afamelanotide is one of those subjects where the details matter more than the headlines. This page pulls together the background, the mechanisms, and the practical points readers ask about most.
Updated 2026-02-09. Numbers and descriptions here follow the published literature rather than marketing material.
Receptor-binding studies classify melanotan II as a non-selective melanocortin agonist. It interacts with MC1R, MC3R, MC4R and MC5R, with reported affinities in the low nanomolar range and no strong subtype preference. Activation of MC1R on dermal melanocytes shifts pigment synthesis toward eumelanin, the dark polymer deposited in melanosomes and transferred to keratinocytes. Because the same peptide engages MC4R in the hypothalamus, it also appears in animal work on food intake and erectile response, which is why it is discussed in both pigment and metabolic research. Which receptor populations dominate after systemic exposure in humans is not fully established.
Published pharmacokinetic information is limited and comes mainly from small studies rather than registrational trials. Plasma half-life is usually described as short, on the order of tens of minutes, followed by rapid tissue distribution and clearance of the intact peptide. Metabolites and low concentrations of parent compound have been reported in urine, a detail relevant to anti-doping and forensic testing. Whether repeated exposure changes receptor sensitivity or clearance over time remains an open question. Values differ noticeably between analytical assays, so published numbers should be read as approximate rather than definitive.
Melanotan II is a synthetic cyclic heptapeptide with the sequence Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, corresponding to a molecular formula of C50H69N15O9 and a monoisotopic mass near 1024 daltons. It was designed as a structural analogue of alpha-melanocyte-stimulating hormone, a peptide hormone produced by cleavage of proopiomelanocortin. A lactam bridge between the aspartate and lysine side chains closes the ring, and the C-terminal amide removes a free carboxyl group. Both modifications increase resistance to enzymatic degradation compared with the linear parent hormone. Four substitutions distinguish it from afamelanotide, the linear analogue studied under the name melanotan I.
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.
Handling guidance for melanotan II follows general practice for small synthetic peptides rather than a product-specific monograph. Lyophilized powder is typically kept at minus twenty degrees Celsius or colder, protected from light and moisture, because warmth and humidity accelerate degradation. Once reconstituted, solutions are usually refrigerated and used within a short window, as hydrolysis and microbial growth both become concerns. Repeated freeze-thaw cycles are generally avoided. These conventions come from laboratory peptide chemistry and not from formal stability studies on this specific compound.
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.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C50H69N15O9 | Cyclic heptapeptide, C-terminally amidated |
| Approximate molecular mass | 1024 Da | Monoisotopic mass of the free peptide |
| Appearance | White to off-white powder | Typically supplied as a lyophilised solid |
| Solubility class | Soluble in water and polar solvents | Also dissolves in neutral aqueous buffer |
| Common synonyms | Melanotan II, MT-II, MT-2 | Described as a melanocortin agonist in early literature |
Receptor binding at MC1R on melanocytes raises intracellular cyclic AMP and increases expression of tyrosinase and related enzymes. The downstream result is greater synthesis of eumelanin, the dark pigment, without ultraviolet exposure acting as the trigger. The compound is not selective, however, and also engages MC3R, MC4R and MC5R, which are expressed in the central nervous system and elsewhere. That lack of selectivity is the explanation usually offered for effects reported outside pigmentation, including appetite suppression and nausea. Selectivity remains a central theme in comparative studies of related peptides.
Human data remain limited and mostly short-term. Reports describe small trials and observational accounts rather than large controlled studies, so questions about dose-response relationships and long-term effects on melanocytes stay open. Whether repeated exposure alters naevus behaviour is not settled in the published record. Researchers also note that self-administered use outside clinical settings makes actual exposure difficult to quantify. Statements about efficacy and safety should therefore be read as preliminary rather than established.
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.
Regulatory treatment of this peptide varies by country. It holds no marketing authorization as a medicine in the United States, the European Union, or most other jurisdictions. Some countries classify products containing it as prescription-only or unlicensed medicines, which restricts lawful supply. Authorities have issued public notices warning that unregulated products may contain undeclared or incorrect ingredients. The molecule also appears on prohibited lists for competitive sport. These measures address supply oversight rather than any approved therapeutic role.
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.
==== Hyperglucagonemia ==== The onset of type 1 diabetes is followed by an increase in glucagon secretion after meals. Increases have been measured up to 37% during the first year of diagnosis, while C-peptide levels (indicative of islet-derived insulin), decline by up to 45%. Insulin production will continue to fall as the immune system destroys beta cells, and islet-derived insulin will continue to be replaced by therapeutic exogenous insulin. Simultaneously, there is measurable alpha cell hypertrophy and hyperplasia in the early stage of the disease, leading to expanded alpha cell mass. This, together with failing beta cell insulin secretion, begins to account for rising glucagon levels that contribute to hyperglycemia. Some researchers believe glucagon dysregulation to be the primary cause of early-stage hyperglycemia. Leading hypotheses for the cause of postprandial hyperglucagonemia suggest that exogenous insulin therapy is inadequate to replace the lost intraislet signalling to alpha cells previously mediated by beta cell-derived pulsatile insulin secretion. Under this working hypothesis intensive insulin therapy has attempted to mimic natural insulin secretion profiles in exogenous insulin infusion therapies. In young people with type 1 diabetes, unexplained deaths could be due to nighttime hypoglycemia triggering abnormal heart rhythms or cardiac autonomic neuropathy, damage to nerves that control the function of the heart.
