If you have been reading about reversed-phase HPLC 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 2026-02-20. Where a claim depends on a specific study, the study is described rather than over-claimed.
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.
The compound emerged from research programs in the 1980s that examined analogues of alpha-melanocyte-stimulating hormone for pigmentation and photoprotection. Investigators modified the native sequence to extend activity duration and potency. A related analogue, afamelanotide, was developed within the same broad line of inquiry and eventually gained approval in certain jurisdictions for a rare light-sensitivity condition. Melanotan-2 itself did not progress through the same regulatory route and has no approved therapeutic indication.
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.
Lyophilised peptide powder is comparatively stable when kept dry, cold and protected from light. Once dissolved, the molecule is exposed to hydrolysis, oxidation and microbial growth, and degradation accelerates at higher temperatures and in alkaline solution. Repeated freeze-thaw cycles concentrate solutes and promote aggregation. Handling guidance for research peptides commonly clusters around freezer temperatures for powder and short refrigerated use for reconstituted solutions, with pH control and sterile technique applied throughout.
Verification of a purchased sample requires documentation linking a batch to a certificate of analysis, and that document should be read for the methods used rather than the headline purity figure. A single chromatographic percentage does not establish identity. Independent laboratories can perform identity and content assays, but no such test establishes that a product is suitable for human use. Claims about efficacy rest largely on small, early studies rather than on replicated controlled trials, and that gap remains open.
Identity testing for a cyclic peptide of this size usually relies on reversed-phase high-performance liquid chromatography coupled to mass spectrometry. The mass spectrum confirms molecular weight, while the chromatographic trace indicates the proportion of related impurities. Tandem mass spectrometry can provide sequence-level information when fragmentation data are compared against a reference standard. Nuclear magnetic resonance is sometimes used to confirm the lactam bridge, although it requires more material and greater operator expertise than routine chromatographic methods.
| Property | Value | Notes |
|---|---|---|
| Molecular formula | C50H69N15O9 | Free base; salt forms differ |
| Molecular weight | Approximately 1024 g/mol | Calculated for the free base |
| Appearance | White to off-white powder | Typically supplied as a lyophilised solid |
| Solubility | Soluble in water and polar solvents | Poorly soluble in non-polar solvents |
| Typical storage | -20 degrees Celsius, dry, protected from light | Refers to the solid form |
The compound was developed in the late 1980s and early 1990s by academic researchers investigating melanocortin signaling and pigmentation. Early work explored whether synthetic analogs could reproduce effects of the natural hormone under controlled conditions. The molecule never advanced through the full regulatory pathway required for approval as a medicine. From the mid-2000s onward it appeared in unregulated consumer markets, often distributed through informal channels. That gap between research origins and commercial availability shapes how the compound is discussed today.
Melanotan-2 is a synthetic peptide designed as an analog of alpha-melanocyte-stimulating hormone, a signaling molecule produced in the pituitary and skin. Its structure is a linear chain of seven amino acids that folds into a ring through an internal lactam bridge joining two side chains. The compound is sometimes written as MT-II or MEL-2 in informal and commercial contexts. It belongs to the melanocortin peptide family, a group of short signaling molecules that share a conserved core sequence recognized by melanocortin receptors.
Two structural changes distinguish the synthetic peptide from the natural hormone. A norleucine residue replaces methionine at one position, and a D-configured phenylalanine replaces the natural L-form at another. Both substitutions slow enzymatic breakdown, which extends the molecule's persistence relative to the parent hormone. The lactam bridge further constrains the backbone into a stable conformation. These features are standard design strategies in peptide chemistry and are not unique to this compound; they appear across many research peptides built for improved stability.
Solid peptide kept dry at minus twenty degrees Celsius, shielded from light and moisture, is generally considered stable for extended periods. Solutions are divided into single-use aliquots and held at minus twenty or minus eighty degrees Celsius, because repeated freeze-thaw cycles promote aggregation and loss of material to container surfaces. Hydrolysis of the backbone and oxidation of tryptophan are the principal degradation routes in aqueous solution, and both accelerate at ambient temperature. Hygroscopic uptake after a vial is opened can also shift the actual mass weighed, which affects any concentration calculated from it.
