of MC1R on melanocytes drives the conversion of tyrosine into melanin and shifts production toward the darker eumelanin form. MC4R signalling in the central nervous system is linked to appetite and energy balance, which helps explain why reduced food intake appeared in early human studies. Effects on MC4R and on vascular tone also account for the erectile responses recorded as unexpected findings in those same trials.
Melanotan-2 is frequently confused with afamelanotide, a linear analogue authorised in the European Union for erythropoietic protoporphyria. The two compounds differ in chain length, ring structure and receptor selectivity, so findings for one cannot be transferred directly to the other. Published controlled human data on melanotan-2 remain sparse, and much of what circulates online derives from small studies or unpublished reports. Questions about effect size, dose-response behaviour and long-term safety therefore remain unresolved.
The compound was developed in the late 1980s and 1990s by academic researchers investigating photoprotection. The rationale held that stimulating melanin production might reduce ultraviolet damage to skin and lower skin cancer risk. Early work examined receptor binding, pigment response, and short-term tolerability in small studies. That program did not produce an approved drug, and formal development stalled after early-phase trials. Whether induced pigmentation confers meaningful photoprotection remains an open question.
Outside regulated medicine, melanotan II circulates through online vendors as a research chemical, often marketed for tanning. Products sold this way vary widely in purity, concentration, and labeling accuracy, and independent testing has documented discrepancies. Published reports describe both pigment effects and adverse reactions, including nausea, flushing, and darkening of existing moles. Long-term safety data are sparse, and no large controlled trial has established a risk profile. Questions about cumulative effects on melanocytes remain unresolved in the literature.
Melanotan II is a synthetic peptide analog modeled on alpha-melanocyte-stimulating hormone, a naturally occurring signaling peptide involved in pigmentation. Its structure is a cyclic heptapeptide containing two non-natural substitutions, norleucine at position four and D-phenylalanine at position seven. These modifications resist enzymatic breakdown and extend the molecule's activity relative to the native hormone. The compound binds melanocortin receptors and is studied mainly as a pharmacological tool rather than a therapeutic product. It has never received approval as a medicine in any major jurisdiction.
| Property | Value | Notes |
|---|---|---|
| Chemical class | Synthetic cyclic heptapeptide | Alpha-MSH analogue with a lactam ring |
| Molecular formula | C50H69N15O9 | Commonly cited value for the neutral peptide |
| Molecular weight | 1024.18 g/mol | Calculated for the free molecule |
| Appearance | White to off-white powder | Typically supplied as a lyophilised solid |
| Solubility | Soluble in water, DMSO and ethanol | Dissolution in pure water is often slow |
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.
Melanocortin receptors comprise five subtypes with distinct tissue distributions and functions. Melanotan-2 is described in the literature as a non-selective agonist that engages several of these subtypes, including MC1R, MC3R, MC4R, and MC5R. MC1R is the subtype most directly linked to melanin production in skin cells. Because the compound is not subtype-selective, its observed effects in experimental settings are generally attributed to activity across multiple receptor pathways rather than to a single target.
Melanotan-2 is a synthetic linear peptide built from seven amino acids arranged in a short chain. Its sequence is commonly written as Ac-Nle-Asp-His-D-Phe-Arg-Trp-Lys-NH2, which includes a modified N-terminus and an amidated C-terminus. The molecule belongs to the melanocortin family and acts as a receptor agonist. Structural features such as the D-phenylalanine residue and the Nle substitution are associated with increased stability against enzymatic degradation relative to the natural parent peptide.
