The short version of cyclic heptapeptide fits in a sentence. The long version — which is the one that helps — is below.
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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.
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.
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.
| 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 |
No regulatory authority has approved melanotan-2 for human use, and several countries classify it as a prescription-only or controlled substance, which restricts lawful supply. Material sold online is generally labelled as a research chemical and is not required to meet pharmaceutical standards of identity or purity. Published human data consist mainly of small uncontrolled studies, case reports and adverse-event notifications, so the evidence base is descriptive rather than confirmatory. Whether repeated melanocyte stimulation alters long-term naevus behaviour remains an open question that no completed trial has resolved.
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.
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.
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.
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.
== Sources == Furlow, John J. (1997). "Betula". In Flora of North America Editorial Committee (ed.). Flora of North America North of Mexico (FNA). Vol. 3. New York and Oxford: Oxford University Press – via eFloras.org, Missouri Botanical Garden, St. Louis, Missouri and Harvard University Herbaria, Cambridge, Massachusetts. Li, Pei-chun; Skvortsov, Alexei K. "Betula". Flora of China. Vol. 4 – via eFloras.org, Missouri Botanical Garden, St. Louis, Missouri and Harvard University Herbaria, Cambridge, Massachusetts. Grimshaw, John (2009). New Trees, Recent introductions to cultivation. Kew Publishing, RBG Kew. pp. 163–174. Chisholm, Hugh, ed. (1911). "Birch" . Encyclopædia Britannica. Vol. 3 (11th ed.). Cambridge University Press. Jonczak, Jerzy; Jankiewicz, Urszula; Kondras, Marek; Kruczkowska, Bogusława; Oktaba, Lidia; Oktaba, Jarosław; Olejniczak, Izabella; Pawłowicz, Edyta; Polláková, Nora; Raab, Thomas; Regulska, Edyta; Słowińska, Sandra; Sut-Lohmann, Magdalena (December 2020). "The influence of birch trees (Betula spp.) on soil environment – A review". Forest Ecology and Management. 477 118486. Bibcode:2020ForEM.47718486J. doi:10.1016/j.foreco.2020.118486.
== Production == Optimer ligands are produced via solid-phase synthesis. Solid-phase chemical synthesis was invented in the 1960s by Robert Bruce Merrifield, for which he was awarded the Nobel Prize for Chemistry in 1984. Solid-phase synthesis is carried out on a solid support held between filters, in columns that enable all reagents and solvents to pass through freely. Solid-phase synthesis has a number of advantages over cell-based manufacturing that is typically used for protein affinity reagents, such as antibodies:
==== Film and television ==== Cartoon Network, the Disney Channel, and Nickelodeon were once staples of children's entertainment among Millennials and Generation Z. But viewership began to drop in the early 2010s. Nielsen figures for 2020 revealed that the viewership of children's cable linear television channels continued their steady decline despite the COVID-19 pandemic, which forced many parents and their children to stay at home, while streaming services saw healthy growth. Among members of Generation Z who regularly watch movies, demand for physical media (DVDs and Blu-rays), both for sale and for rent, has been climbing in the 2020s. Animations, including those made in Japan (known as anime), are in high demand among Generation Z. By the mid-2020s, the most popular television series among Generation Z include My Hero Academia (2016–present), Steven Universe (2013–2019), Invincible (2021–present), Euphoria (2019–2026), Star Wars: The Clone Wars (2008–2020), and Loki (2021–2023). Generations Z and Alpha also enjoy comfort television shows popular with older cohorts or ended before they were born, such as Friends (1994–2004) and Gilmore Girls (2000–2007; 2016), as well as shows featuring characters roughly their age, like Young Sheldon (2017–2024) and Stranger Things (2016–2025), and long-running television drama, like Grey's Anatomy (2005–present). The Netflix science-fiction horror series Stranger Things became a popular TV series to Generation Z by using and evoking nostalgia for the 1980s.