The development of secondary sex characteristics in women is driven by estrogens, to be specific, estradiol. These changes are initiated at the time of puberty, most are enhanced during the reproductive years, and become less pronounced with declining estradiol support after menopause. Thus, estradiol produces breast development, and is responsible for changes in the body shape, affecting bones, joints, and fat deposition. In females, estradiol induces breast development, widening of the hips, a feminine fat distribution (with fat deposited particularly in the breasts, hips, thighs, and buttocks), and maturation of the vagina and vulva, whereas it mediates the pubertal growth spurt (indirectly via increased growth hormone secretion) and epiphyseal closure (thereby limiting final height) in both sexes.
At present, opium poppies are mostly grown in Afghanistan (224,000 hectares (550,000 acres)), and in Southeast Asia, especially in the region known as the Golden Triangle straddling Burma (57,600 hectares (142,000 acres)), Thailand, Vietnam, Laos (6,200 hectares (15,000 acres)) and Yunnan province in China. There is also cultivation of opium poppies in Pakistan (493 hectares (1,220 acres)), Mexico (12,000 hectares (30,000 acres)) and in Colombia (378 hectares (930 acres)). According to the DEA, the majority of the heroin consumed in the United States comes from Mexico (50%) and Colombia (43–45%) via Mexican criminal cartels such as Sinaloa Cartel. However, these statistics may be significantly unreliable, the DEA's 50/50 split between Colombia and Mexico is contradicted by the amount of hectares cultivated in each country and in 2014, the DEA claimed most of the heroin in the US came from Colombia. As of 2015, the Sinaloa Cartel is the most active drug cartel involved in smuggling illicit drugs such as heroin into the United States and trafficking them throughout the United States. According to the Royal Canadian Mounted Police, 90% of the heroin seized in Canada (where the origin was known) came from Afghanistan. Pakistan is the destination and transit point for 40 percent of the opiates produced in Afghanistan, other destinations of Afghan opiates are Russia, Europe and Iran.
Langlykke who visited the Argentine lab once a year. In 1960, he offered Ondetti a job to work in the New Jersey laboratory. Within two days, Ondetti decided to take the job in New Jersey for $7800 a year.
Oviparity in sharks can be categorized as single or retained. With single oviparity, the egg cases are extruded soon after fertilization. With retained oviparity, eggs are kept within the oviduct for a period of time before depositing outside of the body as an unhatched egg case. It is thought that viviparity is the ancestral condition for sharks, and that it evolved through the elongation of retention time of retained oviparity. Oviparous sharks are known to regularly produce unfertilized eggs when kept in captivity without males.
Sources: en.wikipedia.org
=== Pharmacodynamics === Gabapentin is a ligand of the α2δ calcium channel subunit. The α2δ-1 protein is coded by the CACNA2D1 gene. α2δ was first described as an auxiliary protein connected to the main α1 subunit (the channel-forming protein) of high voltage activated voltage-dependent calcium channels (L-type, N-type, P/Q type, and R-type). The same α2δ protein has more recently been shown to interact directly with some NMDA-type and AMPA-type glutamate receptors at presynaptic sites and also with thrombospondin (an extracellular matrix protein secreted by astroglial cells). Gabapentin is not a direct calcium channel blocker: it exerts its actions by disrupting the regulatory function of α2δ and its interactions with other proteins. Gabapentin reduces delivery of intracellular calcium channels to the cell membrane, reduces the activation of the channels by the α2δ subunit, decreases signaling to lead to neurotransmitters release, and disrupts interactions of α2δ with voltage gated calcium channels but also with NMDA receptors, neurexins, and thrombospondin. These proteins are found as mutually interacting parts of the presynaptic active zone, where numerous protein molecules interact with each other to enable and to regulate the release of neurotransmitters from presynaptic vesicles into the synaptic space. Out of the four known isoforms of α2δ protein, gabapentin binds with similar high affinity to two: α2δ-1 and α2δ-2. All of the pharmacological properties of gabapentin tested to date are explained by its binding to just one isoform – α2δ-1.
