This is a working overview of melanocortin receptor, written for readers who want more than a one-paragraph summary but less than a textbook.
Reviewed 2026-01-14. 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.
Two structural changes distinguish the synthetic peptide from the natural hormone. A norleucine residue replaces methionine at one position, and a D-configured phenylalanine replaces the natural L-form at another. Both substitutions slow enzymatic breakdown, which extends the molecule's persistence relative to the parent hormone. The lactam bridge further constrains the backbone into a stable conformation. These features are standard design strategies in peptide chemistry and are not unique to this compound; they appear across many research peptides built for improved stability.
The compound was developed in the late 1980s and early 1990s by academic researchers investigating melanocortin signaling and pigmentation. Early work explored whether synthetic analogs could reproduce effects of the natural hormone under controlled conditions. The molecule never advanced through the full regulatory pathway required for approval as a medicine. From the mid-2000s onward it appeared in unregulated consumer markets, often distributed through informal channels. That gap between research origins and commercial availability shapes how the compound is discussed today.
Melanotan-2 is a synthetic peptide designed as an analog of alpha-melanocyte-stimulating hormone, a signaling molecule produced in the pituitary and skin. Its structure is a linear chain of seven amino acids that folds into a ring through an internal lactam bridge joining two side chains. The compound is sometimes written as MT-II or MEL-2 in informal and commercial contexts. It belongs to the melanocortin peptide family, a group of short signaling molecules that share a conserved core sequence recognized by melanocortin receptors.
| 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 |
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.
The compound emerged from research programs in the 1980s that examined analogues of alpha-melanocyte-stimulating hormone for pigmentation and photoprotection. Investigators modified the native sequence to extend activity duration and potency. A related analogue, afamelanotide, was developed within the same broad line of inquiry and eventually gained approval in certain jurisdictions for a rare light-sensitivity condition. Melanotan-2 itself did not progress through the same regulatory route and has no approved therapeutic indication.
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.
A small "pill" of opium about the size of a pea would be placed on the pipe-bowl, which was then heated by holding it over an opium lamp, a special oil lamp with a distinct funnel-like chimney to channel heat into a small area. The smoker would lie on their side in order to guide the pipe-bowl and the tiny pill of opium over the stream of heat rising from the chimney of the oil lamp and inhale the vaporized opium fumes as needed. Several pills of opium were smoked at a single session depending on the smoker's tolerance to the drug. The effects could last up to twelve hours. In Eastern culture, opium is more commonly used in the form of paregoric to treat diarrhea. This is a weaker solution than laudanum, an alcoholic tincture which was prevalently used as a pain medication and sleeping aid. Tincture of opium has been prescribed for, among other things, severe diarrhea. Taken thirty minutes prior to meals, it significantly slows intestinal motility, giving the intestines greater time to absorb fluid in the stool. Despite the historically negative view of opium as a cause of addiction, the use of morphine and other derivatives isolated from opium in the treatment of chronic pain has been reestablished. If given in controlled doses, modern opiates can be an effective treatment for neuropathic pain and other forms of chronic pain.
Consuming food prior to taking chlorpromazine orally limits its absorption; likewise, cotreatment with benztropine can also reduce chlorpromazine absorption. Alcohol can also reduce chlorpromazine absorption. Antacids slow chlorpromazine absorption. Lithium and chronic treatment with barbiturates can increase chlorpromazine clearance significantly. Tricyclic antidepressants (TCAs) can decrease chlorpromazine clearance and hence increase chlorpromazine exposure. Cotreatment with CYP1A2 inhibitors like ciprofloxacin, fluvoxamine or vemurafenib can reduce chlorpromazine clearance and hence increase exposure and potentially also adverse effects. Chlorpromazine can also potentiate the CNS depressant effects of drugs like barbiturates, benzodiazepines, opioids, lithium and anesthetics and hence increase the potential for adverse effects such as respiratory depression and sedation. Chlorprozamine is also a moderate inhibitor of CYP2D6 and a substrate for CYP2D6 and hence can inhibit its own metabolism. It can also inhibit the clearance of CYP2D6 substrates such as dextromethorphan, potentiating their effects. Other drugs like codeine and tamoxifen, which require CYP2D6-mediated activation into their respective active metabolites, may have their therapeutic effects attenuated. Likewise, CYP2D6 inhibitors such as paroxetine or fluoxetine can reduce chlorpromazine clearance, increasing serum levels of chlorpromazine and potentially its adverse effects. Chlorpromazine also reduces phenytoin levels and increases valproic acid levels.