Routine characterisation relies on reversed-phase high-performance liquid chromatography with ultraviolet detection near 214 nanometres, using a C18 column and a water-acetonitrile gradient containing trifluoroacetic acid. Electrospray ionisation mass spectrometry confirms the expected molecular mass and can reveal truncated or oxidised by-products that co-elute poorly. Sequence and stereochemistry require additional work, such as peptide mapping or amino acid analysis, because a chromatographic purity figure alone does not distinguish a diastereomer from the target peptide. Independent testing of research-grade material frequently shows measured content below the stated label, so a certificate of analysis is best read together with the method that produced it.
Worldwide or global organizations: Generally open to nations worldwide as long as certain criteria are met. This category includes the United Nations and its specialized agencies, World Health Organization, International Telecommunication Union, World Bank, and International Monetary Fund. It also includes globally operating intergovernmental organizations that are not an agency of the UN, including for example: the Hague Conference on Private International Law, an operating intergovernmental organization based in The Hague that pursues the progressive unification of private international law; the International Criminal Court that adjudicates crimes defined under the Rome Statute; and the CGIAR (formerly the Consultative Group for International Agricultural Research), a global partnership that unites intergovernmental organizations engaged in research for a food-secured future. Cultural, linguistic, ethnic, religious or historical organizations: Open to members based on some cultural, linguistic, ethnic, religious or historical link. Examples include the Commonwealth of Nations, Arab League, Organisation internationale de la Francophonie, Community of Portuguese Language Countries, Organization of Turkic States, International Organization of Turkic Culture, Organisation of Islamic Cooperation, and Commonwealth of Independent States (CIS). Economic organizations: Based on macro-economic policy goals. Some are dedicated to free trade and reduction of trade barriers, e.g. World Trade Organization, International Monetary Fund. Others are focused on international development.
== Use == Dehydroascorbic acid has been used as a vitamin C dietary supplement. As a cosmetic ingredient, dehydroascorbic acid is used to enhance the appearance of the skin. It may be used in a process for permanent waving of hair and in a process for sunless tanning of skin. In a cell culture growth medium, dehydroascorbic acid has been used to assure the uptake of vitamin C into cell types that do not contain ascorbic acid transporters. As a pharmaceutical agent, some research has suggested that administration of dehydroascorbic acid may confer protection from neuronal injury following an ischemic stroke. The literature contains many reports on the antiviral effects of vitamin C, and one study suggests dehydroascorbic acid has stronger antiviral effects and a different mechanism of action than ascorbic acid. Solutions in water containing ascorbic acid and copper ions and/or peroxide, resulting in rapid oxidation of ascorbic acid to dehydroascorbic acid, have been shown to possess powerful but short-lived antimicrobial, antifungal, and antiviral properties, and have been used to treat gingivitis, periodontal disease, and dental plaque. A pharmaceutical product named Ascoxal is an example of such a solution used as a mouth rinse as an oral mucolytic and prophylactic agent against gingivitis. Ascoxal solution has also been tested with positive results as a treatment for recurrent mucocutaneous herpes, and as a mucolytic agent in acute and chronic pulmonary disease such as emphysema, bronchitis, and asthma by aerosol inhalation.
== Personal life and death == Yonath was married to Moshe Yonath. Their marriage ended in divorce. They had one daughter, Hagit Yonath, a doctor at Sheba Medical Center, and a granddaughter, Noa. Yonath was the cousin of anti-occupation activist Ruchama Marton as their mothers were sisters. Yonath died on 31 August 2026, at the age of 87.
