mass spectrometry raises a handful of sensible questions. This page answers them in order, starting with the fundamentals and moving to applications.
This page was last updated on 2025-10-01 and is reviewed periodically as new material appears.
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.
Regulatory status varies by jurisdiction, and the substance is frequently described as unapproved for therapeutic use. Some authorities classify it alongside prescription-only medicines or controlled categories, while others address it through general consumer protection rules. Analytical surveys have reported mismatches between label claims and measured content in products sold online, although the scope of such testing is limited. Whether these discrepancies are widespread remains an open question. Discussion in the literature therefore tends to combine chemistry, supply-chain observation and policy analysis.
The material is commonly handled as a lyophilized powder in sealed vials. The solid dissolves readily in water and in polar organic solvents, producing a clear solution after reconstitution. Light, heat and repeated freeze-thaw cycles are the concerns most often raised in handling guidance, because peptide bonds and the constrained ring can degrade. Working solutions are generally prepared fresh, and material left in solution is treated as less stable than the dry form. These properties shape how laboratories store and aliquot reference 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 |
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.
Melanotan II is a synthetic cyclic heptapeptide that acts as an agonist at melanocortin receptors. It was designed as a structural analogue of alpha-melanocyte-stimulating hormone, the endogenous peptide involved in pigment production. The analogue carries a lactam bridge that constrains the ring and slows enzymatic breakdown relative to the native hormone. In research literature it appears under several abbreviations, and naming conventions are not fully standardized. Published descriptions usually place it within the broader melanocortin agonist family.
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.
"You have no idea what the Tour de France is," Henri said. "It's a Calvary. Worse than that, because the road to the Cross has only 14 stations and ours has 15. We suffer from the start to the end. You want to know how we keep going? Here..." He pulled a phial from his bag. "That's cocaine, for our eyes. This is chloroform, for our gums." "This," Ville said, emptying his shoulder bag "is liniment to put warmth back into our knees." "And pills. Do you want to see pills? Have a look, here are the pills." Each pulled out three boxes. "The truth is," Francis said, "that we keep going on dynamite." Henri spoke of being as white as shrouds once the dirt of the day had been washed off, then of their bodies being drained by diarrhea, before continuing:
== Treatment == Only a small proportion of those with co-occurring disorders actually receive treatment for both disorders. Therefore, it was argued that a new approach is needed to enable clinicians, researchers and managers to offer adequate assessment and evidence-based treatments to patients with dual pathology, who cannot be adequately and efficiently managed by cross-referral between psychiatric and addiction services as currently configured and resourced. In 2011, it was estimated that only 12.4% of American adults with co-occurring disorders were receiving both mental health and addictions treatment. Clients with co-occurring disorders face challenges accessing treatment, as they may be excluded from mental health services if they admit to a substance use problem and vice versa. There are multiple approaches to treat concurrent disorders. Partial treatment involves treating only the disorder that is considered primary. Sequential treatment involves treating the primary disorder first, and then treating the secondary disorder after the primary disorder has been stabilized. Parallel treatment involves the client receiving mental health services from one provider, and addictions services from another. Integrated treatment involves a seamless blending of interventions into a single coherent treatment package developed with a consistent philosophy and approach among care providers. With this approach, both disorders are considered primary.
=== Classically activated macrophages === After receiving signaling from both IFNγ and TNF, macrophages acquire a phenotype with higher activity against both pathogens and tumor cells. They also secrete inflammatory cytokines. IFNγ signaling can initially originate from Natural Killer (NK) cells, but adaptive immune cells are required to sustain a population of classically activated macrophages. Toll-like receptor agonists may also cause macrophage activation.
=== Humans and other mammals === Humans and other mammals have chitinase and chitinase-like proteins that can degrade chitin; they also possess several immune receptors that can recognize chitin and its degradation products, initiating an immune response. Chitin is sensed mostly in the lungs or gastrointestinal tract where it can activate the innate immune system through eosinophils or macrophages, as well as an adaptive immune response through T helper cells. Keratinocytes in skin can also react to chitin or chitin fragments.
DCI John Caldwell, an off duty Police Service of Northern Ireland officer, is injured in Omagh after being shot by suspected New IRA gunman. 23 February Labour leader Sir Keir Starmer outlines the five key issues that his party will focus on during the run up to the 2024 general election: higher economic growth, clean energy, improving the NHS, reforming the justice system, and raising education standards. Environment Secretary Thérèse Coffey, commenting on the vegetable shortage, tells MPs "we anticipate the situation will last about another two to four weeks". Three men are arrested in relation to the previous evening's shooting of DCI John Caldwell. 24 February The British Medical Association announces that junior doctors in England will begin a three-day strike on 13 March. An earthquake measuring 3.7 magnitude strikes Brynmawr, Blaenau Gwent at 11.59pm. COVID-19 in the UK: Office for National Statistics data for the week up to 14 February indicates COVID-19 cases continued to rise in England, Scotland and Wales, but remained uncertain in Northern Ireland. In England, the estimated number of people testing positive for COVID-19 was 1,223,000 (or 2.18% of the population and around 1 in 45 people). 27 February New Transgender Policy Guidance for England and Wales came into force on 27 February 2023 under which transgender women offenders would no longer be housed in women's prisons if they had male genitalia or had committed sex crimes.