== Genomics == Hydra has more than 20,000 genes, along with a set of six actinoporin-like toxin genes found in its nematocysts. An ortholog comparison analysis done in 2013 demonstrated that Hydra share a minimum of 6,071 genes with humans. Hydra is becoming an increasingly better model system as more genetic approaches become available. Transgenic hydra have become attractive model organisms to study the evolution of immunity. A draft of the genome of Hydra magnipapillata was reported in 2010. The genus Hydra is divided into two clades, the green hydras (e.g. H. viridissima) and the brown hydras (e.g. H. oligactis, H. vulgaris). The genomes of cnidarians are usually less than 500 Mb (megabases) in size, as in the green hydras, which has a genome size of approximately 300 Mb. In contrast, the genomes of brown hydras are approximately 1 Gb in size. This is because the brown hydra genome is the result of an expansion event involving LINEs, a type of transposable elements, in particular, a single family of the CR1 class. This expansion is unique to this subgroup of the genus Hydra and is absent in the green hydra, which has a repeating landscape similar to other cnidarians. These genome characteristics make Hydra attractive for studies of transposon-driven speciations and genome expansions. Due to the simplicity of their life cycle when compared to other hydrozoans, Hydras have lost many genes that correspond to cell types or metabolic pathways of which the ancestral function is still unknown.
== Resistance == Resistance is a major cause of treatment failure in chemotherapeutic drugs and results in cancer cell survival despite exposure to such toxins. Broadly, resistance types can be classified based on the points at which cancer cells are no longer susceptible to the effects of chemotherapeutic drugs. One form of resistance is known as primary, or natural resistance, where cancer cells possess innate mechanisms that allow them to be unresponsive to chemotherapeutic drug exposure from the very beginning of its administration. Contrarily, acquired resistance is characterized by an initial, brief period of cancer cell susceptibility to the applied chemotherapeutic agent, followed by later stages of poor drug response. Despite these differences between the points at which resistance emerges, either form can result in what is known as multi-drug resistance, essentially allowing cancer cells to evade the effects of both similarly and differently functioning chemotherapeutic drugs regardless of their previous exposure to them. There are various contributors to emerging resistance in cancer, one of which is the presence of small pumps on the surface of cancer cells that actively transport concentrations of chemotherapy drugs from inside the cell to the outside, otherwise known as efflux pumps. However, these pumps are not unique characteristics of cancer cells whereas in normal functioning cells, efflux pumps are actually engaged in life-sustaining processes that help avoid the accumulation of waste and toxin absorption in the body.
== Uses == Helium mass spectrometer leak detectors are used in production line industries such as refrigeration and air conditioning, automotive parts, carbonated beverage containers food packages and aerosol packaging, as well as in the manufacture of steam products, gas bottles, fire extinguishers, tire valves, heat exchangers and numerous other products including all vacuum systems.
Guming Holdings Limited (known under the brand name Good me; Chinese: 古茗; pinyin: Gǔmíng; lit. 'Ancient tea water') is a publicly listed Chinese teahouse chain. Founded in 2010 by Wang Yun'an and headquartered in Hangzhou, Zhejiang, the company operates primarily in China's lower-tier cities, selling beverages such as fruit tea, milk tea, and coffee through a franchise model. As of late 2024, Good me had expanded to nearly 9,800 outlets nationwide, making it one of China's largest bubble tea chains. Guming Holdings went public on the Hong Kong Stock Exchange in February 2025, raising approximately US$233 million in its initial public offering (IPO).
Sources: en.wikipedia.org
Terrestrial television, over-the-air (OTA) television, or broadcast television – the oldest television technology, is the transmission of television signals from land-based television stations to television receivers (called televisions or TVs) in viewer's homes. Terrestrial television broadcasting uses the bands 41 – 88 MHz (VHF low band or Band I, carrying RF channels 1–6), 174 – 240 MHz, (VHF high band or Band III; carrying RF channels 7–13), and 470 – 614 MHz (UHF Band IV and Band V; carrying RF channels 14 and up). The exact frequency boundaries vary in different countries. Propagation is by line-of-sight, so reception is limited by the visual horizon. In the US, the effective radiated power (ERP) of television transmitters is regulated according to height above average terrain. Viewers closer to the television transmitter can use a simple "rabbit ears" dipole antenna on top of the TV, but viewers in fringe reception areas typically require an outdoor antenna mounted on the roof to get adequate reception.