The method is the collection of conditions in which the GC operates for a given analysis. Method development is the process of determining what conditions are adequate and/or ideal for the analysis required. Conditions which can be varied to accommodate a required analysis include inlet temperature, detector temperature, column temperature and temperature program, carrier gas and carrier gas flow rates, the column's stationary phase, diameter and length, inlet type and flow rates, sample size and injection technique. Depending on the detector(s) (see below) installed on the GC, there may be a number of detector conditions that can also be varied. Some GCs also include valves which can change the route of sample and carrier flow. The timing of the opening and closing of these valves can be important to method development.
Sources: en.wikipedia.org
== Oscillatory behavior == When blood glucose levels are too low, the pancreas is signaled to release glucagon, which has essentially the opposite effect of insulin and therefore opposes the reduction of glucose in the blood. Glucagon is delivered directly to the liver, where it connects to the glucagon receptors on the membranes of the liver cells, signals the conversion of the glycogen already stored in the liver cells into glucose. This process is called glycogenolysis. Conversely, when the blood glucose levels are too high, the pancreas is signaled to release insulin. Insulin is delivered to the liver and other tissues throughout the body (e.g., muscle, adipose). When the insulin is introduced to the liver, it connects to the insulin receptors already present, that is tyrosine kinase receptor. These receptors have two alpha subunits (extracellular) and two beta subunits (intercellular) which are connected through the cell membrane via disulfide bonds. When the insulin binds to these alpha subunits, 'glucose transport 4' (GLUT4) is released and transferred to the cell membrane to regulate glucose transport in and out of the cell. With the release of GLUT4, the allowance of glucose into cells is increased, and therefore the concentration of blood glucose might decrease. This, in other words, increases the utilization of the glucose already present in the liver. This is shown in the adjacent image.
== Early life and education == Bibudhendra Sarkar was born on August 2, 1935, in Kushtia, Bengal, British India (now Bangladesh). His father, Surendra Nath Sarkar, was a lawyer, and his mother, Sucheta Sarkar (née Chaki), a homemaker, died when he was one year old. He completed his kindergarten and primary education at Kushtia Mission School, a Catholic institution. Following the Partition of India in 1947, Sarkar's family relocated to Calcutta after losing their possessions. He attended City College School and later City College, Kolkata, earning his Matriculation and Intermediate Science certifications from the University of Calcutta. He pursued higher education at Banaras Hindu University in Uttar Pradesh, specializing in the chemistry of natural products and earning Bachelor of Pharmacy (B.Pharm) and Master of Pharmacy (M.Pharm) degrees. During his undergraduate studies, Sarkar worked as a summer researcher at the Central Drug Research Institute in Lucknow, under the mentorship of Manojit Mohan Dhar, who encouraged him to pursue graduate studies abroad. He subsequently moved to the United States, completing a PhD in biochemistry at the University of Southern California in 1964 under the supervision of Paul Saltman. At USC, his work was influenced by chemists Sydney Benson (chemical kinetics), Arthur Adamson (physical chemistry), and Bo Malmström (metal-activated enzyme chemistry).
== History == Cold hemagglutination was first reported by Landsteiner in 1903 and found to occur in human beings in 1918. The association of cold hemagglutination with hemolysis was described in 1937 by Rosenthal and Corten. During the 1960s, Dacie and Schubothe published systematic descriptions of 16 CAD patients each. The auto antibodies responsible for hemagglutination at low temperatures, cold agglutinins (CA), may be found in the sera of healthy subjects as well as in patients with AIHA of the cold reactive types. CA bind to erythrocyte surface antigens at a temperature optimum of 0–4 °C. In contrast to polyclonal CA in healthy individuals, monoclonal CA often have a high-thermal amplitude, which contributes to their pathogenicity at temperatures approaching 37 °C. Binding of CA causes agglutination of erythrocytes and the antigen–antibody complex induces complement (C) activation and hemolysis. Essential clinical manifestations of primary CAD are hemolytic anemia and cold-induced circulatory symptoms. Exact estimates of the severity of anemia and the frequency of cold-induced symptoms, however, have not been provided until recent years.