Sources: en.wikipedia.org
==== Crown ether-type CSP ==== Crown ethers, like cyclodextrin-type CSPs contain a chiral cavity. Crown ethers are immobilized on the silica surface to form chiral stationary phase. Crown ethers contain oxygen atoms within the cavity. The cyclic structure that contains apolar ethylene groups between oxygen forms hydrophobic inner cavity. Cram et al., introduced CSP based on chiral crown ethers and accomplished separation of amino acid. The crucial chiral recognition principle underlying crown ether-based enantiomer separation is based on the formation of numerous hydrogen bonds between the protonated primary amino group of the analyte and the ether oxygens of the crown structure. This structural requirement confines the application of crown ether-type CSPs to chiral compounds having primary amino groups adjoining the chiral centers, such as amino acids, amino acid derivatives. Progress in the field of crown ether-type CSPs have been reviewed.
The operation of nuclear power plants and other nuclear facilities produces radioactive materials that can have lethal health effects for thousands of years. It is important to note that there is no institution capable of maintaining the necessary knowledge of the dangers over such periods, and of ensuring that warnings about the dangers of nuclear waste in nuclear repositories will be understood by posterity in the distant future. A few years ago, even the capsules of the radionuclide cobalt-60, which were appropriately labeled, went unnoticed. Improper disposal led to the opening of these capsules, resulting in fatal consequences. The dimensions of time exceed previous human standards. For instance, cuneiform writing, which is only about 5000 years old (about 150 human generations), can only be understood after a long period of research and by experts. In 1981, research into the development of atomic semiotics began in the USA, in the German-speaking world, Roland Posner (1942-2020) of the Center for Semiotics at Technische Universität Berlin worked on this in 1982/83. In the USA, the time horizon for such warning signs was set at 10,000 years; later, as in Germany, it was set at a period of one million years, which would correspond to about 30,000 (human) generations. To date, no satisfactory solution to this problem has been found.
=== Inhibition of ACTH production === Corticotropes contain glucocorticoid receptors (GRs) and corticosteroid-binding globulin (CBG, or transcortin). GR is a nuclear receptor that inhibits transcription of ACTH via a negative glucocorticoid recognition element (GRE) that binds cortisol on POMC DNA, but generally transcortin binds glucocorticoids (including cortisol, cortisone, deoxycortisone, and aldosterone) with high affinity and prevents this inhibition. Tonic inhibition of corticotropes requires high concentrations of glucocorticoids, exceeding CBG capacity. This causes ACTH secretion to be vulnerable to inhibition in patients taking glucocorticoids for medical purposes such as treatment of autoimmune disease or as an anti-transplant-rejection medication.
=== Major depressive disorder === The mechanistic rationale for KOR antagonism in major depressive disorder (MDD) derives from the observation that chronic stress and depression are associated with higher activity of the KOR system. KOR activation suppresses dopamine release and prevents dopamine rebound after stress exposure, thereby leading to anhedonia and depressive phenotypes. KOR antagonists reverse this pathway by disinhibiting dopaminergic tone and restoring reward sensitivity. KOR-mediated upregulation of pro-inflammatory signaling in microglia likely drives the depression pathophysiology, and antagonism may provide benefits. The claustrum-prelimbic cortex circuit operates via dynorphin and KOR signaling to modulate cognitive and affective functions. Buprenorphine/samidorphan (ALKS-5461) displayed antidepressant efficacy in randomized controlled trials as an adjunctive therapy and has shown durable effects with a favorable safety profile including low abuse potential and minimal withdrawal symptoms. A phase 2 study demonstrated significant reduction of depressive symptoms and improvement in anhedonia when aticaprant was added to existing antidepressant therapy. A phase 3 clinical trials (KOASTAL-1 and additional studies) of navacaprant failed to achieve statistically significant superiority over placebo across the broader MDD population, with its development discontinued for this purpose in early 2025.
Sources: en.wikipedia.org
=== Contact process === In 1831, British vinegar merchant Peregrine Phillips patented the contact process, which was a far more economical process for producing sulfur trioxide and concentrated sulfuric acid. Today, nearly all of the world's sulfuric acid is produced using this method. In the early to mid 19th century "vitriol" plants existed, among other places, in Prestonpans in Scotland, Shropshire and the Lagan Valley in County Antrim, Northern Ireland, where it was used as a bleach for linen. Early bleaching of linen was done using lactic acid from sour milk, but this was a slow process; the use of vitriol sped up the bleaching process.