A main supply valve with non-return valve, which supplies gas to the main gas supply hose of the umbilical. This is usually a quarter-turn valve, as it must be quick to operate and obvious whether it is open or closed. A pneumofathometer supply valve, which supplies gas to the pneumofathometer for the diver. This valve is usually near the main supply valve but with a different handle. It is usually a needle type valve as it must be finely adjustable, but it must also be large enough to allow a fairly high flow rate, as the air may be used as an alternative breathing air source, or to fill small lift bags. A pneumofathometer gauge is connected to the pneumo line. This is a high resolution pressure gauge calibrated in feet sea water (fsw) and/or metres sea water (msw). and is used to measure the depth of the diver by allowing air to flow through the pneumo hose and out the end attached to the diver. When the air supply is shut off, and the flow stops, the gauge indicates the pressure at the open end at the diver. Each pneumofathometer gauge has an overpressure valve to protect it against gas supply at higher pressure than it is designed to take. This is essential as the main supply pressure is significantly higher than the maximum depth pressure on the pneumo gauge. There is also often a snubbing valve or orifice between the pneumo line and the gauge to restrict flow into the gauge and ensure that the overpressure valve can adequately relieve the pressure.
Laser-based ambient ionization is a two-step process in which a pulsed laser is used to desorb or ablate material from a sample and the plume of material interacts with an electrospray or plasma to create ions. Lasers with ultraviolet and infrared wavelengths and nanosecond to femtosecond pulse widths have been used. Although atmospheric pressure MALDI is performed under ambient conditions, it is not generally considered to be an ambient mass spectrometry technique. Laser ablation was first coupled with mass spectrometry in the 1980s for the analysis of metals using laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). The laser ablates the sample material that is introduced into an ICP to create atomic ions.
In early 2009, the Purchase Brothers, a Toronto-based film company, released a five-minute film based on Half-Life 2: Episode One, Half-Life: Escape from City 17. The film combines live-action footage with 3D animation created using the Source SDK. It was well received by Valve. On August 25, 2010, they released a nearly 15-minute-long sequel.
=== List of well known fractionation effects === A number of common processes fractionate hydrogen isotopes to produce the isotope variations found in nature. Common physical processes include precipitation and evaporation. Chemical reactions can also heavily influence the partitioning of heavy and light isotopes between pools. The rate of a chemical reaction depends in part on the energies of the chemical bonds formed and broken in the reaction. Since different isotopes have different masses, the bond energies differ between isotopologues of a chemical species. This will result in a difference in the rate of a reaction for the different isotopologues, resulting in a fractionation of the different isotopes between the reactant and product in a chemical reaction. This is known as the kinetic isotope effect (KIE). A classic example of KIE is the DHR difference in the equilibrium between H2O and H2 which can have an α value of as much as 3–4.
Sources: en.wikipedia.org
It is a synthetic cyclic heptapeptide modelled on alpha-melanocyte-stimulating hormone. A lactam bridge links two side chains, forming a ring that stabilises the molecule against proteolysis. It belongs to the broader melanocortin peptide family.
No national medicines agency has approved melanotan-2 for clinical use. Afamelanotide, a related but distinct peptide, holds a marketing authorisation in the European Union for a rare photosensitivity disorder. Melanotan-2 itself is handled as a laboratory chemical.
Its broad activity across melanocortin receptors makes it a tool for probing pigmentation, appetite and vascular signalling. Early trials recorded skin darkening and other effects that were not the original focus of the work. Those observations generated hypotheses that later studies have examined.
It is a synthetic cyclic peptide designed as an analog of alpha-melanocyte-stimulating hormone. It acts on melanocortin receptors and is best known from research into pigmentation. It is not an approved pharmaceutical product.