Everything below concerns melanogenesis. We keep the language plain, cite what the science says, and separate well-supported claims from open questions.
Last reviewed on 2025-08-07. Where a claim depends on a specific study, the study is described rather than over-claimed.
Research interest has centred on photoprotection and pigmentation, with a smaller body of work on appetite and sexual function. Published human data remain limited to small, frequently uncontrolled studies, and the compound has never received marketing approval from a national medicines regulator. Most laboratory work treats it as a pharmacological tool for probing melanocortin signalling in cell culture or animal models. Whether pigmentation changes observed in people translate into measurable protection against ultraviolet-induced DNA damage remains an open question.
Melanotan-2 is a synthetic cyclic heptapeptide designed as an analogue of alpha-melanocyte-stimulating hormone, the naturally occurring peptide involved in pigmentation signalling. Its sequence is conventionally written as Ac-Nle-cyclo[Asp-His-D-Phe-Arg-Trp-Lys]-NH2, with a lactam bridge joining the aspartate side chain to the lysine side chain. The empirical formula is C50H69N15O9 and the monoisotopic mass lies near 1023.5 daltons. N-terminal acetylation and the D-configured phenylalanine both increase resistance to enzymatic breakdown compared with the parent hormone.
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.
| Property | Value | Notes |
|---|---|---|
| Common synonyms | Melanotan II; MT-II; N-acetyl-norleucyl-cyclo[Asp-His-D-Phe-Arg-Trp-Lys] amide | Naming follows peptide convention; the numeral distinguishes it from melanotan-1 |
| Molecular formula | C50H69N15O9 | Includes the lactam bridge; no counter-ion assumed |
| Monoisotopic mass | 1023.53 Da | Free base; salts and counter-ions shift the observed value |
| Appearance | White to off-white lyophilised powder | Batch-to-batch colour variation is not itself proof of impurity |
| Typical analytical method | RP-HPLC purity determination with ESI-MS identity confirmation | Retention time alone does not establish sequence identity |
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.
Published human data come mostly from small, short studies rather than large controlled trials. Reported outcomes include increased skin pigmentation and, in some reports, effects on appetite and libido, but sample sizes are small and follow-up is limited. Whether long-term use produces durable pigment changes or adverse effects is not established. Because products sold outside pharmacies are not standardized, the actual content of any given vial is often unknown. Independent testing of such material is uncommon.
Melanotan II is a synthetic cyclic heptapeptide analog derived from the core sequence of alpha-melanocyte-stimulating hormone. Researchers at the University of Arizona synthesized it during the 1980s while studying pigmentation and appetite signaling. The compound is not an approved medicine in any major jurisdiction and appears mainly in laboratory and research-chemical settings. Its structure incorporates a lactam bridge between side chains, which constrains the ring and slows enzymatic breakdown relative to the natural hormone.
Nicotinamide, as a part of the cofactor nicotinamide adenine dinucleotide (NADH / NAD+), is crucial to life. In cells, nicotinamide is incorporated into NAD+ and nicotinamide adenine dinucleotide phosphate (NADP+). NAD+ and NADP+ are cofactors in a wide variety of enzymatic oxidation-reduction reactions, most notably glycolysis, the citric acid cycle, and the electron transport chain. If humans ingest nicotinamide, it will likely undergo a series of reactions that transform it into NAD, which can then undergo a transformation to form NADP+. This method of creation of NAD+ is called a salvage pathway. However, the human body can produce NAD+ from the amino acid tryptophan and niacin without ingestion of nicotinamide. NAD+ acts as an electron carrier that mediates the interconversion of energy between nutrients and the cell's energy currency, adenosine triphosphate (ATP). In oxidation-reduction reactions, the active part of the cofactor is the nicotinamide. In NAD+, the nitrogen in the aromatic nicotinamide ring is covalently bonded to adenine dinucleotide. The shared electrons of the other carbon atoms in the aromatic ring stabilize the formal charge on the nitrogen. When a hydride atom is added onto NAD+ to form NADH, the molecule loses its aromaticity and therefore a good amount of stability. This higher-energy product later releases its energy by donating a hydride, and in the case of the electron transport chain, it assists in forming adenosine triphosphate. When one mole of NADH is oxidized, it releases 158.2 kJ of energy.
Dissolved inorganic carbon (DIC) is made up of bicarbonate (HCO−3), carbonate (CO2−3) and carbon dioxide (including both dissolved CO2 and carbonic acid H2CO3). DIC can be converted to particulate inorganic carbon (PIC) through precipitation of CaCO3 (biologically or abiotically). DIC can also be converted to particulate organic carbon (POC) through photosynthesis and chemoautotrophy (primary production). DIC increases with depth as organic carbon particles sink and are respired. Free oxygen decreases as DIC increases because oxygen is consumed during aerobic respiration. Particulate inorganic carbon (PIC) is the other form of inorganic carbon found in the ocean. Most PIC is the CaCO3 that makes up shells of various marine organisms, but can also form in whiting events. Marine fish also excrete calcium carbonate during osmoregulation. Some of the inorganic carbon species in the ocean, such as bicarbonate and carbonate, are major contributors to alkalinity, a natural ocean buffer that prevents drastic changes in acidity (or pH). The marine carbon cycle also affects the reaction and dissolution rates of some chemical compounds, regulates the amount of carbon dioxide in the atmosphere and Earth's temperature.