Primary algae are those with "primary chloroplasts", i.e. chloroplasts with two membranes, evolved through a single symbiogenetic event with an endosymbiont β-cyanobacterium as early as 1.6 Gya during the Mesoproterozoic. These algae are mainly grouped in the clade Archaeplastida (meaning "ancient plastid"), which includes the major groups Viridiplantae (green algae sensu lato and all land plants) and Rhodophyta (red algae) as well as the minor group Glaucophyta (grey algae). The chloroplasts of red algae have chlorophyll a and c (often) and phycobilins, with extra-plastid starch storage; green algae chloroplasts have chlorophyll a and b without phycobilins, with intra-plastid starch storage; while grey algae chloroplasts have chlorophylls similar to red algae, but with a peptidoglycan outer layer. Land plants (embryophytes) are pigmented similarly to green algae and likely evolved from the freshwater green algae clade Streptophyta, which is sister taxon to Chlorophyta (green algae sensu stricto) and the basal clade Prasinodermophyta. There is also a minor group of amoeboid protists with primary plastids evolved via different origin and at a much later date than archaeplastid chloroplasts. The four species of the euglyphid amoebae genus Paulinella, have cyanobionts (known as cyanelles) that perform photosynthesis, likely originated from the endosymbiosis of a α-cyanobacterium (probably an ancestral member of Chroococcales), about 90–140 Mya during the Cretaceous.
== β-Lipotropin == β-Lipotropin is a 90-amino acid polypeptide that is the carboxy-terminal fragment of POMC. It was initially reported to stimulate melanocytes to produce melanin. It was also reported to perform lipid-mobilizing functions such as lipolysis and steroidogenesis. However, no subsequent studies have been published that support these early findings and no receptor has been identified for β-lipotropin. β-Lipotropin can be cleaved into smaller peptides. In humans, γ-lipotropin, β-MSH, and β-endorphin, are all possible fragments of β-lipotropin. β-endorphin is the predominant opioid of the anterior human and rat pituitary gland. Birdsall and Hulme demonstrated that the C-fragment of lipotropin (β-endorphin) has a high affinity for opiate receptors in the brain, and the binding was reversed by naloxone, a classical antagonist of the opiates (Bradbury et al. 1976a). Alongside this, Feldberg found that β-endorphin administered in cat ventricles was 100 times more potent than morphine as an analgesic agent (Feldberg & Smyth 1976, 1977) and the analgesia persisted for several hours. Feldberg concluded that β-endorphin was the most potent analgesic agent known. β-Lipotropin is found in essentially equimolar concentrations to that of corticotropin. Evidence shows that β-Lipotropin is metabolized into endorphins that can greatly affect mood and behavior and is thus regarded as a prohormone.
== Clinical significance == The importance of the MC4R in the regulation of human body weight first became apparent in 1998 with the reports from two groups of single families in whom heterozygous frameshift mutations in MC4R cosegregated with dominantly inherited severe early-onset obesity. In 2009, two very large genome-wide association studies of body mass index (BMI) confirmed the association of common variants about 150 kilobases downstream of the MC4R gene with insulin resistance, obesity, and other anthropometric traits. MC4R may also have clinical utility as a biomarker for predicting individual susceptibility to drug-induced adverse effects causing weight gain and related metabolic abnormalities. Another GWAS performed in 2012 identified twenty SNPs located ~190 Kb downstream of MC4R in association with severe antipsychotic-induced weight gain. This locus overlapped with the region previously identified in the 2009 studies. The rs489693 polymorphism, in particular, sustained a statistically robust signal across three replication cohorts and demonstrated consistent recessive effects. This finding was replicated again by another research group in the following year. In accordance with the above, MC4 receptor agonists have garnered interest as potential treatments for obesity and insulin resistance, while MC4 receptor antagonists have attracted interest as potential treatments for cachexia. The structures of the receptor in complex with the agonist setmelanotide and the antagonist SHU9119 have been determined.
Multiple factors can trigger HHS, including infection, myocardial infarction, and trauma, as well as infections in the respiratory, digestive, and urinary systems. Rising obesity rates and the greater consumption of high-carbohydrate beverages have both played a role in the increased incidence of HHS. Moreover, certain medications prescribed for different conditions have the potential to cause HHS. As with DKA, urgent medical treatment is necessary, commonly beginning with fluid volume replacement. On the whole, HHS is a medical emergency marked with hyperglycemia, hyperosmolarity, dehydration, and mild or no ketosis.
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.
The dry powder is more stable during transport and storage than a solution. It also allows a known amount of material to be reconstituted at a chosen concentration.