18 August A weak spot in the spike protein of SARS-CoV-2 is described by researchers, which an antibody fragment called VH Ab6 can attach to, potentially neutralising all major variants of the virus. On 11 August, researchers report a single antibody, SP1-77, that could potentially neutralize all known variants of the virus via a novel mechanism, not by not preventing the virus from binding to ACE2 receptors but by blocking it from fusing with host cells' membranes. Multiple gene editing of soybean is shown to improve photosynthesis and boost yields by 20%. A researcher reports that the social media app TikTok adds a keylogger to its, on iOS essentially unavoidable, in-app browser in iOS, which allows its Chinese company to gather, for example, passwords, credit card details, and everything else that is typed into websites opened from taps on any external links within the app. Shortly after the report, the company claims such capabilities are only used for debugging-types of purposes. To date, it has largely not been investigated which and to which extent (other) apps have capacities for such or similar data-collection. A university reports the development of an invisible coating for fireproof wood. 20 August – A GBD systematic analysis reports the (non)progress on cancer and its causes during the 2010-19 decade, with ~44% of all cancer deaths in 2019 – or ~4.5 M deaths or ~105 million lost DALYs – due to known clearly preventable risk factors (contributions), led by smoking, alcohol use and high BMI.
=== Proteomics/metabolomics === LC–MS is used in proteomics as a method to detect and identify the components of a complex mixture. The bottom-up proteomics LC–MS approach generally involves protease digestion and denaturation using trypsin as a protease, urea to denature the tertiary structure, and iodoacetamide to modify the cysteine residues. After digestion, LC–MS is used for peptide mass fingerprinting, or LC–MS/MS (tandem MS) is used to derive the sequences of individual peptides. LC–MS/MS is most commonly used for proteomic analysis of complex samples where peptide masses may overlap even with a high-resolution mass spectrometry. Samples of complex biological material, such as human serum, may be analyzed in modern LC–MS/MS systems, which can identify over 1000 proteins. However, this high level of protein identification is possible only after separating the sample by means of SDS-PAGE gel or HPLC-SCX. Recently, LC–MS/MS has been applied to search peptide biomarkers. Examples are the recent discovery and validation of peptide biomarkers for four major bacterial respiratory tract pathogens (Staphylococcus aureus, Moraxella catarrhalis; Haemophilus influenzae and Streptococcus pneumoniae) and the SARS-CoV-2 virus. LC–MS has emerged as one of the most commonly used techniques in global metabolite profiling of biological tissue such as blood plasma, serum, and urine. LC–MS is also used for the analysis of natural products and the profiling of secondary metabolites in plants.
Sources: en.wikipedia.org
Nutrition-related results A study by researchers from the University of Bergen and Haukeland University Hospital integrates meta-analyses and data in a tool that shows populations' relative general life extension potentials of different food groups according to this available data, mostly consisting of observational studies. Results from the first controlled trial of caloric restriction in healthy non-obese humans, CALERIE, are published, confirming benefits and identifying a key protein that could be harnessed to extend health in humans, PLA2G7. A comprehensive review reaffirms likely beneficial health effects with links to health/life extension of cycles of caloric restriction and intermittent fasting as well as reducing meat consumption in humans. It identifies issues with contemporary nutrition research approaches, proposing a multi-pillar approach, and summarizes findings towards constructing – multi-system-considering and at least age-personalized dynamic – refined longevity diets and proposes inclusion of such in standard preventive healthcare. A study demonstrates that a 30% caloric restriction extended life spans of male C57BL/6J mice by 10% but when combined with daily intermittent fasting and eating during the most active time of the day it extended life span by 35%. A study shows that 50+ aged users of the dietary program SNAP "had about 2 fewer years of cognitive aging over a 10-year period compared with non-users" despite it having nearly no conditions for the sustainability and healthiness of the food products purchased with the coupons (or coupon-credits).