Apoptosis & Caspase 3 – PMAP The Proteolysis Map-animation Cytochrome+c at the U.S. National Library of Medicine Medical Subject Headings (MeSH) Overview of all the structural information available in the PDB for UniProt: P99999 (Cytochrome c) at the PDBe-KB.
=== EC 1.6.5 With a quinone or similar compound as acceptor === EC 1.6.5.1: deleted EC 1.6.5.2: NAD(P)H dehydrogenase (quinone) EC 1.6.5.3: now EC 7.1.1.2 NADH:ubiquinone reductase (H+-translocating) EC 1.6.5.4: monodehydroascorbate reductase (NADH) EC 1.6.5.5: NADPH:quinone reductase EC 1.6.5.6: p-benzoquinone reductase (NADPH) EC 1.6.5.7: 2-hydroxy-1,4-benzoquinone reductase EC 1.6.5.8: Now EC 7.2.1.1, NADH:ubiquinone reductase (Na+-transporting) EC 1.6.5.9: NADH:ubiquinone reductase (non-electrogenic) EC 1.6.5.10: NADPH dehydrogenase (quinone) EC 1.6.5.11: Identical to EC 1.6.5.9, NADH:quinone reductase (non-electrogenic) EC 1.6.5.12: demethylphylloquinone reductase
=== Apical delta === Apical delta refers to the branching pattern of small accessory canals and minor foramina seen at the tip or apex of some tooth roots. The pattern is said to be reminiscent of a river delta when sectioned and viewed using a microscope. Because the anatomy of this area is very small and complex with several portals of entry to the root canal i.e. more than one apical foramen.
Sources: en.wikipedia.org
Depolarization opens both the sodium and potassium channels in the membrane, allowing the ions to flow into and out of the axon, respectively. If the depolarization is small (say, increasing Vm from −70 mV to −60 mV), the outward potassium current overwhelms the inward sodium current and the membrane repolarizes back to its normal resting potential around −70 mV. However, if the depolarization is large enough, the inward sodium current increases more than the outward potassium current and a runaway condition (positive feedback) results: the more inward current there is, the more Vm increases, which in turn further increases the inward current. A sufficiently strong depolarization (increase in Vm) causes the voltage-sensitive sodium channels to open; the increasing permeability to sodium drives Vm closer to the sodium equilibrium voltage ENa≈ +55 mV. The increasing voltage in turn causes even more sodium channels to open, which pushes Vm still further towards ENa. This positive feedback continues until the sodium channels are fully open and Vm is close to ENa. The sharp rise in Vm and sodium permeability correspond to the rising phase of the action potential. The critical threshold voltage for this runaway condition is usually around −45 mV, but it depends on the recent activity of the axon. A cell that has just fired an action potential cannot fire another one immediately, since the Na+ channels have not recovered from the inactivated state. The period during which no new action potential can be fired is called the absolute refractory period.
==== Ecuador ==== Caldo de tronquito is an Ecuadoran cuisine bull penis soup. The soup features grains like hominy and corn, beans like chickpeas and fava beans, and offal like tripe and testicles; the ingredients are comparable to a fanesca with meat. Regional variations include Manabí, where peanuts and milk are added, and La Costa, which favors corn, cassava and carrots. The soup is eaten as a hangover cure, to treat anemia, assist recovery from sickness or post-partum, and as an aphrodisiac. Caldo de tronquito was created in 16th century Quito after the Spanish colonization of Ecuador introduced cattle to the continent.
Continuing improvements led to the furnace and bellows and provided, for the first time, the ability to smelt and forge gold, copper, silver, and lead – native metals found in relatively pure form in nature. The advantages of copper tools over stone, bone, and wooden tools were quickly apparent to early humans, and native copper was probably used from near the beginning of Neolithic times (about 10 kya). Native copper does not naturally occur in large amounts, but copper ores are quite common, and some of them produce metal easily when burned in wood or charcoal fires. Eventually, the working of metals led to the discovery of alloys such as bronze and brass (about 4,000 BCE). The first use of iron alloys such as steel dates to around 1,800 BCE.
== Early life and education == James William Middleton was born on 15 April 1987 at the Royal Berkshire Hospital in Reading, the youngest child and only son of Michael Middleton (born 1949), a former British Airways flight dispatcher, and Carole Middleton (born 1955), a former flight attendant. His father came from a line of solicitors who lived in Leeds, West Yorkshire. His great-grandmother Olive Middleton was a member of the Lupton family, who were landed gentry. His mother's family were from County Durham. Shortly before his birth, Middleton's parents founded Party Pieces, a mail-order party supply company. His elder sisters are Catherine (born 1982) and Philippa (born 1983). The family lived in Bradfield Southend, Berkshire, before moving to the nearby village of Bucklebury in 1995. Middleton was educated at St Andrew's School, Pangbourne, and Marlborough College. In 2006, he attended the University of Edinburgh, studying environmental resources management before dropping out a year later.
Sources: en.wikipedia.org
It is a synthetic cyclic heptapeptide analogue of alpha-melanocyte-stimulating hormone, containing seven amino acids with a lactam ring and a D-configured phenylalanine residue. It is supplied as a lyophilised powder for laboratory research.
The natural hormone is a linear tridecapeptide that is rapidly degraded in circulation. Melanotan-2 is shortened, cyclised, N-terminally acetylated, and carries a D-amino acid substitution, all of which slow enzymatic breakdown.
No national medicines regulator has approved melanotan-2 for therapeutic or cosmetic use. In several jurisdictions it is treated as an unapproved prescription medicine, and its legal classification differs from country to country.
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.