==== Absorption ==== Hydrocodone is only pharmaceutically available as an oral medication. It is well-absorbed, but the oral bioavailability of hydrocodone is only approximately 25%. The onset of action of hydrocodone via this route is 10 to 20 minutes, with a peak effect (Tmax) occurring at 30 to 60 minutes, and it has a duration of 4 to 8 hours. The FDA label for immediate-release hydrocodone with acetaminophen does not include any information on the influence of food on its absorption or other pharmacokinetics. Conversely, coadministration with a high-fat meal increases peak concentrations of different formulations of extended-release hydrocodone by 14 to 54%, whereas area-under-the-curve levels are not notably affected.
Sources: en.wikipedia.org
Di Prisco G, Casola L, Giuditta A (1967). "Purification and properties of a soluble reduced nicotinamide-adenine dinucleotide (phosphate) dehydrogenase from the hepatopancreas of Octopus vulgaris". Biochem. J. 105 (2): 455–60. doi:10.1042/bj1050455. PMC 1198331. PMID 4171422. GIUDITTA A, STRECKER HJ (1961). "Purification and some properties of a brain diaphorase". Biochim. Biophys. Acta. 48: 10–9. doi:10.1016/0006-3002(61)90509-1. PMID 13705804. MAERKI F, MARTIUS C (1960). "[Vitamin K reductase, preparation and properties.]". Biochem. Z. 333: 111–35. PMID 13765127. Misaka E, Nakanishi K. "Studies on menadione reductase of bakers' yeast. I. Purification, crystallization and some properties". J. Biochem. Tokyo: 465–471. WOSILAIT WD (1960). "The reduction of vitamin K1 by an enzyme from dog liver". J. Biol. Chem. 235 (4): 1196–201. doi:10.1016/S0021-9258(18)69504-3. PMID 13846011. Sparla F, Tedeschi G, Trost P (1996). "NAD(P)H:(Quinone-Acceptor) Oxidoreductase of Tobacco Leaves Is a Flavin Mononucleotide-Containing Flavoenzyme". Plant Physiol. 112 (1): 249–258. doi:10.1104/pp.112.1.249. PMC 157943. PMID 12226388. Braun M, Bungert S, Friedrich T (1998). "Characterization of the overproduced NADH dehydrogenase fragment of the NADH:ubiquinone oxidoreductase (complex I) from Escherichia coli". Biochemistry. 37 (7): 1861–7. doi:10.1021/bi971176p. PMID 9485311. Jaiswal AK (2000). "Characterization and partial purification of microsomal NAD(P)H:quinone oxidoreductases". Arch. Biochem. Biophys. 375 (1): 62–8. doi:10.1006/abbi.1999.1650. PMID 10683249.
Protein–protein interactions often result in one of the interacting proteins either being 'activated' or 'repressed'. Such effects can be indicated in a PPI network by "signs" (e.g. "activation" or "inhibition"). Although such attributes have been added to networks for a long time, Vinayagam et al. (2014) coined the term Signed network for them. Signed networks are often expressed by labeling the interaction as either positive or negative. A positive interaction is one where the interaction results in one of the proteins being activated. Conversely, a negative interaction indicates that one of the proteins being inactivated. Protein–protein interaction networks are often constructed as a result of lab experiments such as yeast two-hybrid screens or 'affinity purification and subsequent mass spectrometry techniques. However these methods do not provide the layer of information needed in order to determine what type of interaction is present in order to be able to attribute signs to the network diagrams.
== List of separation techniques == Centrifugation and cyclonic separation, separates based on density differences Chelation Chromatography separates dissolved substances by different interaction with (i.e., travel through) a material. High-performance liquid chromatography (HPLC) Thin-layer chromatography (TLC) Countercurrent chromatography (CCC) Droplet countercurrent chromatography (DCC) Paper chromatography Ion chromatography Size-exclusion chromatography (SEC) Affinity chromatography Centrifugal partition chromatography Gas chromatography and Inverse gas chromatography Crystallization Decantation Demister (vapor), removes liquid droplets from gas streams Distillation, used for mixtures of liquids with different boiling points Drying, removes liquid from a solid by vaporization or evaporation Electrophoresis, separates organic molecules based on their different interaction with a gel under an electric potential (i.e., different travel) Capillary electrophoresis Electrostatic separation, works on the principle of corona discharge, where two plates are placed close together and high voltage is applied. This high voltage is used to separate the ionized particles.
