If you have been reading about mass spectrometry and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Last reviewed on 2025-11-17. 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.
Pharmacologically, melanotan-2 behaves as a non-selective agonist across the melanocortin receptor family. Binding at MC1R on dermal melanocytes promotes eumelanin synthesis, which underlies the tanning response described in early human work. Activity at the centrally expressed MC4R receptor is associated with reported effects on appetite and erectile function. Because the peptide does not discriminate strongly among receptor subtypes, attributing any single observed effect to one receptor pathway is generally not possible without selective antagonists or receptor knockout models.
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.
Published research on the compound remains limited. Much of the human data comes from small, early-stage studies rather than large controlled trials, and several questions about effects and variability between individuals remain open. Investigators have examined receptor activity, pigment pathways, and related physiological responses in laboratory and animal models. Findings from those models do not automatically translate to human outcomes. Reviews frequently note the scarcity of rigorous clinical evidence and call for better-characterized study material.
| 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 |
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.
Regulatory treatment varies by country. In the United States the peptide is not approved as a medicine, and products offered for human use may be treated as unapproved new drugs; some states also restrict sale. Australia, the United Kingdom, and European Union member states apply comparable restrictions to unapproved peptide products. Border agencies have seized shipments labelled as research chemicals. Classification may change over time, and the legal position for personal importation is not clearly settled in most published guidance.
Lyophilised melanotan-2 is supplied as a solid, which is more stable than a solution. The material is hygroscopic, so weighing is done quickly, in low humidity, with the container kept sealed. Reconstitution usually uses water for injection or bacteriostatic water, added down the wall of the vial to limit foaming. A reconstituted solution is held at 2 to 8 °C and kept away from light. Repeated freezing and thawing of the same vial is avoided because ice crystal formation and concentration effects degrade the peptide.
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-2 appears on the World Anti-Doping Agency prohibited list within the peptide hormone class, and several national regulators treat it as an unapproved prescription substance. Some countries restrict importation or sale for personal use. Because the compound is widely traded as a research chemical, the practical legal picture differs between jurisdictions and shifts over time. Human safety data covering long periods are limited, and whether repeated pigmentation changes carry any lasting risk to melanocytes remains an open question.
Freeze-dried melanotan-2 is normally kept as a desiccated powder at minus twenty degrees Celsius or lower, shielded from light and moisture. Peptides of this size degrade through hydrolysis, oxidation and deamidation, and each pathway accelerates as temperature and water activity rise. Repeated freeze-thaw cycles promote aggregation and loss of material, so aliquoting a stock solution before freezing is standard laboratory practice. Once dissolved, the solution is markedly less stable than the powder. In laboratory work, solutions are generally refrigerated and used within days rather than kept for months.
In the war's aftermath, the Iraqi government suppressed a series of uprisings until 5 April 1991. Coalition countries responded by establishing two no-fly zones over Iraq's north and south. The United Nations Special Commission sought to end Iraq's weapons of mass destruction programs. In 2003, another US-led coalition invaded and occupied Iraq, beginning the Iraq War. The conflict's environmental impact included Iraqi forces causing over six hundred oil well fires and the largest oil spill in history until that point. US bombing and demolition of Iraqi chemical weapons facilities were concluded to be the primary cause of Gulf War syndrome, experienced by over 40% of US veterans.
=== Prokaryotes expression vector === Promoter - commonly used inducible promoters are promoters derived from lac operon and the T7 promoter. Other strong promoters used include Trp promoter and Tac-Promoter, which are a hybrid of both the Trp and Lac Operon promoters. Ribosome binding site (RBS) - follows the promoter, and promotes efficient translation of the protein of interest. Translation initiation site - Shine-Dalgarno sequence enclosed in the RBS, 8 base-pairs upstream of the AUG start codon.
In the summer before the election, polling showed at least half of Americans thought that Trump, who was 78 years old, was too old to serve a second term, with 80% unsure he would be able to finish out a second term. Numerous public figures, media sources, and mental health professionals speculated that Trump may have some form of dementia, which runs in his family. Experts for the science publication STAT who analyzed changes in Trump's speeches between 2015 and 2024 noted shorter sentences, more tangents, more repetition, and more confusion of words and phrases. Doctors suggested these changes could relate to Trump's moods or could indicate the beginning of Alzheimer's. One expert noted an increase in expressions of all-or-nothing thinking by Trump; a sharp rise in all-or-nothing thinking is also linked to cognitive decline. The New York Times reported that Trump's 2024 speeches had grown "darker, harsher, longer, angrier, less focused, more profane and increasingly fixated on the past", and that experts considered this increase in tangential speech and behavioral disinhibition as a possible consequence of advancing age and cognitive decline. Trump was also criticized for his lack of transparency around his medical records and health.