== Mechanism of action == Abatacept is a soluble CTLA-4 analog that prevents antigen-presenting cells (APCs) from delivering the co-stimulatory signal. This prevents the T cells from being fully activated, and even downregulates them. Simple signaling without co-stimulation allows the cell to recognize the primary signal as "self" and not ramp-up responses for future responses as well. In order for T cells to be activated and attack an antigen, that antigen must be presented to the T cell by an APC. That activation requires two signals (one of which is called co-stimulatory signal or signal 2): For signal 1, the APC must bind the antigen to a major histocompatibility complex (MHC) molecule, bring that complex to its surface, and present it to the T cell receptor on the surface of the T cell. For signal 2, the APC must present a B7 protein (CD80 or CD86) on its cell surface to a CD28 protein on the surface of the T cell. These two signals activate the T cell. Without signal 2, the T cell will not be activated, and will become anergic. Abatacept, which consists of a fusion protein of the extracellular domain of CTLA-4 and human IgG1, binds to the B7 protein on the APC and prevents it from delivering the co-stimulatory signal to the T cell.
=== In tRNA === Wobble pairing rules. Watson–Crick base pairs are shown in bold. Parentheses denote bindings that work but will be favoured less. A leading x denotes derivatives (in general) of the base that follows.
Le Havre Official website (in French) Official tourism website Archived 23 December 2018 at the Wayback Machine Le Havre Information website (Archive) Le Havre on Lion1906 Slave streets of Le Havre; article on the slave trade here in 17th and 18th century Le Havre on Géoportail, National Geographic Institute (IGN) website (in French) Texts on Wikisource: "Havre, Le". Encyclopædia Britannica. Vol. 11 (9th ed.). 1880. pp. 527–528. "Havre, Le". Encyclopædia Britannica. Vol. 13 (11th ed.). 1911. pp. 83–84. "Havre". The American Cyclopædia. 1879. "Havre". The New Student's Reference Work. 1914. "Havre". Collier's New Encyclopedia. 1921.
Sources: en.wikipedia.org
=== Ending manufacture === Citing health concerns, several manufacturing companies have ended or stated that they plan to end the sale of PFAS or products that contain them. These companies include W. L. Gore & Associates (the maker of Gore-Tex), Patagonia, REI, H&M, and 3M. An alternative for some companies may have been to move production to countries such as Thailand and India, where there is less regulation.
Therefore, stable spiral waves are characterized by once-for-ever selection, which creates the restrictions that, on the one hand, once the information is added to the system, it cannot be easily abandoned; and on the other hand, new information cannot be added. Another model based on cellular automata, taking into account a simpler replicating network of continuously mutating parasites and their interactions with one replicase species, was proposed by Takeuchi and Hogeweg and exhibited an emergent travelling wave pattern. Surprisingly, travelling waves not only proved to be stable against moderately strong parasites, if the parasites' mutation rate is not too high, but the emergent pattern itself was generated as a result of interactions between parasites and replicase species. The same technique was used to model systems that include formation of complexes. Finally, hypercycle simulation extending to three dimensions showed the emergence of the three-dimensional analogue of a spiral wave, namely, the scroll wave.
=== Early life and education === William H. Stein was born on June 25, 1911 in New York City into a Jewish family. His father, Fred M. Stein, was a businessman who retired early to support local New York health organizations. His mother, Beatrice Borg Stein, was a children's rights activist who developed afterschool activities. Staunch advocates for the welfare of society, Stein's parents fostered his interests in the life sciences from a young age. As a child, Stein attended the recently established "progressive" Lincoln School which was sponsored by the Teachers College of Columbia University; there, he was able to explore the natural sciences through field trips and science projects. At the age of sixteen, Stein was transferred to the Phillips Exeter Academy in New England to prepare for higher education. In 1936, during his graduate studies at Columbia University, William H. Stein married Phoebe Hockstader. They had three sons together: William H. Stein, Jr., David F. Stein, and Robert J. Stein. Stein lived with his family in New York the rest of his life—mainly in Manhattan and briefly in Scarsdale, New York.
In the sugar industry vacuum evaporation is used in the crystallization of sucrose solutions. Traditionally this process was performed in batch mode, but nowadays continuous vacuum pans are available.
Temporary muscle weakness Brain fog Fatigue Anxiety Temporary thought disorder, or inability to concentrate Visual problems, such as blurred vision or double vision Headaches Shaking/Trembling Thirst If a person experiences any of these symptoms, a visit to a qualified medical practitioner is advised, and diagnostic blood testing, such as Fasting Insulin Levels, may be required.
Sources: en.wikipedia.org
No. It is a synthetic analogue carrying four amino acid changes, a lactam ring and an amidated C-terminus. The natural hormone is a linear thirteen-amino-acid peptide processed from proopiomelanocortin.
Afamelanotide is the linear analogue [Nle4-D-Phe7]-alpha-MSH, sometimes called melanotan I, while melanotan II is cyclic and carries three further substitutions. The two are distinct molecules and are not interchangeable in analytical testing.
Binding to the four melanocortin receptor subtypes is well documented in vitro. The relative contribution of each subtype to whole-body effects in humans is far less certain.
The lyophilized powder is generally held at minus twenty degrees Celsius or below, away from light and moisture. Reconstituted solutions are typically refrigerated and used quickly. These practices derive from general peptide handling rather than a formal stability study.