== Further reading == Budd, A. (2012). "Introduction to genome biology: features, processes, and structures". Evolutionary Genomics. Methods in Molecular Biology. Vol. 855. pp. 3–4. doi:10.1007/978-1-61779-582-4_1. ISBN 978-1-61779-581-7. PMID 22407704.
== External links == Sugimura T, Nagao M, Wakabayashi K (May 1996). "Carcinogenicity of food mutagens". Environmental Health Perspectives. 104 (Suppl 3): 429–33. doi:10.2307/3432798. JSTOR 3432798. PMC 1469643. PMID 8781358. Louis ED, Zheng W, Jiang W, Bogen KT, Keating GA (June 2007). "Quantification of the neurotoxic beta-carboline harmane in barbecued/grilled meat samples and correlation with level of doneness". Journal of Toxicology and Environmental Health, Part A. 70 (12): 1014–9. Bibcode:2007JTEHA..70.1014L. doi:10.1080/15287390601172015. PMC 4993204. PMID 17497412.
(2026) make the name of the toxodontid Andinotoxodon bolivarensis, originally described in a doctoral dissertation, available under the International Code of Zoological Nomenclature. The first confirmed fossil material of Late Pleistocene Toxodon platensis from the San Luis Province (Argentina), providing information on the intracranial anatomy of members of this species, is described from the Barranquita Formation by Hernández Del Pino et al. (2026). Evidence from the study of tooth wear of Tremacyllus and Paedotherium, interpreted as indicating that pachyrukhine hegetotheriid notoungulates were mainly fruit-seed consumers rather than grazers, is presented by Armella & Croft (2026). A study on the evolution of the morphological similarity to molar teeth in premolar teeth of ungulates, based on data from extant and extinct artiodactyls and perissodactyls, is published by Ashbaugh, Jamniczky & Theodor (2026). A study on tooth wear of early Pleistocene ungulates from the Quibas site (Murcia, Spain), interpreted as indicative of a broad spectrum of feeding behaviours consistent with presence of mosaic environments including grasslands with wooded patches, is published by Ramírez-Pedraza, Agustí & Piñero (2026). Hussain et al. (2026) reconstruct the dietary presences of Pleistocene ungulates from the Pinjor Formation (Pakistan) on the basis of the study of their tooth wear, interpreted as indicating that the studied assemblage was dominated by grazers but also included browsers and mixed-feeders.
=== Food and feed === Microalgae such as Isochrysis galbana, Nannochlor opsisoculata, Chaetoceros muelleri, Chaetoceros gracilis and P. tricornutum have been long utilized in aquaculture as direct or indirect feed sources in hatchery to provide excellent nutritional conditions for early juveniles of farmed fish, shellfish, and shrimp. Furthermore, the EPS layer acts as a nutrient trap, facilitating bacterial growth. The exopolysaccharides of some strains of lactic acid bacteria, e.g., Lactococcus lactis subsp. cremoris, contribute a gelatinous texture to fermented milk products (e.g., Viili), and these polysaccharides are also digestible. An example of the industrial use of exopolysaccharides is the application of dextran in panettone and other breads in the bakery industry. B. subtilis has gained interest for its probiotic properties due to its biofilm which allows it to effectively maintain a favorable microenvironment in the gastrointestinal tract. In order to survive the passage through the upper gastrointestinal tract, B. subtilis produces an extracellular matrix that protects it from stressful environments such as the highly acidic environment in the stomach.