=== EC 1.14.19 With oxidation of a pair of donors resulting in the reduction of O2 to two molecules of water === EC 1.14.19.1: stearoyl-CoA 9-desaturase EC 1.14.19.2: stearoyl-[acyl-carrier-protein] 9-desaturase EC 1.14.19.3: linoleoyl-CoA desaturase EC 1.14.19.4: acyl-lipid (11-3)-desaturase EC 1.14.19.5: acyl-CoA 11-(Z)-desaturase EC 1.14.19.6: acyl-CoA (9+3)-desaturase EC 1.14.19.7: Now EC 1.11.1.23, (S)-2-hydroxypropylphosphonic acid epoxidase EC 1.14.19.8: pentalenolactone synthase EC 1.14.19.9: tryptophan 7-halogenase EC 1.14.19.10: icosanoyl-CoA 5-desaturase EC 1.14.19.11: acyl-[acyl-carrier-protein] 4-desaturase EC 1.14.19.12: acyl-lipid ω-(9-4) desaturase EC 1.14.19.13: acyl-CoA 15-desaturase EC 1.14.19.14: linoleoyl-lipid Δ9 conjugase EC 1.14.19.15: (11Z)-hexadec-11-enoyl-CoA conjugase EC 1.14.19.16: linoleoyl-lipid Δ12 conjugase (11E,13Z-forming) EC 1.14.19.17: sphingolipid 4-desaturase EC 1.14.19.18: sphingolipid 8-(E)-desaturase EC 1.14.19.19: sphingolipid 10-desaturase EC 1.14.19.20: Δ7-sterol 5(6)-desaturase EC 1.14.19.21: cholesterol 7-desaturase EC 1.14.19.22: acyl-lipid ω-6 desaturase (cytochrome b5) EC 1.14.19.23: acyl-lipid (n+3)-(Z)-desaturase (ferredoxin) EC 1.14.19.24: acyl-CoA 11-(E)-desaturase EC 1.14.19.25: acyl-lipid ω-3 desaturase (cytochrome b5) EC 1.14.19.26: acyl-[acyl-carrier-protein] 6-desaturase EC 1.14.19.27: sn-2 palmitoyl-lipid 9-desaturase EC 1.14.19.28: sn-1 stearoyl-lipid 9-desaturase EC 1.14.19.29: sphingolipid 8-(E/Z)-desaturase EC 1.14.19.30: acyl-lipid (8-3)-desaturase EC 1.14.19.31: acyl-lipid (7-3)-desaturase EC 1.14.19.32: palmitoyl-CoA 14-(E/Z)-desaturase EC 1.14.19.33: Δ12 acyl-lipid conjugase (11E,13E-forming) EC 1.14.19.34: acyl-lipid (9+3)-(E)-desaturase EC 1.14.19.35: sn-2 acyl-lipid ω-3 desaturase (ferredoxin) EC 1.14.19.36: sn-1 acyl-lipid ω-3 desaturase (ferredoxin) EC 1.14.19.37: acyl-CoA 5-desaturase EC 1.14.19.38: acyl-lipid Δ6-acetylenase EC 1.14.19.39: acyl-lipid Δ12-acetylenase EC 1.14.19.40: hex-5-enoyl-[acyl-carrier protein] acetylenase EC 1.14.19.41: sterol 22-desaturase EC 1.14.19.42: palmitoyl-[glycerolipid] 7-desaturase EC 1.14.19.43: palmitoyl-[glycerolipid] 3-(E)-desaturase EC 1.14.19.44: acyl-CoA (8-3)-desaturase EC 1.14.19.45: sn-1 oleoyl-lipid 12-desaturase EC 1.14.19.46: sn-1 linoleoyl-lipid 6-desaturase EC 1.14.19.47: acyl-lipid (9-3)-desaturase EC 1.14.19.48: tert-amyl alcohol desaturase EC 1.14.19.49: tetracycline 7-halogenase EC 1.14.19.50: noroxomaritidine synthase EC 1.14.19.51: (S)-corytuberine synthase EC 1.14.19.52: camalexin synthase EC 1.14.19.53: all-trans-retinol 3,4-desaturase EC 1.14.19.54: 1,2-dehydroreticuline synthase EC 1.14.19.55: 4-hydroxybenzoate brominase (decarboxylating) EC 1.14.19.56: 1H-pyrrole-2-carbonyl-[peptidyl-carrier protein] chlorinase EC 1.14.19.57: 1H-pyrrole-2-carbonyl-[peptidyl-carrier protein] brominase EC 1.14.19.58: tryptophan 5-halogenase EC 1.14.19.59: tryptophan 6-halogenase EC 1.14.19.60: 7-chloro-L-tryptophan 6-halogenase EC 1.14.19.61: dihydrorhizobitoxine desaturase EC 1.14.19.62: secologanin synthase EC 1.14.19.63: pseudobaptigenin synthase EC 1.14.19.64: (S)-stylopine synthase EC 1.14.19.65: (S)-cheilanthifoline synthase EC 1.14.19.66: berbamunine synthase EC 1.14.19.67: salutaridine synthase EC 1.14.19.68: (S)-canadine synthase EC 1.14.19.69: biflaviolin synthase EC 1.14.19.70: mycocyclosin synthase EC 1.14.19.71: fumitremorgin C synthase EC 1.14.19.72: (–)-pluviatolide synthase EC 1.14.19.73: (S)-nandinine synthase EC 1.14.19.74: (+)-piperitol/(+)-sesamin synthase EC 1.14.19.75: very-long-chain acyl-lipid ω-9 desaturase EC 1.14.19.76: flavone synthase II EC 1.14.19.77: plasmanylethanolamine desaturase EC 1.14.19.78: decanoyl-[acyl-carrier protein] acetylenase
Integrative Biology 131: General Human Anatomy (Fall 2005) by Professor Marian Diamond. Complete videos of the 40 lectures at Anatomy & Physiology (UC-Berkeley) "Anatomy of the Human Body". 20th edition. 1918. Henry Gray. In public domain. Human anatomy in photo Terminologia Anatomica (names of anatomical features) on FIPAT site
Sources: en.wikipedia.org