=== Toll Holdings === In 1985, Little, along with businessmen Peter Rowsthorn as well as Rowsthorn's son, Mark Rowsthorn, and Lyall McLachlan, led a management buyout team which purchased Toll Holdings which in 1993 listed on the Australian Securities Exchange. Little and his team developed Toll from an 18-truck operation worth $1.5 million, into a $3.8 billion international organisation with 45,000 employees and operations in 50 countries. As a result of his involvement in Toll Holdings, Little has become one of Australia's richest men. Little subsequently further developed his ability to acquire new businesses, buying many between 1989 and 2000. He then began taking over two companies a year until 1997, when Toll paid $145 million for eight TNT businesses. In 2000, it paid $120 million for rival Finemore Holdings. Little also oversaw Toll's investments in technology, wine, rail freight and cargo shipping.
== Current status == Many exogenous agents have been developed since the discovery of 5-HT2C receptors. Thus far a small number of agonists, with sufficient selectivity for the 5-HT2C receptors over the other subtypes have been studied in clinical trials. A variety of other 5-HT2C receptor agonists remain in preclinical development, including Ro60-0175, WAY-163,909, and the inverse agonist SB-243,213. Evidence supports a therapeutic potential of 5-HT2C receptor modulation in the treatment of a variety of pathological conditions, including schizophrenia, obesity, urinary incontinence and sexual dysfunction.
Sources: en.wikipedia.org
Since the missile approached the target as it climbed, each of these intersections would be closer to the target. Taking several of these, in turn, the trajectory of the missile could be determined to some degree of accuracy, and air raid warnings sent to likely areas. Success in this task was aided by the missile fuselage profile, which acted as an excellent quarter-wave reflector for 12 m band HF radar. RAF Fighter Command was also informed of the launch in an effort to attack the sites. However, the German launch convoys were motorized, well camouflaged and highly mobile, making them extremely difficult to find and attack. The only known claim was made when Supermarine Spitfire pilots of No. 602 Squadron RAF squadron came across a V-2 rising from a wooded area, allowing a quick shot of unknown result.
There was also honorary membership bestowed on those who had made unusual services to the Catholic faith, social or economic science, the arts, education, French culture generally, or to any other ideal of the association. 1967 membership 30,424; 1979 membership 26,000. Absorbed Foresters Franco Americains in 1939. The ACA went into rehabilitation in 2008 and later was liquidated. Most of its insurance policies were assumed by the Royal Arcanum.
=== Mitochondrial genetics === Mitochondrial genetics concerns the diagnosis and management of mitochondrial disorders, which have a molecular basis but often result in biochemical abnormalities due to deficient energy production. There exists some overlap between medical genetic diagnostic laboratories and molecular pathology. In the UK, the NHS Highly Specialised Service for Rare Mitochondrial Disorders offers diagnostic testing for patients. Based in laboratories in Newcastle upon Tyne , Oxford and London which are integrated within the NHS Genomic Medicine Service (GMS).
This intracellular screening technique allows for the discovery of ligands that engage targets in their native conformation and cellular environment, enabling screening of targets that are difficult to express or purify, and potentially improving the physiological relevance of identified compounds.
Sources: en.wikipedia.org
No. Melanotan-2 is manufactured synthetically. The naturally occurring peptide in the same family is alpha-melanocyte-stimulating hormone, which the body produces as part of normal endocrine and neural signalling.
Both are synthetic analogues derived from the same parent hormone. Reference descriptions usually characterise afamelanotide as more selective for the MC1R subtype, whereas melanotan-2 is reported to interact with a wider range of melanocortin receptors.
Early studies explored melanocortin signalling and pigmentation, which later led to informal use of the label tanning peptide. That label is not a regulatory category and does not imply approved status for any purpose.
Mass spectrometry combined with liquid chromatography provides both molecular weight confirmation and a measure of related impurities. Tandem mass spectrometry adds sequence information. A purity percentage reported without a mass measurement does not confirm what the material is.