Sources: en.wikipedia.org
=== Benson presidency === Roger Benson made immediate changes in the way PEF conducted its business. He dismissed six staff members and returned to having two administrators share duties over the daily operation of the union. He also named two close associates to the staff, and criticized the decision of the Sheedy-led executive board for enhancing the staff's severance packages. Local newspapers called the changes "bloodletting", and reported that additional layoffs were likely to come. Among PEF's major political initiatives at this time were a cost-of-living increase for worker pensions. Benson also said he would seek improvements to job security; accrual (rather than use-or-lose) for overtime, sick leave, and vacation; eliminate tiers in the pension plan; seek an end to penalties for early retirement; new workplace safety protections; an increase in the size of the state workforce; and new restrictions on contracting out. The state replied that it would seek a four-year wage freeze. Angered by the state's response in a time of budget surpluses, Benson led PEF workers in an extensive lobbying effort. He also said PEF would seek a three-year rather than four-year contract, and 5 percent per year wage increases. Benson also replaced the union's top negotiator in order to adopt a more aggressive stand with the state. The state countered with a 3 percent per year salary increase over four years, coupled with new restrictions on time off for union business, higher health care costs, and new worktime reporting requirements (all of which PEF rejected).
The primary use of dental implants is to support dental prosthetics (i.e. false teeth). Modern dental implants work through a biologic process where bone fuses tightly to the surface of specific materials such as titanium and some ceramics. The integration of implant and bone can support physical loads for decades without failure. The US has seen an increasing use of dental implants, with usage increasing from 0.7% of patients missing at least one tooth (1999–2000), to 5.7% (2015–2016), and was projected to potentially reach 26% in 2026. Implants are used to replace missing individual teeth (single tooth restorations), multiple teeth, or to restore edentulous (toothless) dental arches (implant retained fixed bridge, implant-supported overdenture). While use of dental implants in the US has increased, other treatments to tooth loss exist. Dental implants are also used in orthodontics to provide anchorage (orthodontic mini implants). Orthodontic treatment might be required prior to placing a dental implant. An evolving field is the use of implants to retain obturators (removable prostheses used to fill a communication between the oral and maxillary or nasal cavities). Facial prosthetics, used to correct facial deformities (e.g. from cancer treatment or injuries), can use connections to implants placed in the facial bones. Depending on the situation the implant may be used to retain either a fixed or removable prosthetic that replaces part of the face.
According to Annex 13 of the Convention on International Civil Aviation, an aviation accident is an occurrence associated with the operation of an aircraft, which takes place from the time any person boards the aircraft with the intention of flight until all such persons have disembarked, and in which (a) a person is fatally or seriously injured, (b) the aircraft sustains significant damage or structural failure, or (c) the aircraft goes missing or becomes completely inaccessible. Annex 13 defines an aviation incident as an occurrence, other than an accident, associated with the operation of an aircraft that affects or could affect the safety of operation. A hull loss occurs if an aircraft is damaged beyond repair, is lost, or becomes completely inaccessible.
A common pathological cause for a high BMR is fever, since a rise in body temperature increases the rate of cellular metabolic reactions. It is estimated that for every degree Fahrenheit of rise in body temperature, the BMR increases by 7 percent. Thyroid disease also has a marked effect on BMR, since thyroid hormones regulate the rate of cellular metabolism. Hyperthyroidism—in which there is an increase in the production of thyroid hormones—leads to a high BMR, while hypothyroidism—in which thyroid hormones are depleted—causes a low BMR. Prolonged periods of abnormal nutrition cause an adaptive change in BMR; this helps the body to maintain a stable body weight in response to the change in food supply. In prolonged malnutrition, the BMR declines, while in prolonged overnutrition, the BMR is increased. Cancer sometimes causes an increase in BMR, perhaps because the cancer cells that form tumors have a high level of metabolic activity.
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.
It is a synthetic seven-amino-acid peptide modeled on alpha-melanocyte-stimulating hormone. It carries two non-natural substitutions and a cyclic bridge that increase its stability relative to the natural hormone. It circulates as a research chemical and is not an approved medicine.