Myelin has two important advantages: fast conduction speed and energy efficiency. For axons larger than a minimum diameter (roughly 1 micrometre), myelination increases the conduction velocity of an action potential, typically tenfold. Conversely, for a given conduction velocity, myelinated fibers are smaller than their unmyelinated counterparts. For example, action potentials move at roughly the same speed (25 m/s) in a myelinated frog axon and an unmyelinated squid giant axon, but the frog axon has a roughly 30-fold smaller diameter and 1000-fold smaller cross-sectional area. Also, since the ionic currents are confined to the nodes of Ranvier, far fewer ions "leak" across the membrane, saving metabolic energy. This saving is a significant selective advantage, since the human nervous system uses approximately 20% of the body's metabolic energy. The length of axons' myelinated segments is important to the success of saltatory conduction. They should be as long as possible to maximize the speed of conduction, but not so long that the arriving signal is too weak to provoke an action potential at the next node of Ranvier. In nature, myelinated segments are generally long enough for the passively propagated signal to travel for at least two nodes while retaining enough amplitude to fire an action potential at the second or third node. Thus, the safety factor of saltatory conduction is high, allowing transmission to bypass nodes in case of injury.
Relatives of highly placed Chinese officials, including seven current and former members of the Politburo, have been named in the Panama Papers, including Deng Jiagui, Xi's brother-in-law. Deng had two shell companies in the British Virgin Islands while Xi was a member of the Politburo Standing Committee, which became dormant by the time Xi became CCP general secretary in 2012. According to The New York Times in 2012, after coming to power, Xi told his family to get out of their investments and that Qi Qiaoqiao and Deng Jiagui had divested their investments in at least 10 companies. In 2015, Wang Jianlin, the leader of the company Dalian Wanda, defended Qi and Deng, saying that they sold their shares in the company two months before the IPO in October 2014. The New York Times commented that this information is conflicted with official documents, which state that Qi and Deng transferred the ownership of the holding company to one of their employees in October 2013.
== De-adenylylators == De-AMPylation is the reverse reaction in which the AMP molecule is detached from the amino acid side of a chain protein. There are three known mechanisms for this reaction. The bacterial GS-ATase (GlnE) encodes a bipartite protein with separate N-terminal AMPylation and C-terminal de-AMPylation domains whose activity is regulated by PII and associated posttranslational modifications. De-AMPylation of its substrate AMPylated glutamine synthetase proceeds by a phosphorolytic reaction between the adenyl-tyrosine of GS and orthophosphate, leading to the formation of ADP and unmodified glutamine synthetase. SidD, a protein introduced in the host cell by the pathogenic bacteria Legionella pneumophila, de-AMPylates Rab1 a host protein AMPylated by a different Legionella pneumophila enzyme, the AMPylase SidM. Whilst the benefit to the pathogen of introducing these two antagonistic effectors in the host remains unclear, the biochemical reaction carried out by SidD involves the use of a phosphatase-like domain to catalyse the hydrolytic removal of the AMP from tyrosine 77 of the host's Rab1. In animal cells the removal of AMP from threonine 518 of BiP/Grp78 is catalysed by the same enzyme, FICD, that AMPylates BiP. Unlike the bacterial GS-ATase, FICD carries out both reactions with same catalytic domain.
== Further reading == Quammen, David, "The Sobbing Pangolin: How a threatened animal may be linked to the [Covid-19] pandemic's beginnings", The New Yorker, 31 August 2020, pp. 26–31. "More field research is needed [...]. More sampling of wild animals. More scrutiny of genomes. More cognizance of the fact that animal infections can become human infections because humans are animals. We live in a world of viruses, and we have scarcely begun to understand this one [ COVID-19 ]. (p. 31.)
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.
Only a small number of early-stage human studies have been reported, and most were limited in size and duration. No large late-stage program has established a general efficacy or safety profile. The evidence base is therefore thin compared with approved medicines.