These symbols are also valid for RNA, except with U (uracil) replacing T (thymine). Apart from adenine (A), cytosine (C), guanine (G), thymine (T) and uracil (U), DNA and RNA also contain bases that have been modified after the nucleic acid chain has been formed. In DNA, the most common modified base is 5-methylcytidine (m5C). In RNA, there are many modified bases, including pseudouridine (Ψ), dihydrouridine (D), inosine (I), ribothymidine (rT) and 7-methylguanosine (m7G). Hypoxanthine and xanthine are two of the many bases created through mutagen presence, both of them through deamination (replacement of the amine-group with a carbonyl-group). Hypoxanthine is produced from adenine, and xanthine is produced from guanine. Similarly, deamination of cytosine results in uracil.
== Structure == PnuC of Salmonella typhimurium and Haemophilus influenzae are integral membrane proteins, 239 and 226 amino acyl residues (aas) in length, respectively, with 7 putative transmembrane α-helical segments. The structure of NadR has been determined. Mutations in the nadR gene which interfere with NR uptake occur in the C-terminal part of NadR. A helix-turn-helix DNA binding domain present in NadR of S. enterica serovar Typhimurium could not be found in the NadR homologue of H. influenzae. Therefore, it was proposed that in H. influenzae NadR has no regulatory function at the transcriptional level. The structures of the human NR kinase 1 (2QL6_P) with nucleotide and nucleoside substrates bound have been solved. It is structurally similar to Rossmann fold metabolite kinases. PnuC has been shown to resemble SWEET porters in overall fold, supporting the conclusion that these two families are members of the TOG superfamily.
Sources: en.wikipedia.org
transcriptome The entire set of RNA molecules (often referring to all types of RNA but sometimes exclusively to messenger RNA) that is or can be expressed by a particular genome, cell, population of cells, or species at a particular time or under particular conditions. The transcriptome is distinct from the exome and the translatome.
First, during exercise, carbohydrates with the highest possible rate of conversion to blood glucose (high glycemic index) are ingested continuously. The best possible outcome of this strategy replaces about 35% of glucose consumed at heart rates above about 80% of maximum. Second, through endurance training adaptations and specialized regimens (e.g. fasting, low-intensity endurance training), the body can condition type I muscle fibers to improve both fuel use efficiency and workload capacity to increase the percentage of fatty acids used as fuel, sparing carbohydrate use from all sources. Third, by consuming large quantities of carbohydrates after depleting glycogen stores as a result of exercise or diet, the body can increase storage capacity of intramuscular glycogen stores. This process is known as carbohydrate loading. In general, glycemic index of carbohydrate source does not matter since muscular insulin sensitivity is increased as a result of temporary glycogen depletion. When athletes ingest both carbohydrate and caffeine following exhaustive exercise, their glycogen stores tend to be replenished more rapidly; however, the minimum dose of caffeine at which there is a clinically significant effect on glycogen repletion has not been established.
=== Video games === Major Force appears as a boss in DC Universe Online, voiced by Alexander Brandon. This version works for Amanda Waller. Major Force appears as a character summon in Scribblenauts Unmasked: A DC Comics Adventure.
Due to his later work as the inaugural Chief of the Commonwealth Government's Council for Scientific and Industrial Research (CSIR) Division of Animal Nutrition, he became one of the foremost authorities in the field of animal nutrition.
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 cyclic heptapeptide and an analogue of alpha-melanocyte-stimulating hormone. The molecule is produced by chemical synthesis rather than extracted from a biological source.